ИСТИНА

In the present work the dependence of field emission (FE) from nanographite (NG) films on the pressure of the residual gases in the vacuum chamber has been studied. The films were obtained by the plasma enhanced chemical vapor deposition method. It is remarkable that the FE properties demonstrate long-time stability at operation of NG cathodes with pressure better of 10-5 Torr. With the pressures exceeding 10-5 Torr the decrease of the FE current has been observed at a constant applied voltage up to level depending on the pressure. The duration for the current drop was increased with the gas pressure (Fig. 1). A partial recovery of the current has been observed after pumping out of the measuring cell to the original pressure level of 10-5 Torr. The time dependencies of the current drop show two parts with different characteristic rates (Fig. 2). At the pressure value exceeding 10-2 Torr emitted electrons produce intense ionization of the residual gas. These ions create main part of the total current measured between the cathode and anode. The experimental observations are explained by the action of the ion bombardment and adsorption/desorption processes at the surface of the NG films during field emission measurements.