The Electronic Structures and Energies of the Lowest Excited States of the N[sub.s][sup.0], N[sub.s][sup.+], N[sub.s][sup.−] and N[sub.s]-H Defects in Diamond

• Published in: Materials 2023-02, Vol.16 (5)
• Main Authors: Platonenko, Alexander, Mackrodt, William C, Dovesi, Roberto
• Format: Article
• Language: English
• Subjects: Optical properties; Raman spectroscopy
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma16051979

This paper reports the energies and charge and spin distributions of the mono-substituted N defects, N[sup.0] [sub.s], N[sup.+] [sub.s], N[sup.−] [sub.s] and N[sub.s]-H in diamonds from direct Δ-SCF calculations based on Gaussian orbitals within the B3LYP function. These predict that (i) N[sub.s] [sup.0], N[sub.s] [sup.+] and N[sub.s] [sup.−] all absorb in the region of the strong optical absorption at 270 nm (4.59 eV) reported by Khan et al., with the individual contributions dependent on the experimental conditions; (ii) N[sub.s]-H, or some other impurity, is responsible for the weak optical peak at 360 nm (3.44 eV); and that N[sub.s] [sup.+] is the source of the 520 nm (2.38 eV) absorption. All excitations below the absorption edge of the diamond host are predicted to be excitonic, with substantial re-distributions of charge and spin. The present calculations support the suggestion by Jones et al. that N[sub.s] [sup.+] contributes to, and in the absence of N[sub.s] [sup.0] is responsible for, the 4.59 eV optical absorption in N-doped diamonds. The semi-conductivity of the N-doped diamond is predicted to rise from a spin-flip thermal excitation of a CN hybrid orbital of the donor band resulting from multiple in-elastic phonon scattering. Calculations of the self-trapped exciton in the vicinity of N[sub.s] [sup.0] indicate that it is essentially a local defect consisting of an N and four nn C atoms, and that beyond these the host lattice is essential a pristine diamond as predicted by Ferrari et al. from the calculated EPR hyperfine constants.