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

Abstract

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.

An Overview on the Formation and Processing of Nitrogen-Vacancy Photonic Centers in Diamond by Ion Implantation

“…This value is also in accord with the value (55 eV) for the displacement energy in diamond matrix proposed by Prins et al [54]. However, studies shown that the vacancy aggregates are acceptor defects with a charge transition level at about Ev + 3.5 eV [55]. This is well above the (0/-) level of NV, so they can donate electrons to turn NV(0) into NV(−).…”

Ab initio investigation on the experimental observation of metallic hydrogen

“…The absorption spectra below the band gap is mainly composed of three parts: 520 nm (2.39 eV) band, 360 nm (3.49 eV) band, and a featureless profile. 94 When annealed, the 520 nm band is removed at 1800 • C, while the other two are significantly reduced at 1600 • C. 94 In DS's experiment, the annealing T is 1200 • C, well below 1800 • C. Therefore, the 2.39 eV band should remain.…”

“…We choose two absorption curves from the experiment of Khan et al which include about 1 ppm nitrogen defects resembling the experiments of DS, 94 and correct the calculated diamond/hydrogen reflectance using:…”

Determination of temperature dependent parameters of zero-phonon line in photo-luminescence spectrum of silicon-vacancy centre in CVD diamond thin films

“…Diamond shows a unique combination of physical and chemical properties such as high hardness, thermal conductivity, chemical stability, wide band gap (∼ 5.5 eV) [1,2] and biocompatibility, which make it advantageous for optoelectronics [3,4] and biotechnology [5]. These applications are determined not only by the intrinsic properties of diamond but also by crystallographic defects and impurities.…”