UNIAXIAL-STRESS AND ZEEMAN SPLITTING OF THE 1.681 EV OPTICAL-CENTER IN A HOMOEPITAXIAL CVD DIAMOND FILM

Observation of the 1.681 eV optical center in a homoepitaxial CVD diamond him at the very narrow photoluminescence (PL) linewidth of 0.2 meV allows us to study the defect under uniaxial stress parallel to [100] and in magnetic fields along the three main crystal directions. With no external held, the center exhibits a characteristic fourfold no-phonon PL fine structure plus weak additional components. The four main components are further split apart by uniaxial stress p parallel to[100] at linear rates. The energy level scheme deduced from these data and from thermalization measurements indicate that the center is under internal uniaxial overpressure at zero external stress. This is ascribed to its large size in the narrow diamond lattice. Complex splitting patterns are observed for applied magnetic fields which cannot fully be analyzed at present. The observed anisotropies indicate a non-cubic symmetry of the defect close to tetragonal, possibly slightly distorted towards lower symmetry. This is consistent with simple models of the defect involving silicon, nitrogen and a vacancy which are the established defect constituents.