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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