ELECTRICAL-PROPERTIES OF HETEROGENEOUS CRSI(O,N) THIN-FILMS

The electrical conductivity of the system CrSi(O,N) was investigated in the temperature range from 4 K (50 mK) to 430 K. The composition of the alloys was in the range of 55/45 to 85/15 (Si/Cr atomic ratio) with oxygen or nitrogen concentrations of up to 50 at%. The films are prepared by dc magnetron or rf diode sputtering, respectively, and annealed in order to get small TCRs and high stability. CrSi(O,N) is found to be particularly suited for high ohmic thin film precision resistors with a sheet resistivity of up to 20 kω□. The as-deposited as well as annealed films undergo a metal-insulator transition dependent on oxygen (nitrogen) concentration. The non-metallic samples are well described up to a characteristic temperature by lg σ (T) ∼ T-α with α= 1 2 or 1 4 as known from variable range hopping. It is shown, that the temperature regions, where in each case one of these exponents fits the experimental data, depend strongly on the annealing temperature. Especially, if high annealing temperatures are used and the structure becomes heterogeneous on a macroscopic scale, the corresponding temperature regions in relation to characteristic sample parameters are completely different from those found in systems with heterogeneities on an atomic scale. © 1990.