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Journal Details
Format
Journal
eISSN
2083-134X
First Published
16 Apr 2011
Publication timeframe
4 times per year
Languages
English

Search

Volume 33 (2015): Issue 3 (September 2015)

Journal Details
Format
Journal
eISSN
2083-134X
First Published
16 Apr 2011
Publication timeframe
4 times per year
Languages
English

Search

31 Articles
Open Access

Transparent fluorinate acrylic polyurethane with hydrophobicity obtained by crosslinking of hydroxyl-containing fluoroacrylate copolymer with HDI trimer

Published Online: 30 Aug 2016
Page range: 451 - 459

Abstract

Abstract

Hydroxyl-containing fluoroacrylate copolymers with different fluorine and hydroxyl concentrations were synthesized via free-radical solution polymerization. Transparent fluorinated polyurethane (FPU) films were prepared by curing the copolymers with HDI (hexamethylene diisocyanate) trimer. The Fourier transform infrared spectroscopy (FT-IR) results revealed introduction of fluorine both into the copolymer and polyurethane. X-ray photoelectron spectroscopy (XPS) analyses indicated that a gradient concentration of fluorine existed in the depth profile of the fluorinated polyurethane films. The highest contact angle (CA) was obtained for the FPU film with fluoroacrylate monomer concentration of 22 wt.% because of fluorine present on the film surface. The surface topographies detected by SEM and AFM indicated that surface roughness contributed little to the film hydrophobicity. By increasing the fluoroacrylate monomer concentration, the decreasing of crosslinking degree of hard segment resulted in lowering the first degradation temperature, while more C-F groups in soft segment led to higher second degradation temperature. UV-Vis spectrophotometer measurements indicated that the FPU film with the fluoroacrylate monomer concentration of 16 wt.% still had a high transmittance of more than 90 % in the whole visible wavelength range.

Keywords

  • fluoroacrylate copolymer
  • polyurethane
  • hyrophobicity
  • transparency
  • X-ray photoelectron spectroscopy (XPS)
Open Access

Preparation and photocatalytic activity of multi-walled carbon nanotubes/Mg-doped ZnO nanohybrids

Published Online: 30 Aug 2016
Page range: 460 - 469

Abstract

Abstract

Multi-walled carbon nanotubes/Mg-doped ZnO (MWNTs/Zn1-xMgxO) nanohybrids were prepared by co-precipitation method, and their photocatalytic activity for methyl orange (MO) was studied. Experimental results showed that Mg-doped ZnO nanoparticles were successfully deposited on the surface of MWNTs under annealing at 450 °C and 550 °C. The resultant MWNTs/Zn0.9Mg0.1O nanohybrids had better photocatalytic activity for degradation of methyl orange than pure ZnO: the rates of MO photodegradation were 100 % and 30 % for 1 h, respectively. The enhancement in the photocatalytic activity was attributed to the excellent electronic properties of MWNTs and Mg-doping.

Keywords

  • carbon nanotube
  • Mg-doped ZnO
  • nanohybrids
  • photocatalytic activity
Open Access

Preparation, structure and optical properties of transparent conducting gallium-doped zinc oxide thin films

Published Online: 30 Aug 2016
Page range: 470 - 481

Abstract

Abstract

Highly conductive gallium-doped zinc oxide (GZO) transparent thin films were deposited on glass substrates by RF mag­netron sputtering. The deposited films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), four-point probe and UV-Vis spectrophotometer, respectively. The effect of growth temperature on the structure and optoelectrical properties of the films was investigated. The results demonstrate that high quality GZO films oriented with their crystal­lographic c-axis perpendicular to the substrates are obtained. The structure and optoelectrical properties of the films are highly dependent on the growth temperature. It is found that with increasing growth temperature, the average visible transmittance of the deposited films is enhanced and the residual stress in the thin films is obviously relaxed. The GZO films deposited at the growth temperature of 400°C, which have the largest grain size (74.3 nm), the lowest electrical resistivity (1.31×10-3 Ω·cm) and the maximum figure of merit (1.46×1O-2Ω-1), exhibit the best optoelectrical properties. Furthermore, the optical proper­ties of the deposited films were determined by the optical characterization methods and the optical energy-gaps were evaluated by extrapolation method. A blue shift of the optical energy gap is observed with an increase in the growth temperature.

Keywords

  • zinc oxide
  • thin films
  • magnetron sputtering
  • optical properties
Open Access

Properties of Pd nanograins in C-Pd composite films obtained by PVD method

Published Online: 30 Aug 2016
Page range: 482 - 487

Abstract

Abstract

Properties of palladium nanograins obtained by sedimentation of a soluted C-Pd film prepared by PVD method are presented. These properties were studied using SEM and TEM methods. Dissolved films were prepared by PVD method and after dissolving, they were fractionated to obtain different parts classified with palladium nanograins diameters. Several classes of diameters were determined: below 20 nm, between 20 and 100 nm and above 100 nm. The defects and triple junction were observed. Multishell carbonaceous structures were found in the big and medium size Pd nanograins.

Keywords

  • Pd nanograins
  • PVD
  • defects
Open Access

Synthesis and characterization of graphene oxide composite with Fe3O4

Published Online: 30 Aug 2016
Page range: 488 - 490

Abstract

Abstract

In the paper, a magnetic composite of graphene oxide (MGO) has been successfully synthesized through decomposition of iron (III) acetylacetonate in the mixture solution of triethylene glycol and graphene oxide (GO). Atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and superconducting quantum interference device were used to characterize the material. The results show that the magnetic Fe3O4 nanoparticles modified graphene oxide composite with superparamagnetic properties, and magnetization saturation of 16.4 emu/g has been obtained. The MGO has a good sustained-release performance, and in vitro cytotoxicity confirming its secure use as a potential drug carrier.

Keywords

  • graphene oxide
  • composite
  • magnetic Fe3O4
Open Access

Effect of substrate temperature on structural and optical properties of spray deposited ZnO thin films

Published Online: 30 Aug 2016
Page range: 491 - 496

Abstract

Abstract

Undoped ZnO thin films have been prepared on glass substrates at different substrate temperatures by spray pyrolysis method. The effect of temperature on the structural, morphological and optical properties of n-type ZnO films was studied. The X-ray diffraction (XRD) results confirmed that the ZnO thin films were polycrystalline with wurtzite structure. Scanning electron microscopy (SEM) measurements showed that the surface morphology of the films changed with temperature. The studies demonstrated that the ZnO film had a transmission of about 85 % and energy gap of 3.28 eV at 450 °C. The RBS measurements revealed that ZnO layers with a thickness up to 200 nm had a good stoichiometry.

Keywords

  • ZnO
  • spray deposition
  • Rutherford Backscattering Spectrometry (RBS)
  • structural
  • optical and electrical properties
Open Access

Dispersion of dielectric permittivity and magnetic properties of solid solution PZT–PFT

Published Online: 30 Aug 2016
Page range: 497 - 500

Abstract

Abstract

In this paper we present the results of investigations into ceramic samples of solid solution (1-x)(PbZr0.53Ti0.47O3)- x(PbFe0.5Ta0.503) (i.e. (1-x)PZT-xPFT) with x = 0.25, 0.35 and 0.45. We try to find the relation between the character of dielectric dispersion at various temperatures and the composition of this solution. We also describe the magnetic properties of investigated samples. With increasing the content of PFT also mass magnetization and mass susceptibility increase (i.e. magnetic properties are more pronounced) at every temperature. The temperature dependences of mass magnetization and re­ciprocal of mass susceptibility have similar runs for all the compositions. However, our magnetic investigations exhibit weak antiferromagnetic ordering instead of the ferromagnetic one at room temperature. We can also say that up to room tempera­ture any magnetic phase transition has not occurred. It may be a result of the conditions of the technological process during producing our PZT-PFT ceramics.

Keywords

  • multiferroic
  • ferroelectric
  • antiferromagnetic
  • relaxor
  • ceramics
Open Access

Studies on Inx(As2Se3)1-x thin films using variable angle spectroscopic ellipsometry (VASE)

Published Online: 30 Aug 2016
Page range: 501 - 507

Abstract

Abstract

The results of multi-angle ellipsometrical measurements of thermally evaporated Inx(As2Se3)1-x (x = 0, 0.01,0.05) films are presented. Optical parameters n and Es of thin Inx(As2Se3)1-x films show that indium atoms were incorporated into the host matrix of As2Se3 forming distinct features depending on the indium concentration. Refractive index, n, was found to decrease with the addition of In to the binary As2Se3. The real and imaginary parts of the dielectric function, ε' and ε" were also calculated from the obtained data and correlated with In concentration. It was found that e' decreases with the increase of In content while ε" increases with the increase of In content. Absorption edge is shifted towards lower photon energy with the increase of In content. As a result, the optical energy gap decreases with increasing In content. This has been correlated with the chemical character of the additive as well as with the structural and bonding aspects of the amorphous composition. Nonlinear optical constants (χ(3) and n2) were determined from linear optical parameters using semi-empirical relations in the long wavelength limit.

Keywords

  • chalcogenides
  • ellipsometry
  • optical absorption
  • energy gap
  • nonlinear optics
Open Access

Effects of Cr and Fe co-doping on structural, optical, electrical and magnetic properties of titanium dioxide (TiO2)

Published Online: 30 Aug 2016
Page range: 508 - 514

Abstract

Abstract

A series of Ti0.9Fe0.1-xCrxO2 (where x = 0.0, 0.02, 0.04, 0.6, 0.08, 0.10) was synthesized using the powder metallurgy route. The structural, morphological, magnetic, optical and electrical properties were investigated by X-ray diffractometry (XRD), Raman spectroscopy, scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), UV-Vis spec­troscopy and four probe technique, respectively. The rutile phase was confirmed by XRD analysis which was also verified by Raman spectroscopy. It was observed that the grain size increased as the concentration of Cr increased. M-H loops ex­tracted from VSM analysis revealed anti-ferromagnetic, weak ferromagnetic and paramagnetic behaviors at room temperature. The band gap energy and resistivity measurements exhibited the semiconducting nature of Ti0.9Fe0.1-xCrxO2 based diluted magnetic semiconductors.

Keywords

  • dilute magnetic semiconductors
  • rutile
  • grain size
  • magnetic properties
  • resistivity
Open Access

Fabrication and properties of zinc oxide thin film prepared by sol-gel dip coating method

Published Online: 30 Aug 2016
Page range: 515 - 520

Abstract

Abstract

ZnO thin films were deposited on a glass substrate by dip coating technique using a solution of zinc acetate, ethanol and distilled water. Optical constants, such as refractive index n and extinction coefficient k. were determined from transmittance spectrum in the ultraviolet-visible-near infrared (UV-Vis-NIR) regions using envelope methods. The films were found to exhibit high transmittance, low absorbance and low reflectance in the visible regions. Absorption coefficient α and the thickness of the film t were calculated from interference of transmittance spectra. The direct optical band gap of the films was in the range of 3.98 to 3.54 eV and the thickness of the films was evaluated in the range of 173 to 323 nm, while the refractive index slightly varied in the range of 1.515 to 1.622 with an increase in withdrawal speed from 100 to 250 mm/s. The crystallographic structure of the films was analyzed with X-ray diffractometer. The films were amorphous in nature.

Keywords

  • thin films
  • sol-gel
  • X-ray diffraction
  • optical properties
Open Access

CVD carbon powders modified by ball milling

Published Online: 30 Aug 2016
Page range: 521 - 528

Abstract

Abstract

Carbon powders produced using a plasma assisted chemical vapor deposition (CVD) methods are an interesting subject of research. One of the most interesting methods of synthesizing these powders is using radio frequency plasma. This method, originally used in deposition of carbon films containing different sp2/sp3 ratios, also makes possible to produce carbon structures in the form of powder. Results of research related to the mechanical modification of these powders have been presented. The powders were modified using a planetary ball mill with varying parameters, such as milling speed, time, ball/powder mass ratio and additional liquids. Changes in morphology and particle sizes were measured using scanning electron microscopy and dynamic light scattering. Phase composition was analyzed using Raman spectroscopy. The influence of individual parameters on the modification outcome was estimated using statistical method. The research proved that the size of obtained powders is mostly influenced by the milling speed and the amount of balls. Powders tend to form conglomerates sized up to hundreds of micrometers. Additionally, it is possible to obtain nanopowders with the size around 100 nm. Furthermore, application of additional liquid, i.e. water in the process reduces the graphitization of the powder, which takes place during dry milling.

Keywords

  • carbon powder
  • CVD
  • milling
  • Taguchi method
Open Access

Growth and characterization of NLO crystal: L-leucine phthalic acid potassium iodide

Published Online: 30 Aug 2016
Page range: 529 - 536

Abstract

Abstract

A new semi-organic non linear optical crystal, L-leucine phthalic acid potassium iodide (LLPPI) has been grown from an aqueous solution by slow evaporation method. The grown crystals were subjected to different characterizations, such as single crystal XRD, FT-IR, UV-Vis, TGA, SEM, EDAX, micro hardness, dielectric and powder SHG. Single crystal structure was determined from X-ray diffraction data and it revealed that the crystal belongs to triclinic system with the space group P1. The vibrational frequencies of various functional groups were derived from FT-IR spectrum. Thermal stability of the grown crystal was investigated by TG-DTA studies and it was observed that the crystal was thermally stable up to 192 °C. Optical absorption study was carried out and a good transparency in the entire visible region was observed at the lower cutoff wavelength of 227 nm. Dielectric study was performed as a function of frequency and normal dielectric behavior was observed. The micro hardness test was carried out and the load dependent hardness was measured. Kurtz powder method was employed to explore the NLO characteristics of the grown crystal.

Keywords

  • semi-organic crystal
  • slow evaporation method
  • NLO crystal
  • thermal and SHG studies
Open Access

Microwave-assisted synthesis, characterization and photoluminescence of shuttle-like BaMoO4 microstructure

Published Online: 30 Aug 2016
Page range: 537 - 540

Abstract

Abstract

Shuttle-like BaMoO4 microstructure has been successfully synthesized from Ba(N03)4H20 and Na2MoO2H2O as starting materials in ethylene glycol solvent containing 20 mL 5 M NaOH by microwave radiation at 180 W for 30 min. The as- synthesized BaMoO4 product was characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Raman spectrophotometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photolumines­cence (PL) spectroscopy. XRD patterns revealed that the products was tetragonal BaMoO4 phase. SEM and TEM characteriza­tion showed that the product had a shuttle-like BaMoO4 microstructure. PL of the shuttle-like BaMoO4 microstructure showed a maximum emission at 466 nm excited by 280 nm wavelength.

Keywords

  • BaMoO4
  • shuttle-like particles
  • luminescence
Open Access

Multifractal characteristics of titanium nitride thin films

Published Online: 30 Aug 2016
Page range: 541 - 548

Abstract

Abstract

The study presents a multi-scale microstructural characterization of three-dimensional (3-D) micro-textured surface of titanium nitride (TiN) thin films prepared by reactive DC magnetron sputtering in correlation with substrate temperature variation. Topographical characterization of the surfaces, obtained by atomic force microscopy (AFM) analysis, was realized by an innovative multifractal method which may be applied for AFM data. The surface micromorphology demonstrates that the multifractal geometry of TiN thin films can be characterized at nanometer scale by the generalized dimensions Dq and the singularity spectrum f(α). Furthermore, to improve the 3-D surface characterization according with ISO 25178-2:2012, the most relevant 3-D surface roughness parameters were calculated. To quantify the 3-D nanostructure surface of TiN thin films a multifractal approach was developed and validated, which can be used for the characterization of topographical changes due to the substrate temperature variation.

Keywords

  • atomic force microscopy
  • DC magnetron sputtering
  • multifractal analysis
  • surface roughness
  • titanium nitride (TiN) thin film
Open Access

First-principles study of atomic structure and electronic properties of Si and F doped anatase TiO2

Published Online: 30 Aug 2016
Page range: 549 - 554

Abstract

Abstract

Chemical doping represents one of the most effective ways in engineering electronic structures of anatase TiO2 for practical applications. Here, we investigate formation energies, geometrical structures, and electronic properties of Si-, F-doped and Si/F co-doped anatase TiO2 by using spin-polarized density functional theory calculation. We find that the co-doped TiO2 is thermodynamically more favorable than the Si- and F-doped TiO2- Structural analysis shows that atomic impurity varies crystal constants slightly. Moreover, all the three doped systems show a pronounced narrowing of band gap by 0.33 eV for the F-doped TiO2, 0.17 eV for the Si-doped TiO2, and 0.28 eV for the Si/F-co-doped TiO2, which could account for the experimentally observed redshift of optical absorption edge. Our calculations suggest that the Si/F-co-doping represents an effective way in tailoring electronic structure and optical properties of anatase TiO2.

Keywords

  • anatase TiO2
  • Si/F co-doping
  • first-principles
  • electronic properties
Open Access

UV-Vis studies of 800 keV Ar ion irradiated NiO thin films

Published Online: 30 Aug 2016
Page range: 555 - 559

Abstract

Abstract

We report the evolution of optical absorption properties of 800 keV Ar ion irradiated NiO thin films through UV-Vis characterization. Our results indicate the existence of both Mott-Hubbard (d → d transition) and charge-transfer (p → d transition) characteristic of NiO. The optical band gap of NiO increases from 3.58 to 3.75 eV when irradiated at the fluence of 5 × 1014 ions cm-2 but it does not show any remarkable variation upon 800 keV Ar ion irradiation at higher fluences. The refractive index and electron polarizability at different ion fluences have been determined from the optical band gap. Both refractive index and electron polarizability follow an opposite trend to that of the energy gap as a function of ion fluence.

Keywords

  • ion irradiation
  • nanoparticles
  • UV-Vis spectroscopy
  • band gap
Open Access

The influence of VO2(B) nanobelts on thermal decomposition of ammonium perchlorate

Published Online: 30 Aug 2016
Page range: 560 - 565

Abstract

Abstract

The influence of vanadium dioxide VO2(B) on thermal decomposition of ammonium perchlorate (AP) has not been reported before. In this contribution, the effect of VO2(B) nanobelts on the thermal decomposition of AP was investigated by the Thermo- Gravimetric Analysis and Differential Thermal Analysis (TG/DTA). VO2(B) nanobelts were hydrothermally prepared using peroxovanadium (V) complexes, ethanol and water as starting materials. The thermal decomposition temperatures of AP in the presence of I wt.%, 3 wt.% and 6 wt.% of as-obtained VO2<B) nanobelts were reduced by 39 °C. 62 °C and 74 °C, respectively. The results indicated that VO2(B) nanobelts had a great influence on the thermal decomposition temperature of AP Furthermore, the influence of the corresponding V2Os, which was obtained by thermal treatment of VO2(B) nanobelts, on the thermal decomposition of AP was also investigated. The resufs showed that VO2(B) nanobelts had a greater influence on the thermal decomposition temperature of AP than that of V2Os.

Keywords

  • VO2(B)
  • ammonium perchlorate
  • thermal analysis
  • hydrothermal synthesis
Open Access

Graphene synthesis: a Review

Published Online: 30 Aug 2016
Page range: 566 - 578

Abstract

Abstract

Graphene has achieved a great amount of popularity and interest from the science world because of its extraordinary physical, mechanical and thermal properties. Graphene is an allotrope of carbon, having one-atom-thick planar sheets of sp2 bonded carbon atoms densely packed in a honeycomb crystal lattice. Many methods to synthesize graphene have been developed over a short period and we believe it is necessary to create a list of the most notable approaches. This article focuses on the methods to synthesize graphene in an attempt to summarize and document advancements in the synthesis of graphene research and future prospects.

Keywords

  • graphene
  • synthesis
  • nanomaterials
  • graphite
  • 2D
  • biomass
Open Access

Effects of partial Co replacement by Fe in Sr0.775Y0.225CoO3-δ on its magnetic property, oxygen deficiency and crystal structure

Published Online: 30 Aug 2016
Page range: 579 - 587

Abstract

Abstract

A study has been conducted on the effects of partial, 10 % Co substitution by Fe in the perovskite Sr0.775Y0.225CoO3-δ compound. The XRD data show that the resulted samples of Fe-free and Fe-doped compounds exhibit good 314 single phase quality with a tetragonal I4/mmm crystal structure. The measured M-T curves display the typical feature of ferromagnetic (FM) transition at 335 K for the Fe-free sample, while showing significantly degraded FM ordering for the 10 % Fe-doped sample. The oxygen deficiency determined fro|m our 10 % Fe doped sample is found to decrease by only 0.025. Further detailed analysis of the XRD data also reveals distinctly different structural changes in the Co-O slabs compared to the 50 % Fe-doped sample which exhibits a complete suppression of FM order. The results of this study, thus, have revealed the close relations among the changes induced by Fe doping in the magnetic ordering of crystal, and its oxygen content as well as the associated local structure in the Co-O layers responsible for the magnetic properties in the compound.

Keywords

  • perovskite Sr0.775Y0.225CoO3-δ compound
  • ferromagnetic compound
  • oxygen content
Open Access

Fabrication and characterization of TiO2 nanotube arrays on Ti membrane enlarged by anodic oxidation

Published Online: 30 Aug 2016
Page range: 588 - 592

Abstract

Abstract

TiO2 nanotube arrays have attracted a great deal of attention as photocatalytic and photoelectrode materials due to their large surface area, low cost and easy fabrication. Highly ordered TiO2 nanotube arrays for the photoelectrodes in dye-sensitized solar cells have been fabricated from Ti foil. However, the TiO2 nanotube arrays from Ti foil were not effective for the photocatalytic materials, because it had only one plane for the photocatalytic reaction. We have fabricated the TiO2 nanotube arrays from macroporous Ti metal membrane by anodic oxidation and tried to scale it up. Various factors were controlled to obtain the optimal microstructure of the TiO2 nanotube arrays on the surface of macroporous Ti metallic membrane. Microstructure and phase were studied by SEM and XRD, respectively. Temperature was a very important factor in anodic oxidation of large surface area. 10 μm thick TiO2 nanotube arrays on Ti metallic membrane having a large surface area were fabricated and some factors for scaling-up were discussed.

Keywords

  • TiO2 nanotube arrays
  • anodic oxidation
  • photocatalysis
  • scaling-up
  • anatase
Open Access

Electronic parameters of MIS Schottky diodes with DNA biopolymer interlayer

Published Online: 30 Aug 2016
Page range: 593 - 600

Abstract

Abstract

In this work, we prepared an ideal Cu/DNA/n-InP biopolymer-inorganic Schottky sandwich device formed by coating a n- lP semiconductor wafer with a biopolymer DNA. The Cu/DNA/n-InP contact showed a good rectifying behavior. The ideality factor value of 1.08 and the barrier height (Φb) value of 0.70 eV for the Cu/DNA/n-InP device were determined from the forward ias I-V characteristics. It was seen that the Φb value of 0.70 eV obtained for the Cu/DNA/n-InP contact was significantly larger tan the value of 0.48 eV of conventional Cu/n-InP Schottky diodes. Modification of the interfacial potential barrier of Cu/n-InP iode was achieved using a thin interlayer of DNA biopolymer. This was attributed to the fact that DNA biopolymer interlayer increased the effective barrier height by influencing the space charge region of InP.

Keywords

  • Schottky diodes
  • interfaces
  • semiconductors
  • electrical properties
Open Access

Structural and optical properties of pure and Ag doped ZnO thin films obtained by sol gel spin coating technique

Published Online: 30 Aug 2016
Page range: 601 - 605

Abstract

Abstract

We have investigated the influence of Ag doping on zinc oxide thin films. Pure and Ag doped, preferentially oriented transparent zinc oxide thin films were prepared by sol gel technique on a glass substrate using diethyl amine as a stabilizer. The X-ray diffraction analysis revealed that the films with hexagonal wurtzite type structure were polycrystalline in nature with a preferred grain orientation in the 101 direction. The crystallite sizes decreased from 34 nm to 27 nm after silver doping. Both photoluminescence and optical transmission measurements showed that the band gap increased after the Ag doping. The structure and optical characterization studies clearly indicated the incorporation of Ag in ZnO. Hence, the observed increase in the optical band gap and decrease in crystallite size can be directly attributed to the effect of Ag ion incorporation into the ZnO lattice.

Keywords

  • Ag doped ZnO
  • sol gel
  • structure properties
  • optical band gap
  • defects study
Open Access

Controlled fluoridation of amorphous carbon films deposited at reactive plasma conditions

Published Online: 30 Aug 2016
Page range: 606 - 611

Abstract

Abstract

A study of the correlations between plasma parameters, gas ratios, and deposited amorphous carbon film properties is presented. The injection of a C4F8/Ar/N2 mixture of gases was successfully used in an inductively coupled plasma system for the preparation of amorphous carbon films with different fluoride doping at room-temperature, using silicon as a substrate. This coating was formed at low-pressure and low-energy using an inductively coupled plasma process. A strong dependence between the ratios of gases during deposition and the composition of the substrate compounds was shown. The values of ratios between Ar (or Ar+N2) and C4F8 - 1:1 and between N2 and Ar - 1:2 in the N2/Ar/C4F8 mixture were found as the best for low fluoridated coatings. In addition, an example of improving the etch-passivation in the Bosch procedure was described. Scanning electron microscopy with energy dispersive spectroscopy options, X-ray diffraction, and X-ray reflectivity were used for quantitative analysis of the deposited films.

Keywords

  • carbon deposition
  • reactive plasma
  • fluoridation
Open Access

Photocurrent response of phloxin B-cetyltrimethylammonium bromide photogalvanic cell device

Published Online: 30 Aug 2016
Page range: 612 - 619

Abstract

Abstract

Photocurrent and photovoltage generation using phloxin B dye in aqueous and micellar medium at different concentrations have been studied in a photogalvanic cell. The photopotential and photocurrent generated were 1135.0 mV and 260.0 μA, respectively. The observed solar energy conversion efficiency with CTAB surfactant was 0.64 % and maximum power of the cell was 66.72 mW. The output of the cell was sensitive to various parameters, like dye concentration, reductant concentration, pH, light intensity, electrode area and diffusion length. Current-potential characteristics studied by I-V curve of the cell and the mechanism of cell photovoltage generation have been presented in the paper.

Keywords

  • phloxin B
  • CTAB
  • fill factor
  • conversion efficiency
  • photogalvanic cell
Open Access

Temperature dependence of stress in CVD diamond films studied by Raman spectroscopy

Published Online: 30 Aug 2016
Page range: 620 - 626

Abstract

Abstract

Evolution of residual stress and its components with increasing temperature in chemical vapor deposited (CVD) diamond films has a crucial impact on their high temperature applications. In this work we investigated temperature dependence of stress in CVD diamond film deposited on Si(100) substrate in the temperature range of 30 °C to 480 °C by Raman mapping measurement. Raman shift of the characteristic diamond band peaked at 1332 cm-1 was studied to evaluate the residual stress distribution at the diamond surface. A new approach was applied to calculate thermal stress evolution with increasing tempera­ture by using two commonly known equations. Comparison of the residts obtained from the two methods was presented. The intrinsic stress component was calculated from the difference between average values of residual and thermal stress and then its temperature dependence was discussed.

Keywords

  • Raman spectroscopy
  • stress
  • diamond structure
  • CVD diamond films
Open Access

Poly(N-isopropylacrylamide-co-methacrylic acid) microgel stabilized copper nanoparticles for catalytic reduction of nitrobenzene

Published Online: 30 Aug 2016
Page range: 627 - 634

Abstract

Abstract

Poly(N-isopropylacrylamide-co-methacrylic acid) microgels [p(NIPAM-co-MAAc)] were synthesized by precipitation polymerization of N-isopropylacrylamide and methacrylic acid in aqueous medium. These microgels were characterized by dynamic light scattering and Fourier transform infrared spectroscopy. These microgels were used as micro-reactors for in situ synthesis of copper nanoparticles using sodium borohydride (NaBH4) as reducing agent. The hybrid microgels were used as catalysts for the reduction of nitrobenzene in aqueous media. The reaction was performed with different concentrations of cat­alyst and reducing agent. A linear relationship was found between apparent rate constant (kapp) and amount of catalyst. When the amount of catalyst was increased from 0.13 to 0.76 mg/mL then kapp was increased from 0.03 to 0.14 min-1. Activation parameters were also determined by performing reaction at two different temperatures. The catalytic process has been discussed in terms of energy of activation, enthalpy of activation and entropy of activation. The synthesized particles were found to be stable even after 14 weeks and showed catalytic activity for the reduction of nitrobenzene.

Keywords

  • catalysis
  • copper
  • microgels
  • nanoparticles
Open Access

Application of Aloe vera gel instead of silicon dioxide as organic dielectric material in microelectronics

Published Online: 30 Aug 2016
Page range: 635 - 638

Abstract

Abstract

Organic materials are now being used in a wide range of microelectronic applications in parallel with inorganic materials, because of their superior properties, environmental safety, and low cost. This paper describes the characterization of Aloe vera gel (AVG), a new organic dielectric material. The surface morphology, spatial distribution of elements, and structural characteristics of an AVG layer were examined using scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD), respectively. The resistance of the AVG layer, determined using a four-probe station, was 640 Ω EDX showed that the elements contained in the layer were carbon, oxygen, aluminum, silicon, calcium, potassium, and copper. The XRD results suggested that the sample primarily consisted of bornite (Cu5FeS4), geerite (Cu8S5), sal ammoniac (NH4Cl), and carobbite (KF).

Keywords

  • Aloe vera
  • organic dielectric material
  • four-probe station
  • SEM
  • EDX
  • XRD
Open Access

Structure of AlN films deposited by magnetron sputtering method

Published Online: 30 Aug 2016
Page range: 639 - 643

Abstract

Abstract

AlN films on a Si substrate were synthesized by magnetron sputtering method. A dual magnetron system operating in AC mode was used in the experiment. Processes of synthesis were carried out in the atmosphere of a mixture of Ar/N2. Morphology and phase structure of the AlN films were investigated at different pressures. Structural characterizations were performed by means of SEM and X-ray diffraction methods. Our results show that the use of magnetron sputtering method in a dual magnetron sputtering system is an effective way to produce AlN layers which are characterized by a good adhesion to the silicon substrate. The morphology of the films is strongly dependent on the Ar/N2 gas mixture pressure. An increase of the mixture pressure is accompanied by a columnar growth of the layers. The films obtained at the pressure below 1 Pa are characterized by finer and compacter structure. The AlN films are characterized by a polycrystalline hexagonal (wurtzite) structure in which the crystallographic orientation depends on the gas mixture pressure.

Keywords

  • AlN films
  • magnetron sputtering method
  • crystalline structure
Open Access

Fluctuation conductivity in two-band superconductor SmFeAsO0.8F0.2

Published Online: 30 Aug 2016
Page range: 644 - 648

Abstract

Abstract

In this study we have calculated the fluctuation conductivity near critical temperature of SmFeAsO0.8F0.2 superconductor using two-band Ginzburg-Landau theory. It was illustrated that in the absence of external magnetic field, the two-band model reduced to a single effective band theory with modified temperature dependences. The calculations revealed three-dimensional character of fluctuations of conductivity in the new Fe-based superconductor SmFeAsO0.8F0.2. It has been shown that such a model is in good agreement with experimental data for this compound.

Keywords

  • fluctuation
  • conductivity
  • Ginzburg-Landau theory
  • two-band superconductivity
Open Access

FP-LAPW investigation of mechanical and thermodynamic properties of Na2X (X = S and Se) under pressure and temperature effects

Published Online: 30 Aug 2016
Page range: 649 - 659

Abstract

Abstract

Structural, elastic and thermodynamic properties of sodium chalcogenides (Na2X, X = S, Se) have been calculated using FP-APW+1o method. The ground state lattice parameter, bulk moduli have been obtained. The Zener anisotropy factor, Poisson’s ratio, shear modulus, Young’s modulus, have also been calculated. The calculated structural and elastic constants are in good agreement with the available data. We also determined the thermodynamic properties, such as heat capacities CV and CP, thermal expansion α , entropy S, and Debye temperature θD, at various pressures and temperatures for Na2X compounds. The elastic constants under high pressure and temperature are also calculated and elaborated.

Keywords

  • sodium chalcogenides
  • FP-LAPW
  • GGA
  • structural properties
  • elastic constants
  • thermodynamic properties
Open Access

Mechanical and structural properties of titanium dioxide deposited by innovative magnetron sputtering process

Published Online: 30 Aug 2016
Page range: 660 - 668

Abstract

Abstract

Titanium dioxide thin films were prepared using two types of magnetron sputtering processes: conventional and with modulated plasma. The films were deposited on SiO2 and Si substrates. X-ray diffraction measurements of prepared coatings revealed that the films prepared using both methods were nanocrystalline. However, the coatings deposited using conventional magnetron sputtering had anatase structure, while application of sputtering with modulated plasma made possible to obtain films with rutile phase. Investigations performed with the aid of scanning electron microscope showed significant difference in the surface morphology as well as the microstructure at the thin film cross-sections. The mechanical properties of the obtained coatings were determined on the basis of nanoindentation and abrasion resistance tests. The hardness was much higher for the films with the rutile structure, while the scratch resistance was similar in both cases. Optical properties were evaluated on the basis of transmittance measurements and showed that both coatings were well transparent in a visible wavelength range. Refractive index and extinction coefficient were higher for TiO2 with rutile structure.

Keywords

  • plasma modulated magnetron sputtering
  • titanium dioxide
  • hardness
  • scratch resistance
  • optical and structural properties
31 Articles
Open Access

Transparent fluorinate acrylic polyurethane with hydrophobicity obtained by crosslinking of hydroxyl-containing fluoroacrylate copolymer with HDI trimer

Published Online: 30 Aug 2016
Page range: 451 - 459

Abstract

Abstract

Hydroxyl-containing fluoroacrylate copolymers with different fluorine and hydroxyl concentrations were synthesized via free-radical solution polymerization. Transparent fluorinated polyurethane (FPU) films were prepared by curing the copolymers with HDI (hexamethylene diisocyanate) trimer. The Fourier transform infrared spectroscopy (FT-IR) results revealed introduction of fluorine both into the copolymer and polyurethane. X-ray photoelectron spectroscopy (XPS) analyses indicated that a gradient concentration of fluorine existed in the depth profile of the fluorinated polyurethane films. The highest contact angle (CA) was obtained for the FPU film with fluoroacrylate monomer concentration of 22 wt.% because of fluorine present on the film surface. The surface topographies detected by SEM and AFM indicated that surface roughness contributed little to the film hydrophobicity. By increasing the fluoroacrylate monomer concentration, the decreasing of crosslinking degree of hard segment resulted in lowering the first degradation temperature, while more C-F groups in soft segment led to higher second degradation temperature. UV-Vis spectrophotometer measurements indicated that the FPU film with the fluoroacrylate monomer concentration of 16 wt.% still had a high transmittance of more than 90 % in the whole visible wavelength range.

Keywords

  • fluoroacrylate copolymer
  • polyurethane
  • hyrophobicity
  • transparency
  • X-ray photoelectron spectroscopy (XPS)
Open Access

Preparation and photocatalytic activity of multi-walled carbon nanotubes/Mg-doped ZnO nanohybrids

Published Online: 30 Aug 2016
Page range: 460 - 469

Abstract

Abstract

Multi-walled carbon nanotubes/Mg-doped ZnO (MWNTs/Zn1-xMgxO) nanohybrids were prepared by co-precipitation method, and their photocatalytic activity for methyl orange (MO) was studied. Experimental results showed that Mg-doped ZnO nanoparticles were successfully deposited on the surface of MWNTs under annealing at 450 °C and 550 °C. The resultant MWNTs/Zn0.9Mg0.1O nanohybrids had better photocatalytic activity for degradation of methyl orange than pure ZnO: the rates of MO photodegradation were 100 % and 30 % for 1 h, respectively. The enhancement in the photocatalytic activity was attributed to the excellent electronic properties of MWNTs and Mg-doping.

Keywords

  • carbon nanotube
  • Mg-doped ZnO
  • nanohybrids
  • photocatalytic activity
Open Access

Preparation, structure and optical properties of transparent conducting gallium-doped zinc oxide thin films

Published Online: 30 Aug 2016
Page range: 470 - 481

Abstract

Abstract

Highly conductive gallium-doped zinc oxide (GZO) transparent thin films were deposited on glass substrates by RF mag­netron sputtering. The deposited films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), four-point probe and UV-Vis spectrophotometer, respectively. The effect of growth temperature on the structure and optoelectrical properties of the films was investigated. The results demonstrate that high quality GZO films oriented with their crystal­lographic c-axis perpendicular to the substrates are obtained. The structure and optoelectrical properties of the films are highly dependent on the growth temperature. It is found that with increasing growth temperature, the average visible transmittance of the deposited films is enhanced and the residual stress in the thin films is obviously relaxed. The GZO films deposited at the growth temperature of 400°C, which have the largest grain size (74.3 nm), the lowest electrical resistivity (1.31×10-3 Ω·cm) and the maximum figure of merit (1.46×1O-2Ω-1), exhibit the best optoelectrical properties. Furthermore, the optical proper­ties of the deposited films were determined by the optical characterization methods and the optical energy-gaps were evaluated by extrapolation method. A blue shift of the optical energy gap is observed with an increase in the growth temperature.

Keywords

  • zinc oxide
  • thin films
  • magnetron sputtering
  • optical properties
Open Access

Properties of Pd nanograins in C-Pd composite films obtained by PVD method

Published Online: 30 Aug 2016
Page range: 482 - 487

Abstract

Abstract

Properties of palladium nanograins obtained by sedimentation of a soluted C-Pd film prepared by PVD method are presented. These properties were studied using SEM and TEM methods. Dissolved films were prepared by PVD method and after dissolving, they were fractionated to obtain different parts classified with palladium nanograins diameters. Several classes of diameters were determined: below 20 nm, between 20 and 100 nm and above 100 nm. The defects and triple junction were observed. Multishell carbonaceous structures were found in the big and medium size Pd nanograins.

Keywords

  • Pd nanograins
  • PVD
  • defects
Open Access

Synthesis and characterization of graphene oxide composite with Fe3O4

Published Online: 30 Aug 2016
Page range: 488 - 490

Abstract

Abstract

In the paper, a magnetic composite of graphene oxide (MGO) has been successfully synthesized through decomposition of iron (III) acetylacetonate in the mixture solution of triethylene glycol and graphene oxide (GO). Atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and superconducting quantum interference device were used to characterize the material. The results show that the magnetic Fe3O4 nanoparticles modified graphene oxide composite with superparamagnetic properties, and magnetization saturation of 16.4 emu/g has been obtained. The MGO has a good sustained-release performance, and in vitro cytotoxicity confirming its secure use as a potential drug carrier.

Keywords

  • graphene oxide
  • composite
  • magnetic Fe3O4
Open Access

Effect of substrate temperature on structural and optical properties of spray deposited ZnO thin films

Published Online: 30 Aug 2016
Page range: 491 - 496

Abstract

Abstract

Undoped ZnO thin films have been prepared on glass substrates at different substrate temperatures by spray pyrolysis method. The effect of temperature on the structural, morphological and optical properties of n-type ZnO films was studied. The X-ray diffraction (XRD) results confirmed that the ZnO thin films were polycrystalline with wurtzite structure. Scanning electron microscopy (SEM) measurements showed that the surface morphology of the films changed with temperature. The studies demonstrated that the ZnO film had a transmission of about 85 % and energy gap of 3.28 eV at 450 °C. The RBS measurements revealed that ZnO layers with a thickness up to 200 nm had a good stoichiometry.

Keywords

  • ZnO
  • spray deposition
  • Rutherford Backscattering Spectrometry (RBS)
  • structural
  • optical and electrical properties
Open Access

Dispersion of dielectric permittivity and magnetic properties of solid solution PZT–PFT

Published Online: 30 Aug 2016
Page range: 497 - 500

Abstract

Abstract

In this paper we present the results of investigations into ceramic samples of solid solution (1-x)(PbZr0.53Ti0.47O3)- x(PbFe0.5Ta0.503) (i.e. (1-x)PZT-xPFT) with x = 0.25, 0.35 and 0.45. We try to find the relation between the character of dielectric dispersion at various temperatures and the composition of this solution. We also describe the magnetic properties of investigated samples. With increasing the content of PFT also mass magnetization and mass susceptibility increase (i.e. magnetic properties are more pronounced) at every temperature. The temperature dependences of mass magnetization and re­ciprocal of mass susceptibility have similar runs for all the compositions. However, our magnetic investigations exhibit weak antiferromagnetic ordering instead of the ferromagnetic one at room temperature. We can also say that up to room tempera­ture any magnetic phase transition has not occurred. It may be a result of the conditions of the technological process during producing our PZT-PFT ceramics.

Keywords

  • multiferroic
  • ferroelectric
  • antiferromagnetic
  • relaxor
  • ceramics
Open Access

Studies on Inx(As2Se3)1-x thin films using variable angle spectroscopic ellipsometry (VASE)

Published Online: 30 Aug 2016
Page range: 501 - 507

Abstract

Abstract

The results of multi-angle ellipsometrical measurements of thermally evaporated Inx(As2Se3)1-x (x = 0, 0.01,0.05) films are presented. Optical parameters n and Es of thin Inx(As2Se3)1-x films show that indium atoms were incorporated into the host matrix of As2Se3 forming distinct features depending on the indium concentration. Refractive index, n, was found to decrease with the addition of In to the binary As2Se3. The real and imaginary parts of the dielectric function, ε' and ε" were also calculated from the obtained data and correlated with In concentration. It was found that e' decreases with the increase of In content while ε" increases with the increase of In content. Absorption edge is shifted towards lower photon energy with the increase of In content. As a result, the optical energy gap decreases with increasing In content. This has been correlated with the chemical character of the additive as well as with the structural and bonding aspects of the amorphous composition. Nonlinear optical constants (χ(3) and n2) were determined from linear optical parameters using semi-empirical relations in the long wavelength limit.

Keywords

  • chalcogenides
  • ellipsometry
  • optical absorption
  • energy gap
  • nonlinear optics
Open Access

Effects of Cr and Fe co-doping on structural, optical, electrical and magnetic properties of titanium dioxide (TiO2)

Published Online: 30 Aug 2016
Page range: 508 - 514

Abstract

Abstract

A series of Ti0.9Fe0.1-xCrxO2 (where x = 0.0, 0.02, 0.04, 0.6, 0.08, 0.10) was synthesized using the powder metallurgy route. The structural, morphological, magnetic, optical and electrical properties were investigated by X-ray diffractometry (XRD), Raman spectroscopy, scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), UV-Vis spec­troscopy and four probe technique, respectively. The rutile phase was confirmed by XRD analysis which was also verified by Raman spectroscopy. It was observed that the grain size increased as the concentration of Cr increased. M-H loops ex­tracted from VSM analysis revealed anti-ferromagnetic, weak ferromagnetic and paramagnetic behaviors at room temperature. The band gap energy and resistivity measurements exhibited the semiconducting nature of Ti0.9Fe0.1-xCrxO2 based diluted magnetic semiconductors.

Keywords

  • dilute magnetic semiconductors
  • rutile
  • grain size
  • magnetic properties
  • resistivity
Open Access

Fabrication and properties of zinc oxide thin film prepared by sol-gel dip coating method

Published Online: 30 Aug 2016
Page range: 515 - 520

Abstract

Abstract

ZnO thin films were deposited on a glass substrate by dip coating technique using a solution of zinc acetate, ethanol and distilled water. Optical constants, such as refractive index n and extinction coefficient k. were determined from transmittance spectrum in the ultraviolet-visible-near infrared (UV-Vis-NIR) regions using envelope methods. The films were found to exhibit high transmittance, low absorbance and low reflectance in the visible regions. Absorption coefficient α and the thickness of the film t were calculated from interference of transmittance spectra. The direct optical band gap of the films was in the range of 3.98 to 3.54 eV and the thickness of the films was evaluated in the range of 173 to 323 nm, while the refractive index slightly varied in the range of 1.515 to 1.622 with an increase in withdrawal speed from 100 to 250 mm/s. The crystallographic structure of the films was analyzed with X-ray diffractometer. The films were amorphous in nature.

Keywords

  • thin films
  • sol-gel
  • X-ray diffraction
  • optical properties
Open Access

CVD carbon powders modified by ball milling

Published Online: 30 Aug 2016
Page range: 521 - 528

Abstract

Abstract

Carbon powders produced using a plasma assisted chemical vapor deposition (CVD) methods are an interesting subject of research. One of the most interesting methods of synthesizing these powders is using radio frequency plasma. This method, originally used in deposition of carbon films containing different sp2/sp3 ratios, also makes possible to produce carbon structures in the form of powder. Results of research related to the mechanical modification of these powders have been presented. The powders were modified using a planetary ball mill with varying parameters, such as milling speed, time, ball/powder mass ratio and additional liquids. Changes in morphology and particle sizes were measured using scanning electron microscopy and dynamic light scattering. Phase composition was analyzed using Raman spectroscopy. The influence of individual parameters on the modification outcome was estimated using statistical method. The research proved that the size of obtained powders is mostly influenced by the milling speed and the amount of balls. Powders tend to form conglomerates sized up to hundreds of micrometers. Additionally, it is possible to obtain nanopowders with the size around 100 nm. Furthermore, application of additional liquid, i.e. water in the process reduces the graphitization of the powder, which takes place during dry milling.

Keywords

  • carbon powder
  • CVD
  • milling
  • Taguchi method
Open Access

Growth and characterization of NLO crystal: L-leucine phthalic acid potassium iodide

Published Online: 30 Aug 2016
Page range: 529 - 536

Abstract

Abstract

A new semi-organic non linear optical crystal, L-leucine phthalic acid potassium iodide (LLPPI) has been grown from an aqueous solution by slow evaporation method. The grown crystals were subjected to different characterizations, such as single crystal XRD, FT-IR, UV-Vis, TGA, SEM, EDAX, micro hardness, dielectric and powder SHG. Single crystal structure was determined from X-ray diffraction data and it revealed that the crystal belongs to triclinic system with the space group P1. The vibrational frequencies of various functional groups were derived from FT-IR spectrum. Thermal stability of the grown crystal was investigated by TG-DTA studies and it was observed that the crystal was thermally stable up to 192 °C. Optical absorption study was carried out and a good transparency in the entire visible region was observed at the lower cutoff wavelength of 227 nm. Dielectric study was performed as a function of frequency and normal dielectric behavior was observed. The micro hardness test was carried out and the load dependent hardness was measured. Kurtz powder method was employed to explore the NLO characteristics of the grown crystal.

Keywords

  • semi-organic crystal
  • slow evaporation method
  • NLO crystal
  • thermal and SHG studies
Open Access

Microwave-assisted synthesis, characterization and photoluminescence of shuttle-like BaMoO4 microstructure

Published Online: 30 Aug 2016
Page range: 537 - 540

Abstract

Abstract

Shuttle-like BaMoO4 microstructure has been successfully synthesized from Ba(N03)4H20 and Na2MoO2H2O as starting materials in ethylene glycol solvent containing 20 mL 5 M NaOH by microwave radiation at 180 W for 30 min. The as- synthesized BaMoO4 product was characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Raman spectrophotometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photolumines­cence (PL) spectroscopy. XRD patterns revealed that the products was tetragonal BaMoO4 phase. SEM and TEM characteriza­tion showed that the product had a shuttle-like BaMoO4 microstructure. PL of the shuttle-like BaMoO4 microstructure showed a maximum emission at 466 nm excited by 280 nm wavelength.

Keywords

  • BaMoO4
  • shuttle-like particles
  • luminescence
Open Access

Multifractal characteristics of titanium nitride thin films

Published Online: 30 Aug 2016
Page range: 541 - 548

Abstract

Abstract

The study presents a multi-scale microstructural characterization of three-dimensional (3-D) micro-textured surface of titanium nitride (TiN) thin films prepared by reactive DC magnetron sputtering in correlation with substrate temperature variation. Topographical characterization of the surfaces, obtained by atomic force microscopy (AFM) analysis, was realized by an innovative multifractal method which may be applied for AFM data. The surface micromorphology demonstrates that the multifractal geometry of TiN thin films can be characterized at nanometer scale by the generalized dimensions Dq and the singularity spectrum f(α). Furthermore, to improve the 3-D surface characterization according with ISO 25178-2:2012, the most relevant 3-D surface roughness parameters were calculated. To quantify the 3-D nanostructure surface of TiN thin films a multifractal approach was developed and validated, which can be used for the characterization of topographical changes due to the substrate temperature variation.

Keywords

  • atomic force microscopy
  • DC magnetron sputtering
  • multifractal analysis
  • surface roughness
  • titanium nitride (TiN) thin film
Open Access

First-principles study of atomic structure and electronic properties of Si and F doped anatase TiO2

Published Online: 30 Aug 2016
Page range: 549 - 554

Abstract

Abstract

Chemical doping represents one of the most effective ways in engineering electronic structures of anatase TiO2 for practical applications. Here, we investigate formation energies, geometrical structures, and electronic properties of Si-, F-doped and Si/F co-doped anatase TiO2 by using spin-polarized density functional theory calculation. We find that the co-doped TiO2 is thermodynamically more favorable than the Si- and F-doped TiO2- Structural analysis shows that atomic impurity varies crystal constants slightly. Moreover, all the three doped systems show a pronounced narrowing of band gap by 0.33 eV for the F-doped TiO2, 0.17 eV for the Si-doped TiO2, and 0.28 eV for the Si/F-co-doped TiO2, which could account for the experimentally observed redshift of optical absorption edge. Our calculations suggest that the Si/F-co-doping represents an effective way in tailoring electronic structure and optical properties of anatase TiO2.

Keywords

  • anatase TiO2
  • Si/F co-doping
  • first-principles
  • electronic properties
Open Access

UV-Vis studies of 800 keV Ar ion irradiated NiO thin films

Published Online: 30 Aug 2016
Page range: 555 - 559

Abstract

Abstract

We report the evolution of optical absorption properties of 800 keV Ar ion irradiated NiO thin films through UV-Vis characterization. Our results indicate the existence of both Mott-Hubbard (d → d transition) and charge-transfer (p → d transition) characteristic of NiO. The optical band gap of NiO increases from 3.58 to 3.75 eV when irradiated at the fluence of 5 × 1014 ions cm-2 but it does not show any remarkable variation upon 800 keV Ar ion irradiation at higher fluences. The refractive index and electron polarizability at different ion fluences have been determined from the optical band gap. Both refractive index and electron polarizability follow an opposite trend to that of the energy gap as a function of ion fluence.

Keywords

  • ion irradiation
  • nanoparticles
  • UV-Vis spectroscopy
  • band gap
Open Access

The influence of VO2(B) nanobelts on thermal decomposition of ammonium perchlorate

Published Online: 30 Aug 2016
Page range: 560 - 565

Abstract

Abstract

The influence of vanadium dioxide VO2(B) on thermal decomposition of ammonium perchlorate (AP) has not been reported before. In this contribution, the effect of VO2(B) nanobelts on the thermal decomposition of AP was investigated by the Thermo- Gravimetric Analysis and Differential Thermal Analysis (TG/DTA). VO2(B) nanobelts were hydrothermally prepared using peroxovanadium (V) complexes, ethanol and water as starting materials. The thermal decomposition temperatures of AP in the presence of I wt.%, 3 wt.% and 6 wt.% of as-obtained VO2<B) nanobelts were reduced by 39 °C. 62 °C and 74 °C, respectively. The results indicated that VO2(B) nanobelts had a great influence on the thermal decomposition temperature of AP Furthermore, the influence of the corresponding V2Os, which was obtained by thermal treatment of VO2(B) nanobelts, on the thermal decomposition of AP was also investigated. The resufs showed that VO2(B) nanobelts had a greater influence on the thermal decomposition temperature of AP than that of V2Os.

Keywords

  • VO2(B)
  • ammonium perchlorate
  • thermal analysis
  • hydrothermal synthesis
Open Access

Graphene synthesis: a Review

Published Online: 30 Aug 2016
Page range: 566 - 578

Abstract

Abstract

Graphene has achieved a great amount of popularity and interest from the science world because of its extraordinary physical, mechanical and thermal properties. Graphene is an allotrope of carbon, having one-atom-thick planar sheets of sp2 bonded carbon atoms densely packed in a honeycomb crystal lattice. Many methods to synthesize graphene have been developed over a short period and we believe it is necessary to create a list of the most notable approaches. This article focuses on the methods to synthesize graphene in an attempt to summarize and document advancements in the synthesis of graphene research and future prospects.

Keywords

  • graphene
  • synthesis
  • nanomaterials
  • graphite
  • 2D
  • biomass
Open Access

Effects of partial Co replacement by Fe in Sr0.775Y0.225CoO3-δ on its magnetic property, oxygen deficiency and crystal structure

Published Online: 30 Aug 2016
Page range: 579 - 587

Abstract

Abstract

A study has been conducted on the effects of partial, 10 % Co substitution by Fe in the perovskite Sr0.775Y0.225CoO3-δ compound. The XRD data show that the resulted samples of Fe-free and Fe-doped compounds exhibit good 314 single phase quality with a tetragonal I4/mmm crystal structure. The measured M-T curves display the typical feature of ferromagnetic (FM) transition at 335 K for the Fe-free sample, while showing significantly degraded FM ordering for the 10 % Fe-doped sample. The oxygen deficiency determined fro|m our 10 % Fe doped sample is found to decrease by only 0.025. Further detailed analysis of the XRD data also reveals distinctly different structural changes in the Co-O slabs compared to the 50 % Fe-doped sample which exhibits a complete suppression of FM order. The results of this study, thus, have revealed the close relations among the changes induced by Fe doping in the magnetic ordering of crystal, and its oxygen content as well as the associated local structure in the Co-O layers responsible for the magnetic properties in the compound.

Keywords

  • perovskite Sr0.775Y0.225CoO3-δ compound
  • ferromagnetic compound
  • oxygen content
Open Access

Fabrication and characterization of TiO2 nanotube arrays on Ti membrane enlarged by anodic oxidation

Published Online: 30 Aug 2016
Page range: 588 - 592

Abstract

Abstract

TiO2 nanotube arrays have attracted a great deal of attention as photocatalytic and photoelectrode materials due to their large surface area, low cost and easy fabrication. Highly ordered TiO2 nanotube arrays for the photoelectrodes in dye-sensitized solar cells have been fabricated from Ti foil. However, the TiO2 nanotube arrays from Ti foil were not effective for the photocatalytic materials, because it had only one plane for the photocatalytic reaction. We have fabricated the TiO2 nanotube arrays from macroporous Ti metal membrane by anodic oxidation and tried to scale it up. Various factors were controlled to obtain the optimal microstructure of the TiO2 nanotube arrays on the surface of macroporous Ti metallic membrane. Microstructure and phase were studied by SEM and XRD, respectively. Temperature was a very important factor in anodic oxidation of large surface area. 10 μm thick TiO2 nanotube arrays on Ti metallic membrane having a large surface area were fabricated and some factors for scaling-up were discussed.

Keywords

  • TiO2 nanotube arrays
  • anodic oxidation
  • photocatalysis
  • scaling-up
  • anatase
Open Access

Electronic parameters of MIS Schottky diodes with DNA biopolymer interlayer

Published Online: 30 Aug 2016
Page range: 593 - 600

Abstract

Abstract

In this work, we prepared an ideal Cu/DNA/n-InP biopolymer-inorganic Schottky sandwich device formed by coating a n- lP semiconductor wafer with a biopolymer DNA. The Cu/DNA/n-InP contact showed a good rectifying behavior. The ideality factor value of 1.08 and the barrier height (Φb) value of 0.70 eV for the Cu/DNA/n-InP device were determined from the forward ias I-V characteristics. It was seen that the Φb value of 0.70 eV obtained for the Cu/DNA/n-InP contact was significantly larger tan the value of 0.48 eV of conventional Cu/n-InP Schottky diodes. Modification of the interfacial potential barrier of Cu/n-InP iode was achieved using a thin interlayer of DNA biopolymer. This was attributed to the fact that DNA biopolymer interlayer increased the effective barrier height by influencing the space charge region of InP.

Keywords

  • Schottky diodes
  • interfaces
  • semiconductors
  • electrical properties
Open Access

Structural and optical properties of pure and Ag doped ZnO thin films obtained by sol gel spin coating technique

Published Online: 30 Aug 2016
Page range: 601 - 605

Abstract

Abstract

We have investigated the influence of Ag doping on zinc oxide thin films. Pure and Ag doped, preferentially oriented transparent zinc oxide thin films were prepared by sol gel technique on a glass substrate using diethyl amine as a stabilizer. The X-ray diffraction analysis revealed that the films with hexagonal wurtzite type structure were polycrystalline in nature with a preferred grain orientation in the 101 direction. The crystallite sizes decreased from 34 nm to 27 nm after silver doping. Both photoluminescence and optical transmission measurements showed that the band gap increased after the Ag doping. The structure and optical characterization studies clearly indicated the incorporation of Ag in ZnO. Hence, the observed increase in the optical band gap and decrease in crystallite size can be directly attributed to the effect of Ag ion incorporation into the ZnO lattice.

Keywords

  • Ag doped ZnO
  • sol gel
  • structure properties
  • optical band gap
  • defects study
Open Access

Controlled fluoridation of amorphous carbon films deposited at reactive plasma conditions

Published Online: 30 Aug 2016
Page range: 606 - 611

Abstract

Abstract

A study of the correlations between plasma parameters, gas ratios, and deposited amorphous carbon film properties is presented. The injection of a C4F8/Ar/N2 mixture of gases was successfully used in an inductively coupled plasma system for the preparation of amorphous carbon films with different fluoride doping at room-temperature, using silicon as a substrate. This coating was formed at low-pressure and low-energy using an inductively coupled plasma process. A strong dependence between the ratios of gases during deposition and the composition of the substrate compounds was shown. The values of ratios between Ar (or Ar+N2) and C4F8 - 1:1 and between N2 and Ar - 1:2 in the N2/Ar/C4F8 mixture were found as the best for low fluoridated coatings. In addition, an example of improving the etch-passivation in the Bosch procedure was described. Scanning electron microscopy with energy dispersive spectroscopy options, X-ray diffraction, and X-ray reflectivity were used for quantitative analysis of the deposited films.

Keywords

  • carbon deposition
  • reactive plasma
  • fluoridation
Open Access

Photocurrent response of phloxin B-cetyltrimethylammonium bromide photogalvanic cell device

Published Online: 30 Aug 2016
Page range: 612 - 619

Abstract

Abstract

Photocurrent and photovoltage generation using phloxin B dye in aqueous and micellar medium at different concentrations have been studied in a photogalvanic cell. The photopotential and photocurrent generated were 1135.0 mV and 260.0 μA, respectively. The observed solar energy conversion efficiency with CTAB surfactant was 0.64 % and maximum power of the cell was 66.72 mW. The output of the cell was sensitive to various parameters, like dye concentration, reductant concentration, pH, light intensity, electrode area and diffusion length. Current-potential characteristics studied by I-V curve of the cell and the mechanism of cell photovoltage generation have been presented in the paper.

Keywords

  • phloxin B
  • CTAB
  • fill factor
  • conversion efficiency
  • photogalvanic cell
Open Access

Temperature dependence of stress in CVD diamond films studied by Raman spectroscopy

Published Online: 30 Aug 2016
Page range: 620 - 626

Abstract

Abstract

Evolution of residual stress and its components with increasing temperature in chemical vapor deposited (CVD) diamond films has a crucial impact on their high temperature applications. In this work we investigated temperature dependence of stress in CVD diamond film deposited on Si(100) substrate in the temperature range of 30 °C to 480 °C by Raman mapping measurement. Raman shift of the characteristic diamond band peaked at 1332 cm-1 was studied to evaluate the residual stress distribution at the diamond surface. A new approach was applied to calculate thermal stress evolution with increasing tempera­ture by using two commonly known equations. Comparison of the residts obtained from the two methods was presented. The intrinsic stress component was calculated from the difference between average values of residual and thermal stress and then its temperature dependence was discussed.

Keywords

  • Raman spectroscopy
  • stress
  • diamond structure
  • CVD diamond films
Open Access

Poly(N-isopropylacrylamide-co-methacrylic acid) microgel stabilized copper nanoparticles for catalytic reduction of nitrobenzene

Published Online: 30 Aug 2016
Page range: 627 - 634

Abstract

Abstract

Poly(N-isopropylacrylamide-co-methacrylic acid) microgels [p(NIPAM-co-MAAc)] were synthesized by precipitation polymerization of N-isopropylacrylamide and methacrylic acid in aqueous medium. These microgels were characterized by dynamic light scattering and Fourier transform infrared spectroscopy. These microgels were used as micro-reactors for in situ synthesis of copper nanoparticles using sodium borohydride (NaBH4) as reducing agent. The hybrid microgels were used as catalysts for the reduction of nitrobenzene in aqueous media. The reaction was performed with different concentrations of cat­alyst and reducing agent. A linear relationship was found between apparent rate constant (kapp) and amount of catalyst. When the amount of catalyst was increased from 0.13 to 0.76 mg/mL then kapp was increased from 0.03 to 0.14 min-1. Activation parameters were also determined by performing reaction at two different temperatures. The catalytic process has been discussed in terms of energy of activation, enthalpy of activation and entropy of activation. The synthesized particles were found to be stable even after 14 weeks and showed catalytic activity for the reduction of nitrobenzene.

Keywords

  • catalysis
  • copper
  • microgels
  • nanoparticles
Open Access

Application of Aloe vera gel instead of silicon dioxide as organic dielectric material in microelectronics

Published Online: 30 Aug 2016
Page range: 635 - 638

Abstract

Abstract

Organic materials are now being used in a wide range of microelectronic applications in parallel with inorganic materials, because of their superior properties, environmental safety, and low cost. This paper describes the characterization of Aloe vera gel (AVG), a new organic dielectric material. The surface morphology, spatial distribution of elements, and structural characteristics of an AVG layer were examined using scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD), respectively. The resistance of the AVG layer, determined using a four-probe station, was 640 Ω EDX showed that the elements contained in the layer were carbon, oxygen, aluminum, silicon, calcium, potassium, and copper. The XRD results suggested that the sample primarily consisted of bornite (Cu5FeS4), geerite (Cu8S5), sal ammoniac (NH4Cl), and carobbite (KF).

Keywords

  • Aloe vera
  • organic dielectric material
  • four-probe station
  • SEM
  • EDX
  • XRD
Open Access

Structure of AlN films deposited by magnetron sputtering method

Published Online: 30 Aug 2016
Page range: 639 - 643

Abstract

Abstract

AlN films on a Si substrate were synthesized by magnetron sputtering method. A dual magnetron system operating in AC mode was used in the experiment. Processes of synthesis were carried out in the atmosphere of a mixture of Ar/N2. Morphology and phase structure of the AlN films were investigated at different pressures. Structural characterizations were performed by means of SEM and X-ray diffraction methods. Our results show that the use of magnetron sputtering method in a dual magnetron sputtering system is an effective way to produce AlN layers which are characterized by a good adhesion to the silicon substrate. The morphology of the films is strongly dependent on the Ar/N2 gas mixture pressure. An increase of the mixture pressure is accompanied by a columnar growth of the layers. The films obtained at the pressure below 1 Pa are characterized by finer and compacter structure. The AlN films are characterized by a polycrystalline hexagonal (wurtzite) structure in which the crystallographic orientation depends on the gas mixture pressure.

Keywords

  • AlN films
  • magnetron sputtering method
  • crystalline structure
Open Access

Fluctuation conductivity in two-band superconductor SmFeAsO0.8F0.2

Published Online: 30 Aug 2016
Page range: 644 - 648

Abstract

Abstract

In this study we have calculated the fluctuation conductivity near critical temperature of SmFeAsO0.8F0.2 superconductor using two-band Ginzburg-Landau theory. It was illustrated that in the absence of external magnetic field, the two-band model reduced to a single effective band theory with modified temperature dependences. The calculations revealed three-dimensional character of fluctuations of conductivity in the new Fe-based superconductor SmFeAsO0.8F0.2. It has been shown that such a model is in good agreement with experimental data for this compound.

Keywords

  • fluctuation
  • conductivity
  • Ginzburg-Landau theory
  • two-band superconductivity
Open Access

FP-LAPW investigation of mechanical and thermodynamic properties of Na2X (X = S and Se) under pressure and temperature effects

Published Online: 30 Aug 2016
Page range: 649 - 659

Abstract

Abstract

Structural, elastic and thermodynamic properties of sodium chalcogenides (Na2X, X = S, Se) have been calculated using FP-APW+1o method. The ground state lattice parameter, bulk moduli have been obtained. The Zener anisotropy factor, Poisson’s ratio, shear modulus, Young’s modulus, have also been calculated. The calculated structural and elastic constants are in good agreement with the available data. We also determined the thermodynamic properties, such as heat capacities CV and CP, thermal expansion α , entropy S, and Debye temperature θD, at various pressures and temperatures for Na2X compounds. The elastic constants under high pressure and temperature are also calculated and elaborated.

Keywords

  • sodium chalcogenides
  • FP-LAPW
  • GGA
  • structural properties
  • elastic constants
  • thermodynamic properties
Open Access

Mechanical and structural properties of titanium dioxide deposited by innovative magnetron sputtering process

Published Online: 30 Aug 2016
Page range: 660 - 668

Abstract

Abstract

Titanium dioxide thin films were prepared using two types of magnetron sputtering processes: conventional and with modulated plasma. The films were deposited on SiO2 and Si substrates. X-ray diffraction measurements of prepared coatings revealed that the films prepared using both methods were nanocrystalline. However, the coatings deposited using conventional magnetron sputtering had anatase structure, while application of sputtering with modulated plasma made possible to obtain films with rutile phase. Investigations performed with the aid of scanning electron microscope showed significant difference in the surface morphology as well as the microstructure at the thin film cross-sections. The mechanical properties of the obtained coatings were determined on the basis of nanoindentation and abrasion resistance tests. The hardness was much higher for the films with the rutile structure, while the scratch resistance was similar in both cases. Optical properties were evaluated on the basis of transmittance measurements and showed that both coatings were well transparent in a visible wavelength range. Refractive index and extinction coefficient were higher for TiO2 with rutile structure.

Keywords

  • plasma modulated magnetron sputtering
  • titanium dioxide
  • hardness
  • scratch resistance
  • optical and structural properties

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