摘要:

Exciton polaritons are considered in infinite multiple quantum wells which are periodic except that one well (impurity) has a different well width from the others (host). Under certain circumstances it is possible to have a long‐lived exciton‐polariton mode localized about the impurity. From the viewpoint of the electromagnetic field, this corresponds to waveguide modes in the vicinity of an exciton resonance in such structures. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113823

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The fact that the Meyer–Neldel rule is obeyed in many liquid semiconductors has led to the examination of its origin. An explanation based on a statistical shift of the Fermi energy with temperature is shown to be unrealistic. Multiphonon hopping is suggested as an explanation of the temperature and composition dependence of the electrical conductivity. This mechanism has the advantage of being universally valid for amorphous, crystalline, and liquid semiconductors. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113824

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have prepared Ba1−xKxBiO3grain‐boundary junctions on SrTiO3bicrystal substrates and observed the quasiparticle tunneling current for a superconductor–insulator–superconductor (SIS) junction. The current–voltage (I–V) characteristics were investigated by using a gap‐energy distribution model to consider the effect of the inhomogeneity of &Dgr; at the grain‐boundary junction interface. The broadening of theI–Vcharacteristics around the gap voltage of a SIS junction and its temperature dependence could be explained by assuming the Gaussian distribution of gap energies with &Dgr;0(0)=3.8 meV and &dgr;&Dgr;=0.8 meV, where &Dgr;0(0) and &dgr;&Dgr; denoted the mean value and variance of the distribution, respectively. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113585

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Using a novel bilayer deposition process, we have grown composite films of Au with YBa2Cu3O7−&dgr;on various substrates. Our composites have well‐segregated regions of Au and YBa2Cu3O7−&dgr;, and we have not observed structural degradation of the grains or grain boundaries in the films. Transition temperatures and critical current density measurements have behaviors consistent with regions of weakened grain boundary coupling in the films. Photoresponse measurements are also reported. We believe that Au is diffusing into the grain boundaries and weakening the coupling between YBa2Cu3O7−&dgr;grains. By varying the amount of Au in the films, the coupling can be adjusted. These Au/YBa2Cu3O7−&dgr;composite films are promising materials for device applications relying on vortex motion.

ISSN:0003-6951    

DOI:10.1063/1.113586

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

One‐dimensional‐like Co structures 50‐A˚‐wide and 3000‐A˚‐long have been grown by decoration of the monoatomic steps of a Cu(111) surface and visualized with scanning tunneling microscopy. In order to achieve step‐flow growth, terrace width, evaporation rate, and substrate temperature have been carefully adjusted. The choice of the (111) terrace orientation and ⟨11¯0⟩ compact steps ensures a homogeneous width of the Co wires and a lateral confinement of minority‐spin electrons. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113587

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Magnetostriction data are reported for NiFe/Ag multilayer thin films displaying giant magnetoresistance. Magnetostriction and magnetoresistance were measured as functions of annealing temperature for NiFe/Ag samples having different numbers of NiFe/Ag bilayers and Ag spacer thicknesses. They varied systematically with annealing temperature in a manner consistent with residual stress reduction and microstructural changes such as grain‐boundary diffusion and grain growth. Zero magnetostriction concurrent with high magnetoresistance ratio (5%) and field sensitivity [7.5%/(kA/m) (0.6%/Oe)] was observed for an optimal multilayer configuration and annealing temperature. This combination of zero magnetostriction and high magnetoresistive response makes the NiFe/Ag multilayer system an attractive candidate for high‐performance magnetic recording read‐head sensors. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113588

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An atomic force microscope tip is used as a vector positioner to manipulate nanometer‐size preformed Au clusters deposited on atomically smooth substrates. Using this technique, two‐dimensional cluster nanostructures can be assembled at room temperature. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.113589

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Infrared transmission, electron spin resonance, and x‐ray diffraction measurements show unambiguously that RbC60and KC60are stable in air, in contrast to Rb6C60which decomposes rapidly upon exposure. The specimens studied transform to pure C60and other by‐products when heated above 100 °C, approximately the temperature of the orthorhombic‐fcc phase transition. The stability of these compounds raises the possibility of applying them as protective layers for the superconducting fullerides. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113590

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Capacitively coupled radio frequency (cc‐rf) plasmas offer advantages over microwave (MW) induced plasmas for the growth of large area homogeneous thin films. However, conventionally designed cc‐rf sources lead, at best, to extremely poor quality material when diamond growth is attempted. The first complete diamond overlayer to be grown with cc‐rf is reported here, where a novel magnetically enhanced source with ring electrodes has been used. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113591

出版商:AIP    

年代:1995

数据来源: AIP