Transmission electron microscopy and thermal residual stress analysis of AlN crystal

Presented in this thesis is an investigation into the residual thermal stress distribution in AlN single crystal (film), grown using W (substrate) as a crucible material, and appropriate crucibles, sapphire, tantalum carbide, niobium carbide and silicon carbide, are also investigated. An optimal choice of crystal growth conditions results in the formation of coalesced boundaries known as island structures. A finite element model has been used that accounts for different arrangements of these island structures. The model is based on the dimensionless coordinates that significantly reduces the number of variables to be computed. Experimentally grown aluminum nitride crystal with rough and smooth surface was examined by Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). The special technique, Convergent Beam Electron Diffraction (CBED), was used to determine the polarity of the rough and smooth surface, and High Resolution Transmission Electron Microscopy (HRTEM) image was used to investigate the dislocation in aluminum nitride crystal.