Search results for "thin film"

Josephson junctions and superconducting field effect transistors based on epitaxial Bi2Sr2Can-1CunO2(n+2) thin films

1998

Abstract Josephson junctions based on thin films of the Bi2Sr2Ca2Cu3O10+δ compound show IcRn products compatible with YBa2Cu3O7−δ samples. Using quasiparticle tunneling experiments we found evidence for a superconductor–insulator–superconductor tunneling process via localized states in the barrier. The Bi2Sr2CaCu2O8+δ compound is investigated regarding possible applications in superconducting field effect devices. We present thin films of four unit cells thickness that are superconducting at 58 K. An inverted metal–insulator–superconductor structure was prepared. From the modulation of the normal state resistance we estimate a carrier density of 7×1019 cm−3 for a superconducting sample. The…

Growth characteristics of sputter-deposited thin films

1996

Thin films of the heavy-fermion superconductor were deposited on various substrate materials in various orientations by means of a quasi-multilayer sputter process. Strongly (0001)-textured growth of the hexagonal compound was found for a uranium content in the range of 23% to 28% on sapphire and with perfect in-plane order on the latter substrate material. Atomic force microscopy and scanning electron microscopy revealed a Vollmer - Weber-like growth mode resulting in the development of large compressive strain in films on . As a result the electronic transport properties - in particular the temperature dependence of the resistivity - were strongly renormalized. Strong deviations from the …

Broadband infrared conductivity in an YBa2Cu3O6.7 thin film

2001

Infrared reflectivity of an oxygen reduced YBa2Cu3O6.7 thin film was measured in the frequency range 30 cm-1 < v < 7000 cm-1 and for temperatures 5 K < T < 300 K. At lower frequencies, 3 cm-1 < v < 40 cm-1, the complex conductivity σ*=σ1+iσ2 was measured directly using a transmission technique. Both data sets were combined to obtain the reflectivity in a broad frequency range and thus to improve substantially the quality of the Kramers-Kronig analysis at low frequencies. The analysis of the conductivity spectra reveals that the low-frequency spectral weight strongly depends on temperature directly above TC but saturates for T ≥ 150 K.

Superconductivity in high‐quality (Hg 0.9 Re 0.1 )Ba 2 CaCu 2 O 6+ δ HTSC thin films

2004

High-quality epitaxial (Hg0.9Re0.1)Ba2CaCu2O6+δ (HgRe-1212) HTS thin films were successfully prepared using pulsed laser deposition (PLD) of the Re0.1Ba2CaCu2O6+δ precursor and subsequent Hg vapor annealing. The thin films exhibit a sharp superconducting transition at Tc ≈ 120 K. The resistive transitions have been investigated in magnetic fields up to 6 T parallel and perpendicular to the c-axis. We have determined the activation energy of thermally activated flux-motion for both magnetic field orientations. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of carrier transfer on the PL intensity in self-assembled In (Ga) As/GaAs quantum rings

2006

We present results concerning the carrier transfer between In(Ga)As quantum rings in a stacked multilayer structure, which is characterised by a bimodal size distribution. This transfer of carriers explains the observed temperature behaviour of diode lasers based on that kind of stacked layer structures. The inter-ring carrier transfer can be possible by phonon assisted tunnelling from the ground state of the smallring family towards the big-ring family of the bimodal size distribution. This process is thermally activated in the range 40–80 K.

Surface and Thin Film Analysis by Mössbauer Spectroscopy and Related Techniques

1996

The main trend in current high-tech development is miniaturization. This holds for complex electronic devices, such as microprocessors, as well as for coatings, such as Langmuir-Blodgett coatings, optical components, such as fiber couplers, chemical devices, such as microreactors, mechanical components, such as micromotors, and many others. Development and production of components with dimensions in the micron and submicron range require the availability of appropriate analytical tools for chemical, physical, and morphological analyses. In close interaction with the development of microcomponents, many, more and more efficient, analytical methods have been developed, many of which are “surf…

Polarity Effects on ZnO Films Grown along the Nonpolar[112¯0]Direction

2005

The surface electrical properties of ZnO thin films grown along the nonpolar $[11\overline{2}0]$ direction have been investigated by Kelvin probe microscopy on a nanometer scale. Two different charge domains, with a 75 meV work function difference, coexist within the ZnO surface, which is covered by rhombohedral pyramids whose sidewalls are shown to be ${10\overline{1}1}$-type planes. The presence and relative orientation of the two kinds of charge domains are explained in terms of the atomic arrangement at the ${10\overline{1}1}$ polar surfaces.

Theoretical Simulations of Surface Relaxation for Perovskite Titanates

2000

The (100) and (110) surface relaxations are calculated for SrTiO3 and BaTiO3 perovskite thin films Using a semiempirical shell model, the positions of atoms in 16 near-surface layers placed atop a slab of rigid ions are calculated. Surface rumpling and surface-induced dipole moments perpendicular to the surface are calculated for different surface terminations. Surface relaxation is found much larger for the (110) surface. Our results for the (100) surfaces are compared with ab initio calculations and LEED experiments.

Surface and thin film analysis: an introductory survey

1995

Spinodal decomposition in thin films: Molecular-dynamics simulations of a binary Lennard-Jones fluid mixture

2005

We use molecular dynamics (MD) to simulate an unstable homogeneous mixture of binary fluids (AB), confined in a slit pore of width $D$. The pore walls are assumed to be flat and structureless, and attract one component of the mixture (A) with the same strength. The pair-wise interactions between the particles is modeled by the Lennard-Jones potential, with symmetric parameters that lead to a miscibility gap in the bulk. In the thin-film geometry, an interesting interplay occurs between surface enrichment and phase separation. We study the evolution of a mixture with equal amounts of A and B, which is rendered unstable by a temperature quench. We find that A-rich surface enrichment layers fo…