The 1.40 eV and 2.56 eV centres in synthetic diamond

Spin-orbit coupling and Jahn-Teller effect in Td symmetry: an ab initio study on the substitutional nickel defect in diamond

We analyse the spin-orbit and Jahn-Teller interactions in [Formula: see text] symmetry that are relevant for substitutional transition metal defects in semiconductors. We apply our theory to the substitutional nickel defect in diamond and compute the appropriate fine-level structure and magneto-optical parameters by means of hybrid density functional theory. Our calculations confirm the intepretations of previous experimental findings that the 2.56 and 2.51 eV optical centres are associated with this defect. Our analysis of the electronic structure unravels possible mechanisms behind the observed optical transitions and the optically detected magnetic resonance signal, too. This article is part of the Theo Murphy meeting issue 'Diamond for quantum applications'.

Low-Power Laser Graphitization of High Pressure—High Temperature Nanodiamond Films

Laser-induced graphitization of 100 nm monocrystals of diamond particles synthesized by high-pressure high-temperature (HP-HT) methods is not typically observed. The current study demonstrates the graphitization of 150 nm HP-HT nanodiamond particles in ca. 20-μm-thick thin films formed on a glass substrate when the intensity of a focused 633 nm He-Ne laser exceeds a threshold of ~ 33 kW/cm2. Graphitization is accompanied by green luminescence. The structure and morphology of the samples were investigated before and after laser excitation while using X-ray diffraction (XRD), Raman spectroscopy, atomic force (AFM), and scanning electron microscopy (SEM). These observations are explained by photoionization of [Ni-N]- and [N]-centers, leading to the excitation of electrons to the conduction band of the HP-HT nanodiamond films and an increase of the local temperature of the sample, causing the transformation of sp3 HP-HT nanodiamonds to sp2-carbon.

Analysis of Nickel Defect in Diamond with Photoluminescence upon Excitation near 200 nm

Photoluminescent (PL) spectra of synthetic diamond powders at temperatures between 10 and 300 K were excited with synchrotron radiation in the wavelength range 125-375 nm. Prominent spectral PL features were detected at 484.6 and 489.0 nm (2.559 and 2.535 eV), associated with nickel defect. During our measurement of PL excitation (PLE) spectra of Ni defect in diamond, we observed a distinct PLE line at 215 nm for the first time. We thereby suggest the use of UV-PL spectra excited in the region 200-220 nm to analyze and to identify nickel defect in diamonds.