The Size and Arrangement of Bismuth Microcrystals Formed from Vapor

The magneto-resistance of films of bismuth, deposited on glass and mica, has been measured at room and liquidair temperatures and for various angles between the film normal and the magnetic field ($H=16,000\mathrm{}$). The ratio $\frac{\Delta R_{{-180\mathrm{}}^{\circ }\mathrm{C}}}{\Delta R_{{+20\mathrm{}}^{\circ }\mathrm{C}}}$ rises steeply for thicknesses between 0.1 μ and 0.4 μ and then much more gradually to a thickness of 4μ. The thermal coefficient of resistance shows no corresponding anomaly. X-ray analysis shows all the films to be composed principally of small crystals with (111) parallel to the backing. $\Delta R$ varies with the direction of $H$, the current remaining always in one direction in the film, as predicted, from experiments on monocrystals for such an assembly. The bearing of these results on the structure of metallic films is briefly discussed.