Longwei YIN
,
Musen LI
,
Dongsheng SUN
,
Fengzhao LI
,
Zhaoyin HAO
,
Xiumei DONG
材料科学技术（英文）
Some dislocations, which are generated in the diamond single crystal during the diamond crystal growth from Fe-Ni-C system, may affect diamond crystal growth mode at high temperature-high pressure (HPHT). The concentric dislocation loops were successfully examined by Moiré images. The surface morphologies of growing and as-grown diamond single crystals were observed by scanning electron microscopy (SEM). The concentric dislocation loops formation process and their effect on the diamond crystal growth mode were analyzed. It should be noted that whatever the nature of the dislocation is, should the Burgers vector of dislocation has a component at the direction normal to the growth interface, the dislocation will make the face parallel to the growth interface grow into spiral face. The presence of consecutive spiral steps on the diamond crystal surface also provides a direct evidence of the dislocation mechanism of diamond crystal growth.
关键词:
High temperature-high pressure
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Jianjun CUI
,
Musen LI
,
Longwei YIN
,
Guiyi WAN
,
Zhaoyin HAO
材料科学技术（英文）
In this paper, crystal growth instability of diamond was studied in a Fe-Ni-C system at high temperature-high pressure (HPHT). As any other crystal grown from solution, the flat or smooth growth interface of the diamond crystal is highly sensitive to growth conditions. The growth front interface should be of great importance to understand the diamond growth process. The presence of cellular growth interface by transmission electron microscopy indicated that there existed a narrow constitutional supercooling zone in front of the growth interface. Several parallel layers with cellular interface by TEM directly suggested that the diamond grows from the solution of carbon in the molten catalyst layer by layer, which is in accordance with the result obtained by scanning electron microscopy in this paper. Impurities are trapped by rapidly advancing growth layers during the diamond growth and they impose a great effect on the growth front stability. As the growth front interface approaches the impurity particle to a distance of about 10-5~10-7 cm, appreciable molecular forces begin to operate between them, and the impurity particle is trapped as the growth rate reaches a critical value. As a result, the driving force for crystallization under the impurity particles becomes smaller, the front buckles under the particle. An impurity naturally reduces the growth rate to a different extent.
关键词:
HPHT diamond growth
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