1：Experimental Design and Method Selection:

Brillouin light scattering (BLS) was used to measure acoustic properties of amorphous SiO2 thin films on Si(100) substrates. The method involves inelastic light scattering caused by acoustic waves, with a tilted scattering geometry to investigate both longitudinal acoustic (LA) and surface acoustic wave (SAW) modes.

2：Sample Selection and Data Sources:

Samples were amorphous SiO2 thin films grown by RF reactive sputtering on Si(100) substrates. 14 samples were prepared under a standard Ar:O2 ratio of 70:35, and additional 9 samples under three different Ar:O2 ratios (

3：43 to 3). Thicknesses were approximately 1 μm. Refractive index was measured using ellipsometry. List of Experimental Equipment and Materials:

Equipment includes a tandem multi-pass Fabry-Perot interferometer (TFP-2, JRS Co.), a diode-pumped solid-state single-mode laser (Excelsior 532-300, Spectra Physics) at 532 nm wavelength, a modified microscope (BH-2, Olympus), a tilting mount, a photon-counting system with multichannel analyzer (1024 channels), and an ellipsometer (ASET-F5X, KLA Tencor). Materials include Si target for sputtering, Ar and O2 gas mixture.

4：Experimental Procedures and Operational Workflow:

Films were deposited by sputtering. Refractive index was measured at 532 nm. Brillouin spectra were obtained by tilting the sample at angles of 30°, 45°, or 60° in a backscattering setup. P-polarized incident and scattered light were used. Spectra were measured with a free spectral range of 75 GHz, taking 2-8 hours per spectrum. Data were fitted using a Voigt function.

5：Data Analysis Methods:

Sound velocities were calculated using equations VLA = λνB/2n and VSAW = λνB/2 sinθ, where λ is laser wavelength, n is refractive index, νB is Brillouin shift, and θ is tilting angle. Elastic moduli and Poisson ratio were derived from sound velocities and density (calculated from refractive index using Lorentz-Lorenz relation). Statistical analysis included standard deviation calculations.