Strain Relaxation via Phase Transformation in SrSnO3

TL;DR

This study investigates how strain relaxation occurs in Nd-doped SrSnO3 thin films grown on GdScO3 substrates, revealing phase transformations, dislocation formation, and their effects on electronic transport relevant for high-power electronics.

Contribution

It provides new insights into strain relaxation mechanisms and phase stability in epitaxial SrSnO3 films, crucial for optimizing high-power electronic device performance.

Findings

Thinnest films (12 nm) remain fully coherent tetragonal phase at room temperature.

Phase transformation from tetragonal to orthorhombic occurs with increasing film thickness.

Misfit dislocations form at thicknesses above 110 nm, aiding strain relaxation.

Abstract

SrSnO3 (SSO) is an emerging ultra-wide bandgap (UWBG) semiconductor with potential for highpower applications. In-plane compressive strain was recently shown to stabilize the high temperature tetragonal phase of SSO at room temperature (RT) which exists at T > 1062 K in bulk. Here, we report on the study of strain relaxation in epitaxial, tetragonal phase of Nd-doped SSO films grown on GdScO3 (110) (GSO) substrates using radical-based hybrid molecular beam epitaxy. The thinnest SSO film (thickness, t = 12 nm) yielded a fully coherent tetragonal phase at RT. At 12 nm < t < 110 nm, the tetragonal phase first transformed into orthorhombic phase and then at t > 110 nm, the orthorhombic phase began to relax by forming misfit dislocations. Remarkably, the tetragonal phase remained fully coherent until it completely transformed into the orthorhombic phase. Using thickness- and temperature-dependent electronic transport measurements, we discuss the important roles of the surface, phase coexistence, and misfit dislocations on carrier density and mobility in Nd-doped SSO. This study provides unprecedented insights into the strain relaxation behavior and its consequences for electronic transport in doped SSO with implications in the development of high-power electronic devices.