Changes in electron localization and density of states near E\u3csub\u3eF\u3c/sub\u3e across the nonmetal-metal transition in Mg overlayers

A nonmetal-to-metal transition in Mg monolayers on Mo(112) has been indicated by photoemission and resonant photoemission. The dramatic changes of the density of states, the dispersion of bands near EF, and screening are observed across the nonmetal-to-metal transition. The changes of the resonance photon energy and the intensity of Mg 2p→εd excitation, with different coverages, indicate that there exists a correlation between the electronic structure (particularly final-state screening effects) and the overlayer structure. The commensurate-to-incommensurate transition beyond 0.5 monolayer of coverage corresponds to the overlayer nonmetal-to-metal transition, which is due to the hybridization of Mg s and p bands and represents a transition from a localized (bondlike) to a delocalized (bandlike) phase for divalent atoms

Changes in electron localization and density of states near E\u3csub\u3eF\u3c/sub\u3e across the nonmetal-metal transition in Mg overlayers

A nonmetal-to-metal transition in Mg monolayers on Mo(112) has been indicated by photoemission and resonant photoemission. The dramatic changes of the density of states, the dispersion of bands near EF, and screening are observed across the nonmetal-to-metal transition. The changes of the resonance photon energy and the intensity of Mg 2p→εd excitation, with different coverages, indicate that there exists a correlation between the electronic structure (particularly final-state screening effects) and the overlayer structure. The commensurate-to-incommensurate transition beyond 0.5 monolayer of coverage corresponds to the overlayer nonmetal-to-metal transition, which is due to the hybridization of Mg s and p bands and represents a transition from a localized (bondlike) to a delocalized (bandlike) phase for divalent atoms

Changes in electron localization and density of states near E\u3csub\u3eF\u3c/sub\u3e across the nonmetal-metal transition in Mg overlayers

A nonmetal-to-metal transition in Mg monolayers on Mo(112) has been indicated by photoemission and resonant photoemission. The dramatic changes of the density of states, the dispersion of bands near EF, and screening are observed across the nonmetal-to-metal transition. The changes of the resonance photon energy and the intensity of Mg 2p→εd excitation, with different coverages, indicate that there exists a correlation between the electronic structure (particularly final-state screening effects) and the overlayer structure. The commensurate-to-incommensurate transition beyond 0.5 monolayer of coverage corresponds to the overlayer nonmetal-to-metal transition, which is due to the hybridization of Mg s and p bands and represents a transition from a localized (bondlike) to a delocalized (bandlike) phase for divalent atoms

Nickel doping of boron carbide grown by plasma enhanced chemical vapor deposition

We have nickel doped boron carbide grown by plasma enhanced chemical vapor deposition. The source gas closo-1,2-dicarbadodecaborane (ortho-carborane) was used to grow the boron carbide, while nickelocene [Ni(C5H5)2] was used to introduce nickel into the growing film. The doping of nickel transformed a p-type, B5C material, relative to lightly doped n-type silicon, to an n-type material. Both n-n heterojunction diodes and n-p heterojunction diodes were constructed, using as substrates n- and p-type Si(111), respectively. With sufficient partial pressures of nickelocene in the plasma reactor, diodes with characteristic tunnel diode behavior can be successfully fabricated

THE PARAMAGNETIC CORRELATION LENGTH OF Mn THIN FILMS

We have utilized Ginzberg-Landau mean field theory to analyze the branching ratio and soft X-ray magnetic circular dichroism measurements of the L3 and L2 adsorption edges of thin Mn overlayers on ferromagnetic fcc Co(001) at room temperature. We have determined a short range magnetic correlation of 4.25Å and that the long range magnetic order has a decay length of 1.29Å. These results indicate that the first monolayer of Mn ferromagnetically couple with the Co substrate. The paramagnetic Mn layer exhibits short range magnetic order, but lacks long range magnetic order. Due to the exponential decrease of both the branching ratio and dichroism signals, we have concluded that the magnetization of the Mn overlayer is substrate induced

Correlation between screening and electron effective mass across the nonmetal-metal transition in ultrathin films

Angle-resolved photoemission and resonant photoemission have been used to determine the relative changes of the electron effective mass and the screening parameter across the nonmetal to metal transition in the magnesium thin films on Mo(112). Both the screening length and the electron effective mass exhibit a gradual change with Mg coverage in the transition range between half and one monolayer. The relationship of these two different measures of metallicity is in surprisingly good agreement with the relationship predicted by theory for the Mott-Hubbard transition. Our results indicate the importance of electron-electron correlation within the overlayer

A novel design for a small retractable cylindrical mirror analyzer

In this paper we will review the performance of a “miniature” single pass cylindrical mirror analyzer (CMA) which we have used successfully in a variety of experiments. The underlying premise behind this CMA design was to minimize spatial requirements while maintaining an acceptable level of instrumental resolution. While we are presenting the results of a single pass cylindrical mirror analyzer, improvements on the present design, such as going to a double pass design, will undoubtedly improve the instrumental resolution

Strain-induced distortion of the bulk bands of gadolinium

Thin films of gadolinium, approximately 8 ML thick, have been grown on the corrugated (112) surface of molybdenum and the electronic structure has been investigated with angle-resolved photoelectron spectroscopy. The unfavorable lattice match between the ‘‘steplike’’ Mo(112) substrate and the preferred hexagonally ordered Gd film results in an incommensurate Gd structure that appears to be ordered, but strained along the direction of the corrugations. The hexagonal Gd lattice is expanded by more than 20% along the ‘‘step’’ lines of the substrate, as determined from the reduced Brillouin-zone size along the ΓΣM high-symmetry line and low-energy electron diffraction. The induced strain substantially alters the conventional Gd 5d/6s bulk bands to exhibit a dispersion opposite to that of the relaxed Gd(0001) structure. Dislocations destroy the long-range crystallographic order in the direction orthogonal to the corrugations, which results in the localization of the bands along the ΓTK symmetry line

Nickel doping of boron–carbon alloy films and corresponding Fermi level shifts

We have grown nickel doped boron–carbon alloy films by the technique of plasma enhanced chemical vapor deposition. The source gas closo-1,2-dicarbadodecaborane (orthocarborane) was used to grow the boron–carbon alloy, while nickelocene [Ni)C5H5)2] was used as the dopant source for nickel. With sufficient levels of Ni doping, diodes with characteristic tunnel diode behavior can be fabricated. The doping of nickel transformed a B5C p-type material, relative to lightly doped n-type silicon, to a strongly n-type material. In order to gain insight into the shift of the Fermi level of the Ni-doped material, we have examined the changes in the electronic structure of sodium doped films of the precursor molecule orthocarborane which has an icosahedral structure similar to that of boron–carbon materials. The establishment of unoccupied states at the Fermi level with Na doping of the orthocarborane films is consistent with the transformation of the p-type B5C to an n-typ