EXCIMER LASER-INDUCED ELECTRON-EMISSION FROM DIAMOND FILMS

Diamond films with a thickness from submicron to a few microns were th e choice to study the electron emission induced by UV laser pulses and by electric fields. One of the goals of the research was to compare p hotoelectron emission behaviour under irradiation with XeCl (lambda=30 8 nm) and KrCl (lambda=222 nm) laser pulses, i.e. with a photon energy being respectively smaller (4.02 eV) and larger (5.58 eV) than the di amond band gap. The effects of the film thickness (grain size) and pos t-growth plasma treatments on the photoelectron yield were also studie d, fn addition, the results on the field electron emission from these diamond films are presented. A correlation between the photoemission a nd field electron emission is discussed based on an analysis of deep l evel distribution in the films examined with a charge-based deep level transient spectroscopy (Q-DLTS). The role of defect states in the gap is shown to be important in the processes of electron emission from t hin diamond films. It is pronounced in the wavelength-dependent photoe mission behaviour and, especially, in the negative effect on photocurr ent of the plasma treatments. The reduction of the photocurrent signal s from both the H and Ar plasma-treated films was interpreted with the help of Q-DLTS spectra which give information on the parameters of el ectrically active defects (concentration, activation energy, capture c ross-section). The field electron emission behaviour is shown to depen d on the film thickness, and the lowest turn-on field of 25 V mu m(-1) was obtained for the thinnest diamond film. (C) 1997 Elsevier Science S.A.