Influence of gamma irradiation on chemical vapor deposited boron-doped diamond films

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Carbon based materials such as graphite, fullerene, amorphous carbon and diamond in all forms and specifically doped diamond is of great interest owing to their several unsurpassable physical (mechanical, thermal, electrical, chemical, and biological) properties for multiple technological applications. In addition, diamond is reputed as radiation hard semi conducting material, thus predestined its usage for space/ extreme environment in contrast to existing Si, GaAs and GaN semiconductors. Boron-doped diamond films were synthesized using an ASTeX 5kW microwave plasma-assisted chemical vapor deposition (MWCVD) reactor with varying boron concentrations ranging from 100 to 4000 ppm in the gas phase. These samples were subjected to gamma radiation doses of 5, 10 and 100 Mrads. They were analyzed prior to and post-irradiation in terms of morphology, microscopic structure and physical property using various complementary analytical tools including scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy (RS), X-ray diffraction (XRD) and electrical (I-V) to establish the property-structure-processing relationship. The influence of both boron and gamma irradiation on structural and physical properties are presented. For instance the XRD measurements exhibited the borocarbide phase formation, while micro-Raman scattering studies reveal electronic property modifications (quasi metallic to semi conducting). Possible explanations for these findings are discussed in terms of multiple roles of (B, H) in diamond (C).