Optical Characterization of Heteroepitaxial BN Films Grown on Diamond

The current knowledge of the optical properties of cBN films is limited to few reports involving thin films (~200 nm) growth on c-Si substrates with, undesired, amorphous and hexagonal BN (aBN and hBN, respectively) interlayers. This project will study the optical properties of thick, high quality cBN films grown heteroepitaxially on diamond substrates using spectroscopic ellipsometry (SE). The dielectric function of cBN deduced from SE in the spectral range from near infrared (0.7 eV) to the ultraviolet (6.5 eV) will be correlated to the mechanical and electrical properties of cBN films and in turn with its phase purity, crystal size, defect density, and stress. The results obtained from this project will provide the foundations for advanced optical characterization of thick, high quality cBN films that will be beneficial in the advancement of cBN for electronic applications. Cubic boron nitride (cBN) has many potential applications due to its unique combination of excellent physical and chemical properties including high hardness -second only to diamond; high thermal conductivity; and ability to be doped p- and n- type. Recent developments have made it possible to fabricate thick (several microns) cBN films grown heteroepitaxially on diamond film substrates. Such films are prepared using fluorine-assisted plasma enhanced chemical vapour deposition (FA PECVD) and high substrate temperature (~800 oC). These advances reinforce the possibility to develop electronic applications based on cBN films. As with other semiconductor applications of thin films, optical characterization techniques are expected to play a major role in the development of future cBN technologies.