POLYCRYSTALLINE BETA-FESI2 THIN-FILMS ON NON-SILICON SUBSTRATES

beta-FeSi2 films of 600 to 630 nm thickness are prepared by co-evapora tion of iron and silicon on various glass and sapphire substrates. Str ess induced cracks arising from the crystallization of the amorphous l ayers can be avoided using glass materials with a thermal expansion co efficient slightly above that of beta-FeSi2, Si and FeSi precipitates arranged in layers parallel to the substrate can be attributed to inho mogeneities of the atomic ratio Si/Fe caused by irregular evaporation rates. Nucleation and grain growth of beta-FeSi2 are studied by heatin g up the amorphous films either slowly or rapidly. A significantly hig her nucleation rate is found in the rapid heating process which is int erpreted using the model of homogeneous nucleation. Crystallization at a high deposition temperature of 800-degrees-C gives a fine-grained, columnar grain structure. beta-FeSi2 films crystallized at a low tempe rature of 400-degrees-C/15 h exhibits a considerable subband absorptio n probably due to defect states in the band gap. With increasing annea ling temperature the subband absorption as well as the electrical cond uctivity decrease significantly. This is interpreted by the reduction of the acceptor density of the p-type semiconducting material.