Large magnetoresistance of bismuth/gold films thermally deposited onto glass substrates

Bismuth thin films deposited onto glass substrates by thermal sublimation are polycrystalline with short mean free paths, multiple grain orientations, and disappointingly small magnetoresistance when compared to single crystals. Direct deposition onto thin gold buffer layers followed by a post-deposition anneal leads to significantly improved properties, namely, large grains oriented in the trigonal direction and a 5-T magnetoresistance higher than 250% at room temperature. For a Bi0.93Au0.07 stoichiometry, we show that optimal results are obtained when the annealing temperature is above the BiAu eutectic point (241 degreesC) and below the melting temperature (271 degreesC) of bismuth, thus indicating a mechanism in which the presence of gold in the bismuth facilitates grain-boundary motion and grain growth. (C) 2003 American Institute of Physics.