CONTROLLED DEPOSITION OF DIAMOND FROM AN ACETYLENE OXYGEN COMBUSTION FLAME

An experimental set-up for the deposition of diamond by an acetylene-o xygen combustion flame was developed in which it is possible to contro l the deposition temperature within 10-degrees-C during long-term expe riments. This degree of accuracy is obtained by cooling the back of th e substrate holder with an electronically controlled water injection s ystem and using soldered substrates, ensuring a good thermal contact. With this set-up a large number of experiments were performed with dep osition times of 1 h. Special attention was given to the growth of dia mond layers with uniform thickness and morphology because these proper ties are considered essential for future applications. It was found th at the deposition temperature, the total gas flow, the composition of the gas phase and the position of the substrate in the flame all have major influences on the deposit. Not only the growth rate and the qual ity of the diamond are strongly influenced by the deposition condition s, but also the preferred crystal habit and the homogeneity.