Defect detection in nano-scale transistors based on radio-frequency reflectometry

Radio-frequency reflectometry in silicon single-electron transistors (SETs) is presented. At low temperatures (<4 K), in addition to the expected Coulomb blockade features associated with charging of the SET dot, quasi-periodic oscillations are observed that persist in the fully depleted regime where the SET dot is completely empty. A model, confirmed by simulations, indicates that these oscillations originate from charging of an unintended floating gate located in the heavily doped polycrystalline silicon gate stack. The technique used in this experiment can be applied for detailed spectroscopy of various charge defects in nanoscale SETs and field effect transistorsComment: 3 pages, 3 figure

Dopant effects on the photoluminescence of interstitial-related centers in ion implanted silicon

The dopant dependence of photoluminescence(PL) from interstitial-related centers formed by ion implantation and a subsequent anneal in the range 175–525 °C is presented. The evolution of these centers is strongly effected by interstitial-dopant clustering even in the low temperature regime. There is a significant decrease in the W line (1018.2 meV) PL intensity with increasing B concentration. However, an enhancement is also observed in a narrow fabrication window in samples implanted with either P or Ga. The annealtemperature at which the W line intensity is optimized is sensitive to the dopant concentration and type. Furthermore, dopants which are implanted but not activated prior to low temperature thermal processing are found to have a more detrimental effect on the resulting PL. Splitting of the X line (1039.8 meV) arising from implantation damage induced strain is also observed.This work is supported by a grant from the Australian Research Council. B.C.J. is partially supported by the Japan Society for the Promotion of Science (JSPS) (Grant-in-aid for Scientific Research, 22.00802)

2D-3D crossover in a dense electron liquid in silicon

Doping of silicon via phosphene exposures alternating with molecular beam epitaxy overgrowth is a path to Si:P substrates for conventional microelectronics and quantum information technologies. The technique also provides a new and well-controlled material for systematic studies of two-dimensional lattices with a half-filled band. We show here that for a dense ($n_s=2.8\times 10^{14}$\,cm$^{-2}$) disordered two-dimensional array of P atoms, the full field angle-dependent magnetostransport is remarkably well described by classic weak localization theory with no corrections due to interaction effects. The two- to three-dimensional cross-over seen upon warming can also be interpreted using scaling concepts, developed for anistropic three-dimensional materials, which work remarkably except when the applied fields are nearly parallel to the conducting planes.Comment: 9 pages, 4 figures, supplementary informatio

Form III-like conformation and Form I-like packing in a chloroform channel solvate of the diuretic drug chlortalidone

Chlortalidone (CTD) is an antihypertensive drug for which only two solid state phases have been structurally elucidated thus far. Here, we have prepared a chloroform solvate thereof, namely, CTD Form IV, and its structure was compared to those of Form I and Form III. Its two conformers exhibit a dual structural feature in relation to the antecedent polymorphs. Both CTD molecules of Form IV adopt a Form III-like conformation, which is featured, if the conformation of CTD Form I is used as a reference, by a rotation of about 90 degrees on the axis of the C-C bond bridging the substituted benzene and isoindolinyl rings. However, CTD Form IV assembles as in the Form I crystal packing despite the different stacking fashion of their centrosymmetric dimers. In contrast to Form I, there is no offset stacking in Form IV, which forces a bend of ca. 24 degrees between the planes passing through the isoindolinyl moieties of two [100]-stacked dimers. Chloroform molecules at a maximum stoichiometry of 0.25 mol per mol of the drug play a stabilizing role in the assembly of Form IV by filling the channels formed on the crystals.FAPEMIG [APQ-02685-09, APQ-01093-10]FAPEMIGFINEPFINEP [134/08]CAPESCAPES [AUXPE-PNPD 1865/2008]CNPqCNPq [472623/2011-7, 476870/2011-9

Factors influencing success in quality-improvement collaboratives: development and psychometric testing of an instrument

Contains fulltext : 88630.pdf (publisher's version ) (Open Access)ABSTRACT: BACKGROUND: To increase the effectiveness of quality-improvement collaboratives (QICs), it is important to explore factors that potentially influence their outcomes. For this purpose, we have developed and tested the psychometric properties of an instrument that aims to identify the features that may enhance the quality and impact of collaborative quality-improvement approaches. The instrument can be used as a measurement instrument to retrospectively collect information about perceived determinants of success. In addition, it can be prospectively applied as a checklist to guide initiators, facilitators, and participants of QICs, with information about how to perform or participate in a collaborative with theoretically optimal chances of success. Such information can be used to improve collaboratives. METHODS: We developed an instrument with content validity based on literature and the opinions of QIC experts. We collected data from 144 healthcare professionals in 44 multidisciplinary improvement teams participating in two QICs and used exploratory factor analysis to assess the construct validity. We used Cronbach's alpha to ascertain the internal consistency. RESULTS: The 50-item instrument we developed reflected expert-opinion-based determinants of success in a QIC. We deleted nine items after item reduction. On the basis of the factor analysis results, one item was dropped, which resulted in a 40-item questionnaire. Exploratory factor analysis showed that a three-factor model provided the best fit. The components were labeled 'sufficient expert team support', 'effective multidisciplinary teamwork', and 'helpful collaborative processes'. Internal consistency reliability was excellent (alphas between .85 and .89). CONCLUSIONS: This newly developed instrument seems a promising tool for providing healthcare workers and policy makers with useful information about determinants of success in QICs. The psychometric properties of the instrument are satisfactory and warrant application either as an objective measure or as a checklist

Understanding resonant charge transport through weakly coupled single-molecule junctions

Off-resonant charge transport through molecular junctions has been extensively studied since the advent of single-molecule electronics and it is now well understood within the framework of the non-interacting Landauer approach. Conversely, gaining a qualitative and quantitative understanding of the resonant transport regime has proven more elusive. Here, we study resonant charge transport through graphene-based zinc-porphyrin junctions. We experimentally demonstrate an inadequacy of the non-interacting Landauer theory as well as the conventional single-mode Franck-Condon model. Instead, we model the overall charge transport as a sequence of non-adiabatic electron transfers, the rates of which depend on both outer and inner-sphere vibrational interactions. We show that the transport properties of our molecular junctions are determined by a combination of electron-electron and electron-vibrational coupling, and are sensitive to the interactions with the wider local environment. Furthermore, we assess the importance of nuclear tunnelling and examine the suitability of semi-classical Marcus theory as a description of charge transport in molecular devices.Comment: version accepted in Nature Communications; SI available at https://researchportal.hw.ac.uk/en/publications/understanding-resonant-charge-transport-through-weakly-coupled-s

Corrigendum: Coherent creation and destruction of orbital wavepackets in Si:P with electrical and optical read-out

The ability to control dynamics of quantum states by optical interference, and subsequent electrical read-out, is crucial for solid state quantum technologies. Ramsey interference has been successfully observed for spins in silicon and nitrogen vacancy centres in diamond, and for orbital motion in InAs quantum dots. Here we demonstrate terahertz optical excitation, manipulation and destruction via Ramsey interference of orbital wavepackets in Si:P with electrical read-out. We show milliradian control over the wavefunction phase for the two-level system formed by the 1s and 2p states. The results have been verified by all-optical echo detection methods, sensitive only to coherent excitations in the sample. The experiments open a route to exploitation of donors in silicon for atom trap physics, with concomitant potential for quantum computing schemes, which rely on orbital superpositions to, for example, gate the magnetic exchange interactions between impurities

Brain-behaviour modes of covariation in healthy and clinically depressed young people.

Understanding how variations in dimensions of psychometrics, IQ and demographics relate to changes in brain connectivity during the critical developmental period of adolescence and early adulthood is a major challenge. This has particular relevance for mental health disorders where a failure to understand these links might hinder the development of better diagnostic approaches and therapeutics. Here, we investigated this question in 306 adolescents and young adults (14-24 y, 25 clinically depressed) using a multivariate statistical framework, based on canonical correlation analysis (CCA). By linking individual functional brain connectivity profiles to self-report questionnaires, IQ and demographic data we identified two distinct modes of covariation. The first mode mapped onto an externalization/internalization axis and showed a strong association with sex. The second mode mapped onto a well-being/distress axis independent of sex. Interestingly, both modes showed an association with age. Crucially, the changes in functional brain connectivity associated with changes in these phenotypes showed marked developmental effects. The findings point to a role for the default mode, frontoparietal and limbic networks in psychopathology and depression.Wellcome Trus