Multifunctional nanocrystalline chromium boride thin films

Abstract

The present study highlights the growth and properties of chromium diboride films (100-300 nm thickness) deposited on to various substrates (Cu, borosilicate glass and fused silica) by thermal evaporation process. X-ray diffraction patterns showed that films were slightly boron deficient. This was confirmed using EDX measurements which indicated a nominal composition of CrB 1.5. However, electron diffraction patterns showed the presence of CrB 2 leading to the inference that the films were composites of CrB 2 and CrB 1.5. The films were nanocrystalline with crystallite sizes of the order of 15-20 nm. Scanning electron micrographs revealed that the film morphology is substrate dependent. The films on borosilicate glass and fused silica were optically transparent and insulating at thickness of ∼100 nm. The thicker films were opaque and conducting. There was enhancement in reflectance of Cu substrates from 25 to 50% in the near IR wavelength region due to the chromium boride coatings. The hardness of the films was 10 GPa on Cu while it was 8 GPa on glass substrates. © 2011 Elsevier B.V. All rights reserved.