1,721,214 research outputs found
Barrier parameters and superconducting gap structure of the etched surface of Y-Ba-Cu-O by scanning tunnelling spectroscopy
No full textUsing a scanning tunnelling microscope, the tunnelling current vs. voltage is measured between a gold tip and the chemically etched (001) surface of YBa2Cu8Ox crystals at room temperature. The tunnelling barrier height and thickness are derived by modelling the system in the normal state as a conventional N-I-N junction. The I(V) and G(V) curves are computed for the same junction in the superconducting state (N-I-S junction). The predicted gap structure for a single BCS-Dynes-like gap is simple and has low zero-bias conductance. The complex G(V) spectra measured below T(c) on the etched junctions with approximately 50% zero-bias conductance suggest a possible multilayer contribution in the unit cell
The evolution of self-assembled InAs/GaAs(001) quantum dots grown by growth-interrupted molecular beam epitaxy
No full textSelf-assembled InAs quantum dots (QDs) grown on GaAs(001) by molecular beam epitaxy under continuous and growth-interruption modes exhibit two families of QDs, quasi-three-dimensional (quasi-3D; Q3D) and three-dimensional (3D) QDs, whose volume density evolution is quantitatively described by a classical rate-equation kinetic model. The volume density of small Q3D QDs decreases exponentially with time during the interruption, while the single-dot mean volume of the large QDs increases by Ostwald ripening. The kinetics of growth involves the conversion of Q3D to 3D QDs at a rate determined by the superstress and the participation of the wetting layer adatoms. The data analysis excludes Q3D QDs being extrinsic surface features due to inefficient cooling after growth
Ge epitaxy on patterned and unpatterned Si surfaces
No full textNanotechnology aims at exploiting the remarkable size effects that arise when materials are reducec to nanoscale dimensions. So far, promising quantum structures have been fabricated using techniques based on self assembling, but their ordering is possible only by appropriate substrate nanopatterning. In this paper we describe different ways of patterning a silicon substrate and how they affect the growth and ordering of the quantum dots
X-ray absorption of crystalline titanium compounds:Evidence of electronic relaxation effects
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