1：Experimental Design and Method Selection:

The study involved preparing and characterizing thin films of WO2, WO3, SnO2, and Sn-doped WO3 using reactive ion sputtering and annealing to optimize grain size for gas sensing. Gas sensing was performed by exposing films to acetone gas and measuring resistance changes.

2：Sample Selection and Data Sources:

n-type silicon wafers with thermally grown silicon dioxide (1 micron thick) were used as substrates. Films were deposited and annealed at specific temperatures (WO2 and WO3 at 500°C, SnO2 at 300°C, Sn-doped WO3 at 400°C).

3：List of Experimental Equipment and Materials:

Equipment included reactive ion sputtering system, DEKTAK surface profiler, XRD (Rigaku smartlab guidance), AFM, SEM (FESEM Zeiss Sigma), gas sensing setup with computerized gas mixer, gas testing chamber, digital multimeter, and power supply. Materials included argon and oxygen gases, tungsten and tin targets.

4：Experimental Procedures and Operational Workflow:

Films were deposited via reactive ion sputtering with specific gas ratios (80:20 Ar:O2 for WO films, 60:40 for SnO2). Sn-doped WO3 was made by sputtering a thin tin layer and annealing. Films were annealed for 1 hour, characterized using XRD, AFM, SEM, and thickness measurement. Gas sensing involved exposing films to acetone concentrations (1.5-20 ppm) at optimum temperatures and recording resistance changes.

5：2). Sn-doped WO3 was made by sputtering a thin tin layer and annealing. Films were annealed for 1 hour, characterized using XRD, AFM, SEM, and thickness measurement. Gas sensing involved exposing films to acetone concentrations (5-20 ppm) at optimum temperatures and recording resistance changes. Data Analysis Methods:

5. Data Analysis Methods: Response percentage was calculated using S = (Rf - Ri) * 100 / Ri, where Rf is final resistance and Ri is initial resistance. XRD patterns were compared to databases for phase identification. AFM and SEM images were analyzed for grain size and roughness.