Spatially and spectrally resolved cathodoluminescence of hot-filament chemical-vapor-deposited diamond particles

Abstract

Spectrally resolved cathodoluminescence (CL) images and spatially resolved CL spectra were obtained from two specimens grown by hot-filament chemical vapor deposition. Each specimen consisted of a large number of unconnected diamond particles with cubo-octahedral and pseudo-fivefold twinned growth habits. The growth temperature was nominally 600 °C for one specimen and 750 °C for the other. In the 1.5–3.5 eV range, the spectra are composed of four defect and impurity related bands: there are three bands with zero-phonon lines at 1.68 eV, 2.156 eV, and 2.325 eV, and one broad band centered at 2.85 eV. A weak peak at 5.27 eV, due to exciton recombination, was also observed. Spectrally resolved images of the two most intense CL bands, at 2.156 eV and 2.85 eV, were obtained for several particles. In the low-temperature specimen, bright regions in images of the 2.156 eV band are correlated with {111} facets; bright regions in images of the 2.85 eV band are correlated in some cases with the central regions of {100} facets and in other cases with {111} facets. In the intermediate-temperature specimen, bright regions in the images of both bands are correlated with {100} facets. A model of competing recombination at different types of CL centers and nonradiative centers is proposed to facilitate the interpretation of the experimental results. For the low-temperature specimen, the model suggests that the 2.156 eV CL centers are located primarily in {111} growth sectors and the 2.85 eV CL centers are distributed relatively uniformly; images of the two dominant CL bands are predicted to have a complementary relationship in particles where there are few competing nonradiative centers. For the intermediate-temperature specimens, the model suggests that nonradiative recombination is dominant, and that the CL image contrast arises primarily from a nonuniform distribution of nonradiative centers.