ELECTRICAL-CONDUCTIVITY AND METAL-INSULATOR-TRANSITION IN THE AMORPHOUS SYSTEM CRXGE1-X

Amorphous films of the system Ge1-xCr(x) with x = 0.04-0.25 have been prepared by electron-beam evaporation and their electrical conductivity in the as-grown state measured in the temperature range T = 50 mK-300 K. The critical concentration for the metal-insulator transition (MIT) was found to be x(c) = 0.10. For x < 0.10 the low-temperature conductivity obeys the law sigma(T) = sigma-1 exp {-(T0/T)1/2} sigma(T) = sigma-0 + beta-T1/2 + gamma-T. For 0.10 < x < 0.20 a new conductivity mechanism is observed at low-temperatures. The results are discussed with respect to the MIT and Mott's minimum metallic conductivity.