Three phonon decay mode of the 1136-cm(-1) nu(3) vibration of oxygen in silicon

The (1136-cm(-1)) nu(3) vibration of oxygen in silicon is known to decay at low temperature primarily by emitting two phonons. We show here that the temperature dependence of the decay is caused by a three-phonon process. In both natural-isotope and single-isotope Si-30, the three-phonon process is identified as the emission of one nu(1) (612 cm(-1)) local mode, one nu(2) low-energy local mode, and one lattice mode of 524 cm(-1) (where the quoted values are for O-16 in natural-isotope silicon). The common assumption that the decay of a vibration proceeds through one dominant process is clearly not applicable here

Colour-causing defects and their related optoelectronic transitions in single crystal CVD diamond

Defects causing colour in nitrogen-doped chemical vapour-deposited (CVD) diamond can adversely affect the exceptional optical, electronic and spintronic properties of the material. Several techniques were used to study these defects, namely optical absorption spectroscopy, thermoluminescence (TL) and electron paramagnetic resonance (EPR). From our studies, the defects causing colour in nitrogen-doped CVD diamond are clearly not the same as those causing similar colour in natural diamonds. The brown colour arises due to a featureless absorption profile that decreases in intensity with increasing wavelength, and a broad feature at 360 nm (3.49 eV) that scales in intensity with it. Another prominent absorption band, centred at 520 nm (2.39 eV), is ascribed to the neutral nitrogen–vacancy–hydrogen defect. The defects responsible for the brown colour possess acceptor states that are 1.5 eV from the valence band (VB) edge. The brown colour is removed by heat treatment at 1600 ° C, whereupon new defects possessing shallow (<1 eV) trap states are generated