Gas Impact, Field Etching, and Field Deformation

Abstract

The rate of arrival of gas molecules at a specimen tip is enhanced by polarization effects at moderate field strengths, but at high field strengths field ionization of the gas in space drastically reduces the net arrival rate. The gas kinetic arrival rate per unit area, n ₀, is given by

$$ {n_{0}} = p{\left( {2\pi MkT} \right)^{{ - \frac{1}{2}}}} $$

((4.1))

where p is the gas pressure; M, the molecular weight of the gas; and T, the gas temperature in °K. If p is measured in µtorr equation (4.1) becomes

$$ {n_{0}} = 3.54 \times {10^{{16}}}p{\left( {MT} \right)^{{ - \frac{1}{2}}}} $$

((4.2))