Insulator-to-metal transition of SrTiO3:Nb single crystal surfaces induced by Ar+ bombardment

TL;DR

This study investigates how Ar+ ion bombardment induces an insulator-to-metal transition on SrTiO3:Nb surfaces, revealing reversible changes in electronic structure and surface conductivity at the nanoscale.

Contribution

It demonstrates that Ar+ bombardment causes a reversible insulator-to-metal transition in SrTiO3:Nb surfaces by altering surface stoichiometry and electronic states.

Findings

Formation of conducting islands during bombardment

Reversibility of metallic state through oxidation or heating

Change of Ti electronic state from d0 to d1/d2

Abstract

In this paper, the effect of Ar+ bombardment of SrTiO3:Nb surface layers is investigated on the macro- and nanoscale using surface-sensitive methods. After bombardment, the stoichiometry and electronic structure are changed distinctly leading to an insulator-to-metal transition related to the change of the Ti "d" electron from d0 to d1 and d2. During bombardment, conducting islands are formed on the surface. The induced metallic state is not stable and can be reversed due to a redox process by external oxidation and even by self-reoxidation upon heating the sample to temperatures of 300{\deg}C.