Abstract
UDC 539.216.1
We present here the effect observed for the first time, namely, that of the negative magnetoresistance (NMR) at a transverse magnetic field (B ⊥ I) in quantum Bi wires. The single crystal bismuth wires in a glass cover were prepared by liquid phase casting methods. Bi wires are of a strictly cylindrical shape with (1011) orientation along the wire axis with diameters ranging from 50 to 400 nm and the length up to several millimeters. In wires with the diameter of d < 80 nm the semimetal-semiconductor transition associated with the quantum size effect has been observed. We have found the transition accompanied by the “semiconductor” temperature dependence of the resistance R(T) in the temperature range of 2.1–300K, and the NMR in the weak transverse magnetic fields (both at B || C2 and at B || C3) at T < 5K. Increasing the diameter of the wires, temperature T and magnetic field B leads to the weakening of the negative transverse MR effect connected with the suppression effect of size quantization. To interpret this effect of the NMR we have used a theoretical model in which the electrical conductivity is calculated using the Cubo formula, taking into account the elastic scattering carriers on phonons and the size quantization of the energy spectrum. Compression of experimental results with the theoretical model allows us to conclude that the observed effect of the NMR in Bi-nanowires is of a quantum nature.
Keywords: quantum size effect, Bi nanowires, negative magnetoresistance, semimetal-semiconductor transition.