Electrical ageing of carbon nanotube composite cathode layers

Effect of electrical ageing (EA) on the field emission parameters of thin multiwall carbon nanotube composite (t-MWCNTs-composite) was studied. Initially, t-MWCNTs were mixed with a-terpineol and ethyl cellulose and subjected to three roll milling process to obtain t-MWCNTs-composite. Following this, the composite was screen printed on a conducting substrate, annealed for 10 min and employed to the electrical ageing process for a period of 6 h. The ageing, on each cathode layer, was repeated for five times and J-E characteristics have been collected before and after each ageing attempt. The analysis revealed that, the magnitude of threshold turn-on-field gradually increased from its virgin value of 1.223 to 1.968 V mu m(-1) and corresponding mean field enhancement factor, gamma(m). gradually decreased from 2700 +/- 210 to 1940 +/- 30 with a sequential increase in the ageing attempts, The degradation rate, delta J/delta t, estimated for untreated and EA samples, indicated that the magnitude of delta J/delta t reached to an equilibrium value of -0.785 mu A cm(-2) min(-1), which shows a stable emission state of the emitters. To investigate the effect of EA on the physical state of the emitters, a few virgin,and all EA samples were subjected to scanning electron microscopy, micro Raman spectroscopy and X-ray photoelectron spectroscopy. The details of the analysis are presented. (C) 2008 Elsevier B.V. All rights reserved.