Enhanced optical properties of chemical vapor deposited single crystal diamond by low-pressure/high-temperature annealing

Abstract

Single crystal diamond produced by chemical vapor deposition (CVD) at very high growth rates (up to 150 m/h) has been successfully annealed without graphitization at temperatures up to 2200°C and pressures <300 torr. Crystals were annealed in a hydrogen environment by using microwave plasma techniques for periods of time ranging from a fraction of minute to a few hours. This low-pressure/high-temperature (LPHT) annealing enhances the optical properties of this high-growth rate CVD single crystal diamond. Significant decreases are observed in UV, visible, and infrared absorption and photoluminescence spectra. The decrease in optical absorption after the LPHT annealing arises from the changes in defect structure associated with hydrogen incorporation during CVD growth. There is a decrease in sharp line spectral features indicating a reduction in nitrogen-vacancy-hydrogen (NVH ؊ ) defects. These measurements indicate an increase in relative concentration of nitrogen-vacancy (NV) centers in nitrogencontaining LPHT-annealed diamond as compared with as-grown CVD material. The large overall changes in optical properties and the specific types of alterations in defect structure induced by this facile LPHT processing of high-growth rate single-crystal CVD diamond will be useful in the creation of diamond for a variety of scientific and technological applications. microwave plasma ͉ hydrogen ͉ vacancy ͉ nitrogen

Catalyst-free synthesis of transparent, mesoporous diamond monoliths from periodic mesoporous carbon CMK-8

“…A smaller nitrogen content at higher temperature is plausible due to the higher nitrogen fugacity associated with higher temperature. It has been reported that the low-pressure/high-temperature annealing in a hydrogen environment can significantly enhance the optical properties of chemical vapor deposition (CVD) single-crystal diamond (19). We suggest that the similar treatment might apply to nanopolycrystalline diamond.…”

A Microscopy and FTIR and PL Spectra Study of Polycrystalline Diamonds from Mengyin Kimberlite Pipes

“…The emission lines at 2.313 eV (535.9 nm) and 2.153 eV (575 nm) have been observed previously in some natural brown diamonds and can also be produced in diamonds containing nitrogen (mainly in the B form) by radiation damage and annealing at high temperature. Vibronic system with 2.153 eV (575 nm) ZPL corresponds to the [N-V] 0 [15]. The 2.024 eV (613 nm) center can be observed in some natural type I diamonds.…”

“…In the hydrogen-related absorption bands, the ∼3107 cm −1 absorption peak is attributed to the stretching vibration of vinylidene group (>C=CH 2 ), the ∼2923 cm −1 , ∼2854 cm −1 peaks are due to the asymmetrical and symmetrical stretching vibration of sp 3 -hybridized C-H bonds [13][14][15], and the 3762 cm −1 and ∼3660 cm −1 peaks are, respectively, related to the stretching vibration of hydroxyl group and H 2 O. Comparing the FTIR spectra of the EFPCDs (Figures 3(a) and 3(b)) with those of the ARPCDs (Figures 3(c) and 3(d)), we find that the intensity of hydrogen-related absorption peaks of the ARPCDs is stronger than that of the EFPCDs, especially the ∼2923 cm −1 and ∼2854 cm −1 peaks are very weak in the FTIR spectra of the EFPCDs.…”

Spectroscopic Characteristics of Treated-Color Natural Diamonds

“…Generally, the gemologists have begun to enhance the color of diamond since the 1930s [2] and diamond treatments in the modern era mostly involve high-energy irradiation, high pressure and high temperature (HPHT) treatment, low pressure and high temperature (LPHT) annealing, and combination of these treatments [3][4][5][6][7][8][9][10][11]. Such as Vins [12] reported that natural diamonds with brown hue could be altered to display purple to red color, through multiprocess treatments including HPHT treatment (6-7 GPa at over 2150°C), high-energy irradiation, and LPHT annealing (lower than 1100°C).…”