Characterization of Growth Hillocks on the Surface ofHigh-Pressure Synthetic Diamond

Abstract

Diamond crystals, with dimensions of about 0.5-0.6 mm, weresynthesized in the presence of Fe-Ni and Fe-Ni-Si catalyst solventsunder high-pressure-high-temperature (HPHT) conditions. The as-knowndendritic pattern was clearly seen on the (111) or (100) planes ofdiamond single crystals grown using Fe-Ni as a catalyst solvent.However, the conventional dendritic pattern was not observed indiamonds grown in the presence of Fe-Ni-Si alloy catalyst.Trigonal-type, pyramid-type, polygonal-type and rectangular-typegrowth hillocks were clearly observed on the (111) and (100) surfacesof diamonds grown from the Fe-Ni-Si-C system, and the density of thehillocks is very high at some positions. Clear successive growthlayers can also be found on the (111) planes of the high-pressurediamond single crystals grown in the presence of Fe-Ni-Si alloycatalyst. The growth hillocks distributed on the (111) and (100)planes of the diamonds generally occur on or near growth steps, andsome of the hillocks terminate at certain solid inclusions and voids.Growth hillocks on the (111) and (100) surfaces directly indicate thespiral growth mechanism under HPHT. Apossible formation process for growth hillocks is proposed.