Weak Antilocalization Tailor-Made by System Topography in Large Scale Bismuth Antidot Arrays.

Abstract

Using a two-carriers model and the Hikami-Larkin-Nagaoka (HLN) theory, we investigate the influence of large area patterning on magnetotransport properties in bismuth thin films with a thickness of 50 nm. The patterned systems have been produced by means of nanospheres lithography complemented by RF-plasma etching leading to highly ordered antidot arrays with the hexagonal symmetry and a variable antidot size. Simultaneous measurements of transverse and longitudinal magnetoresistance in a broad temperature range provided comprehensive data on transport properties and enabled us to extract the values of charge carrier densities and mobilities. Weak antilocalization signatures observed at low temperatures provided information on spin-orbit scattering length ranging from 20 to 30 nm, elastic scattering length of approx. 60 nm, and strong dependence on temperature phase coherence length. We show that in the absence of antidots the charge carrier transport follow 2-dimensional behavior and the dimensionality for phase-coherent processes changes from two to three dimensions at temperature higher than 10 K. For the antidot arrays, however, a decrease of the power law dephasing exponent is observed which is a sign of the 1D-2D crossover caused by the geometry of the system. This results in changes of scattering events probability and phase coherence lengths depending on the antidot diameters, which opens up opportunity to tailor the magnetotransport characteristics.