Characterisation of a saddle field fast atom beam source and its application to the growth of diamond-like carbon films

The use of saddle field fast atom beam (FAB) sources to grow diamond-like carbon (DLC) films is attractive due to its de and rf attributes. This paper reports the detailed analysis of the beam coming out from the FAB source using argon (Ar), methane (CH4) and acetylene (C2H2) as source gases. Three operation modes of the FAB source are found, viz. glow discharge mode, transition mode and oscillation mode. A new process parameter, applied power, is defined for characterisation of the FAB source. Energy distribution analysis shows that the mean energy of the radicals coming out of the FAB source lies within 50% of the applied voltage to the FAB source. The neutralisation coefficient of the beam was estimated to bl: more than 90% and was found to be almost independent of the discharge current of the FAB source. It will be seen through this characterisation study that a completely novel technique has been found to deposit DLC films, simultaneously by neutral and ionic radicals. The mechanical and opto-electronic properties of these DLC films are discussed. The role of ion assistance is seen in hardening the films. DLC films deposited by ionic radicals show better opto-electronic properties as measured by photothermal deflection spectroscopy (PDS). (C) 2000 Elsevier Science Ltd. All rights reserved.