Raising Tc in charge density wave superconductor ZrTe3 by Ni intercalation

We report discovery of bulk superconductivity in Ni0.05ZrTe3 at Tc = 3.1 K, obtained through Ni intercalation. Superconductivity coexists with charge density wave (CDW) state with TCDW = 41 K. When compared to parent material ZrTe3, filamentary superconducting transition is substantially increased whereas TCDW was suppressed. The analysis of superconducting state indicates that Ni0.05ZrTe3 is an intermediately coupled superconductor.Comment: 5 pages, 5 figure

Multi-residue enantioselective analysis of chiral drugs in freshwater sediments.

Pharmaceutical and illicit drugs are emerging contaminants found in the environment globally. Many are chiral and stereochemistry plays an important role on their environmental fate and effects. However, investigations at the enantiomeric level are limited, particularly for complex particulate matrices such as sediments. This is due to further sample processing requirements and a lack of suitable analytical methods. Therefore, here a new enantioselective methodology is proposed for 15 drugs in sediment. Sample treatment by accelerated solvent extraction and solid phase extraction was critical for subsequent enantioselective separations. Using liquid chromatography–tandem mass spectrometry, a Chiral-V enantioselective column enabled multi-residue separations of anti-depressants, beta-blockers, beta-agonist, anti-histamine and stimulants. Method trueness for all enantiomers was 86–121% and method quantitation limits were below 3 ng g−1 dry weight. Application of the method revealed the enantiomeric composition of fluoxetine, amphetamine, propranolol, venlafaxine and citalopram in sediment for the first time. All drugs except venlafaxine were present in non-racemic form, i.e. unequal enantiomer concentrations. This is significant considering drug toxicity towards benthic organisms could be enantiospecific

Interfacial and surface energetics of CoSi2

The energetics of the CoSi2‐Si interface and the CoSi2 surface have been investigated by analyzing the equilibrium shapes of isolated silicide precipitates. CoSi2 precipitates grown by heating 2 Å of Co on a clean, reconstructed Si{100} surface formed with a number of orientations that remained stable upon annealing to high temperatures. Precipitates buried by a Si capping layer were shown to form along {111} and {100} interfaces. A ratio of the CoSi2‐Si interfacial free energies has been measured from the shapes of a large number of buried precipitates indicating that γ{100}/γ{111}=1.43±0.07. It is suggested that the shape of CoSi2 equilibrated within vacuum consists of {111}, {100}, and {110} facets.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70558/2/JAPIAU-76-9-5190-1.pd

Surface roughening during low temperature Si(100) epitaxy

Reflection high energy electron diffraction (RHEED) was used to investigate surface roughening during low temperature Si(100) homoepitaxy. The use of RHEED allowed in situ real-time collection of structural information from the growth surface. RHEED patterns were analyzed using a simple kinematic diffraction model which related average surface roughness and average in-plane coherence lengths to the lengths and widths of individual RHEED diffraction features, respectively. These RHEED analyses were quantified by calibrating against cross-section transmission electron microscopy (TEM) analyses of surface roughening. Both the RHEED and TEM analyses revealed similar scaling of surface roughness with deposited thickness, with RHEED analyses resulting in roughness values a factor of ∼2 times lower than those obtained from TEM analyses. RHEED was then used to analyze surface roughening during Si(100) homoepitaxial growth in a range of temperatures, 200–275 °C. Initially, surface roughness increased linearly with deposited thickness at a roughening rate that decreased with increasing growth temperature. At each growth temperature, near the crystalline/amorphous Si phase transition, the rate of surface roughening decreased. This decrease coincided with the formation of facets and twins along Si{111} planes. Surface roughness eventually saturated at a value which followed an Arrhenius relation with temperature Eact ∼ 0.31±0.1Eact∼0.31±0.1 eV. This activation energy agrees well with the activation energy for the crystalline/amorphous Si phase transition, Eact ∼ 0.35Eact∼0.35 eV, and suggests that limited thickness epitaxy is characterized by this saturation roughness. Once the saturation roughness was reached, no significant changes in surface roughness were detected. In addition, the decay of average in-plane coherence lengths was also temperature dependent. Values of average coherence lengths, at the crystalline/amorphous Si phase transition, also increased with growth temperature. All of these data are consistent with a model that links surface roughening to the formation of critically sized Si{100} facets and the eventual breakdown in crystalline growth. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70948/2/JAPIAU-82-3-1157-1.pd

Effect of hydrogen on surface roughening during Si homoepitaxial growth

Hydrogen is shown to have a strong influence on the evolution of surface morphology during low temperature (310 °C) Si(100) homoepitaxy. Molecular beam epitaxy growth in the presence of deuterium shows a surface roughness within the epitaxial film that increases rapidly until the Si film exhibits a crystalline to amorphous transition. The rate at which the surface roughens depends critically on the partial pressure of deuterium. Although the kinetics of growth are sensitive to small pressures (4×10−8 Torr) of D, it appears that the breakdown of epitaxy does not result from a ‘‘critical’’ D concentration at the surface. This work suggests that the crystalline to amorphous transition, instead, results from increased roughening during epitaxy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71213/2/APPLAB-63-26-3571-1.pd

Nanoscale Equilibrium Crystal Shapes

The finite size and interface effects on equilibrium crystal shape (ECS) have been investigated for the case of a surface free energy density including step stiffness and inverse-square step-step interactions. Explicitly including the curvature of a crystallite leads to an extra boundary condition in the solution of the crystal shape, yielding a family of crystal shapes, governed by a shape parameter c. The total crystallite free energy, including interface energy, is minimized for c=0, yielding in all cases the traditional PT shape (z x3/2). Solutions of the crystal shape for c≠0 are presented and discussed in the context of meta-stable states due to the energy barrier for nucleation. Explicit scaled relationships for the ECS and meta-stable states in terms of the measurable step parameters and the interfacial energy are presented.Comment: 35 page

Global transition path search for dislocation formation in Ge on Si(001)

Global optimization of transition paths in complex atomic scale systems is addressed in the context of misfit dislocation formation in a strained Ge film on Si(001). Such paths contain multiple intermediate minima connected by minimum energy paths on the energy surface emerging from the atomic interactions in the system. The challenge is to find which intermediate states to include and to construct a path going through these intermediates in such a way that the overall activation energy for the transition is minimal. In the numerical approach presented here, intermediate minima are constructed by heredity transformations of known minimum energy structures and by identifying local minima in minimum energy paths calculated using a modified version of the nudged elastic band method. Several mechanisms for the formation of a 90{\deg} misfit dislocation at the Ge-Si interface are identified when this method is used to construct transition paths connecting a homogeneously strained Ge film and a film containing a misfit dislocation. One of these mechanisms which has not been reported in the literature is detailed. The activation energy for this path is calculated to be 26% smaller than the activation energy for half loop formation of a full, isolated 60{\deg} dislocation. An extension of the common neighbor analysis method involving characterization of the geometrical arrangement of second nearest neighbors is used to identify and visualize the dislocations and stacking faults

Mortality differences and inequalities within and between 'protected characteristics' groups, in a Scottish Cohort 1991-2009

Background: Little is known about the interaction between socio-economic status and 'protected characteristics' in Scotland. This study aimed to examine whether differences in mortality were moderated by interactions with social class or deprivation. The practical value was to pinpoint population groups for priority action on health inequality reduction and health improvement rather than a sole focus on the most deprived socioeconomic groups. Methods: We used data from the Scottish Longitudinal Study which captures a 5.3 % sample of Scotland and links the censuses of 1991, 2001 and 2011. Hazard ratios for mortality were estimated for those protected characteristics with sufficient deaths using Cox proportional hazards models and through the calculation of European age-standardised mortality rates. Inequality was measured by calculating the Relative Index of Inequality (RII). Results: The Asian population had a polarised distribution across deprivation deciles and was more likely to be in social class I and II. Those reporting disablement were more likely to live in deprived areas, as were those raised Roman Catholic, whilst those raised as Church of Scotland or as 'other Christian' were less likely to. Those aged 35-54 years were the least likely to live in deprived areas and were most likely to be in social class I and II. Males had higher mortality than females, and disabled people had higher mortality than non-disabled people, across all deprivation deciles and social classes. Asian males and females had generally lower mortality hazards than majority ethnic ('White') males and females although the estimates for Asian males and females were imprecise in some social classes and deprivation deciles. Males and females who reported their raised religion as Roman Catholic or reported 'No religion' had generally higher mortality than other groups, although the estimates for 'Other religion' and 'Other Christian' were less precise. Using both the area deprivation and social class distributions for the whole population, relative mortality inequalities were usually greater amongst those who did not report being disabled, Asians and females aged 35-44 years, males by age, and people aged <75 years. The RIIs for the raised religious groups were generally similar or too imprecise to comment on differences. Conclusions: Mortality in Scotland is higher in the majority population, disabled people, males, those reporting being raised as Roman Catholics or with 'no religion' and lower in Asians, females and other religious groups. Relative inequalities in mortality were lower in disabled than nondisabled people, the majority population, females, and greatest in young adults. From the perspective of intersectionality theory, our results clearly demonstrate the importance of representing multiple identities in research on health inequalities.Publisher PDFPeer reviewe

Historical trends of PBDEs and HBCDs in sediment cores from Sydney estuary, Australia

This paper presents the first historical data on the occurrence of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDs) in estuarine sediment from Australia. Sediment cores and surficial sediment samples were collected from four locations within Sydney estuary, Australia. Large increases in concentrations were observed for all compounds between 1980 and 2014, especially for BDE-209 (representative usage of Deca-BDE commercial mixture), which was found in surficial sediment at an average concentration of 42 ng/g thy wt (21-65 ng/g dry wt). PBDE congeners representative of both the Penta- and Octa-BDE commercial mixtures (Sigma 6PBDEs) were also found in their highest concentrations in surficial sediments (average: 1.3 ng/g dry wt; range: 0.65-2.5 ng/g dry wt). PBDE concentrations in surficial sediments were relatively high when compared with those presented in the available literature. This suggests that their input into the Sydney estuary has not decreased since their bans almost a decade earlier. After a sharp increase in the 1990s, HBCD concentrations peaked at an average of 3.5 ng/g dry wt (1.8-53 ng/g dry wt) in surficial samples. With global legislation on HBCDs allowing its usage for the next 10 years, it is expected that its input into the estuary is likely to continue. (C) 2015 Elsevier B.V. All rights reserved

Effect of H on Si molecular‐beam epitaxy

In Si crystal growth by molecular‐beam epitaxy (MBE) at low temperatures there is known to be an epitaxial thickness: an initially crystalline regime before the deposited film becomes amorphous. The predominant impurity in MBE is hydrogen, but the role of background H in low‐temperature MBE has not previously been assessed. Here the effect of deliberate dosing of the Si surface with atomic H during low‐T growth is studied. The epitaxial thickness is shown to be sensitive to very small additional H fluxes (≊10−9 Torr, i.e., an increase in H only marginally above ambient). With further increases in dose rate, the epitaxial thickness decreases as hepi=h0−k(ln PH). Using secondary‐ion‐mass spectrometry data on the segregated H at the interface, we argue that breakdown in epitaxy is not caused directly by the surface concentration of adsorbed impurities. It is deduced that very small concentrations of H may influence the Si surface diffusion rate. The possible effect of background H adsorption on previous experiments on Si steps and surface diffusion is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69704/2/JAPIAU-74-11-6615-1.pd