We present tunneling spectroscopy measurements that directly reveal the existence of a superconducting gap in the insulating state of homogenously disordered amorphous indium oxide films. Two films on both sides of the disorder induced superconductor to insulator transition show the same energy gap scale. This energy gap persists up to relatively high magnetic fields and is observed across the magnetoresistance peak typical of disordered superconductors. The results provide useful information for understanding the nature of the insulating state in the disorder induced superconductor to insulator transition.

We present the results of a magnetoresistance study of the disorder-induced superconductor-insulator transition in an amorphous indium-oxide thin film patterned by a nanoscale periodic array of holes. We observed Little-Parks-like oscillations over our entire range of disorder spanning the transition. The period of oscillations was unchanged and corresponded to the superconducting flux quantum in the superconducting as well as in the insulating phases. Our results provide direct evidence for electron pairing in the insulator bordering with superconductivity.

We present the concept of magnetic gas detection by the Extraordinary Hall effect (EHE). The technique is compatible with the existing conductometric gas detection technologies and allows simultaneous measurement of two independent parameters: resistivity and magnetization affected by the target gas. Feasibility of the approach is demonstrated by detecting low concentration hydrogen using thin CoPd films as the sensor material. The Hall effect sensitivity of the optimized samples exceeds 240% per 104 ppm at hydrogen concentrations below 0.5% in the hydrogen/nitrogen atmosphere, which is more than two orders of magnitude higher than the sensitivity of the conductance detection

A recent report of ferromagnetism appearing in silicon after etching in hot KOH (Kopnov et al., Adv. Mater. 2007, 19, 925) is shown to be due to iron from the pyrex glassware, which precipitates on the silicon surface in the form of well‐separated ferromagnetic nanoparticles. The reaction is explained in terms of the Pourbaix diagram.

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Tilted off-plane magnetic anisotropy induces two unusual characteristic magnetotransport phenomena: extraordinary Hall effect in the presence of an in-plane magnetic field, and non-monotonic anisotropic magnetoresistance in the presence of a field normal to the sample plane. We show experimentally that these effects are generic, appearing in multiple ferromagnetic systems with tilted anisotropy introduced either by oblique deposition from a single source or in binary systems co-deposited from separate sources. We present a theoretical model demonstrating that these observations are natural results of the standard extraordinary Hall effect and anisotropic magnetoresistance, when the titled anisotropy is properly accounted for. Such a scenario may help explaining various previous intriguing measurements by other groups.

The effect of the surface treatments on the transport properties of a two-dimensional electron gas was studied at the quantum limit. The surface of the Al 0.36 Ga 0.64 As/ GaAs heterostructure was either coated with gold or etched with HCl solution, or etched and then coated by a self-assembled monolayer ͑SAM͒ of either phosphonated ͑ODP-C 18 H 39 PO 3 ͒ or thiolated ͑ODT-C 18 H 37 S͒ molecules. The etching process was found to reduce significantly both the mobility and the charge density. This effect was reversed upon sequential adsorption of the phosphonated SAM. We propose fine tuning of the device performance by the flexible chemistry of the assembled molecules, two of them demonstrated here. The results indicate that the surface oxidation does not necessarily play the dominant role in this respect and, in particular, that octadecane phosphonic acid ͑ODP͒ can protect the substrate from both oxidation and the formation of a passivating carbon layer. In contrast, octadecanethiol ͑ODT͒ is not stable enough and is not effective in eliminating surface states, as a result devices covered with ODT behave like those with etched surfaces.

Aviv, 69978 Tel Aviv, Israel Effect of hydrogen adsorption on the extraordinary Hall phenomenon (EHE) in ferromagnetic CoPd films is studied as a function of composition, thickness, substrate and hydrogen concentration in atmosphere. Adsorption of hydrogen adds a positive term in the extraordinary Hall effect coefficient and modifies the perpendicular magnetic anisotropy with the respective changes in coercivity and remanence of hysteresis loops. Hydrogen sensitive compositions are within the Co concentration range 20%  x  50% with the strongest response near the EHE polarity reversal point 0~3 8%. Depending on the film composition and field of operation the EHE response of CoPd to low concentration hydrogen can reach hundreds percent, which makes the method and the material attractive for hydrogen sensing. 2 Introduction. Hydrogen is a combustible gas present in practically every chemical process. The detection and concentration measurement of hydrogen is of a paramount importance in limitless cases of human activity from chemical, metallurgical, semiconductor and nuclear power industry to the emerging hydrogen energy economy. Many types of hydrogen sensors are commercially available or are in development. Following the classification by Hübert et al 1 they can be divided in eight groups as: catalytic, thermal conductivity; electrochemical, resistance based, work function based, mechanical, optical and acoustic.Yet, there is a continued need for faster, more accurate and more selective detection of hydrogen gas. It was suggested recently 2 that accuracy and selectivity of gas detection in general and hydrogen in particular, could be improved by measuring two or more independent gas-dependent parameters, e.g. resistance and magnetization. To execute a sensitive magnetic measurement in a compact and handy apparatus it was proposed to use the extraordinary Hall effect (EHE), which is an electric replica of magnetization compatible with a standard four-probe resistance measurement. Successful implementation of the technique would enrich the gas detection arsenal by magnetic type of sensors using the spintronics effect. In this paper, we present a systematic study of hydrogen detection using the extraordinary Hall effect in thin CoPd films. Experimental.Polycrystalline CoxPd(100-x) films with Co atomic concentration x (at. %) varying over an entire range 0  x  100 were deposited by rf co-sputtering from Co and Pd targets onto room temperature glass and GaAs substrates. The base pressure prior to deposition was 5 × 10 -7 mbar. Sputtering was carried out at Ar-pressure of 5 × 10 -3 mbar. Composition of samples was controlled by rf-power of the respective sputtering sources. Co and Pd are