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Study of structural and morphological properties of RF-sputtered SnO2 thin films and their effect on gas-sensing phenomenon

Ajay Kumar Arora
Ajay Kumar Arora
, 
Sandeep Mahajan
Sandeep Mahajan
, 
Maya Verma
Maya Verma
 and 
Divya Haridas
Divya Haridas
   | Feb 16, 2023
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Article Category: Article
Published Online: Feb 16, 2023
Page range: -
Received: Jun 14, 2022
DOI: https://doi.org/10.2478/ijssis-2023-0003
Keywords
© 2023 Ajay Kumar Arora, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Figure 1

Structure of the SnO2 thin film sensor.
Structure of the SnO2 thin film sensor.

Figure 2

XRD of the as-grown SnO2 thin film (graph a) and the SnO2 thin film annealed in air at 300°C for 2 h (graph b). XRD, X-ray diffraction.
XRD of the as-grown SnO2 thin film (graph a) and the SnO2 thin film annealed in air at 300°C for 2 h (graph b). XRD, X-ray diffraction.

Figure 3

XRD pattern of the annealed SnO2 thin film of varying thicknesses. XRD, X-ray diffraction.
XRD pattern of the annealed SnO2 thin film of varying thicknesses. XRD, X-ray diffraction.

Figure 4

Influence of the thickness of the SnO2 thin film on the normalized intensities of various XRD peaks. XRD, X-ray diffraction.
Influence of the thickness of the SnO2 thin film on the normalized intensities of various XRD peaks. XRD, X-ray diffraction.

Figure 5

Variation of crystallite size of annealed SnO2 thin film as a function of film thickness.
Variation of crystallite size of annealed SnO2 thin film as a function of film thickness.

Figure 6

Variation of lattice constants “c” and “a” with the thickness of SnO2 thin films.
Variation of lattice constants “c” and “a” with the thickness of SnO2 thin films.

Figure 7

AFM images of 90 nm SnO2 thin films: (A) as-deposited film; and (B) postdeposition annealing in air at 300°C. AFM, atomic force microscopy.
AFM images of 90 nm SnO2 thin films: (A) as-deposited film; and (B) postdeposition annealing in air at 300°C. AFM, atomic force microscopy.

Figure 8

AFM images of SnO2 films of varying thicknesses: (A) 30 nm; (B) 60 nm; (C) 90 nm; (D) 120 nm; (E) 150 nm; and (F) 180 nm. AFM, atomic force microscopy.
AFM images of SnO2 films of varying thicknesses: (A) 30 nm; (B) 60 nm; (C) 90 nm; (D) 120 nm; (E) 150 nm; and (F) 180 nm. AFM, atomic force microscopy.

Figure 9

Response of SnO2 thin film sensors of varying thicknesses (30–180 nm) to 200 ppm of LPG as a function of temperature. LPG, liquefied petroleum gas.
Response of SnO2 thin film sensors of varying thicknesses (30–180 nm) to 200 ppm of LPG as a function of temperature. LPG, liquefied petroleum gas.

Figure 10

Variation of sensor resistance in air (Ra) as a function of temperature for different thickness values of SnO2 film.
Variation of sensor resistance in air (Ra) as a function of temperature for different thickness values of SnO2 film.

Figure 11

Temperature dependence of sensor resistance (Rg) measured in the presence of 200 ppm LPG for different thickness values of the SnO2 film. LPG, liquefied petroleum gas.
Temperature dependence of sensor resistance (Rg) measured in the presence of 200 ppm LPG for different thickness values of the SnO2 film. LPG, liquefied petroleum gas.

Figure 12

Sensor response of SnO2 thin film sensor as a function of sensing layer thickness for detection of 200 ppm of LPG. LPG, liquefied petroleum gas.
Sensor response of SnO2 thin film sensor as a function of sensing layer thickness for detection of 200 ppm of LPG. LPG, liquefied petroleum gas.

Figure 13

Transient response of the 90 nm SnO2 thin film under repeated exposures to 200 ppm LPG. LPG, liquefied petroleum gas.
Transient response of the 90 nm SnO2 thin film under repeated exposures to 200 ppm LPG. LPG, liquefied petroleum gas.

Sputtering parameters used for deposition of SnO2 thin film.

Technique RF diode sputtering
Target Tin (99.99%)
Gas 50% Ar + 50% O2
Sputtering pressure 14 mTorr
Power 150 W
Substrate-to-target distance 7.5 cm
Substrate temperature 25°C (no heating)
Rate of deposition: 60 nm/h

Resistance and sensor response variations of SnO2 films as a function of thickness

SnO2 thickness (nm) Ra (Ω) (at room temperature) Rg (Ω) (at operating Temperature) Operating temperature (°C) Sensor response
30 1.2 × 105 3.6 × 104 240 1.05
60 1.0 × 105 2.7 × 104 220 1.19
90 8.6 × 104 1.3 × 104 240 2.90
120 6.0 × 104 1.4 × 104 220 1.97
150 5.8 × 104 1.2 × 104 200 1.40
180 5.4 × 104 1.1 × 104 180 1.15
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