EPR of a defect in CVD diamond involving both silicon and hydrogen that shows preferential alignment

A defect involving both silicon and hydrogen has been characterized using multifrequency electron paramagnetic resonance. The defect, denoted WAR3, was observed in a single-crystal chemical-vapor deposition diamond, which was homoepitaxially grown on a {110}-oriented substrate and doped with isotopically enriched silicon (90% ²⁹Si). The obtained data are explained by a silicon divacancy structure which is decorated by a hydrogen atom and is in the neutral charge state, (Si-V₂:H)⁰(S= 1/2). The experimentally derived ²⁹Si and ¹H hyperfine parameters are in agreement with values calculated using the spin-density-functional technique, ruling out a nonplanar structure. Defects are usually randomly oriented such that there is an equal probability for the symmetry axis of the defect to lie along each of the crystallographically equivalent directions. However, the WAR3 defect shows preferential alignment with respect to the {110} growth plane of the sample. Approximately four times as many WAR3 centers were aligned with their mirror planes lying perpendicular to the growth plane, compared to a statistical distribution. This indicates that the majority of WAR3 defects grew in as units rather than by the diffusion and aggregation of constituents. Analysis of the increase in the WAR3 concentration and the decrease in preferential alignment upon annealing the sample at 1400°C shows that WAR3 can also be created post growth.