Surface Properties of Etched Tungsten Single Crystals

Abstract

An examination of the surface properties of chemically etched W single crystals has been made to determine the possibility of developing a macroscopic surface with adsorption properties equivalent to an ideal crystal plane.Crystals up to three inches in length have been grown in 0.003-inch W wires by a thermal gradient technique. The crystals completely filled the wire cross section.The etching appeared to have produced a surface which was homogeneous on a microscopic level. Thermionic emission was observed to be identical for the three crystallographic directions, [112], [$11\overline{2}$], and [110], with a value of ${{\ensuremath{\varphi}}_{0}}^{*}=5.25\ifmmode\pm\else\textpm\fi{}0.05$ v. Surface ionization measurements gave the same value of the work function within experimental error.