AbstractA reactor has been designed to investigate diamond growth by varying the ratio of carbon:hydrogen incident on both silicon and diamond substrates. A well characterised
atomic hydrogen source developed in this laboratory is positioned at right angles to a carbon sputter source, which has been characterised using a quartz crystal monitor. Substrates are positioned at 45° to the two sources on a molybdenum holder which can be temperature controlled up to 1000°C.
The etching of both graphite and diamond by atomic hydrogen has been investigated as a function of temperature and intensity. A model has been developed which explains both the temperature and intensity variation of the graphite sputtering yield. The etch rate of diamond has been shown to possess a temperature dependence not previously reported. A new atom source has been built, allowing enhanced versatility in adjusting the hydrogen intensity, and incorporating an "in-phase" radiator.
To investigate a proposed mechanism for diamond growth based on surface interactions occurring between a surface and incoming carbon and hydrogen atoms, the ratio of carbon:hydrogen incident on the substrate surface has been varied. Increasing the ratio up to 1:2500 resulted in diminishing amounts of amorphous carbon being deposited on the substrate, until eventually no deposition occurred. For larger ratios, no growth or etching occurred on silicon substrates. In contrast, subjecting diamond substrates to these higher ratios resulted in enhanced etching.
This study has confirmed the role of atomic hydrogen in the diamond growth process - both in the preferential etching of graphite over diamond, and in its interaction with atomic carbon on a diamond growth surface. However, under the low pressure conditions of this reactor, where surface interactions should be the only significant reactions occurring, no diamond was grown, suggesting that the proposed surface mechanism is not valid. The present findings suggest that gas phase interactions fulfil a vital role in the mechanism of diamond growth.
|Date of Award||Dec 1997|
|Supervisor||John Geddes (Supervisor) & Robert McCullough (Supervisor)|