Bulk transport properties of Bismuth selenide thin films approaching the two-dimensional limit

TL;DR

This study explores how the electrical transport properties of Bi2Se3 thin films change as they become very thin, revealing significant effects on resistivity, mobility, and band gap that are relevant for future electronic and spintronic devices.

Contribution

It provides detailed insights into the thickness-dependent transport behavior of Bi2Se3, especially near the two-dimensional limit, highlighting the tunability of its properties for device applications.

Findings

Resistivity and Hall mobility change significantly below 6 quintuple layers.

Bulk band gap increases as the film becomes thinner.

Ultra-thin films show a crossover from metallic to insulating behavior.

Abstract

We have investigated the transport properties of topological insulator Bi2Se3 thin films grown using magnetron sputtering with an emphasis on understanding the behavior as a function of thickness. We show that thickness has a strong influence on all aspects of transport as the two-dimensional limit is approached. Bulk resistivity and Hall mobility show disproportionately large changes below 6 quintuple layer which we directly correlate to an increase in the bulk band gap of few-layer Bi2Se3, an effect that is concomitant with surface gap opening. A tendency to crossover from a metallic to an insulating behavior in temperature-dependent resistivity measurements in ultra-thin Bi2Se3 is also consistent with an increase in the bulk band gap along with enhanced disorder at the film-substrate interface. Our work highlights that the properties of few-layer Bi2Se3 are tunable that may be attractive for a variety of device applications in areas such as optoelectronics, nanoelectronics and spintronics.