The Mg doping efficiency is found to be drastically enhanced in the p-GaN films grown on the free-standing GaN substrates by metal organic chemical vapor deposition. The free hole concentrations are five and ten times higher in the lightly and heavily Mg-doped homoepitaxial p-GaN, respectively, than those in the p-GaN-on-GaN/sapphires grown and activated at the same conditions although the Mg incorporation concentrations {[Mg]} are much lower. The indication of the p-type conductivity in the photoluminescence spectra at room temperature in p-GaN-on-GaN substrates is found to be the dominant ultraviolet luminescence band located at around 3.26 eV. This behavior is different in the heteroepitaxial p-GaN, for which the fingerprint of the p-type conductivity is the emergence of blue luminescence bands at around 2.9 eV. The markedly enhanced activation efficiency is attributed to the suppression of self-compensation centers in the high-quality homoepitaxial films. The Mg-Ga-O disordered layer, which is typically observed on the surface of p-GaN-on-GaN/sapphires due to the Mg diffusion along edge-type dislocations, is also inhibited on the homoepitaxial p-GaN film, which is beneficial for the stable operation of the vertical-type metal-oxide-semiconductor field effect transistors.
This is a repository copy of Versailles Project on Advanced Materials and Standards interlaboratory study on intensity calibration for x-ray photoelectron spectroscopy instruments using low-density polyethylene.
We have observed images and local electron spectra of an oxide pattern on Si(100) using metastable electron emission microscopy (MEEM) recently developed at our laboratory. Low-energy electron microscopy (LEEM) was also used. For both MEEM and LEEM, the energy-filtered images were obtained for the first time. It was shown that MEEM gives the information on the outermost surface layer selectively, while LEEM provides averaged information on several surface layers. The intensity of the band in the local electron spectrum of MEEM can be related to the distribution of the relevant orbitals exposed outside the surface, with which metastable atoms interact effectively. Thus, using energy-filtered MEEM, we can observe the map reflecting the distribution of individual orbitals at the outermost surface layer.
We observed surface images of the Au islands periodically deposited on a Ta sheet by means of an energy-filtered XPEEM using a retarding Wien-filter energy analyzer and a high energy X-ray. By changing the passing photoelectron kinetic energy (Ekin), we had a brighter Au island image at the Ekin=0 eV and 60 eV while we had a brighter Ta substrate image at Ekin=102 eV, corresponding to a Ta 3p3/2 photoelectron peak.
We estimate how well we will know the parameters of solar neutrino oscillations after KamLAND and Borexino. The expected error on ∆m 2 is few per-mille in the VO and QVO regions, few per-cent in the LMA region, and around 10% in the LOW region. The expected error on sin 2 2θ is around 5%. KamLAND and Borexino will tell unambiguously which specific new measurement, dedicated to pp solar neutrinos, is able to contribute to the determination of θ and perhaps of ∆m 2 . The present data suggest as more likely outcomes: no measurement, or the total pp rate, or its day/night variation.
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