Stress-Dependent Contact Potential in Copper

Abstract

We have measured the compressionally induced change in contact potential for the (100) face of a single crystal of copper. For a change in stress of about 34 atm we observed a negative contact-potential change which is interpreted as a decrease in work function. This change is (-2.0 \ifmmode\pm\else\textpm\fi{} 1.2) \ensuremath{\mu}V/atm, which gives an equivalent gravitationally induced field of (-1.8 \ifmmode\pm\else\textpm\fi{} 1.0) \ensuremath{\mu}V/m. The crystal face was cleaned by ${\mathrm{Ar}}^{+}$ bombardment and measurements made at 2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ Torr. Some experiments on polycrystalline copper in different environments are also reported. A simple calculation based on the Gordy equation as interpreted by Steiner and Gyftopoulos gives, for a stress applied along the [001] cube axis, an increase of the work function with stress of 4.3 \ensuremath{\mu}V/atm for the (100) face but a decrease of 3.8 \ensuremath{\mu}V/atm for the (110) face.