We present a quantitative conduction model for nonalloyed ohmic contacts to n-type GaAs ~n:GaAs! which employ a surface layer of low-temperature-grown GaAs ~LTG:GaAs!. The energy band edge profile for the contact structure is calculated by solving Poisson’s equation and invoking Fermi statistics using deep donor band and acceptor state parameters for the LTG:GaAs which are consistent with measu...

We report scanning tunneling microscopy and scanning tunneling spectroscopy (STS) measurements of monolayer and bilayer WSe_{2}. We measure a band gap of 2.21±0.08  eV in monolayer WSe_{2}, which is much larger than the energy of the photoluminescence peak, indicating a large excitonic binding energy. We additionally observe significant electronic scattering arising from atomic-scale defects. U...

The band structure of matter determines its properties. In solids, it is typically mapped with angle-resolved photoemission spectroscopy, in which the momentum and the energy of incoherent electrons are independently measured. Sometimes, however, photoelectrons are difficult or impossible to detect. Here we demonstrate an all-optical technique to reconstruct momentum-dependent band gaps by expl...

A comparative study of surfaces prepared by sulfide passivation and by UHV cleaving using cross-sectional scanning tunneling microscopy and spectroscopy (XSTM/S) is performed. Test sample~ used include both GaAs/(AlGa)As heterojunctions and GaAs pn junctions. Sulfidepassivated heterojunction surfaces allow much useful electronic information to be deduced from the tunneling spectroscopy since th...

ScN(001) 1×1 surfaces have been prepared by growing ScN on MgO(001) using radio frequency molecular beam epitaxy. In-situ ultra-high vacuum scanning tunneling spectroscopy indicates that the Fermi level at the surface lies slightly above the Sc 3d conduction band edge, which is attributed to a downward band bending at the surface. In-situ scanning tunneling microscopy is used to image the Sc an...

We report in situ scanning tunneling microscopy studies of graphene growth on Pd(111) during ethylene deposition at temperatures between 723 and 1023 K. We observe the formation of monolayer graphene islands, 200-2000 A in size, bounded by Pd surface steps. Surprisingly, the topographic image contrast from graphene islands reverses with tunneling bias, suggesting a semiconducting behavior. Scan...

The effect of air exposure on 2H-WSe2/HOPG is determined via scanning tunneling microscopy (STM). WSe2 was grown by molecular beam epitaxy on highly oriented pyrolytic graphite (HOPG), and afterward, a Se adlayer was deposited in situ on WSe2/HOPG to prevent unintentional oxidation during transferring from the growth chamber to the STM chamber. After annealing at 773 K to remove the Se adlayer,...