Influence of Nanocrystalline Structure on Work Function of Tungsten

Summary form only given. The enhanced interest to nanocrystalline (NC) materials is attributed to their unusual physical properties significantly different from those of usual coarse-grained counterparts. A large volume fraction of grain boundaries within NC metals and their special, non-equilibrium states play a significant role in formation of its specific properties. The specific behavior of physical properties from NC materials allows waiting the features of the electronic structure from these materials. Specific features of an electron structure of the NC tungsten and NC nickel were studied by a method of field electron emission spectroscopy. The NC structure with average grain size about 100 nm was processed in specimens of tungsten by severe plastic deformation. The microstructure was studied by ion and transmission electron microscopy. Specific features of an electron structure of the NC specimens were studied by a method of field electron emission spectroscopy. Depending on a probing area on the emitter surface (near grain boundary or far from grain boundary) the energy distribution of field-emitted electrons for NC samples either have additional maximum or have one-peak form. On the basis of the theoretical analysis it supposed that due to formation Of NC structures (by means of severe plastic shear straining under quasi-hydrostatic pressure) paths of currents with low work function at grain boundaries can occur in metal. The work function was determined by electron-beam measurements of the contact potential difference. It has been revealed that the formation of a nanocrystalline structure results in a decrease in the electron work function of a metal. For tungsten with a grain size of about 100 nm, this decrease is equal to 0.8 V