Structural stability of Cr-related defect complex in diamond for single photon sources: A first-principles study

We performed first-principles calculations to characterize the structure and electronic properties of Cr-related centers in diamond when oxygen or nitrogen is involved. We found that Cr-2V-N-C center with C-s symmetry is energetically favored under N-rich condition, with respect to Cr-int, Cr-C, Cr-2V, and Cr-2V-O-C. In analogy to the Cr-2V defect, Cr-2V-N-C center also introduces strongly spin polarized impurity levels into the diamond band, in favor of single-photon emission. The yield of optically active centers of the single photon emitters could be improved by incorporation of N, since the formation energy of Cr-2V-N-C complex is lower than that of Cr-2V under N rich condition. Meanwhile, our calculations indicated that the additional incorporation of O to Cr or (Cr, N) defects introduces not well-separated impurity levels, which will broaden the emission lines. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794993]