J. P. Garno

Mesotaxy: Single‐crystal growth of buried CoSi2 layers

Buried single‐crystal CoSi2 layers in silicon have been formed by high dose implantation of cobalt followed by annealing. These layers grow in both the (100) and (111) orientations—those in (111) have better crystallinity, but those in (100) are of higher electrical quality. Electrical transport measurements on the layers give values for the resistance ratios and superconducting critical temperatures that are better than the best films grown by conventional techniques and comparable to bulk CoSi2.

Implantation, damage, and regrowth of high Tc superconductors

Abstract We have observed superconductivity in thin films of (La1−xSrx)2CuOy which are fabricated by implanting evaporated La/Cu multilayer films with Sr and annealing in oxygen. The films are insulating and partially transparent as-implanted, but they darken and become conducting at annealing temperatures as low as 500°C. The resistive behavior is very sensitive to the annealing conditions and the superconducting layer appears to be buried beneath the surface. Similarly, implantation of F, O, and Ne into single crystals and high quality (χmin

Electron tunneling studies of ultrathin films near the superconductor-to-insulator transition

Abstract Electron tunneling measurements on ultrathin quench-condensed films near the superconductor-to-insulator (SI) transition reveal that the superconducting state degrades with increasing normal state sheet resistance, R□, in a manner that depends strongly on film morphology. In homogeneously disordered films, the superconducting energy gap Δo decreases continuously and appears to go to zero at the SI transition. In granular films the transport properties degrade while Δo remains constant. Measurements in the normal state reveal disorder enhanced e- -e- interaction corrections to the density of states. These effects are strong and depend on morphology in a manner that is consistent with their playing an important role in driving the SI transition.

Mesotaxy: Formation of Buried Single-Crystal CoSi2 Layers by Implantation

Using high dose implantation of 200 keV Co ions followed by high temperature annealing, we have created buried layers of CoSi 2 in crystalline Si of both (100) and (111) orientations. For a dose of 3 × 10 17 Co/cm 2 , the layer that forms is ∼1100A thick and the overlying Si is ∼600A thick. A lower dose of 2 × 10 17 Co/cm 2 yields a thinner layer, 700A thick, under 1200A of crystalline Si. Rutherford Backscattering and channeling analysis of the layers shows that they are aligned with the substrate (χ min of the Co as low as 6.4%.) and TEM inspection of the (100) CoSi 2 /Si interfaces shows that they are abrupt and epitaxial (with occasional small facets). Moreover, electrical characterization of these layers yields resistance ratios that are better than epitaxial CoSi 2 films grown by more conventional UHV methods.

The time dependent specific heat of dielectric glasses

Abstract Measurements on the time dependence of the specific heat exist now both at short and long timescales. Below 0.3 K the short time (}10 μs) specific heat of all the materials studied is smaller than the long time specific heat, but larger than the Debye value. Above 0.2 K most of the specific heat is coupled to the phonons already at 10 μs. However, measurements at very long timescales reveal that the specific heat has a component with a logarithmic time dependence, as proposed by the tunneling model, although only part of the total specific heat can be ascribed to it.