Effect of Strain on the Growth of InAs/GaSb Superlattices: An X-Ray Study

We present a detailed x-ray diffraction study of the strain in InAs/GaSb superlattices grown by molecular beam epitaxy. The superlattices were grown with either InSb or GaAs interfaces. We show that the superlattice morphology, either planar or nanostructured, is dependent on the chemical bonds at the heterointerfaces. In both cases, the misfit strain has been determined for the superlattice layers and the interfaces. We also determined how the magnitude and sign of this strain is crucial in governing the morphology of the superlattice. Our analysis suggests that the growth of self-assembled nanostructures may be extended to many systems generally thought to have too small a lattice mismatch.Comment: 40 pages, 14 figures, 2 tables. Submitted to Journal of Applied Physics in November 200

Corrosion and tribocorrosion behaviour of titanium nitride thin films grown on titanium under different deposition times

Ti and its alloys exhibit combination of unique properties for biomedical applications, however their poor tribo-electrochemical behaviour is a major concern. Therefore, TiN coatings were deposited on cp-Ti (grade 4) by sputtering technique aiming the improvement of its tribocorrosion behaviour. The properties of the coated samples, using different TiN deposition times, were characterized by using grazing incidence X-ray diffraction, FIB-SEM, and nanoindentation. The corrosion behaviour was studied by electrochemical impedance spectroscopy and potentiodynamic polarization in 9 g/L NaCl solution at body temperature. Tribocorrosion tests were employed under open circuit potential by using a ball-on-plate tribometer with 1 N normal load, 3 mm total stroke length, 1 Hz frequency, and 1800 s sliding duration. The results suggested that the TiN coatings deposited during 80 min presented better corrosion and tribocorrosion behaviour as compared to the bare metal and TiN coatings deposited during 30 min.This work is supported by FCT with the reference project UID/EEA/04436/2013, COMPETE 2020 with the code POCI-01-0145-FEDER-006941, and M-ERA-NET/0001/2015 (FAPESP proc. #2015/50.280-5) project. I. Caha grateful for financial support through PhD grant under NORTE-08-5369-FSE-000012 project. The authors would also like to acknowledge Dr. Paulo Ferreira and Dr. Enrique Carbo-Argibay (International Iberian Nanotechnology Laboratory) for the provision of FIB facilities, and Prof. Grata Minas (Universidade do Minho) for the provision of profilometry

Interband absorption edge in the topological insulators Bi-2(Te1-xSex)(3)

We have investigated the optical properties of thin films of topological insulators Bi2Te3, Bi2Se3, and their alloys Bi-2(Te1-x Se-x)(3) on BaF2 substrates by a combination of infrared ellipsometry and reflectivity in the energy range from 0.06 to 6.5 eV. For the onset of interband absorption in Bi2Se3, after the correction for the Burstein-Moss effect, we find the value of the direct band gap of 215 +/- 10 meV at 10 K. Our data support the picture that Bi2Se3 has a direct band gap located at the Gamma point in the Brillouin zone and that the valence band reaches up to the Dirac point and has the shape of a downward-oriented paraboloid, i.e., without a camel-back structure. In Bi2Te3, the onset of strong direct interband absorption at 10 K is at a similar energy of about 200 meV, with a weaker additional feature at about 170 meV. Our data support the recent GW band-structure calculations suggesting that the direct interband transition does not occur at the Gamma point but near the Z-F line of the Brillouin zone. In the Bi-2(Te1-x Se-x)(3) alloy, the energy of the onset of direct interband transitions exhibits a maximum near x = 0.3 (i.e., the composition of Bi2Te2Se), suggesting that the crossover of the direct interband transitions between the two points in the Brillouin zone occurs close to this composition

The change in capacity and service delivery at public and private hospitals in Turkey: A closer look at regional differences

<p>Abstract</p> <p>Background</p> <p>Substantial regional health inequalities have been shown to exist in Turkey for major health indicators. Turkish data on hospitals deserves a closer examination with a special emphasis on the regional differences in the context of the rapid privatization of the secondary or tertiary level health services.</p> <p>This study aims to evaluate the change in capacity and service delivery at public and private hospitals in Turkey between 2001-2006 and to determine the regional differences.</p> <p>Methods</p> <p>Data for this retrospective study was provided from Statistical Almanacs of Inpatient Services (2001-2006). Hospitals in each of the 81 provinces were grouped into two categories: public and private. Provinces were grouped into six regions according to a development index composed by the State Planning Organisation. The number of facilities, hospital beds, outpatient admissions, inpatient admissions (per 100 000), number of deliveries and surgical operations (per 10 000) were calculated for public and private hospitals in each province and region. Regional comparisons were based on calculation of ratios for Region 1(R1) to Region 6(R6).</p> <p>Results</p> <p>Public facilities had a fundamental role in service delivery. However, private sector grew rapidly in Turkey between 2001-2006 in capacity and service delivery. In public sector, there were 2.3 fold increase in the number of beds in R1 to R6 in 2001. This ratio was 69.9 fold for private sector. The substantial regional inequalities in public and private sector decreased for the private sector enormously while a little decrease was observed for the public sector. In 2001 in R1, big surgical operations were performed six times more than R6 at the public sector whereas the difference was 117.7 fold for the same operations in the same regions for the private sector. These ratios decreased to 3.6 for the public sector and 13.9 for the private sector in 2006.</p> <p>Conclusions</p> <p>The private health sector has grown enormously between 2001-2006 in Turkey including the less developed regions of the country. Given the fact that majority of people living in these underdeveloped regions are uninsured, the expansion of the private sector may not contribute in reducing the inequalities in access to health care. In fact, it may widen the existing gap for access to health between high and low income earners in these underdeveloped regions.</p

Nonmagnetic band gap at the Dirac point of the magnetic topological insulator Bi1 xMnx 2 Se3

Magnetic doping is expected to open a band gap at the Dirac point of topological insulators by breaking time-reversal symmetry and to enable novel topological phases. Epitaxial (Bi$_{1-x}$Mn$_{x}$)$_{2}$Se$_{3}$ is a prototypical magnetic topological insulator with a pronounced surface band gap of $\sim100$ meV. We show that this gap is neither due to ferromagnetic order in the bulk or at the surface nor to the local magnetic moment of the Mn, making the system unsuitable for realizing the novel phases. We further show that Mn doping does not affect the inverted bulk band gap and the system remains topologically nontrivial. We suggest that strong resonant scattering processes cause the gap at the Dirac point and support this by the observation of in-gap states using resonant photoemission. Our findings establish a novel mechanism for gap opening in topological surface states which challenges the currently known conditions for topological protection.Comment: 26 pages, 7 figure

Minimalist C/case

This article discusses A-licensing and case from a minimalist perspective, pursuing the idea that argument NPs cyclically enter a number of A-relations, rather than just a single one, resulting in event-licensing, case-licensing and phi-licensing. While argument case commonly reflects Voice/v-relations, canonical A-movement is driven by higher elements, either in the C-T system or in a superordinate v-system (in ECM constructions). In addition, there is a distinction to be drawn between the triggering of A-movement, by for example C, and the licensing of the landing site, by for instance T, C-probing leading to tucking-in into Spec-T. Much of the evidence presented comes from quirky case constructions in Icelandic and from ECM and raising constructions in Icelandic and English. It is argued that T in ECM constructions inherits phi-licensing from the matrix v, regardless of the case properties of v

Interband absorption edge in the topological insulators Bi 2 ( Te 1 − x Se x ) 3

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