The vibrational spectra of diamond polytypes and defects in diamond and cubic boron nitride

This thesis examines a variety of closely related issues all of which concern the relationship between the structure of cubic diamond, of its hexagonal and rhombohedral polytypes, and of structural defects and their respective vibrational spectra. The calculations, experimental results, and analyses of those results are presented in this work as a first attempt to build a systematic model of the diamond polytype and its related system of planar growth defects. The diamond polytypic structural system is reviewed and shown to form an internally consistent system based on the stacking sequences of silicon carbide and zinc sulfide. The space group of the 4H, 6H, and 8H diamond polytypes was determined to be P6{dollar}sb3{dollar}/mmc (194) while that of the 15R and 21R diamond polytypes was determined to be R3m (166). Elastic constant values for hexagonal diamond polytypes were also calculated from data for cubic diamond. The selection rules for the individual polytypes of diamond were determined via factor group analysis. Diamond polytypes are predicted to contain infrared active modes in contrast to cubic diamond and Ionsdaleite (2H diamond). The band positions of the Raman and infrared active modes of the polytypes were predicted from the parent structures by a folded zone model. A physical model of the structure of CVD diamond films is one that contains many discontinuities such as twins and stacking offsets spaced within tens of atomic layers of each other in the form of a one-dimensional glass. The spectra obtained from the CVD films showing broad Raman bands at wavenumber positions below that of the diamond Raman band is proposed to be the result of a breakdown of selection rules caused by stacking defects in the structure. An examination of a shock formed diamond powder served to confirm an earlier analysis. CVD diamond films were grown in the presence of various amounts of diborane gas. The Raman spectra of these films show marked effects due to the amount of diborane in the growth system. The model of the effects of stacking defects on the vibrational spectra of diamond was extended to cubic boron nitride. Raman and infrared spectra of cubic boron nitride were found to have features that could be explained by a breakdown of vibrational selection rules.