Identification of Pink-Coloured CVD Synthetic Diamonds from Huzhou Sino-C Semiconductor Co. in China

Abstract

In recent years, increasing numbers of pink-coloured CVD synthetic diamonds have appeared on the market. One of the major sources is Huzhou SinoC Semiconductor Science and Technology Co., Ltd., Zhejiang province of China. In this article, seven pink-coloured CVD-grown diamonds produced in the last two years by Huzhou have been investigated and identified, including their gemological and spectroscopic characteristics. In DiamondView, they fluoresced orange–red, with an obscure striated growth structure, which is common for CVD synthetics. The mid-IR absorption spectra of these samples showed some single nitrogen and hydrogen-related features (1130, 1344, 3123, 3323 cm−1), which indicated that the diamonds were type Ib and were CVD-grown diamonds. The H1a defect annealed out at approximately 1400 °C, whereas the 3107 cm−1 defect was produced by annealing above 1700 or 1800 °C. This implied that the samples had undergone two separate heat treatments: first, a high-temperature anneal (possibly an HPHT treatment to reduce any brown colour), which would have produced the 3107 cm−1 defects and a small number of A centres, followed by irradiation, followed by annealing above 800 °C to make the vacancies mobile. The UV–Vis–NIR absorption spectra showed distinct NV-related features (575 and 637 nm), the main reason for the pink colour. Photoluminescence spectra obtained at liquid nitrogen temperature recorded radiation-related emissions (388.9, 503.5 nm), a strong N-V centre, H3 and H2 defects, and many unassigned emissions. These pink CVD products can be separated from natural and treated pink-coloured diamonds by a combination of optical spectroscopic properties, such as fluorescence colour, and absorption features in the infrared and UV–Vis regions.

Synthesis of Diamonds and Their Identification

“…41) are dominated by NV centers, but also show other nitrogen-related features such as the 270 nm broad band from N S 0 and the 503.2 nm peak from H3 (N 2 V 0 ). Additionally, they include features associated with irradiation such as ND1 (V -, 393.5 nm), GR1 (V 0 , 741 nm), or irradiation and annealing such as the "595 nm" (594.3 nm) defect (Wang et al 2010;Zaitsev et al 2018;Song et al 2021). FTIR spectra further indicate treatment, containing the dinitrogen 〈001〉 split-interstitial H1a (1450 cm −1 ) and the 1502 cm −1 peak (Wang et al 2010;Song et al 2021).…”

“…Additionally, they include features associated with irradiation such as ND1 (V -, 393.5 nm), GR1 (V 0 , 741 nm), or irradiation and annealing such as the "595 nm" (594.3 nm) defect (Wang et al 2010;Zaitsev et al 2018;Song et al 2021). FTIR spectra further indicate treatment, containing the dinitrogen 〈001〉 split-interstitial H1a (1450 cm −1 ) and the 1502 cm −1 peak (Wang et al 2010;Song et al 2021). As "NV-pink" CVD samples are nitrogen-containing, the CVD-specific 3123 cm −1 (NVH 0 ) peak may be detected (Wang et al 2010;Zaitsev et al 2018).…”

“…As "NV-pink" CVD samples are nitrogen-containing, the CVD-specific 3123 cm −1 (NVH 0 ) peak may be detected (Wang et al 2010;Zaitsev et al 2018). However, it is worth noting that this feature will be absent or weakened in samples that underwent HPHT treatment for brown color removal prior to irradiation and annealing (Wang et al 2010;Song et al 2021). Diamonds colored pink by NV centers are likely to be treated natural or laboratory-grown diamonds and thus should be thoroughly tested (Moses et al 1993;Shigley et al 2004a,b;Wang et al 2005a,b, Eaton-Magaña et al 2018a).…”

“…The PL spectra for CVD diamonds that have been treated pink by irradiation and annealing for nitrogen-vacancy formation are unsurprisingly dominated by emission from both NV 0 and NVcenters, but also include peaks at 389, 495.9 (H4, N 4 V 0 ), 503.5 (3H, interstitial-related), 796.9, 806.4, and 949.0 nm (Wang et al 2010;Eaton-Magaña and Shigley 2016;Song et al 2021). Strong absorption from the "595 nm" (594.3 nm) and GR1 (V 0 , 741 nm) centers, which overlap with the vibronic bands associated with NV 0 and NVluminescence, are detected as negative peaks.…”