Diamond-like-carbon thin films produced in a low pressure hollow cathode discharge and measurement of its work function

Abstract

Thin films of carbon such as diamond, diamond-like-carbon (DLC) and/or amorphous carbon have been grown from gas phase of hydrogen-hydrocarbon gas mixtures using several variations of chemical vapor deposition (CVD) system such as hot filament CVD and plasma assisted CVD. It has been shown that similar films can be produced in the presence of carbon atoms and radicals even without the introduction of the hydrogen-hydrocarbon gas mixtures. However, for successful diamond film formation the pressure usually ranges from a few Torr for the electron cyclotron resonance (ECR) and microwave (MW) plasma devices to atmospheric pressure for plasma jet techniques. Formation of thin films at low pressure is desirable as it may lead to more oriented thin films.
Production of carbon hydrides and carbon radicals at the surface of a graphite wall in fusion plasma experiments is a well-known phenomenon. Carbon materials are widely used as wall materials for fusion reactors due to their good thermal properties and low charge number. Several types of hydrogen plasma generators are used to simulate plasma-graphite wall interaction with hydrogen pressure less than 10 mTorr. In this range of pressure deposition of diamond had never been reported due to the enhancement of the production of hydrogen ion which is known to be detrimental to diamond film formation.
It is the purpose of this paper to present studies in the formation of diamond thin films using a low pressure compact hydrogen plasma generator with graphite immersed in the plasma as a source of carbon flux and to measure the work function and photon yield of the film.