Critical role of terminating layer in formation of 2DEG state at the $LaInO_{3}$/$BaSnO_{3}$ interface

TL;DR

This study reveals that the formation of a 2DEG at the LaInO3/BaSnO3 interface critically depends on the terminating layer of the BaSnO3 surface, with SnO2 termination being essential for 2DEG emergence, supporting the interface polarization model.

Contribution

It demonstrates experimentally that only SnO2-terminated BaSnO3 surfaces lead to 2DEG formation at LaInO3/BaSnO3 interfaces, highlighting the importance of surface termination in 2DEG engineering.

Findings

2DEG forms only with SnO2-terminated BaSnO3 surface

Surface termination was controlled via additional SnO2 deposition

CAICISS confirmed the termination layer composition

Abstract

Based on the interface polarization model, the two-dimensional electron gas (2DEG) at $LaInO_{3}$(LIO)/$BaSnO_{3}$(BSO) interfaces is understood to originate from a polarization discontinuity at the interface and the conduction band offset between LIO and BSO. In this scenario, the direction of polarization at the interface is determined by whether the first atomic LIO layer at the interface is LaO$^{+}$ or InO$_{2}^{-}$. We investigate the role of the terminating layer at the LIO/BSO interface in creating the 2DEG. Based on conductance measurements of our in-situ grown LIO/BSO heterostructures, we report in this work that the 2DEG only forms when the BSO surface is terminated with a SnO$_{2}$ layer. We controlled the terminating layer by additional SnO$_{2}$ deposition on the BSO surface. We show that the as-grown BSO surface has a mixed terminating layer of BaO and SnO$_{2}$ while the BSO surfaces prepared with additional SnO$_{2}$ deposition are terminated mainly with the SnO$_{2}$ layer. The terminating layer was confirmed by coaxial impact collision ion scattering spectroscopy (CAICISS). Our finding is consistent with the interface polarization model for 2DEG formation at LIO/BSO interfaces, in which the direction of the interfacial polarization in LIO is determined by the terminating layer of the BSO surface.