Step- and terrace-resolved crystal truncation rod scattering from vicinal surfaces under coherent heteroepitaxy

TL;DR

This paper presents a comprehensive theory for crystal truncation rod scattering from vicinal surfaces with coherently strained heteroepitaxial films, enabling detailed structural analysis during growth.

Contribution

It introduces a unified formalism that accounts for elastic distortions, surface features, and growth dynamics, improving interpretation of CTR measurements in heteroepitaxy.

Findings

Elastic lattice distortions significantly affect non-specular CTRs.

The model accurately interprets static and real-time CTR data.

Vicinal CTRs reliably probe terrace and surface reconstructions despite coherent films.

Abstract

We develop a general theory of crystal truncation rod (CTR) scattering from vicinal surfaces with a coherently strained heteroepitaxial film. The formalism incorporates film-induced interference fringes, full elastic lattice distortion, terrace ordering, surface reconstruction, and real-time growth evolution within a unified description. Comparison between Nagai model and elasticity-based model shows that the lattice tilt is nearly identical in the two approaches, whereas the elasticitybased model predicts an additional triclinic deformation arising from shear strain. This deformation has little effect on specular CTRs but strongly modifies non-specular rods, making them a sensitive probe of the full elastic state of coherent epitaxial films. We further show that the characteristic sensitivity of vicinal CTRs to terrace ordering, surface reconstruction, and terrace-resolved compositional modification remains robust in the presence of a coherent film. Representative calculations for InGaN/GaN demonstrate that the framework enables quantitative interpretation of both static and real-time CTR measurements and provides access to step- and terrace-resolved structural and kinetic information during heteroepitaxial growth.