The Surface Electronic Microstructure Of Bulk Nanocrystalline Metal Materials

In this paper, X-ray Photoelectron Spectroscopy (XPS), Ultraviolet Photoelectron Spectroscopy (UPS), and XPS valence band spectra experiments were carried with the ESCALAB250 multifunction surface analysis system, and characterized the surface electronic microstructure after Ar~+ sputtering for different intervals of bulk nanocrystalline SS304(BN-SS304) and conventional polycrystalline SS304 (CP-SS304), and the surface electronic microstructure were preliminarily characterized by that system for bulk nanocrystalline industrial pure iron and aluminum.The XPS results of BN-SS304 and CP-SS304 indicated that the surface after Ar~+ sputtering for 150 seconds was the clean surface; there were the same kinds of energy states of C and O elements, and the different binding energy of energy states for BN-SS304 and CP-SS304; The XPS areas of C and O elements indicated that the surface states intensity of BN-SS304 was lower than that of CP-SS304; the binding energys of metal elements on clean BN-SS304 surface were different from that of CP-SS304 indicating that the metal elements binding strength of the valence electrons changed after the nanocrystallization.The UPS results of the natural surface and after Ar~+ sputtering for 300 seconds of BN-SS304 and CP-SS304 indicated that there were flat energy band on the surface after Ar~+ sputtering 300 seconds, the energy band of the natural surface appeared to be bended, and the bend amplitude of the energy band for BN-SS304 natural surface was smaller than that of CP-SS304; the natural surface activation energy respectively reduced by 0.17 eV and 0.77 eV , and thus the natural surface work function of BN-SS304 and CP-SS304 increased by 0.17eV and 0.77eV , respectively.The XPS valence band results of BN-SS304 and CP-SS304 surfaces after Ar~+ sputtering for different intervals indicated that the surface Fermi level of BN-SS304 had been moving down until it had a stable state, and the surface Fermi level of CP-SS304 had been moving down then moving up until it had a stable state with the Ar~+ sputtering intervals increases.The XPS results of the bulk nanocrystalline metal and their conventional polycrystalline counterparts indicated that the surface photoelectric yield of natural and clean surface for bulk nanocrystalline metal were lower than their conventional polycrystalline counterparts.The characterization of surface eletronic microstructure with UPS and XPS could systematically analyze the difference of the possible reasons and mechanism from the bulk nanocrystalline metals and their conventional polycrystalline counterparts, and provide the experimental basis of the future work to further study the surface physical properties and chemical properties of the bulk nanocrystalline metal.