Search

AlN has been used as electrostatic chucks due to its high volume resistivity. It has been reported that the doping of MgO can further increase the volume resistivity even at high temperature. The enhancement was proposed to be correlated with its internal defects: inversion domain boundaries (IDBs), but the detailed mechanism is still not clear. In this study, we clarify the origin of increased volume resistivity from the atomic and electronic structures of the IDBs. We performed atomic-scale structural analysis of IDBs in MgO doped AlN using aberration corrected scanning transmission electron microscope (STEM) and energy dispersive X-ray spectroscopy (EDS). It was found that two types of IDBs coexist alternately in the MgO doped AlN, with strong segregation of Mg and O at both IDBs. Furthermore, band structure calculations were performed using the hybrid density functional theory (hybrid DFT) method, and it was found that the interfacial segregation of Mg and O may form a potential barrier at the IDB. These results suggest that the segregation of Mg and O at IDBs should be the origin of increased volume resistivity in the MgO doped AlN. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: One-electron capture and target-ionization cross-sections in collisions of He+ ions with neutral atoms: He+ +A→He+A+ and He+ +A→He+ +A+ + e, A=H, He(1s2, 1s2s), Ne, Ar, Kr, Xe, are calculated and compared with available experimental data over the broad energy range E =0.1keV/u–10MeV/u of He+ ions. The role of the metastable states of neutral helium atoms in such collisions, which are of importance in plasma physics applications, is briefly discussed. The recommended cross-section data for these processes are presented in a closed analytical form (nine-order polynomials) which can be used for a plasma modeling and diagnostics. [Copyright &y& Elsevier]

The interaction of hydrogen with tungsten is investigated by means of the Density Functional Theory (DFT) and statistical methods based on the transition-state theory and thermodynamics. This model yields temperature-dependent data that can help understanding macro-scale experimental results. Within this model, the concentrations of trapped hydrogen atoms at thermodynamic equilibrium are established. Taking into account the configurational entropy, hydrogen is shown to induce vacancy formation below 1000 K. Based on this model, TDS spectra are simulated with a basic kinetic model to provide some better insight into the desorption process of hydrogen. Finally, revised mechanisms for hydrogen diffusion in tungsten are proposed; we conclude that the discrepancy existing between the experimental diffusion coefficient measured by Frauenfelder (1969) and the one calculated by DFT would be reconciled provided one uses two different diffusion regimes that would depend on temperature and vacancies concentration. [ABSTRACT FROM AUTHOR]

Atomic energy levels and E2 and M1 transition rates are reported for the [Xe]4 f 11 ground configuration in Er 3+ from relativistic multiconfiguration Dirac–Hartree–Fock and configuration interaction calculations. The Breit transverse interaction and leading QED effects are included as perturbations. Different strategies for describing electron correlation effects are tested and evaluated. The calculated energy levels are compared with experiment and results from semi-empirical methods. [ABSTRACT FROM AUTHOR]

• Canine transitional cell carcinoma (cTCC) is invasive and metastatic. • Epithelial-mesenchymal transition contributed to tumour invasion and metastasis. • Expressions of mesenchymal cell markers were detected in cTCC tissues. • Higher expression of vimentin was significantly associated with poor prognosis. Canine transitional cell carcinoma (cTCC) is the most common malignant tumour in the urinary bladder: it is highly invasive and exhibits metastatic characteristics. Inflammation is also strongly related to cTCC. Epithelial tumours often exhibit a mesenchymal cell phenotype during tumour invasion and metastasis owing to epithelial-mesenchymal transition (EMT), which is often induced in chronic inflammation. The aim of this retrospective study was to investigate the expression of epithelial and mesenchymal cell markers in tumour cells and to evaluate its relationship with prognosis of cTCC. In this study, 29 dogs with cTCC who underwent surgical treatment were enrolled. Clinical parameters were reviewed using medical records. Tissue expression of epithelial and mesenchymal markers was evaluated by immunohistochemical analysis. The association between the expression of mesenchymal cell markers and clinical parameters, including prognosis, was statistically examined. In five normal bladder tissues used as controls, no expression of mesenchymal markers was observed, except for one tissue that expressed fibronectin. Conversely, epithelial tumour cells expressed vimentin and fibronectin in 23/29 and 19/28 cTCC tissues, respectively. Regarding clinical parameters, vimentin score in Miniature Dachshunds was significantly higher than those in other dog breeds (P < 0.001). Multivariate survival analyses revealed that age>12 years was related to shorter progression-free survival (P = 0.02). Higher vimentin score, lower fibronectin score, and advanced clinical T stage were significantly correlated with shorter median survival time (P < 0.05). The results of this study indicate that vimentin expression was associated with cTCC progression. Further studies are needed to examine the incidence and relevance of EMT in cTCC. [ABSTRACT FROM AUTHOR]

• Chemical states of well-defined ultrathin hafnium film on Si(111) were evaluated by core-level photoelectron spectroscopy of Si 2 p 1/2, 3/2 and Hf 4 f 5/2, 7/2 levels. • Surface images were taken after annealing with a scanning electron microscope. • Ultrathin Hf layers grow on clean Si(111)-7 × 7 surfaces by a lever rule that the first phase is not consumed when subsequent phases form. • Small dot-shaped islands of HfSi 2 appeared after annealing two-monolayer Hf sample. • Rectangular HfSi 2 islands appeared after annealing six-monolayer Hf sample. Herein, well-defined ultrathin hafnium films on Si(111) -7 × 7 [Hf/Si(111)] were prepared by using electron beam heating in an ultrahigh vacuum (UHV) chamber at a pressure below 1.1 × 10−8 Pa. High-resolution core-level photoelectron spectroscopy of the Si 2 p 1/2, 3/2 and Hf 4 f 5/2, 7/2 levels combined with a synchrotron radiation X-ray light source was employed to reveal the chemical states at the interface and surface of ultrathin Hf/Si(111) films. Ultrathin Hf layers grow on clean Si(111)-7 × 7 surfaces by a lever rule that the first phase is not consumed when subsequent phases form. Therefore, it was found that the surface and interface of Hf/Si(111) certainly contains three components, which can be ascribed as metallic Hf layers, Hf monosilicide (HfSi), and Si-rich Hf silicide just above the Si substrate (HfSi 4). The metallic Hf layers were observed to comprise some diffused Si atoms. According to the results obtained from photoelectron spectroscopy and scanning electron microscopy, ultrathin Hf layers change into HfSi 2 islands on a bare Si(111)-7 × 7 surface after annealing at 1073 K. Small dot-shaped islands of HfSi 2 appeared after annealing a two-monolayer thick Hf sample; whereas, rectangular HfSi 2 islands including metallic Hf species randomly appeared after annealing a six-monolayer thick Hf sample. The long axes of the rectangle islands expanded in a direction that connected the corner holes in a model with dimers, adatoms, and stacking-faults (DAS model) of a clean Si(111)-7 × 7 surface. Our precise chemical analyses will be very useful for preparing well-defined interfaces and surface structures for obtaining next generation 3D metal-oxide-semiconductor field effect transistors and ferroelectric devices. Image, graphical abstract [ABSTRACT FROM AUTHOR]