NOISE IN FIELD-INDUCED ELECTRON-EMISSION FROM GRAPHITE COMPOSITE - SPECTRAL DENSITY AND AUTOCORRELATION INVESTIGATIONS

Noise in field-induced electron emission from graphite composite (pencil lead) has been investigated by spectral analysis and autocorrelation measurements in addition to its characterization by recording I-V and I-t curves. The I-V curves for the field emission from pencil lead exhibit several glitches leading to oscillatory behaviour in Fowler-Nordheim plots. The I-t characteristics of field emission current display trains of pulses with characteristic distribution which appears to change unpredictably from one train to another. Sometimes a train will exhibit a totally random noise. Analysis of the behaviour of the power spectrum and autocorrelation of individual trains indicates that the observed noise originates from a variety of processes such as adsorption, flip-flop, diffusion and desorption of residual gases on the heterogeneous surface of submicrometre-sized graphite a planes.