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The strong temperature dependence of the contribution of nitrogen to diamond growth enhancement by microwave plasma chemical vapor deposition (MPCVD) have been firstly reported and systematically studied. Generally, an enhanced hydrogen desorption from the growing surface induced by the incorporated nitrogen atoms in diamond sublayer has been successfully used to explain the weak temperature depended growth enhancement of diamond by nitrogen addition, but cannot be employed to explain the observed strong temperature dependence of nitrogen contribution to diamond growth enhancement observed in this work. This indicates a significant change of surface kinetics of diamond growth induced by nitrogen addition should be occurred around 700 °C where a maximum value achieved. At this relative low temperature, the growing surface sites should be almost fully covered with hydrogen atoms with relative low nitrogen incorporated in the diamond. The adsorbed nitrogen may then make a contribution to promote hydrogen desorption, which is believed to play a dominant role in affecting the contribution of nitrogen. Experimental and calculation results do show that both the nitrogen adsorbed on the growing surface and incorporated in the sublayer may have different contribution to the growth rate enhancement, resulting in strong and weak temperature dependence, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Silicon vacancies in diamond, one of the most promising single photon sources, is difficult to be achieved in a controlled and reproducible way due to complicated doping behavior of silicon in diamond by microwave plasma CVD. In this work, the underneath mechanism of silicon vacancies formed by unintentional silicon (The silicon source is SiO 2 from the microwave plasma CVD quartz window) doping in diamond was investigated from the view of growing surface kinetics through a series of experiments. During deposition, the addition of N 2 to the CH 4 -H 2 reaction gas mixture is beneficial to the formation of silicon vacancies in diamond from unintentional silicon doping, and the addition of a minor amount of oxygen will enhance the plasma etching. The increased number of the dangling bonds is beneficial to the formation of silicon vacancies and nitrogen vacancies in diamond, while excessive oxygen will passivation the dangling bonds and thus inhibit the formation of vacancies. Finally, the vertical distributions of the surface topography, growth rate, intensity of photoluminescence of NV and SiV color centers doped in the diamond film, are measured with high spatial resolution on growth surface, which are also related to the plasma electron temperature and density. These findings are of importance for searching of optimal growth regimes of NV and SiV doped single crystals by microwave plasma CVD. • The addition of nitrogen to the growth gas is beneficial to the formation of SiV−. • A minor amount of oxygen promotes while excessive oxygen inhibits the formation of NV− and SiV−. • The growth and distribution of NV− and SiV− in diamonds are related to the plasma on the surface of the substrate. [ABSTRACT FROM AUTHOR]

A weak negative thermal quenching (NTQ) effect of nitrogen vacancy centers in nitrogen-doped diamond is investigated by low-temperature photoluminescence technology. Results show that a weak NTQ phenomenon of the NV− centers was observed in the range of 10–40 K. Aiming to explain the observed NTQ effect, three hypotheses are proposed to classify the underlying physical mechanism, including (a) electron transfer from nitrogen atom to NV centers, (b) electron transfer between NV0 and NV− centers, and (c) the shallow traps of charge carriers in diamond. What is more, with incorporating sulfur, sulfur-nitrogen complex defects are formed with an impurity level of 0.65 eV below the conduction band. The activation energies of nonradiative recombination of NV− centers were obviously decreased with doping sulfur, which maybe related to the substitutional nitrogen (deep donor) replaced by sulfur-nitrogen complex structure defect (relatively shallow donor). The presented work provides a comprehensive understanding on the physical mechanism of NTQ effect of nitrogen vacancy centers in diamond, which would provide guidance for application of NV centers, especially in low temperatures. • A weak negative thermal quenching (NTQ) effect of NV- centers was observed. And the physical mechanism is investigated. • Sulfur-nitrogen complex defects are formed and behave like donors (impurity level is ∼0.65 eV below the conduction band). • The presented work provides a comprehensive understanding on the physical mechanism of NTQ effect in diamond. [ABSTRACT FROM AUTHOR]