BN protective coating for high temperature applications

Abstract

We report on the fabrication, characterization, and processing of boron nitride films for use in high temperature applications such as field passivation, capping layers for thermal annealing of SiC, and protecting metallic filaments from their working environments. The BN films have been fabricated by pulsed laser deposition and spray techniques. The deposited films were characterized by X-ray Diffraction, Fourier Transform Infrared Spectroscopy, Ultraviolet-Visible Spectroscopy, Rutherford Backscattering Spectrometry and Transmission Electron Microscopy. The BN films deposited in the temperature range of 200-500°C have been found to be poorly crystalline, whereas the films fabricated above 600°C have been found to be microcrystalline. The as-deposited films were annealed at various temperatures ranging from 900°C to 1700°C in order to densify the films and study the applicability of the coatings. An AlN buffer layer was also applied in a few cases to improve chemical bonding with the substrate. Adhesion of the films with the heater components was greatly improved for high temperature annealed samples due to good interfacial bonding with the substrate material. Our results on the properties of BN films with an emphasis on characterization, processing, and implications for high temperature applications are discussed.