Influence of film deposition parameters on the field emission properties of diamond-like carbon films

Considerable interest exists in the use of carbon-based materials as the active phase in field emission devices for flat panel displays and vacuum electronics, in view of the observation that efficient field emission can take place in fields as low as 0.2 V mu m(-1). Diamond has often been the focus of study since the material is generally very well characterised. Diamond-like carbon (DLC) is, however, possibly a more interesting candidate for practical devices since it is cheaply produced over large areas. Variation in the nature of DLC films is much greater than is the case for diamond, and understanding how the field emission characteristics relate to the film properties is a key issue. In this work, we therefore investigate field emission from DLC films and study the relationship between emission properties and film deposition parameters. DLC films were deposited on p-type and n-type Si substrates from CH4/Ar and CH4/N-2 plasmas created by a pulsed mid-frequency symmetrical discharge operated at a few Torr. Film thicknesses in the range of 0.05-1.5 mu m were explored with optical band gaps ranging from 0.8 to 2.4 eV. The field emission properties of such films were found to vary markedly with the film characteristics, with turn-on fields as low as 1 V mu m(-1) being observed in some instances. The mechanisms that influence the field emission characteristics of the films are discussed. (C) 1998 Published by Elsevier Science S.A.