Oxygen Adsorption Induced Superconductivity in Ultrathin FeTe Film on SrTiO3(001)

The phenomenon of oxygen incorporation-induced superconductivity in iron telluride (Fe1+yTe, with antiferromagnetic (AFM) orders) is intriguing and quite different from the case of FeSe. Until now, the microscopic origin of the induced superconductivity and the role of oxygen are far from clear. Here, by combining in situ scanning tunneling microscopy/spectroscopy (STM/STS) and X-ray photoemission spectroscopy (XPS) on oxygenated FeTe, we found physically adsorbed O2 molecules crystallized into c (2/3 × 2) structure as an oxygen overlayer at low temperature, which was vital for superconductivity. The O2 overlayer were not epitaxial on the FeTe lattice, which implied weak O2 –FeTe interaction but strong molecular interactions. The energy shift observed in the STS and XPS measurements indicated a hole doping effect from the O2 overlayer to the FeTe layer, leading to a superconducting gap of 4.5 meV opened across the Fermi level. Our direct microscopic probe clarified the role of oxygen on FeTe and emphasized the importance of charge transfer effect to induce superconductivity in iron-chalcogenide thin films.

A Study on the Effect of SiC Reinforcement on the Surface and Tribological Behavior on Al-Metal Matrix Composites

Al matrix composites (Al-MMC) were reinforced with SiC and flyash particulate. The effects on the variation of SiC (5 %, 10 % and 15 %) were investigated by dry sliding method, whereas the flyash content was maintained at 14 %. Effect on the SiC on the mechanical and tribology was discussed in detail. Friction wear properties SiC reinforced was investigated. Coefficient of friction was estimated and is discussed for the various SiC compositions. Powder X-ray diffraction (XRD) was carried out to identify the homogeneous formation of the composites. Surface morphology was investigated by the use of optical microscope and scanning electron microscopic probe. Hardness of the prepared samples was subjected to Vickers microhardness test.