The model of photo- and field electron emission from thin DLC films

To understand the nature and peculiarities of electron field emission (FE) from silicon tips coated with diamond-like carbon (DLC) films the photoelectron (PE) spectroscopy have been used. The results of PE spectroscopy have been analyzed and compared with electron FE. The DLC films were radiated by vacuum ultraviolet (VUV) light with energies 7.7 and 10.2 eV. The main results can be summarized as follow: (i) the two peaks are observed on photoemission spectra, (ii) after VUV radiation the spectra are shifted in region of positive energy and relationship between peaks are changed, namely low energy peak is decreased and high energy one is increased, remarkably, (iii) low temperature annealing promotes the recovery of spectra of DLC films, (iv) hydrogen implantation shifts the spectra in positive energy region, (v) argon implantation with following annealing at 450 °C exludes the changes photoemission spectra at VUV light excitation. The photoemission spectra allowed to estimate work function and it was compared with data obtained from electron FE measurements. On base of the experimental results the model of DLC surface with two specific emission areas was analyzed. In this model the transformation of surface layer and its influence on emission properties have been considered. The important role of hydrogen, its diffusion, creation and dissociation of CH bonds is emphasized. In particular, the first (left) peak corresponds to area with large work function (about 4 eV) and relates to domination of sp2 configuration of atoms bonds. The second one corresponds to region with substantially less work function due to sp3 configuration, stimulated by coupling the hydrogen on surface.