Growth of Diamond at High Temperatures and Pressures

Abstract

Single crystals of diamond (1∼3 mm in diameter) were grown at high temperatures and pressures by the temperature gradient method using metal solvent. The effect of metal solvent, Fe, Co, Ni and Ni-j binary alloys (j=Fe, Mn, Cr, V, Ti, Zr), on optical properties and morphological features of grown crystals has been studied. The intensity of the four absorption bands in the UV, visible and IR regions (270 nm, 600∼660 nm, 680 nm and 1130∼1350 cm^-1) varied by changing the metal solvent. The 270 nm and 1130 cm^-1 bands, which are due to substitutional nitrogen, were most intense for crystals grown in nickel solvent, while they were undetectably weak for those grown in iron solvent. The addition of the metals ( j) to Ni resulted in the decrease of substitutional nitrogen and this effect was found to increase in the order described above, i. e. Fe<Mn< … <Ti. This tendency was shown to correlate with affinity of the metal with nitrogen. The affinities were estimated from the reported values of solubility of nitrogen in iron-based alloys. Inclusion of solvent metals cccurred when Fe or some of the Ni-j alloys were used. Contrary to what was reported, the absorption band at 680 nm showed little correlation with the bands due to substitutional nitrogen. The occurrence of the 600∼680 nm band is reported in this paper for the first time.