Quantum structures were fabricated by immersing a crystalline silicon (Si) or germanium (Ge) wafer in hydrofluoric acid followed by laser‐induced etching with a laser photon energy of 2.41 eV. Atomic force microscopy (AFM) investigations of Si(100) etched samples reveal a complex surface morphology with pits from the top view and pillar‐like structures from the three‐dimensional view of the pit wall. For Ge(111) laser‐etched samples, AFM shows parallel wall‐type structures and Ge quantum structures on the surface of the walls. Laser‐induced etching of Ge is reported for the first time. Observation of photoluminescence spectra from both samples confirms the presence of quantum confined structures. Line‐shape analysis of Raman spectra is used to estimate the size of the quantum structures. The sizes of nanoparticles can be controlled by the laser power density and irradiation time for etching. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We report the spontaneous formation of superconducting NiBi3 phase in thermally evaporated Ni-Bi bilayer films. High reaction-diffusion coefficient of Bi is believed to drive the formation of NiBi3 during the deposition of Bi on the Ni film. Cross sectional transmission electron microscopy and glancing incidence X-ray depth profiling confirmed the presence of NiBi3 throughout the top Bi layer. Superconducting transition at ∼3.9 K, close to the bulk value, was confirmed by transport and magnetization measurements. The bilayers were irradiated with varying fluence of 100 MeV Au ions to study the robustness of superconducting order in presence of large concentration of defects. Superconducting parameters of NiBi3, such as transition temperature and upper critical field, remained unchanged upto an ion dose of 1 × 1014 ions/cm2. The diffusive formation of NiBi3 in Ni opens the possibility of studying superconducting proximity effect at a truly clean superconductor-ferromagnet interface.

No abstract

No abstract

Bulk Ge15Te83Si2 glass has been found to exhibit memory-type switching for 1mA current with a threshold electric field of 7.3kV∕cm. The electrical set and reset processes have been achieved with triangular and rectangular pulses, respectively, of 1mA amplitude. In situ Raman scattering studies indicate that the degree of disorder in Ge15Te83Si2 glass is reduced from off to set state. The local structure of the sample under reset condition is similar to that in the off state. The Raman results are consistent with the switching results which indicate that the Ge15Te83Si2 glass can be set and reset easily.