摘要:

We have laterally patterned the narrowest conducting wires of two‐dimensional electron gas (2DEG) material reported to date. The depletion induced by low‐energy ion etching of GaAs‐AlGaAs 2DEG structures was used to define narrow conducting channels. We employed high voltage electron beam lithography to create a range of channel geometries with widths as small as 75 nm. Using ion beam assisted etching by Cl2gas and Ar ions with energies as low as 150 eV, conducting channels were defined by etching only through the thin GaAs cap layer. This slight etching is sufficient to entirely deplete the underlying material without necessitating exposure of the sidewalls that results in long lateral depletion lengths. At 4.2 K, without illumination, our narrowest wires retain a carrier density and mobility at least as high as that of the bulk 2DEG and exhibit quantized Hall effects. Aharonov–Bohm oscillations are seen in rings defined by this controlled etch‐damage patterning. This patterning technique holds promise for creating one‐dimensional conducting wires of even smaller sizes.

ISSN:0003-6951    

DOI:10.1063/1.98970

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Gold film has been deposited by ultaviolet‐light‐induced photolysis of ammonium tetrachloroaurate/nitrocellulose film. The minimum feature size achieve is about 1 &mgr;m, and the film exhibits good adhesion. The effect of temperature on the photolyzing rate has been examined.

ISSN:0003-6951    

DOI:10.1063/1.98971

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Transmission electron microscopy and Rutherford backscattering were used with polycrystalline Si films implanted at 100 keV with 3×1016arsenic ions/cm2. During annealing, grain growth occurred first in the implanted portion, then arsenic diffused into the unimplanted poly‐Si, and finally grain growth occurred in this region. We believe that arsenic in the implanted region accumulates on grain boundaries during grain growth and subsequently diffuses along grain boundaries into the unimplanted region where grain growth occurs when arsenic can diffuse into the interior of the polycrystalline Si grains.

ISSN:0003-6951    

DOI:10.1063/1.98972

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Hydrogenated amorphous silicon nitride (a‐SiNxH) films have been deposited on InP substrates by the low‐temperature (185 °C) plasma enhanced chemical vapor deposition technique in order to realize metal‐insulator‐semiconductor capacitors. It has been found that the electronic properties of the InP‐insulator interface are greatly improved if the insulator deposition is carried out in the presence of AsH3during the first stage of the process (interface state density in the range of a few 1011eV−1 cm−2in the upper part of the gap). The deposited films exhibit very high resistivity (1017&OHgr; cm) and high breakdown voltage (3×106V/cm). In similar conditions, no beneficial effect of PH3during the deposition has been noticed.

ISSN:0003-6951    

DOI:10.1063/1.98973

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Epitaxial orthorhombic GdSi2was grown byinsituvacuum annealing of a 50‐nm Gd layer on ⟨100⟩ silicon. The epitaxy was proved by x‐ray diffraction, electron diffraction, and ion channeling measurements. The lattice mismatch between the orthorhombic GdSi2and ⟨100⟩ silicon substrate was found to be 4%.

ISSN:0003-6951    

DOI:10.1063/1.98974

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Superconducting stoichiometric YBa2Cu3O7−xfilms have been grown by rf sputtering of a single bulk material target in an Ar+10% O2sputtering atmosphere on a variety of substrates. Films on SrTiO3substrates exhibited the best post‐annealing superconducting properties with the critical onset temperature of 90 K and zero resistance at 67 K. The maximum current density for these samples was 1×105A/cm2at 4.2 K. An extensive loss of film underneath the target was observed during the growth of these films which can be attributed to resputtering due to oxygen anion or energetic neutral particle bombardment of the substrate.

ISSN:0003-6951    

DOI:10.1063/1.98975

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Thin films of YBa2Cu3O7−ywere prepared by magnetron sputtering. The films were characterized by x‐ray diffraction,insitux‐ray photoelectron spectroscopy to determine the as‐deposited oxygen content for various substrate temperatures, and scanning electron microscopy to analyze the microstructure. The orthorhombic phase was observed after anexsitu700 °C anneal. We have obtained films which were completely superconducting at 82 K with 6 K transition widths.

ISSN:0003-6951    

DOI:10.1063/1.98976

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Metalorganic deposition (MOD) is a nonvacuum method of thin‐film deposition which allows easy alteration of chemical components and is compatible with thin‐film processing. We report the preparation of thin‐film superconductors by MOD. Rutherford backscattering spectrometry was used to determine film compositions and thicknesses. Films, approximately 500 nm thick, of YBa2Cu4Oz(zundetermined) were deposited on ⟨100⟩ single‐crystal SrTiO3. A superconducting onset temperature of 90 K was measured with 37 K the zero resistance temperature. Scanning electron microscopy revealed grain sizes approximately 250 nm in diameter.

ISSN:0003-6951    

DOI:10.1063/1.98978

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Superconducting YBa2Cu3O7thin films have been prepared by using a magnetron sputtering system in the single‐source mode. Samples deposited on [100] single‐crystal MgO with and without a Au buffer layer all show high transition temperatures (82–87 K). The use of a Au buffer layer significantly improves the superconducting properties, particularly the Meissner effect and critical current density (3.3×106A/cm2atT=2 K and 3.5×104A/cm2atT=77 K). The Au films remain metallic after high‐temperature annealing in an oxygen atmosphere. We propose to use Au buffer layers as current shunts to protect superconducting films and devices.

ISSN:0003-6951    

DOI:10.1063/1.98979

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Superconducting YBa2Cu3O7−&dgr;oxide specimens (Tc∼91 K) formed by sintering were annealed in He gas ambient at constant temperatures ranging from 300 to 440 °C. Outdiffusion of oxygen during the annealing procedure was monitored byinsituelectrical resistivity measurement. Below 350 °C, no resistivity changes were observed with time. From 370 to 440 °C, resistivity increased linearly with annealing time except the very initial period. Indiffusion of oxygen monitored by switching He to O2(or air) during the annealing occurred extremely rapidly as indicated by a precipitous drop of resistivity. Assuming that the outdiffusion of oxygen is interfacial‐reaction limited, an activation energy of 1.7 eV was measured. The effects of oxygen diffusion on resistivity indicate that oxygen atoms mediate majority carriers in the oxide.

ISSN:0003-6951    

DOI:10.1063/1.98980

出版商:AIP    

年代:1987

数据来源: AIP