Surface band bending and surface defects on the UV-transparent conducting oxide β-Ga2O3 (100) are studied with hard x-ray photoemission spectroscopy and scanning tunneling microscopy. Highly doped β-Ga2O3 shows flat bands near the surface, while the bands on nominally undoped (but still n-type), air-cleaved β-Ga2O3 are bent upwards by ≳0.5 eV. Negatively charged surface defects are observed on vacuum annealed β-Ga2O3, which also shows upward band bending. Density functional calculations show oxygen vacancies are not likely to be ionized in the bulk, but could be activated by surface band bending. The large band bending may also hinder formation of ohmic contacts.

Single crystals of transition metal (TM) doped β–Ga2O3, a wide gap semiconductor system of interest for transparent conductive oxide and diluted magnetic semiconductor applications, have been studied in the dilute, non-interacting limit (≤0.06 cation %). Based on optical absorption, particle induced x-ray emission, and Rutherford backscattering measurements, Mn does not incorporate as well as Cr, and Mn degrades the crystal quality. Using superconducting quantum interference device (SQuID) magnetometry, a Brillouin type paramagnetic magnetization is observed for Mn or Cr doped crystals with an effective number of Bohr magnetons per TM ion of 5.88 ± 0.1 or 3.95 ± 0.1, respectively. A trace ferromagnetic signal is consistent with a very small concentration of secondary phases in the Mn-doped crystal. The position of the edge in x-ray absorption near edge structure (XANES) measurements suggests that the Cr takes the 3+ valence, while a mixture of Mn2+ and Mn3+ are present; based on the absence of a prominent pre-edge feature in the XANES, both TM predominantly occupy an octahedral site in β–Ga2O3. Density functional theory (DFT) results, optical absorption and SQuID data are consistent with this assignment. While the Cr-doped crystal is conductive, the Mn-doped crystal is insulating, which is consistent with the Mn2+/Mn3+ mixed valence, assuming the Fermi level is pinned mid-gap at the Mn 2+/3+ transition level, which is predicted by DFT to be 1.8 eV above the valence band maximum.

Articles you may be interested inDissolving, trapping and detrapping mechanisms of hydrogen in bcc and fcc transition metals AIP Advances 3, 012118 (2013); 10.1063/1.4789547 Atomic diffusion bonding of wafers with thin nanocrystalline metal films J. Vac. Sci. Technol. B 28, 706 (2010); 10.1116/1.3437515 Molecular simulation on interfacial structure and gettering efficiency of direct silicon bonded (110)/(100) substrates

Let ϕ(z) = (ϕ1(z),…,ϕn(z)) be a holomorphic self-map of B and ψ(z) a holomorphic function on B, where B is the unit ball of ℂn. Let 0 < p, s < +∞, -n - 1 < q < +∞, q+s > -1 and α ≥ 0, this paper characterizes boundedness and compactness of weighted composition operator Wψ,ϕ induced by ϕ and ψ between the space F(p, q, s) and α-Bloch space [Formula: see text].

Effective control of the dose of diffused phosphorus emitter profiles is crucial for optimization of crystalline silicon solar cells, but it requires detailed understanding of the POCl3 doping process. We measure concentration profiles within the deposited phosphosilicate glass (PSG) layer for a range of POCl3 doping conditions and find that (i) its composition is nearly independent of process conditions and (ii) it is separated from Si by a thin SiO2 layer. We also find strong accumulation of P at the SiO2-Si interface. As common linear-parabolic models cannot fully explain the observed kinetics of PSG thickness and phosphorus dose in Si, we present an improved model including oxygen depletion and dose saturation, giving a better explanation of the experimental data. In contrast to previous models that adjust the peak phosphorus concentration at the Si surface to match the measured profiles, our models accurately predict the time-dependent dose behavior under different experimental conditions. We further couple this growth model with previously reported phosphorus diffusion and deactivation models in silicon, providing full modeling of the POCl3 doping process.

6We have performed extensive analysis of the correlation factors for interstitial-mediated self-diffusion via various 7 possible mechanisms and hopping networks in the diamond lattice using the kinetic lattice Monte Carlo (KLMC) 8 approach. The correlation factor for the kick-out mechanism in the tetrahedral hopping network is calculated to be 9 0.73, in agreement with previous results; and the value for the hexagonal hopping network is 0.47 for the dominant 10 mechanism. For the mechanism where a split interstitial is stable ("stable-split" mechanism), the correlation factor 11 for the tetrahedral network stays the same while that for the hexagonal network increases to 0.62. We then 12 performed simulations for the diffusion process of silicon involving multiple mechanisms. The choice of 13 mechanisms is justified by ab initio calculations. We conclude that unlike vacancy diffusion, interstitial self-14 diffusion has a temperature dependent correlation factor. This conclusion holds in general for diffusion processes

Experiments and simulations are used to elucidate a new class of chemical reactions occurring near the tip-sample interface during high field chemistry of diphenylgermane. Current data during writing and bias dependent growth rate are analyzed, supplemented with data from ionization mass spectrometry, and compared with the simulation results.

A sensitive and specific IgG4 enzyme-linked immunosorbent assay (ELISA) with urine samples has been reported. To confirm elimination of bancroftian filariasis, the ELISA was used in a study conducted in Yongjia County and Gaoan City, People's Republic of China, where filariasis elimination was declared, with 10,409 students 5-16 years of age. The antibody positive rates were 0.08% in Yongjia and 0.34% in Gaoan. All positive samples were re-examined and found to be negative. Our results show that this ELISA is practical and useful for confirmation of the elimination of filariasis. If similar results are obtained in different filariasis-endemic countries, this method may be useful in global filariasis elimination programs.