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Thermal co-deposition of Sn and TeO2 in vacuum is used for preparing thin Sn-O-Te films, build-up of an oxide matrix and a finely dispersed phase of Te, Sn and/or SnTe. The method allows further doping with desired elements both in the microcrystallites and at their interfaces with the aim to obtain films with improved gas sensing properties. The as-deposited films are amorphous and show very good characteristics as humidity sensors, operating at room temperature. Upon thermal treatment the structure and composition change and depending on the doping elements and the working temperature the observed nanocrystalline films show sensitivity to some reduction gases (ethanol, etc.). No cross-sensitivity of the crystalline films to water vapor is observed. [ABSTRACT FROM AUTHOR]

The polyimide layers are prepared by thermal vacuum coevaporation of the precursors pyromellitic dianhydride (PMDA) and 4,4'- oxydianiline (ODA) and subsequent thermal treatment up to 250 or 300°C. In this paper it is investigated the humidity sensing properties of polyimide layers (with thickness of 50 and 630 nm) by measuring the electrical resistance R [Ω] and the capacitance C [pF] as a function of the relative humidity RH [%]. The layers show very good characteristics as humidity sensors operating at room temperature - the electrical resistance changes by more than 4 decades and the capacitance - by 40% in the range of 20-100% RH. [ABSTRACT FROM AUTHOR]