HRTEM Analysis of Defect Structures in AIN Thin Films

Abstract HRTEM analysis and conventional TEM techniques were used to determine the nature and density of defects in AIN thin films grown by Molecular Beam Epitaxy (MBE). Extended defects, which act as phonon scattering sites, are detrimental to the thermal properties for which AIN is sought. [1] Previous research on defect structures in AIN has focused primarily on bulk materials. [2-5] This investigation extends previous studies by concentrating on defects native to AIN thin films. The thin films for this study were grown by MBE onto annealed Al2O3 (corundum structure) substrates with a nominal (0001) surface orientation. The steps and structure of such (0001) Al2O3 surfaces have been previously characterized. [6] Films with thicknesses of 50 to 120 nm were grown at substrate temperatures between 700°C and 900°C. An RF driven source for atomic nitrogen and an aluminum effusion cell were used to generate deposition fluxes. TEM samples were prepared in plan-view and cross-section using conventional dimpling and ion milling techniques.