Field electron emission from a nanostructured tungsten surface

In this paper, the electron emission from a nanostructured tungsten surface was investigated. A method for measuring an extremely low current (10−12 – 10−14 A) has been tested. It made possible to reduce the effect of the electric field on the sample surface and to minimize the probability of spontaneous breakdowns. For a detailed study of tungsten fuzz, a point tungsten anode (diameter 90 μm) was used. Field enhancement factor (β = 2000 – 3000) and effective emission area were calculated using the Fowler–Nordheim plots. The pre-breakdown current rise was studied. The emission current waveforms suggest the formation of several emission structures before the breakdown.

Десять способов определения площади полевой эмиссии

A variety of types for formal determination of one of the main parameters of field emission systems - the emission area was investigated. Using hemisphere on a cylindrical post model built using the COMSOL Multiphysics software package the relationship between known types of emission area estimation was shown. The corresponding values of emission currents were calculated. It was shown that the formal emission area (the ratio of the total current to the current density at the top) provides only ~ 75% of the emission current value. The effect of the anomalous behavior of the effective emission area (intercept of the trend line of current-voltage characteristics) is obtained when the voltage level changes in standard Fowler-Nordheim coordinates. A method for an experimental estimate of the field emission area using the modified Fowler-Nordheim coordinates ln (I/U^(2-η/6)) vs 1/U is proposed. The method is applied to the analysis of field emission data of a multi-tip nanocomposite emitter with carbon nanotubes.

Electron Field Emission from Undoped and Doped DLC Films

ABSTRACTElectron 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 CH4:H2 and CH4:H2:N2 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 10−6 Torr using the diode method with emitter-anode spacing set at 20 gm. The current - voltage characteristics of the Si field electron emission arrays covered with DLC films show that threshold voltage (Vth) varies in a complex manner with nitrogen content. As a function of nitrogen content, Vth 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 (sp3 bonded) matrix with graphite-like inclusions.