GROWTH TEMPERATURE EFFECTS OF IMPURITIES IN HP HT DIAMONDS/

Diamond crystals have been grown by the temperature gradient method un der high temperature and pressure conditions, using Co and Ni catalyst s with and without the use of Ti as a nitrogen getter. For each growth run the growth temperature has been changed during the run in order t o observe the effect which temperature has on the incorporation of the impurities nitrogen, boron and nickel. The concentration of nitrogen in the diamonds grown from both Co and Ni without the use of a nitroge n getter decreased with increases in temperature. On the other hand, w hen the getter was added the nitrogen concentration increased with inc reasing temperature. This suggests that the effect of the nitrogen get ter decreases with increasing temperature. In the case of boron-doped crystals grown from Co and Ni, the yellow colour changed to blue with increases in the growth temperature. The change was reversed when the nitrogen getter was added. Based on the knowledge that the depth of bl ue colour is proportional to the concentration of uncompensated accept or, N-boron - N-nitrogen, the Change in colour is reasonably understoo d if the concentration of nitrogen changes in the same manner as it do es for boron-free crystals. A distinct green or brown coloured stripe caused by incorporation of nickel appeared in sample regions formed du ring decreases in the growth temperature, but not in regions correspon ding to increases in temperature. This suggests that the concentration of nickel depends on growth rate rather than on the growth temperatur e itself, in contrast to the case for nitrogen and boron.