Real-time X-ray Monitoring of the Nucleation and Growth of AlN Epitaxial Films on Sapphire (0001)

TL;DR

This study uses in situ x-ray scattering to monitor the real-time nucleation and growth of AlN films on sapphire, revealing growth dynamics, strain evolution, and relaxation processes during epitaxial film formation.

Contribution

It provides the first real-time insights into AlN epitaxial growth on sapphire using in situ x-ray techniques, highlighting growth rate transients and strain relaxation mechanisms.

Findings

Initial island formation with oxygen incorporation

Steady state growth after island coalescence

Full relaxation achieved at ~30 nm thickness

Abstract

We report the results of x-ray scattering studies of AlN on c-plane sapphire during reactive radiofrequency magnetron sputtering. The sensitivity of in situ x-ray measurements allowed us to follow the structural evolution of strain and roughness from initial nucleation layers to fullyrelaxed AlN films. A growth rate transient was observed, consistent with the initial formation of non-coalesced islands with significant oxygen incorporation from the substrate. Following island coalescence, a steady state growth rate was seen with a continuous shift of the c and a lattice parameters towards the relaxed bulk values as growth progressed, with films reaching a fully relaxed state at thicknesses of about 30 nm.