EFFECT OF GE OVERLAYERS ON THE ELECTRICAL-RESISTANCE OF THIN CR FILMS

Cr films were prepared by evaporation on Corning glass plates. The base pressure of the vacuum system was in the 10(-9) to 10(-8) Torr range. The resistance R of the Cr films was measured at room temperature. The deposition of NaCl on a Cr film lead to practically no change in the resistance. However, Ge overlayers reduce R by about 10% for films about 10-nm thick. The maximum resistance decrease was found for a Cr film with a thickness of about 3 nm. There the Ge overlayer reduced R by nearly 40%. The resistance decrease due to Ge overlayers cannot be explained with conduction in the Ge overlayer. It seems also unlikely that one can contribute it to the formation of a compound at the interface between the Cr film and the Ge overlayer. It is suggested that the change in R may be associated with the exciton mechanism, but more work is required before we can understand the effect.