Anomalous Green Luminescent Properties in CVD Synthetic Diamonds

Abstract

In this paper, the authors explore the spectral properties of a sharp emission line centered at 499.6 nm (reported previously as 499 nm) observed in the UV‐luminescence spectrum of synthetic CVD diamond gemstones. These gemstones also exhibit spectrally prompt broad blue luminescence centered at 435 nm which is similar in character to the 425 nm blue luminescence characteristic of type IIa natural diamonds. By comparing the results against synthetic CVD diamond material which has been subjected to high temperature anneals, the authors can speculate on the nature of the defect associated with this color center. Since the 499 nm spectral line has only been observed in synthetic CVD diamonds to date, the authors further propose that it can be helpful in the identification of synthetic diamonds, in particular those showing the blue luminescence signature usually associated with type IIa natural diamonds.

Separation of Natural Laboratory-Grown Diamond Using Time-Gated Luminescence Imaging

“…Delayed luminescence from the H3 defect has been discussed for the natural diamond D3 (again, see figure 6). It is also a good indication that this synthetic diamond has undergone post-growth annealing, as this delayed luminescence has been previously observed in such samples that have undergone annealing at around 1700°C (Wassell et al, 2018).…”

“…Sample C3 is a commercially available CVD synthetic diamond from Gemesis that has been reported previously (Wassell et al, 2018). At first glance, the delayed luminescence CMOS image (figure 10B) appears very similar to that of sample C2 in figure 9.…”

“…Rather, it is the decay profile of the 499 nm feature in this sample. It was also suggested by Wassell et al (2018) that prompt luminescence of 499 nm could not be ruled out due to swamping by blue prompt luminescence. A commercially available CVD synthetic diamond from Diamond Foundry (sample C4) shows both a green prompt and green delayed luminescence (figures 11A and 11B).…”

“…The De Beers Group screened many millions of individual colorless diamonds to verify this concept, and it is this principle that is used in both the De Beers SYNTHdetect jewelry screening instrument and the second version of the Automated Melee Screener (AMS2) (figures 1 and 2) (Martineau and McGuinness, 2018). More recently, this technique has identified a previously unknown green luminescence feature at 499 nm (Wassell et al, 2018) observable in lab-grown diamonds obtained from Gemesis Inc. (now Pure Grown Diamonds) and in silicon-containing samples sourced by Element Six that had undergone postgrowth annealing.…”

The n–Si/p–CVD Diamond Heterojunction

“…They are presented in Figure 3 . It should be noted that both synthesized layers types the DFI and the DFII showed similar radiation recombination centers in positions 2.88 and 2.56 eV, but in the second sample, an additional recombination center appeared at 2055 eV [ 34 , 35 ]. These defects were due to nitrogen incorporated into synthesized material from residual gas in the reaction chamber.…”