Carbon films for use as the electron source in a parallel e-beam lithography system

The overall aim of this work is to produce a parallel e-beam lithography sy stem using an array of field-emitting microguns independently driven by an active matrix array. This paper will describe the work carried out on optim isation of suitable carbon-based materials for use as the electron emitter source in such a system. From initial experiments on field emission from te trahedrally bonded amorphous carbon (ta-C) and nanocluster carbon films, it has been deduced that emission occurs from nanometre-size sp(2) sites with in an insulating sp(3) matrix. Hence, we have carried out a series of exper iments to investigate the possibility of deliberately producing such sp(2) regions within a predominantly sp(3) matrix using e-beam irradiation, high energy ion beam irradiation and post deposition plasma processing of ta-C. Unfortunately, although the use of I GeV uranium ions successfully produced arrays of sp(2) rich regions on the required nanometre scale, no preferent ial field emission from such sites could be obtained. The final series of e xperiments were thence carried out using aligned carbon nanotubes (CNTs) as the electron sources. Results on aligned CNTs, grown using a dc plasma tec hnique and a Ni catalyst, are presented. Both the diameter and length of th e CNTs are dependent upon the thickness of the catalytic layer used. Field emission from an array of CNTs was obtained.