Local charge transfer doping in suspended graphene nanojunctions

We report electronic transport measurements in nanoscale graphene transistors with gold and platinum electrodes whose channel lengths are shorter than 100 nm, and compare them with transistors with channel lengths from 1 \textmu{}m to 50 \textmu{}m. We find a large positive gate voltage shift in charge neutrality point (NP) for transistors made with platinum electrodes but negligible shift for devices made with gold electrodes. This is consistent with the transfer of electrons from graphene into the platinum electrodes. As the channel length increases, the disparity between the measured NP using gold and platinum electrodes disappears.Comment: 11 pages, 3 figures, to appear in Appl. Phys. Let

Non-intrinsic superconductivity in InN epilayers: role of Indium Oxide

In recent years there have been reports of anomalous electrical resistivity and the presence of superconductivity in semiconducting InN layers. By a careful correlation of the temperature dependence of resistivity and magnetic susceptibility with structural information from highresolution x-ray diffraction measurements we show that superconductivity is not intrinsic to InN and is seen only in samples that show traces of oxygen impurity. We hence believe that InN is not intrinsically a superconducting semiconductor.Comment: pdf file with figure

Competing effects of surface phonon softening and quantum size effects on the superconducting properties of nanostructured Pb

The superconducting transition temperature (Tc) in nanostructured Pb decreases from 7.24 to 6.4 K as the particle size is reduced from 65 to 7 nm, below which superconductivity is lost rather abruptly. In contrast, there is a large enhancement in the upper critical field (Hc2) in the same size regime. We explore the origin of the unusual robustness of Tc over such a large particle size range in nanostructured Pb by measuring the temperature dependence of the superconducting energy gap in planar tunnel junctions of Al/Al2O3/nano-Pb. We show that below 22 nm, the electron–phonon coupling strength increases monotonically with decreasing particle size, and almost exactly compensates for the quantum size effect, which is expected to suppress Tc