LASER-INDUCED REVERSIBLE CHANGE OF ELECTRICAL-RESISTIVITY OF COSI2 THIN-FILM SENSORS

Formation of thin crystalline layers of cobalt silicide, CoSi2, deposi ted by coevaporation of cobalt and silicon mixtures on SiO2/Si substra tes, has been attained by Q-switched YAG:Nd and CO2 lasers. The electr ical and optical properties of the CoSi2 layers have been studied by s imultaneous laser irradiation. It is shown that high-quality resistive crystalline CoSi2 films can be obtained by treatment with CO2 laser r adiation of 2 to 8 MW cm(-2) intensity. Besides, the resistance of the layer decreases by a factor of nine. When such a layer is subjected t o Q-switched YAG:Nd laser radiation of 20-35 MW cm(-2) intensity, the magnitude of the resistance increases by a factor of three due to the formation of clusters of vacancies in CoSi2. The CoSi2 phase and rise of concentration of vacancies are determined by X-ray diffraction. A c orrelation between changes in optical and electrical properties as wel l as structural changes of the silicide layer is found. It is shown th at the change in optical parameters of the resistive film subjected to laser treatment can be used for both remote resistivity measurements and quality control. (C) 1998 Elsevier Science S.A, All rights reserve d.