Electron field emission from undoped and doped DLC films

Electron field emission and electrical conductivity of undoped and nitrogen doped DLC films have been investigated. The films were grown by the PE CVD method from CH{sub 4}:H{sub 2} and CH{sub 4}:H{sub 2}:N{sub 2} gas mixtures, respectively. By varying nitrogen content in the gas mixture over the range 0 to 45%, corresponding concentrations of 0 to 8 % (atomic) could be achieved in the films. Three different gas pressures were used in the deposition chamber: 0.2, 0.6 and 0.8 Torr. Emission current measurements were performed at approximately 10{sup -6} Torr using the diode method with emitter-anode spacing set at 20 {micro}m. The current - voltage characteristics of the Si field electron emission arrays covered with DLC films show that threshold voltage (V{sub th}) varies in a complex manner with nitrogen content. As a function of nitrogen content, V{sub th} initially increases rapidly, then decreases and finally increases again for the highest concentration. Corresponding Fowler-Nordheim (F-N) plots follow F-N tunneling over a wide range. The F-N plots were used for determination of the work function, threshold voltage, field enhancement factor and effective emission area. For a qualitative explanation of experimental results, we treat the DLC film as a diamond-like (sp{sup 3} bonded) matrix with graphite-like inclusions