Defects and Morphology of Homoepitaxial Diamond Films on Natural Nonplanar and Isotopically Pure Planar Substrates

Abstract

ABSTRACTWe have carried out diamond deposition by microwave plasma-assisted chemical vapor deposition (MPCVD) on planar and nonplanar diamond substrates at temperatures between 850° and 2000° C. The nonplanar and planar substrates were the polished (100) surfaces of type Ia natural diamond anvils and isotopically pure (99.95% 12C) type Ila synthetic crystals, respectively. The extremely low level of lattice and optical defects in the isopure substrates relative to natural crystals makes them ideal for optical characterization and defect studies, as well as high performance optical and electronic applications [1's (1) geometry, (2) type (defect density), and (3) temperature. The phase purity and defect structure of the films were analyzed by micro-Raman and low temperature photoluminescence (PL) spectroscopy. Optical and atomic force microscopy (AFM) were used to examine the surface morphology of the films. High temperature growth on the nonplanar anvil tip was anisotropic and extremely rapid (50-400 μm/hr), with significant incorporation of optically active defects. A possible model for the observed rapid growth is discussed. The films grown at lower temperatures on planar isopure substrates showed a dense array of oriented, stepped, square growth hillocks with penetration twins at their tops, while those grown at higher temperatures exhibited reasonably smooth, <110> oriented macrosteps. The higher temperature planar films showed a larger variety of incorporated optical centers than the lower temperature films.