The decay time of luminescence from neutral nitrogen-vacancy (NV(0)) centres in synthetic diamond is reported. The intrinsic luminescence lifetime of NV (0) is measured as τ(r) = 19 ± 2 ns. Neutral substitutional nitrogen atoms (N(S)(0)) are shown to quench luminescence from NV(0) by dipole-dipole resonant energy transfer at a rate such that the transfer time would equal τ(r) if one (N(S)(0)) atom was ~3 nm from the NV(0). In chemical-vapour-deposited diamonds grown with a small nitrogen content, that are brown as a result of vacancy-cluster defects, the decay time of NV(0) equals τ(r) in the as-grown material. However, after annealing at ≥1700 °C to remove the brown colour, luminescence from the NV(0) centres is severely quenched. This effect is suggested to be a result of the destruction of NV(0) centres and the creation of new NV(0) centres localized in vacancy-rich regions of the crystals.

This paper introduces a new technique to the study of diamonds: mapping the luminescence lifetime of optical centres. The understanding of luminescence lifetimes in diamond is briefly reviewed. Since lifetime mapping involves extended measuring times with focused laser excitation, the stability of the H3 optical centre is investigated. We show that saturation of the H3 luminescence requires excitation power densities in excess of 10 MW cm(-2). The non-radiative energy transfer time from an H3 centre to an A aggregate is found to be equal to that from N3 centres to A aggregates, at ∼3 × 10(-16)r(8) s, where there are r bond lengths between the H3 and A centres. Non-radiative energy transfer is shown to occur from the NV(-) band to the single substitutional nitrogen atoms: the single N atoms may quench luminescence as well as the A aggregates of nitrogen. In contrast, a comparison of the decays from the very similar H3 and H4 centres demonstrates that the B aggregate produces very weak quenching of the visible luminescence from diamond.

No abstract

Excess carrier dynamics in compensated n-type and p-type 3C-SiC layers grown by sublimation epitaxy and doped with nitrogen and aluminum has been studied using time-resolved optical pump-probe techniques. We show that carrier recombination pathway in both layers is strongly affected by the optical recharge of compensating aluminum impurities (Al − ) through trapping of holes and their thermal release, providing recovery to the initial state within 0.1 ms to 10 ns in the 80-300 K range. The dynamics of aluminum charge states and hole density were also analysed using numerical modelling, which provided a hole capture cross-section for aluminum s h (Al) = (1.0 ± 0.3) × 10 −15 cm −2 and its activation energy E a (Al) = (176 ± 4) meV in both layers. Free carrier lifetimes of 0.5 and 2 ns (for the p-and n-type layer, respectively) were measured at the injected carrier densities ( N 0 ) well above that of Al. We also observed a strong impact of the compensating Al impurities on carrier diffusivity at room temperature, which dropped to negligible values of D < 0.1 cm 2 s −1 at injection levels below the aluminum trap density ( N 0 < [Al − ] eq ) and reached its typical value of D = 2 cm 2 s −1 only at N 0 10 19 cm −3 .

No abstract