1：Experimental Design and Method Selection:

RF magnetron sputtering was chosen for ZnO thin film deposition due to advantages like high deposition rate and good adhesion. The sensor includes a Pt micro-heater, PRT, and Au electrodes fabricated on a Si/SiO2 substrate. Annealing was performed to improve film properties.

2：Sample Selection and Data Sources:

A 3-inch diameter Si/SiO2 substrate with (100) orientation and 350 μm thickness was used. ZnO target of

3：99% purity was employed. List of Experimental Equipment and Materials:

Equipment includes RF magnetron sputtering unit, oxidation furnace, PECVD system, photolithography tools (spin coater, positive photo resist SU1818), ultrasonicator, XRD (Bruker Discover D8), SEM (JEOL JSM6390LV), EDX (Oxford INCA Energy 400), mass flow controller, gas mixer (Environics series 2000), reaction chamber controller, and Keithley digital multimeter (mod. no. 195A). Materials include Si wafer, ZnO target, Pt, Au, gases (O2, Ar, N2, NH3, synthetic air), and chemicals for cleaning.

4：Experimental Procedures and Operational Workflow:

The fabrication process involved cleaning the Si wafer, thermal oxidation for SiO2 growth, PECVD for additional SiO2, photolithography for window opening, deposition of Pt heater, ZnO sensing layer, and Au electrodes via sputtering and lift-off, annealing ZnO films, dicing the sensor, and performing gas sensing measurements in a controlled chamber.

5：Data Analysis Methods:

XRD for crystal structure analysis using Scherrer formula, SEM for surface morphology, EDX for composition, resistance measurements with multimeter, and sensitivity calculation using S = (Ra - Rg)/Ra * 100%.