1：Experimental Design and Method Selection:

The study used glancing angle deposition (GLAD) to fabricate randomly ordered vertical SnO2 nanorod arrays, followed by Pd nanoparticle coating via DC magnetron sputtering. The design aimed to optimize H2 sensing performance by controlling nanorod length and density.

2：Sample Selection and Data Sources:

SiO2/Si substrates were used, cleaned with acetone, methanol, and deionized water. SnO2 grains (4N purity) were sourced from Kojundo Chemical Laboratory Co., Ltd. Mineral oil (KS 1#2) was from DONGNAM Petroleum Ind. Co. Ltd. H2 gas concentrations varied from 0.2 to 10,000 ppm in N2 and dissolved in oil.

3：2 to 10,000 ppm in N2 and dissolved in oil. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included an electron-beam evaporator, DC magnetron sputtering system (SNTEK Co., Ltd), FE-SEM (JSM-7100F, JEOL Ltd.), Keithley 236 SMU, mass flow controller, gas chromatography (Agilent 7890A, Agilent Technologies), and a home-made gas chamber. Materials included SnO2 grains, Pd for sputtering, silver paste (P-100, Cans Inc.), and mineral oil.

4：Experimental Procedures and Operational Workflow:

Substrates were tilted at angles (70°, 80°, 85°) and rotated at 15 rpm during GLAD deposition. SnO2 NRs were deposited at a rate of 1 ?/s under 5.0×10^-6 Torr pressure, followed by heat treatment at 550°C for 2h. Pd films (5 nm) were sputtered at 4.7 ?/s under 2.3×10^-3 Torr. Sensors were mounted on PCBs with silver paste electrodes. H2 sensing measurements were conducted in N2 at room temperature and in oil at 20-80°C, with resistance measured using a Keithley 236 SMU at 0.1V constant voltage.

5：0×10^-6 Torr pressure, followed by heat treatment at 550°C for 2h. Pd films (5 nm) were sputtered at 7 ?/s under 3×10^-3 Torr. Sensors were mounted on PCBs with silver paste electrodes. H2 sensing measurements were conducted in N2 at room temperature and in oil at 20-80°C, with resistance measured using a Keithley 236 SMU at 1V constant voltage. Data Analysis Methods:

5. Data Analysis Methods: Response was defined as R = (R0 - Rg)/Rg, where R0 and Rg are resistances before and after H2 exposure. Response time was time to 90% resistance change. Data were analyzed for linear dependence using Sievert's Law, and TCR was calculated from resistance changes with temperature.