Disorder-driven carrier transport in atomic layer deposited ZnO thin films

TL;DR

This study investigates how disorder affects carrier transport in atomic layer deposited ZnO thin films, revealing temperature-dependent transitions and quantum effects linked to growth conditions and structural disorder.

Contribution

It provides new insights into the disorder-induced transport mechanisms and quantum corrections in ZnO thin films grown at different temperatures.

Findings

Disorder varies with growth temperature and influences electrical properties.

Metal to semiconductor transition occurs at low temperatures in certain films.

Quantum corrections explain resistivity behavior below transition temperatures.

Abstract

This paper addresses the effect of disorder on the carrier transport mechanism of atomic layer deposited ZnO thin films as has been investigated by temperature dependent electrical resistivity measurements in the temperature range of 4.2K to 300K. Films were grown on (0001) sapphire substrate at different substrate temperatures varying from 150 to 350 C. The defects and structural disorder in the films were found to be strongly dependent on their growth temperature. The films grown at 150, 300 and 350 C were found to be semiconductor-like in the whole measurement temperature range of resistivity due to the enhanced disorder in these films. However, a metal to semiconductor transition (MST) at low temperature has been observed in the films grown at 200 and 250 C. It was also observed that the film grown at 250 C with higher residual resistivity, the transition temperature shifted towards the higher value due to the increased disorder in this film as compared to that grown at 200 C. The upturn in resistivity below the transition temperature has been well explained by considering quantum corrections to the Boltzmanns conductivity which includes the effect of weak localization and coulomb electron-electron interactions related to the existence of disorder in these films.