The effect of exposure to ozone on the frequency shift (ΔF) and pressure (P) of a quartz oscillator was observed to check its resistance against the gas. After every ozone exposure, the ΔF-P characteristic curves shifted toward lower frequencies, indicating that the oscillator lost its repeatability. The oscillator electrode consisted of an Au-Cr film deposited on a quartz substrate; an evaluation using a scanning electron microscope (SEM) showed that each film layer had a thickness of 65 nm. The surface composition of the electrode was analyzed by Auger electron spectroscopy (AES). The AES intensities of Cr and Au showed that Cr oxide was present on top of the Au film layer; we speculate that ozone exposure may proceed the Cr oxidation with higher atomic valence. AES depth analysis showed that a small amount of Cr was detected in the Au film layer; we believe that Cr oxidation could progress by either Cr diffusion through the Au layer or by O diffusion from the surface.
