The granularity effect in amorphous InGaZnO$_4$ films prepared by rf sputtering method

TL;DR

This study examines how granularity affects electrical transport in amorphous InGaZnO films prepared by rf sputtering, revealing that inhomogeneities at the particle boundaries influence conductivity and Hall effect behaviors.

Contribution

It demonstrates that the linear ln T behavior of conductivity and Hall coefficient in amorphous InGaZnO films can be explained by electron-electron interactions considering granularity, supported by SEM imaging.

Findings

Conductivity peaks at a specific temperature T_max.

Conductivity and Hall coefficient show linear ln T dependence at low temperatures.

Granularity at particle boundaries significantly impacts electron transport.

Abstract

We systematically investigated the temperature behaviors of the electrical conductivity and Hall coefficient of two series of amorphous indium gallium zinc oxides (a-IGZO) films prepared by rf sputtering method. The two series of films are $\sim$700\,nm and $\sim$25\,nm thick, respectively. For each film, the conductivity increases with decreasing temperature from 300\,K to $T_{\rm max}$, where $T_{\rm max}$ is the temperature at which the conductivity reaches its maximum. Below $T_{\rm max}$, the conductivity decreases with decreasing temperature. Both the conductivity and Hall coefficient vary linearly with $\ln T$ at low temperature regime. The $\ln T$ behaviors of conductivity and Hall coefficient cannot be explained by the traditional electron-electron interaction theory, but can be quantitatively described by the current electron-electron theory due to the presence of granularity. Combining with the scanning electron microscopy images of the films, we propose that the boundaries between the neighboring a-IGZO particles could make the film inhomogeneous and play an important role in the electron transport processes.