摘要:

The magnetization of (100)Cu‐Ni, (100)Cu‐Co, and (100)Ni‐Co superlattices has been studied. The structures were grown on the (100)Cu/Si substrates, with the (100)Cu epitaxially grown on the (100)Si as the seed. The (100)oriented superlattices show different magnetization curves from the (111) structures and from bulk (100)Ni and Co films. A much enhanced magnetization is observed for the (100)Cu‐Ni superlattice with the field perpendicular to the film plane. The remanence is larger than that for the field parallel to the film plane. Negative remanence and coercivity are observed for the (100)Cu‐Co and Ni‐Co structures. The magnetization curve for the (100)Ni‐Co superlattice is further shown to resemble a superposition of the Cu‐Ni and Cu‐Co ones. Upon heating the Ni‐Co structure to 400 °C to consume more Ni than Co, a magnetization curve similar to that of the Cu‐Co one is observed.

ISSN:0003-6951    

DOI:10.1063/1.103719

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

New alloys of hydogenated amorphous silicon with Al, Ga, S, and Se have been prepared by the rf glow discharge method. The energy gap of these materials can be varied in the 1–2 eV range, with the Al and Ga alloys being low band‐gap semiconductors, and the S and Se alloys having higher energy gaps. The light to dark conductivity ratios of the various systems have been measured. The best photoresponse (102–103) was obtained with the Se and S alloys.

ISSN:0003-6951    

DOI:10.1063/1.103720

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The internal tensile stress in polycrystalline diamond films deposited on silicon substrates has been measured from 100 to 700 K by a vibrating‐membrane method. The stress increases strongly with temperature, in a manner consistent with the elastic accommodation of the differential thermal strain between diamond and silicon. The results indicate that the films contain a tensile growth stress of about 500 MPa at the deposition temperature of 1123 K. Derived values of the biaxial elastic modulus fall in the range 730–850 GPa.

ISSN:0003-6951    

DOI:10.1063/1.103721

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Superconducting YBa2Cu3O7−xthin films were deposited on Si substrates at 500 °C by rf magnetron sputtering from a stoichiometric oxide target. Metallic oxide RuO2, sputtered by reactive dc magnetron, was used as a buffer layer to nucleate the superconducting film and minimize the reactions between Si and superconductor. The as‐deposited thin films, without further post high‐temperature annealing, were completely superconductive at 79 K. Very smooth surface morphology was demonstrated by scanning electron microscopy. X‐ray diffraction data indicated that the films had a randomly oriented polycrystalline structure. Auger electron spectroscopy did not reveal interdiffusion of elements in the three layers.

ISSN:0003-6951    

DOI:10.1063/1.104218

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

High‐resolution photoemission has been used to probe the electronic structure of the gold/Bi2Sr2CaCu2O8and gold/EuBa2Cu3O7−&dgr;interface formed by a low‐temperature (20 K) gold evaporation on cleaved high quality single crystals. We find that the metallicity of the EuBa2Cu3O7−&dgr;substrate in the near surface region (∼5 A˚) is essentially destroyed by the gold deposition, while the near surface region of Bi2Sr2CaCu2O8remains metallic. This has potentially wide ranging consequences for the applicability of the different types of superconductors in real devices.

ISSN:0003-6951    

DOI:10.1063/1.104219

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have used a scanning tunneling microscope (STM) to record and image magnetic regions on the surface of a hard disk. The usual rigid STM tip was replaced by a compliant magnetized Fe film tip. As a result, tunneling images were combinations of the surface topography and variations in the magnetic force between the Fe film tip and the disk surface. We believe that the recording process relied on maintaining the proximity of the magnetized Fe film tip near the disk surface. Apparently, the magnetic field was focused near the Fe film tip with sufficient intensity to change the surface magnetization of the disk. We have recorded spots on the disk within a 500 nm×500 nm area. These spots were subsequently imaged with the same STM tip. Our best magnetic image resolution was 20 nm. The compliance of the Fe film tips was such that image contrast due to variation of the magnetic force on the tip corresponded tozmotions of the piezoelectric translator as large as 50 nm.

ISSN:0003-6951    

DOI:10.1063/1.103676

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Harmonic generation and mixing in the 8∼80 GHz region has been studied in point‐contact junctions made with sharply tipped tungsten whisker and sintered polycrystalline YBa2Cu3O7−yor single‐crystal Bi2Sr2CaCu2Oxat room temperature. The signal‐to‐noise ratio (SNR) of beat notes as a function of harmonic numbernis observed up to the tenth order and decreases with a slope ofn−5.6for even harmonic numbers. The dependence of the SNR of the beat note on a dc bias voltage and the current‐voltage characteristics have been measured simultaneously and theoretically analyzed using the current‐dependent mixing characteristics. The potential barrier and the insulating thickness for YBa2Cu3O7−yare estimated.

ISSN:0003-6951    

DOI:10.1063/1.104239

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Novel force‐sensing microcantilevers with sharp tips have been used to obtain atomic force microscope images of atomically flat, layered compounds as well as microfabricated samples with large‐scale topographies. When imaging atomically flat samples using cantilevers with sharp protruding tips, atomic corrugations are observed more consistently and with a higher signal‐to‐noise ratio than in the absence of tips. Some asymmetric distortions arise when tipped cantilevers are used with forces larger than 10−7N. Side by side comparisons of images of rough samples obtained using cantilevers with and without tips reveal that the presence of a sharp tip yields superior image quality of vertical features and trenches. The cantilever assembly is a microfabricated, silicon nitride cantilever with an integral, single‐crystal silicon tip. The silicon tip is self‐aligned to the end of the cantilever and is created by a process which simultaneously fabricates and sharpens the silicon tip. Initial transmission electron microscopy studies show that the single‐crystal silicon tips have radii of curvature of 220–400 A˚.

ISSN:0003-6951    

DOI:10.1063/1.103677

出版商:AIP    

年代:1990

数据来源: AIP