Effects of phosphorus doping MnP on diamond growth along the (100) surfaces

In this study, diamond crystals were synthesized via the temperature gradient method at 5.6 GPa and 1230-1245 °C by adding a Mn 3 P 2 dopant and FeNi catalyst. Experimental results showed that Mn 3 P 2 shifted the V-shaped growth region to the upper right by influencing the catalytic properties. The scanning electron microscopy (SEM) photographs of the diamonds synthesized at 1245 °C revealed that there were many dendritic structures in the (100) surfaces. The diamond crystal quality could be improved when the added Mn 3 P 2 was less than 6 wt% at 1245 °C, but it would be seriously damaged when the diamond was heavily doped with Mn 3 P 2 . Pits and uneven layered structures appeared on the diamond surfaces when the additive was included at 12 wt% at 1245 °C. The Fourier transform infrared spectroscopy (FTIR) results revealed that the Mn 3 P 2 additive increases the N content of the crystal and that N is present in the diamond crystal in the form of a "C" center. It is worth noting that phosphorus could be doped into diamond crystals by using the Mn 3 P 2 additive and that the other impurities in diamonds were mostly C-N and C-O forms, as confirmed by X-ray photoelectron spectroscopy (XPS). The phosphorus in the sample crystals mainly formed C-P bonds with carbon, while a smaller amount of phosphorus formed P-O bonds with oxygen. The test results of the electrical properties as assessed by the van der Pauw method for the diamond crystals with Mn 3 P 2 doped at 1245 °C revealed a resistivity of 0.516 × 10 6 -9.729 × 10 6 Ω cm and a negative Hall coefficient, indicative of an n-type semiconductor. In this study, n-type diamond crystals were synthesized via the temperature gradient method at 5.6 GPa and 1230-1245 °C by adding a Mn 3 P 2 dopant and FeNi catalyst.