Hybrid Molecular Beam Epitaxy of Ge-based Oxides

TL;DR

This paper introduces a novel hybrid molecular beam epitaxy method using germanium tetraisopropoxide to grow high-quality Ge-based oxide films, demonstrated on Sn1-xGexO2 and SrSn1-xGexO3, with detailed structural and compositional analysis.

Contribution

The study presents the first use of GTIP as a precursor for hybrid MBE growth of Ge-containing oxides, enabling high-quality epitaxial films with controlled Ge incorporation.

Findings

Successful epitaxial growth of Sn1-xGexO2 up to x=0.54

Successful epitaxial growth of SrSn1-xGexO3 up to x=0.16

Ge preferentially occupies Sn sites in the crystal lattice

Abstract

Germanium-based oxides such as rutile GeO2 are garnering attention owing to their wide band gaps and the prospects for ambipolar doping for application in high-power devices. Here, we present the use of germanium tetraisopropoxide (GTIP) (an organometallic chemical precursor) as a source of Ge for the demonstration of hybrid molecular beam epitaxy (MBE) for Ge-containing compounds. We use Sn1-xGexO2 and SrSn1-xGexO3 as model systems to demonstrate this new synthesis method. A combination of high-resolution X-ray diffraction, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy confirms the successful growth of epitaxial rutile Sn1-xGexO2 on TiO2(001) substrates up to x = 0.54 and coherent perovskite SrSn1-xGexO3 on GdScO3(110) substrates up to x = 0.16. Characterization and first-principles calculations corroborate that Ge preferentially occupies the Sn site, as opposed to the Sr site. These findings confirm the viability of the GTIP precursor for the growth of germanium-containing oxides by hybrid MBE, and thus open the door to high-quality perovskite germanate films.