ビスマス蒸着膜の電流磁気効果

抄録

Resistivity, Hall effect and magnetoresistance of evaporated bismuth film are measured at temperatures between 77 and 293°K in a steady magnetic field of flux density up to 16000 gauss. From the experimental results, the concentrations of conduction electrons and holes and their mobilities are calculated by the use of a two band model. The concentration of electrons is found to be nearly equal to that of holes. It is larger in the film than in the bulk; it increases with the decrease of thickness. On the other hand, the mobilities of conduction electrons and holes in the film are much smaller than in the bulk. In films thinner than 1000Å, the mobility increases with the rise of temperature. The effective mean free paths are calculated from the carrier concentrations and mobilities. They are found to be much smaller in the film than in the bulk; they decrease with the decrease of thickness. The ratio d/l_∞ (d is the thickness and l_∞, the mean free path determined by the internal scattering) becomes always larger than l in the thickness range between 300 and 18000Å. This means that the size effect by the diffuse scattering at surface is difficult to detect, and whether the scattering at surface is diffuse or specular remains unascertained. It is concluded that the thickness dependence of the resistivity of the evaporated bismuth film is mainly caused by the change of the mean free path, l_∞, and of carrier concentrations with thick-ness. The negative temperature coefficient of the resistivity observed is due to the difference in temperature dependence of the mobility between the bulk and the thin film.