Accession Number : AD0697280

Title :   FIELD EVAPORATION RATES OF TUNGSTEN.

Descriptive Note : Technical rept.,

Corporate Author : PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF PHYSICS

Personal Author(s) : Tsong,Tien Tzou ; Mueller,Erwin W.

Report Date : 17 NOV 1969

Pagination or Media Count : 46

Abstract : Essential parameters of the theory of field evaporation are the higher ionization potentials of the metal, the surface atom's distance from the effective electronic surface plane of the metal, the polarizability of the surface atom in its site, the energy difference between the atomic and the ionic states of the surface atom, the rate and temperature dependent activation energy, and the pre-exponential factor of the Arrhenius equation. It is shown how these data can be obtained from field evaporation rate measurements. Experiments with the (110) plane of tungsten were carried out in a range from 0.01 layer/sec to 10,000,000 layers/sec using both DC and pulsed field evaporation techniques. Results are discussed. It is also shown that the well known reduction of the evaporation field by the imaging gas is to a considerable extent due to the field induced adsorption of the gas. (Author)

Descriptors :   (*TUNGSTEN, FIELD EMISSION), ELECTRIC FIELDS, EVAPORATION, HEAT OF ACTIVATION, ADSORPTION, SURFACES, MICROSCOPY, CRYOGENICS

Subject Categories : Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE