The Synthesis And Annealing Of New Type Of Hydrogen Doped Large Single Crystal Diamond Under HPHT

As is known to all, hydrogen and nitrogen are two main impurity elements in natural diamond. Because that it is quite difficult to control the hydrogen doping in high pressure synthesis chamber, many previous investigations on diamond have been focused on the nitrogen element. Hence, the relatively less research on hydrogen leads to the blank in the synthesis of hydrogen doped new type of diamond single crystal. Therefore the synthesis of different hydrogen doped new type of large single crystal diamonds is of great significance for enriching the types of synthetic diamond. High-pressure annealing research is another way to explore the formation mechanism of diamond. The annealing treatment, on the basis of the synthesis of hydrogen doped new type of diamond with high nitrogen concentration, is of great significance on the further understanding interaction mechanism of hydrogen and nitrogen in internal natural diamond. At the same time, the latest geological scientific research reported that in the internal mantle, a large amounts of hydrogen can be released continuously and then react with oxygen in mantle to form water. More interesting, the diamond grows under such conditions in mantle. The simulations of effects of the hydrogen-oxygen environment in interior earth on diamond growth not only have great help to understand the natural diamond formation, but also show important scientific significance to explore the geological problems in the interior earth such as the form of the water.In this paper, we investigate the synthesis of new type of hydrogen doped diamond in Ni7oMn25Co5-C system with adding hydrogen additives by temperature gradient growth method in China-made cubic anvil high-pressure apparatus. We systematically investigated the synthesis of hydrogen doped Ib, hydrogen doped diamond with high nitrogen concentration and hydrogen doped Ⅱa large single crystal diamonds under high temperature and high pressure (HPHT) conditions. After the HPHT annealing treatment of the hydrogen doped diamond with high nitrogen concentration, we successfully obtained natural-like type la single crystal diamond. We also explore the effect of hydrogen and oxygen elements synergistically doping on the diamond crystal growth. Based on multiple advanced measurements (optical microscope, scanning electron microscope (SEM), micro Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), single crystal XRD and XPS), the existence form of hydrogen atoms in internal diamond and the multiple elements interaction in coexistence system are analyzed. Our works are divided into the following sections:1. By adding Fe(C5H5)2 into the synthetic system, the various characteristics of hydrogen doped large single crystal diamonds from different seed crystal faces are investigated in detail. The experimental results show that the existence of hydrogen raises the synthetic conditions and makes more defects and crystal stocks on{100} surfaces than{111} surfaces. There is an obvious relationship between temperature and the crystal quality: high temperature condition is a key factor for growing high quality hydrogen doped new type Ib large single crystal diamond. In the pressure range of 5.5 to 6.0 GPa and temperature range of 1280 to 1480℃, we successfully synthesize hydrogen doped new type Ib large single crystal diamond with maximum size up to 3.5 mm.2. By adding C3N6H6 into the synthetic system, we systematically investigate the effects of hydrogen and nitrogen co-doping on diamond growth from different seed crystal faces. We find that high nitrogen and hydrogen content environment increases the synthetic condition and obviously reduces the growth rate of the diamond. Although it is a very challenging topic for the synthesis of hydrogen doped high nitrogen single crystal diamond, meanwhile, the hydrogen and nitrogen co-doping will generates negative influences on diamond growth, we still successfully synthesize hydrogen doped high nitrogen large single crystal diamonds with nitrogen concentration up to 1700 ppm and 2100 ppm from{100} and{111} faces, respectively. The diamond with 2100 ppm nitrogen concentration from{111} face is the highest quality of hydrogen doped large single crystal diamond with high nitrogen concentration reported so far.3. By adding C3N6H6 and Ti into the synthetic system, the separately controllable adjustment of the specific element in the multiple elements coexistence system is examined. We successfully implement the synthesis of new type of hydrogen doped single crystal diamonds with controllable nitrogen concentration from≤1 ppm to 1800 ppm. The results reveal that hydrogen atoms in the form of C-H bonding by sp3 hybridization have no effect on the color of diamond; the titanium atoms in the synthetic chamber only play an important role in removing nitrogen, but show no influence on the hydrogen content. Under pressure of 6.2 GPa and temperature range of 1380 to 1440℃, we successfully synthesize hydrogen doped Ⅱa large single crystal diamond for the first time.4. Based on the annealing treatments of hydrogen doped diamonds with high nitrogen concentration, we investigate the interaction mechanism of hydrogen and nitrogen elements. By comparing the annealing results we find that the higher concentrations of nitrogen in the crystal, the easier nitrogen atoms aggregation. The different nitrogen polymerization degree occurs in different crystal faces. The polymerization degree in{111} crystal face is higher than that in{100} crystal face, which leads to obvious color difference region. More importantly, we find that the crystal with existence of hydrogen is in favor of nitrogen aggregation. After the annealing treatment under pressure of 6.0 GPa and temperature of 1650℃, it is the first time that the obtained hydrogen doped la large single crystal diamond can be comparable to natural diamond.5. For the first time, we add rich in hydrogen and oxygen compounds C6H8O7 into the cavity to simulate the hydrogen and oxygen environment in the interior earth so as to explore the growth characteristics of large single crystal diamond. We find that the diamond synthetic conditions become higher with increasing addition of the citric acid. The presence of hydrogen and oxygen not only easily leads to the hole defects, growth texture type, and irregular crystal, but also generates quadrilateral shape pits defects and hexagonal shape dissolution in the{100} and{111} faces respectively. The FTIR test shows that the peaks at 2850 and 2920 cm-1 are corresponding to hydrogen related strong absorption peaks of symmetric stretching vibration and antisymmetric stretching vibration of sp3 hybridization of C-H bonding, which implies that large amount of hydrogen atoms are doped into the crystal. The investigations of hydrogen and oxygen synergistically doped diamonds can not only provide the possibility to survey the existence mechanism of water in diamond, but also offer help to explore the formation mechanism of natural diamond and to solve the hydrosphere mystery in interior earth.