Growth of adherent diamond films on optically transparent sapphire substrates

The growth of continuous adherent diamond thin films on optically transparent substrates is important for the development of corrosion and erosion resistant infrared windows for many applications. Until now, the growth of adherent diamond films on optically transparent substrates like sapphire has been unsuccessful due to the large thermal mismatch between the film and the subs rate and the absence of an interfacial carbide "glue" layer. By employing a low temperature (500-550°C), low pressure (∼1 Torr) electron-cyclotron-resonance chemical-vapor-deposition process, and utilizing a dispersed-particulate diamond suspension for nucleation, adherent diamond thin films have been fabricated on sapphire substrates. Raman spectroscopy showed that the diamond peak was shifted approximately 6 cm^-1 above its equilibrium position suggesting the presence of very large compressive stresses (∼3.2 GPa) in the film.