Origin of the emergence of higher T c than bulk in iron chalcogenide thin films

Fabrication of epitaxial FeSe_xTe_1−x thin films using pulsed laser deposition (PLD) enables improving their superconducting transition temperature (T_c) by more than ~40% than their bulk T_c. Intriguingly, T_c enhancement in FeSe_xTe_1−x thin films has been observed on various substrates and with different Se content, x. To date, various mechanisms for T_c enhancement have been reported, but they remain controversial in universally explaining the T_c improvement in the FeSe_xTe_1−x films. In this report, we demonstrate that the controversies over the mechanism of T_c enhancement are due to the abnormal changes in the chalcogen ratio (Se:Te) during the film growth and that the previously reported T_c enhancement in FeSe_0.5Te_0.5 thin films is caused by a remarkable increase of Se content. Although our FeSe_xTe_1−x thin films were fabricated via PLD using a Fe_0.94Se_0.45Te_0.55 target, the precisely measured composition indicates a Se-rich FeSe_xTe_1−x (0.6 < x < 0.8) as ascertained through accurate compositional analysis by both wavelength dispersive spectroscopy (WDS) and Rutherford backscattering spectrometry (RBS). We suggest that the origin of the abnormal composition change is the difference in the thermodynamic properties of ternary FeSe_xTe_1−x, based on first principle calculations.

Effect of titanium carbide coating on the osseointegration response in vitro and in vivo

Titanium has limitations in its clinical performance in dental and orthopaedic applications. This study describes a coating process using pulsed laser deposition (PLD) technology to produce surfaces of titanium carbide (TiC) on titanium substrates and evaluates the biological response both in vitro and in vivo. X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of 18.6-21.5% TiC in the surface layer, accompanied by oxides of titanium 78.5-81.4% in the following concentrations: 11.1-13.0% Ti(2)O(3), 50.8-55.8% TiO(2), 14.5-14.7% TiO. Expression of genes central to osteoblast differentiation (alkaline phosphatase, A2 pro-collagen type 1, osteocalcin, BMP-4, TGFbeta and Cbfa-1) were up-regulated in all cell lines (primary human osteoblasts, hFOB1.19 and ROS.MER#14) grown on TiC compared with uncoated titanium when measured by semiquantitative PCR and real time-PCR, whilst genes involved in modulation of osteoclastogenesis and osteoclast activity (IL-6 and M-CSF) were unchanged. Bone density was shown to be greater around TiC-coated implants after 2 and 4 weeks in sheep and both 4 and 8 weeks in rabbits compared to uncoated titanium. Rapid bone deposition was demonstrated after only 2 weeks in the rabbit model when visualized with intravital staining. It is concluded that coating with TiC will, in comparison to uncoated titanium, improve implant hardness, biocompatibility through surface stability and osseointegration through improved bone growth.