Electron and ion emission of faces of a tungsten crystal

The emission properties of the close-packed (110) and porous (111) faces of a tungsten crystal were studied with band-shaped samples in planar devices at a residual gas pressure of 10^–9 torr. The experimental apparatus has a provision for simultaneous measurement of the emission currents from two samples. The orientation of the samples is determined by chemical etching and by x-ray diffraction. The most probable values of _(hkl) for the (110) and (111) faces were found to be 5. 30 ± 0. 03 and 4. 40 ± 0. 02 eV, respectively, by the method of thermionic emission and the method of positive surface ionization of lithium atoms. The peak observed at temperatures < 1500 °K on the logI⁺ = f(5040/T) curve for the (111) face is explained, following Dobretsov, in terms of an increase in the work function of this surface at low coverages (­ 1) by adsorbed lithium atoms.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 6, pp. 7–11, June, 1970.