Resonant Ta Doping for Enhanced Mobility in Transparent Conducting SnO2

Transparent conducting oxides (TCOs) are ubiquitous in modern consumer electronics. SnO2 is an earth abundant, cheaper alternative to In2O3 as a TCO. However, its performance in terms of mobilities and conductivities lags behind that of In2O3. On the basis of the recent discovery of mobility and conductivity enhancements in In2O3 from resonant dopants, we use a combination of state-of-the-art hybrid density functional theory calculations, high resolution photoelectron spectroscopy, and semiconductor statistics modeling to understand what is the optimal dopant to maximize performance of SnO2-based TCOs. We demonstrate that Ta is the optimal dopant for high performance SnO2, as it is a resonant dopant which is readily incorporated into SnO2 with the Ta 5d states sitting ∼1.4 eV above the conduction band minimum. Experimentally, the band edge electron effective mass of Ta doped SnO2 was shown to be 0.23m0, compared to 0.29m0 seen with conventional Sb doping, explaining its ability to yield higher mobilities and conductivities

Measurement of arsenic compounds in water by HPLC-ICP-MS

This report provides a brief introduction to the application of high-pressure liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICP-MS) to determine the concentration of various arsenic species in water samples. It describes the validation of this arsenic speciation method developed under the Laboratory Maintenance and Development Capability Programme to provide data on arsenic speciation in a range of challenging sample matrices to support BGS science projects and university collaborative research projects. The validation was carried out in two stages. Firstly, the chromatographic conditions for separating five arsenic species and coupling of the HPLC to the ICP-MS instrument for subsequent measurement of arsenic at mass 75 were optimised, together with establishing the stability of standards and reagents. Once the methodology had been optimised, validation data were obtained based on the method of Cheeseman and Wilson (Cheeseman & Wilson, 1989). The measurement of arsenobetaine (AB) and dimethylarsinous acid (DMA) by the proposed methodology provided good performance data with respect to certified values for the certified reference material NIES CRM 18 human urine. Performance data obtained for spiked low and high TDS solutions was generally within acceptance criteria outlined in the validation plan (Appendix 1) for all of the arsenic species