The high-bias electrical characteristics of back-gated field-effect transistors with chemical vapor deposition synthesized bilayer MoS 2 channel and Ti Schottky contacts are discussed. It is found that oxidized Ti contacts on MoS 2 form rectifying junctions with ≈0.3 to 0.5 eV Schottky barrier height. To explain the rectifying output characteristics of the transistors, a model is proposed based on two slightly asymmetric back-to-back Schottky barriers, where the highest current arises from image force barrier lowering at the electrically forced junction, while the reverse current is due to Schottkybarrier-limited injection at the grounded junction. The device achieves a photoresponsivity greater than 2.5 A W −1 under 5 mW cm −2 white-LED light. By comparing two-and four-probe measurements, it is demonstrated that the hysteresis and persistent photoconductivity exhibited by the transistor are peculiarities of the MoS 2 channel rather than effects of the Ti/MoS 2 interface.

Electronic transport and magnetic properties of Ge 1-x Mn x /Ge(100) films are investigated as a function of Mn dilution. Depending on x, characteristic temperatures separate different regimes in both properties. Resistivity exhibits an insulator-like behavior in the whole temperature range and, below about 80 K, two distinct activation energies are observed. At a higher temperature value, T R , resistivity experiences a sudden reduction. Hall coefficient shows a strong contribution from the anomalous Hall effect and, at T R , a sign inversion, from positive to negative, is recorded. The magnetic properties, inferred from magneto-optical Kerr effect, evidence a progressive decrease of the ferromagnetic long range order as the temperature is raised, with a Curie temperature T C not far from T R . The transport and magnetic results are qualitatively consistent with a percolation mechanism due to bound magnetic polarons in a GeMn diluted magnetic semiconductor, with localized holes [A. Kaminski and S. Das Sarma, Phys. Rev. B 68, 235210 (2003)].

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This letter reports a method to produce porous-silicon waveguides by means of a laser local oxidation process. The estimated losses of the waveguides are below 1 dB/cm. This demonstrates the applicability of this material in integrated optics and telecommunications. Moreover, our results disclose the opportunity to integrate optoelectronic devices onto Si substrates. The laser writing method is achievable at low laser power, thus it is highly efficient and achievable with the standard equipment present in most laboratories. Another advantage is that oxidation is achieved without heating the complete chip, thus simplifying the integration process, i.e., the oxidation is inherently local through the direct-write process. This method opens the opportunity to build microstructures, like channel and membrane filters, in a flexible manner by R&D laboratories.