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Article history:Received 13 June 2014Accepted 5 October 2014Available online 12 October 2014Keywords:Angle resolved photoemissionAlkali-metalCharge accumulationMolecular beam epitaxyInN surface “We present angle resolved photoemission study of quantized electron accumulation subbands obtained fromboth clean and potassium deposited InN(0001) surfaces. Shifting of the quantized accumulation states towardhigherbindingenergiesuponlowenergyN 2+ ionbombardmentorasmallamountofpotassiumadsorptionisex-plainedbythemodificationoftheIn-adlayerinducedsurfacestates.N 2+ ionbombardmentleadstoahigherden-sity of donor-type surface states by creating nitrogen vacancies near the surface. On the other hand, a smallamount of K adsorbates initially donate their free electron to InN and result in more pronounced downwardbandbending.Eventually,furtherKadsorptionleadstopassivation ofsurfacestatesandreduction ofthesurfaceelectron accumulation.With theincrease of the electron density, enhancedmany-body interactionsof electronswithin the electron accumulation layer are observed.”© 2014 Elsevier B.V. All rights reserved.

The electronic structure of wurtzite $\mathrm{In}\mathrm{N}(000\overline{1})$ thin films has been studied using a combination of soft x-ray emission and absorption spectroscopies. We measured the elementally and orbitally resolved InN valence and conduction bands by recording the N $K$-edge spectra. Theoretical calculations of the $\mathrm{N}\phantom{\rule{0.2em}{0ex}}2p$ partial density of states were performed within the GW framework of many body perturbation theory. Good agreement between the experimental spectra and the calculations was obtained, most notably with the energetic location of the $\mathrm{In}\phantom{\rule{0.2em}{0ex}}4d--\mathrm{N}\phantom{\rule{0.2em}{0ex}}2p$ hybridized state in the emission spectrum and the angular dependence of the absorption spectra.

Electron accumulation states in InN have been measured using high resolution angle-resolved photoemission spectroscopy (ARPES). The electrons in the accumulation layer have been discovered to reside in quantum well states. ARPES was also used to measure the Fermi surface of these quantum well states, as well as their constant binding energy contours below the Fermi level E(F). The energy of the Fermi level and the size of the Fermi surface for these quantum well states could be controlled by varying the method of surface preparation. This is the first unambiguous observation that electrons in the InN accumulation layer are quantized and the first time the Fermi surface associated with such states has been measured.

We report the development of large 50 mm diameter free standing wafers of GaN. GaN layers up to 350 /spl mu/m thick have been grown by HVPE on lattice-matched LiAlO/sub 2/ substrates. The original oxide substrates were removed by wet chemical etching, and the defect structure of the GaN wafers has been investigated. The issue of stacking faults vs. polar inversion domains has been resolved in favor of ABABACAC stacking sequences. A UV-emitting LED (368 nm) has been developed on these substrates, using molecular beam epitaxy.

Vitamin D (represented by D2 or D3) is considered essential for normal calcium homeostasis. It is either synthesized in the skin following ultraviolet-B irradiation of provitamin D3 (7-dehydrocholesterol), or ingested in the diet as vitamin D2 or vitamin D3. Most neotropical bats are nocturnal, roost in dark places, and consume diets that lack vitamin D and thus have no other known source of this important nutrient. A few species, namely fish-eating (piscivores) and blood-eating (sanguivores), however, have the potential to ingest large quantities of dietary vitamin D. In this study, blood serum collected from five nocturnal, neotropical bats (including three plant-visiting species, one fish-eating species and one blood-eating species), was analyzed using a competitive protein binding assay (CPBA) to determine concentrations of 25-hydroxyvitamin D [25(OH)D], the major circulating vitamin D metabolite. Caveroosting (absence of sunlight), plant-visiting species (Artibeus jamaicensis, Brachyphylla cavernarum...

The dispersion of the valence band within the electron accumulation layer of n-type has been directly measured using angle-resolved photoemission spectroscopy. Intermixing between the heavy-hole and light-hole valence bands in the intrinsic quantum well potential associated with the near-surface electron accumulation layer results in an inverted band structure, with the valence band maximum lying away from the Brillouin zone center. Such an inverted band structure has not previously been observed in an intrinsic accumulation layer.