Effects of additive NaN3 on the HPHT synthesis of large single crystal diamond grown by TGM

Abstract

In this paper, large single crystal diamond with perfect shape and high nitrogen concentration approximately 1671-1742 ppm was successfully synthesized by temperature gradient method (TGM) under high pressure and high temperature (HPHT). The HPHT synthesis conditions were about 5.5 GPa and 1500-1550 K. Sodium azide (NaN 3 ) with different amount was added as the source of nitrogen into the synthesis system of high pure graphite and kovar alloy. The effects of additive NaN 3 on crystal growth habit were investigated in detail. The crystal morphology, nitrogen concentration and existing form in synthetic diamond were characterized by means of scanning electron microscope (SEM) and infrared (IR) absorption spectra, respectively. The results show that with an increase of the content of NaN 3 added in the synthesis system, the region of synthesis temperature for high-quality diamond becomes narrow, and crystal growth rate is restricted, whereas the nitrogen concentration in synthetic diamond increases. Nitrogen exists in diamond mainly in dispersed form (C-centers) and partially aggregated form (A-centers). The defects occur more frequently on crystal surface when excessive NaN 3 is added in the synthesis system. HPHT, high nitrogen concentration, TGM, large single crystal diamond

Evolution of nitrogen structure in N-doped diamond crystal after high pressure and high temperature annealing treatment

“…C N , in A-center form, is determined by an absorption coefficient of 1282 cm −1 which multiplies the absorption factor (16.5 atomic ppm per cm −1 ) after the IR spectrum is decomposed into two individual components according to the procedure described in Refs. [18] and [19]. C N , in C-center form, is obtained from an absorption coefficient of 1130 cm −1 , namely, 25.0 atomic ppm per cm −1 .…”

Doping of Diamond Crystals with a Dopant of P₃N₅

“…The concentrations of nitrogen in the form of A-center (N A ) and C-center (N C ) were calculated from the absorption coefficient which were multiplied by converting factor of 16.5 ppm/(cm -1 ) and 25 ppm/(cm -1 ) at 1282 cm -1 and 1130 cm -1 , respectively , after the spectra decomposed into two individual components using the procedure described in Ref. [7]. The calculation results with uncertainties around 5 % are shown in Table 1.…”

“…[wt%] In Table 1, it is demonstrated that, with increasing the content of additive P 3 N 5 , the concentrations of nitrogen in the form of C-center and A-center are both gradually increased, and the highest value of total nitrogen concentration can approach 2186 ppm, which is the much higher than those specimens doped with other nitride additive [7][8][9]. This result might be attributed to phosphorus decomposed from P 3 N 5 entering diamond lattice.…”

“…Previously, it was reported that the highest concentration of nitrogen in diamond crystals grown by TGM could reach 1671-1742 ppm with NaN 3 as an additive [7]. In order to synthesize diamond crystals containing higher nitrogen concentration, in this literature, a new kind of additive P 3 N 5 was employed as the doping agent to grow diamonds by TGM.…”

Effects of additive boron on HPHT diamond single crystals grown by TGM

“…Different impurities have different influences on the properties of diamond crystals [1][2][3]. For example, by doping phosphorus and boron, n-type and p-type diamond crystals can be synthesized, respectively.…”