Study of thin-film SO2 gas sensors by photometric and ellipsometric methods

Pt-, Pd-, and Zr-doped SnO2 thin films and dopant-free VOx films were fabri cated by planar magnetron sputtering. Tests for sensitivity to SO2 for all samples were conducted at 180 degreesC, and the sensitivities were investig ated ex situ with photometric and ellipsometric methods at room temperature . It was found that the optical sensitivities as well as the sensitive wave length region for SnO2 films could be tuned by doping. The Pd-doped SnO2 fi lms had good sensitivity in the visible range, and the Zr-doped in the near IR. The dominant sensitive wavelength region for VOx films fell into the v isible range, and the ratio of the sensitivity in the visible to that in th e near IR increased with O-2/Ar in the depositing atmosphere. (C) 2001 soci ety of Photo-Optical instrumentation Engineers .