X-ray photoelectron spectroscopy measurement of valence-band offsets for Mg-based semiconductor compounds

We have used x-ray photoelectron spectroscopy to measure the valence-band offsets for the lattice matched MgSe/Cd0.54Zn0.46Se and MgTe/Cd0.88Zn0.12Te heterojunctions grown by molecular beam epitaxy. By measuring core level to valence-band maxima and core level to core level binding energy separations, we obtain values of 0.56+/-0.07 eV and 0.43+/-0.11 eV for the valence-band offsets of MgSe/Cd0.54Zn0.46Se and MgTe/Cd0.88Zn0.12Te, respectively. Both of these values deviate from the common anion rule, as may be expected given the unoccupied cation d orbitals in Mg. Application of our results to the design of current II-VI wide band-gap light emitters is discussed

Queer Representation and Public Pedagogy in American Musical Theatre

This paper explores the Broadway musical as a site of queerness and queer representation through the lens of queer public pedagogy

Refining Outreach to Woodland Owners in West Virginia--Preferred Topics and Assistance Methods

Four hundred and fourteen private forest landowners in West Virginia responded to a questionnaire assessing their forest management assistance topics and delivery methods of interest. Logistic regression was used to analyze 39 independent variables in relation to the dependent variables of wanting a specific topic of forestry assistance or not. Ownership of property for investment, cultivation of wildlife food crops, and receiving assistance from the West Virginia State Division of Forestry were recurrent significant variables characterizing landowners wanting a specific assistance topic. These results can be used to develop forestry assistance programs that achieve landowner objectives and good forest management

Accommodation of lattice mismatch in Ge_(x)Si_(1−x)/Si superlattices

We present evidence that the critical thickness for the appearance of misfit defects in a given material and heteroepitaxial structure is not simply a function of lattice mismatch. We report substantial differences in the relaxation of mismatch stress in Ge_(0.5)Si_(0.5)/Si superlattices grown at different temperatures on (100) Si substrates. Samples have been analyzed by x‐ray diffraction, channeled Rutherford backscattering, and transmission electron microscopy. While a superlattice grown at 365 °C demonstrates a high degree of elastic strain, with a dislocation density <10^5 cm^(−2) , structures grown at higher temperatures show increasing numbers of structural defects, with densities reaching 2×10^(10) cm^(−2) at a growth temperature of 530 °C. Our results suggest that it is possible to freeze a lattice‐mismatched structure in a highly strained metastable state. Thus it is not surprising that experimentally observed critical thicknesses are rarely in agreement with those predicted by equilibrium theories

Chemisorption of Al and Ga on the GaAs (110) surface

We have studied the initial stages of the chemisorption of Al and Ga on the clean GaAs (110) surface by applying quantum chemical methods to small clusters representing Al or Ga on GaAs (110). These calculations suggest that at smallest coverages Al or Ga bind to a surface Ga atom; for higher coverages Al and the surface Ga interchange positions. We have obtained the binding energy, the chemical shifts of the Ga–3d, As–3d and Al–2p states, and the microscopic dipole associated with chemisorption of Al or Ga on GaAs (110). These results are compared to experimental values and further experiments are suggested

Charge order, dynamics, and magneto-structural transition in multiferroic LuFe2_2O4_4

We investigated the series of temperature and field-driven transitions in LuFe$_2$O$_4$ by optical and M\"{o}ssbauer spectroscopies, magnetization, and x-ray scattering in order to understand the interplay between charge, structure, and magnetism in this multiferroic material. We demonstrate that charge fluctuation has an onset well below the charge ordering transition, supporting the "order by fluctuation" mechanism for the development of charge order superstructure. Bragg splitting and large magneto optical contrast suggest a low temperature monoclinic distortion that can be driven by both temperature and magnetic field.Comment: 4 pages, 3 figures, PRL in prin

Ohmic contacts to n-type GaAs

We present a model of the metal–semiconductor junction, for heavily doped GaAs, so that tunneling dominates the current. It is assumed that the imaginary part of the wave vector in the semiconductor is given by the two-band model. Modifications in the barrier potential due to image charge, negative charge near the interface, and the degenerate doping of the semiconductor are included. The role of the L-point minimum in the GaAs in determining the position of the Fermi level in the semiconductor is included. The energy distribution of the conductance as a function of doping and barrier height is given. The contact resistance as a function of doping and barrier height is also presented. The results suggest that previous calculations are substantially in error due to the simple models that were used for the dependence of the imaginary part of the wave vector on energy

Finite-size effects in two-dimensional continuum percolation

We have investigated the finite-size effects of anisotropic continuum percolation in two dimensions. The elements that percolate are widthless sticks. We have developed a simple theory to explain the dependence of longitudinal and transverse critical lengths on anisotropy and the finite number of sticks in the sample. By comparing the theory to simulations, we find good agreement