Semiconductor–metal–semiconductor transition in Bi and Bi–Ag nanowires

Abstract

We report on the experimental observation of temperature dependent (195–475 K) semiconductor–metal–semiconductor transition in the electrical resistance of 50 nm Bi nanowires grown in polymer. The distorted lattice structure of Bi nanowires opens up a semiconducting band gap (162 meV) in contrast to semi-metallic bulk as supported by the electron transport and infrared absorption data. The electron transport plausibly arises out of both surface electronic and bulk-like states, where the former dominates at lower temperatures and the latter at higher temperatures. In the intermediate temperature range, electron transport is dominated by phonon interactions, giving rise to the metal-like transport of Bi nanowires. Attempts to dope Bi nanowires with silver results in a significant modification of Bi–Ag nanowire surface states without changing the crystal structure. The modification of surface states plays an important role in shifting the transition temperatures significantly without any appreciable change in the semiconducting gap of Bi nanowires.