Computational Prediction of an Antimony-Based n-Type Transparent Conducting Oxide: F-Doped Sb2O5.

Transparent conducting oxides (TCOs) possess a unique combination of optical transparency and electrical conductivity, making them indispensable in optoelectronic applications. However, their heavy dependence on a small number of established materials limits the range of devices that they can support. The discovery and development of additional wide bandgap oxides that can be doped to exhibit metallic-like conductivity are therefore necessary. In this work, we use hybrid density functional theory to identify a binary Sb(V) system, Sb2O5, as a promising TCO with high conductivity and transparency when doped with fluorine. We conducted a full point defect analysis, finding F-doped Sb2O5 to exhibit degenerate n-type transparent conducting behavior. The inherently large electron affinity found in antimony oxides also widens their application in organic solar cells. Following our previous work on zinc antimonate, this work provides additional support for designing Sb(V)-based oxides as cost-effective TCOs for a broader range of applications.

Limits to Hole Mobility and Doping in Copper Iodide.

Over one hundred years have passed since the discovery of the p-type transparent conducting material copper iodide, predating the concept of the "electron-hole" itself. Supercentenarian status notwithstanding, little is understood about the charge transport mechanisms in CuI. Herein, a variety of modeling techniques are used to investigate the charge transport properties of CuI, and limitations to the hole mobility over experimentally achievable carrier concentrations are discussed. Poor dielectric response is responsible for extensive scattering from ionized impurities at degenerately doped carrier concentrations, while phonon scattering is found to dominate at lower carrier concentrations. A phonon-limited hole mobility of 162 cm2 V-1 s-1 is predicted at room temperature. The simulated charge transport properties for CuI are compared to existing experimental data, and the implications for future device performance are discussed. In addition to charge transport calculations, the defect chemistry of CuI is investigated with hybrid functionals, revealing that reasonably localized holes from the copper vacancy are the predominant source of charge carriers. The chalcogens S and Se are investigated as extrinsic dopants, where it is found that despite relatively low defect formation energies, they are unlikely to act as efficient electron acceptors due to the strong localization of holes and subsequent deep transition levels.

Phase Quantification of Heterogeneous Surfaces Using DFT-Simulated Valence Band Photoemission Spectra.

Quantifying the crystallographic phases present at a surface is an important challenge in fields such as functional materials and surface science. X-ray photoelectron spectroscopy (XPS) is routinely employed in surface characterization to identify and quantify chemical species through core line analysis. Valence band (VB) spectra contain characteristic but complex features that provide information on the electronic density of states (DoS) and thus can be understood theoretically using density functional theory (DFT). Here, we present a method of fitting experimental photoemission spectra with DFT models for quantitative analysis of heterogeneous systems, specifically mapping the anatase to rutile ratio across the surface of mixed-phase TiO2 thin films. The results were correlated with mapped photocatalytic activity measured using a resazurin-based smart ink. This method allows large-scale functional and surface composition mapping in heterogeneous systems and demonstrates the unique insights gained from DFT-simulated spectra on the electronic structure origins of complex VB spectral features.

Computational Prediction and Experimental Realization of Earth-Abundant Transparent Conducting Oxide Ga-Doped ZnSb2O6.

Transparent conducting oxides have become ubiquitous in modern optoelectronics. However, the number of oxides that are transparent to visible light and have the metallic-like conductivity necessary for applications is limited to a handful of systems that have been known for the past 40 years. In this work, we use hybrid density functional theory and defect chemistry analysis to demonstrate that tri-rutile zinc antimonate, ZnSb2O6, is an ideal transparent conducting oxide and to identify gallium as the optimal dopant to yield high conductivity and transparency. To validate our computational predictions, we have synthesized both powder samples and single crystals of Ga-doped ZnSb2O6 which conclusively show behavior consistent with a degenerate transparent conducting oxide. This study demonstrates the possibility of a family of Sb(V)-containing oxides for transparent conducting oxide and power electronics applications.

Prediction and realisation of high mobility and degenerate p-type conductivity in CaCuP thin films.

Phosphides are interesting candidates for hole transport materials and p-type transparent conducting applications, capable of achieving greater valence band dispersion than their oxide counterparts due to the higher lying energy and increased size of the P 3p orbital. After computational identification of the indirect-gap semiconductor CaCuP as a promising candidate, we now report reactive sputter deposition of phase-pure p-type CaCuP thin films. Their intrinsic hole concentration and hole mobility exceed 1 × 1020 cm-3 and 35 cm2 V-1 s-1 at room temperature, respectively. Transport calculations indicate potential for even higher mobilities. Copper vacancies are identified as the main source of conductivity, displaying markedly different behaviour compared to typical p-type transparent conductors, leading to improved electronic properties. The optical transparency of CaCuP films is lower than expected from first principles calculations of phonon-mediated indirect transitions. This discrepancy could be partly attributed to crystalline imperfections within the films, increasing the strength of indirect transitions. We determine the transparent conductor figure of merit of CaCuP films as a function of composition, revealing links between stoichiometry, crystalline quality, and opto-electronic properties. These findings provide a promising initial assessment of the viability of CaCuP as a p-type transparent contact.

Angiogenesis as a novel component of inflammatory bowel disease pathogenesis.

BACKGROUND & AIMS: Angiogenesis is a critical component of neoplastic and chronic inflammatory disorders, but whether angiogenesis also occurs in inflammatory bowel disease (IBD) has yet to be established. We assessed mucosal vascularization, expression of endothelial alphaVbeta3 integrin, angiogenic factors, and their bioactivity in Crohn's disease (CD) and ulcerative colitis (UC) mucosa. METHODS: Mucosal endothelium was immunostained for CD31 and factor VIII and quantified by digital morphometry. alphaVbeta3 expression was studied in vivo by confocal microscopy and in vitro by flow cytometric analysis of human intestinal microvascular endothelial cells (HIMECs). Vascular endothelial growth factor (VEGF), interleukin (IL)-8, and bFGF levels were measured in mucosal extracts and cells and angiogenic bioactivity shown by induction of HIMEC migration and the corneal and chorioallantoic membrane angiogenesis assays. RESULTS: Microvessel density was increased in IBD mucosa. Endothelial alphaVbeta3 was strongly expressed in IBD but only sporadically in normal mucosa and was up-regulated in HIMECs by VEGF, tumor necrosis factor alpha, and bFGF. IBD mucosal extracts induced a significantly higher degree of HIMEC migration than control mucosa, and this response was mostly dependent on IL-8 and less on basic fibroblast growth factor or vascular endothelial growth factor. Compared with normal mucosa, IBD mucosal extracts induced a potent angiogenic response in both the corneal and chorioallantoic membrane assays. CONCLUSIONS: These results provide morphological, phenotypic and functional evidence of potent angiogenic activity in both CD and UC mucosa, indicating that the local microvasculature undergoes an intense process of inflammation-dependent angiogenesis. Thus, angiogenesis appears to be an integral component of IBD pathogenesis, providing the practical and conceptual framework for anti-angiogenic therapies in IBD.

Outcome of an optional HCV screening program for blood transfusion recipients in Ireland.

BACKGROUND: An optional (general) HCV testing program for blood and blood component recipients before the introduction of routine donor anti-HCV screening (October 1991) was launched in Ireland in 1995 to complement the targeted lookback program in progress at that time and to identify transfusion-transmitted hepatitis C. STUDY DESIGN AND METHODS: The public were informed of the opportunity to avail of screening by widespread media coverage. Screening was by an initial ELISA (Abbott 3.0, Abbott Laboratories) at the transfusion center laboratories. Reactive samples were referred to a virus reference laboratory where two additional ELISAs (Ortho 3.0, Ortho Clinical Diagnostics; and Murex 3.0, Murex) were performed. Confirmation of ELISA-positive samples was by a RIBA (RIBA 3.0, Chiron Corp.). All patients found to be anti-HCV- seropositive were tested for HCV RNA by PCR and were referred to a hepatologist. RESULTS: A total of 14,917 persons have been tested for hepatitis C in this program to date (85% women). Sixty-one people were confirmed positive for HCV by RIBA 3.0 (0.4%). Excluding persons with other risk factors (n = 15), the HCV positivity rate for blood component transfusion recipients (n = 46) was 0.3 percent. Of the 46 confirmed hepatitis C-positive blood component transfusion recipients, 32 were women (70%), 24 of whom received transfusion for obstetric or gynecologic indications (75%). Thirty-eight of 46 (83%) anti-HCV seropositive transfusion recipients tested had detectable HCV RNA by PCR. CONCLUSION: This program identified 46 transfusion recipients and 10 coagulation factor concentrate recipients, all of whom were previously unaware of their infection. The majority of HCV-positive transfusion recipients identified were women. This may reflect that women are longer living survivors of transfusion therapy or alternatively, in our experience, that Irish women perceive themselves at greater risk of hepatitis C because of the well-publicized association of this virus with recipients (women) of Irish RhIG.