CONTROLLED DEPOSITION OF DIAMOND FROM AN ACETYLENE OXYGEN COMBUSTION FLAME

An experimental set-up for the deposition of diamond by an acetylene-oxygen combustion flame was developed in which it is possible to control the deposition temperature within 10-degrees-C during long-term experiments. This degree of accuracy is obtained by cooling the back of the substrate holder with an electronically controlled water injection system and using soldered substrates, ensuring a good thermal contact. With this set-up a large number of experiments were performed with deposition times of 1 h. Special attention was given to the growth of diamond layers with uniform thickness and morphology because these properties are considered essential for future applications. It was found that 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 quality of the diamond are strongly influenced by the deposition conditions, but also the preferred crystal habit and the homogeneity.