Hysteresis of pulsed characteristics of field emission from nanocarbon materials

摘要

Characteristics of pulsed-field electron emission from nanocarbon films were investigated in experiments with a wide (1.5-5 mm) quasiplanar test gap. Parameters of the applied voltage (amplitude, shape and duration of pulsed component and d.c. bias) were varied; the maximum peak voltage value amounted to 40-45 kV. Dynamic I-V plots measured in 10-100 mu s pulses combined inherent features of field emission (linearity in Fowler-Nordheim (FN) coordinates) with strong hysteresis. For the explanation of the latter, a model of emission via intermediate electron energy states is proposed. The simple quantitative model excellently agrees with the measured characteristics for different emitter samples and over a broad range of voltage parameters, but fails to simulate the phenomenon of emission efficiency boosting by fast voltage drops, also observed in the experiment. A possible mechanism of this dynamic effect may consist in the redistribution of electrons among the different field focuses at the nonuniform emitter surface under the effect of a strong nonstationary electric field. Copyright (C) 2007 John Wiley & Sons, Ltd.