The correlation between the atomic structure of semi-infinite plane surfaces and the electron work function j of crystalline metals is investigated for nine d transition metals. An (hkl)-dependent scalar parameter Dt, expressed in terms of the linear atomic and broken-bond densities, for metal surfaces treated as a plasma of free electrons and atomic cores, is used to linearly approximate j. A linear regression procedure employed yields a high correlation with mean values of experimental j for different planes of a given metal. Two structural ranges of j linearity are found. The trend of work-function variation known from theory and experiment is confirmed. A high correlation is also found for 2nd, 3rd, 4th, 1/2 and 3/2 powers of Dt. Polycrystalline j range from ca. 5.40 (Pt) through 4.90 (Re) and 4.52 (W) to ca. 4.13 eV (Ta), and the dipole term varies from 0.23 (W) to ca. 0.38 (Cu) or 0.17 eV (Re). Values of j for crystal planes which lack reported data are predicted.

Metal-lattice plasma is treated as a neutral two-component two-phase system of 2D surface and 3D bulk. Free electron density and bulk chemical potential are used as intensive parameters of the system with the phase boundary position determined in the crystalline lattice. A semiempirical expression for the electron screened electrostatic potential is constructed using the lattice-plasma polarization concept. It comprises an image term and three repulsion/attraction terms of second and fourth orders. The novel curve has two extremes and agrees with certain theoretical forms of potential. A practical formula for the electron work function of metals and a simplified schema of electronic structure at the metal/vacuum interface are proposed. This yields 10.44 eV for the Fermi energy of free electron gas; −5.817 eV for the Fermi energy level; 4.509 eV for the average work function of bcc tungsten. Selected data are also given for fcc Cu and hcp Re. For harmonic frequencies ∼ 10E16 per s of the self-excited metal-lattice plasma, energy gaps of 14.54 and 8.02 eV are found, which correspond to the bulk and surface plasmons, respectively. Further extension of this thermodynamics and metal-lattice theory based approach may contribute to a better understanding of theoretical models which are employed in chemical physics, catalysis and materials science of nanostructures.

No abstract

The surface of 6H-SiC(0001) samples was subjected to etching under H 2 /Ar gas mixture in a cold-wall tubular furnace. Its topography and properties were characterized by atomic force microscopy and X-ray photoelectron spectroscopy before and after hydrogen etching. The conditions have been found, under which surface polishing-related damages could be removed. Si droplets were observed under certain etching conditions. The effect of the samples' cooling rate on the obtained surface morphology and chemistry was investigated to unveil the mechanism of Si recrystallization onto the crystal surface upon etching.

No abstract