We have studied the transport properties of disordered WSi films near the metal/insulator transition (MIT) and we have also reviewed the data for several other disordered materials near their MIT. In all cases, we found the presence of enhanced superconductivity. We constructed a superconductivity "phase diagram" (i.e., T(c) versus sigma) for each system, which reveals a striking correlation: In all cases, T(c) values are significantly enhanced only for samples whose conductivities lie within a narrow range on the metallic side of, and moderately near, the MIT. We present a heuristic model to explain this phenomenon.

Using thermal CVD, the synthesis of multi-walled carbon nanotubes exhibiting roots anchored directly onto ␣-alumina supports, rather than the catalyst particle, is reported. At such roots, the alignment of the graphitic planes with the support lattice fringes depends on the support crystal structure and orientation.Surface defects may alter the reactivity of the surface or control the anchoring of supported atoms or nanoparticles.We argue this surface defect is provided by the catalyst particle's edge interaction with the support, in other words its circumference. The development of oxide-based catalysts is attractive in that they potentially provide an appropriate solution to directly integrate the synthesis of carbon nanotubes and graphene into silicon-based technology.

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