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Interfacial chemical bonding states between polyimides (PI) and sputter coated Cr-SiO2 thin film have been investigated mainly by XPS to obtain a reliability basis for thin film resistor application of Cr-SiO2.We tried to leave different level of etch residue by applying two etchants of different etching power, then analyzed the etched surfaces by XPS, TEM and EXAFS. It proved that at first Cr in the sputtered Cr-SiO2 reacts with oxygen atoms which were introduced during O2 plasma treatment of the PI surface and also with original carbonyl oxygen of the PI to offer Cr-O-C bond at the Cr-SiO2/PI interface. This was concluded from the attenuation of Cls peak intensity corresponding to the carbonyl group. Then after thermal annealing, Cr extracted most of the interface oxygen to give a Cr2O3 layer of a discrete thickness. These phenomena were supported by TEM and SR-EXAFS as well.

The structure change of a Cr-Si-O thin film with regard to heat-treatment was investigated not only by the transmission XAFS method but by the surface sensitive XAFS method using synchrotron radiation. As a result of transmission XAFS, the Cr-Si-O thin film as sputtered has an amorphous structure like a mixture of SiO2, Cr and CrSix. After heat-treatment to 650 K, Si-Cr bonds decreased and Si-O and Cr-Cr bonds increased. CrSix is unstable in the system. The interfacial studies by the surface XAFS method showed i) at the interface with polyimide, there is a thin layer which is dominantly made of Cr2O3 and ii) at the interface with Al, Cr atoms are mainly coordinated to Cr. Analyses by the XAFS method gave consistent results with chemical analyses by x-ray photoelectron spei roscopy and observation by transmission electron microscopy.

The effect of ambient gases on degradation and rejuvenation of ZnO varistors was investigated from the viewpoint of voltage-current characteristics. Ambient oxygen gas suppressed increases in the leakage current during ac biasing, while it rejuvenated degraded samples. The time dependence of rejuvenation indicated that ion migrations, possibly the desorption and adsorption of oxygen ions at the grain boundaries, occur reversibly in degradation and rejuvenation. Moreover, a noticeable difference was observed between V–I curve shapes after ac biasing in nitrogen and in oxygen atmospheres.