Depth-Resolved Subsurface Defects in Chemically Etched SrTiO3

TL;DR

This study compares two chemical etching methods for SrTiO3 surfaces, revealing that HCl-HNO3 treatment results in significantly fewer subsurface defects than traditional HF etching, leading to higher quality oxide surfaces.

Contribution

It introduces a novel HCl-HNO3 etching process that produces fewer native defects in SrTiO3 compared to conventional HF etching, enhancing surface quality for oxide heterostructures.

Findings

HCl-HNO3 etching results in fewer oxygen vacancies.

Defect depths are significantly shallower with HCl-HNO3 treatment.

HCLNO method avoids HF handling and yields higher quality surfaces.

Abstract

Depth-resolved cathodoluminescence spectroscopy of atomically flat TiO2-terminated SrTiO3 single crystal surfaces reveals dramatic differences in native point defects produced by conventional etching with buffered HF (BHF) and an alternative procedure using HCl-HNO3 acidic solution (HCLNO), which produces three times fewer oxygen vacancies before and nearly an order of magnitude fewer after pure oxygen annealing. BHF-produced defect densities extend hundreds of nm below the surface, whereas the lower HCLNO-treated densities extend less than 50 nm. This "Arkansas" HCLNO etch and anneal method avoids HF handling and provides high quality SrTiO3 surfaces with low native defect density for complex oxide heterostructure growth