摘要:

N‐channel field effect transistors with excellent device characteristics have been fabricated by utilizing C60as the active element. Measurements on C60thin films in ultrahigh vacuum show on‐off ratios as high as 106and field effect mobilities up to 0.08 cm2/V s. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115503

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Quantum dots and quantum wires based on CdZnSe/ZnSe single quantum well heterostructures have been achieved using electron beam lithography and wet chemical etching. Photoluminescence spectra of the dot and wire structures show a blue shift due to lateral quantization for lateral dimensions below 40 nm. For the dot ground state, a lateral confinement energy of 16 meV is obtained for 28 nm diameter structures. For wires with widths on the order of 20 nm, lateral confinement energies of about 5 meV are observed. The dot diameter and wire width dependence of the emission energies can be described based on a square well potential and the measured sizes of the structures. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115504

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The effects of strain and In content on dislocation reduction was studied by introducing an InGaAs strained layer into a GaAs layer on a Si substrate. The two effects were separated by using the strain energy that accumulates in the InGaAs layer, since the strain in an InGaAs layer varies with In content. The results show that the variation in dislocation density depends on the strain and not on the In content. A strain energy of 250 dyn/cm was sufficient for effectively reducing dislocations in both the InGaAs layer and in the GaAs overlayer. However, when the strain energy was over 500 dyn/cm, the number of dislocations increased when an InGaAs layer was introduced. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115505

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The transport critical current densityJcof oxide‐powder‐in‐tube mono‐ and multifilamentary Bi‐2223/Ag tapes has been determined before and after irradiation by 0.8 GeV protons at fluences up to 7.0×1016protons/cm2. Proton‐induced fission of the Bi nuclei produced up to 8.6×1013fissions/cm3, creating long tracks at densities equivalent to matching fields up to 1.1 T. Relative to unirradiated tapes,Jcvalues at 75 and 64 K show no decrease in self field, indicating no breakdown of intergranular coupling, and show large, dose‐dependent enhancements in magnetic fields oriented parallel to the tape normal. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115506

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have measured 1/fresistance noise at room temperature in laser‐ablated YBa2Cu3Oy(YBCO) thin films over a wide range of normal‐state resistivities. Surprisingly, the high resistivity films exhibit lower normalized noise powers than the low resistivity films. The lowest normalized noise power is 100 times lower than any previously reported values for single crystals of YBCO and is comparable to the lowest noise levels found in other cuprates. Upon oxygen reduction, the noise power in the high resistivity films increases monotonically whereas it decreases in the low resistivity films. We conclude that the high noise level in YBCO is most likely intrinsic to the structure and due to conduction along the Cu‐O chains. Therefore, the low noise power in high resistivity films appears to indicate a degraded chain conductivity. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115507

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Superconducting glass‐ceramics in the Bi–Sr–Ca–Cu–O (BSCCO) system were found to be successfully joined together by welding with an LNG‐O2flame. Two edge portions of the glass‐ ceramics to be joined were set in close contact to each other and melted by the high‐temperature flame. After the welding, the joined portion was annealed with a soft flame, so that no crack formed in the product. The directly joined product was converted into a superconductor withTc&bartil;90 K by a postheating at ∼830 °C. Its critical current densityJc, was almost the same as the of the original glass‐ceramic. This technique is very important for fabrication of large‐sized superconducting apparatus such as current leads or magnetic shields. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115508

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We suggest a new design of rapid single flux quantum (RSFQ) logic circuits which is based on a single superconducting layer and does not require a superconducting ground plane. Small inductances of about 10 pH, obligatory for RSFQ circuits, are formed as narrow slits of widths comparable to the London penetration depth (&bartil;0.15 &mgr;m). The design allows us to decrease the geometric size of the RSFQ cell. Test circuits with YBaCuO grain boundary junctions on asymmetric 32° Y– ZrO2bicrystals were used to measure the slit inductance per unit length and the mutual inductance of neighboring slits. A typical inductance of a 0.4 &mgr;m slit was found to be 0.7–0.8 pH/&mgr;m. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115472

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We present the crystal‐orientation dependence of the magnetic circular dichroism (MCD) spectra of ferromagnetic (11¯01) and (0001) MnSb epitaxial films grown by molecular beam epitaxy on (001) GaAs and (0001) sapphire substrates, respectively, where very large anisotropy is clearly observed at around 3.0 and 4.7 eV. The anisotropy of the MCD spectra is discussed in connection with the magnetocrystalline anisotropy. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115474

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The spatial profile of methyl radical concentration in a hot‐filament reactor has been measured using cavity ring‐down spectroscopy (CRDS) at a wavelength of 213.9 nm for which the CH3absorption cross section has been shown to be nearly independent of temperature. Methyl radicals are generated with a 25 mm long tungsten filament heated to 2400 K in a slowly flowing mixture of 0.6% CH4in H2(20 Torr total pressure). CRDS is employed to measure CH3absorbance as a function of a distance perpendicular to the axis of the filament. The CH3absorbance profiles do not change when the direction of the process gas flow through the reactor is reversed, which indicates cylindrical symmetry of the CH3distribution about the filament. Consequently, the radial CH3concentration in the reactor is determined by Abel inversion of the CH3absorbance profile. The CH3concentration peaks ∼4 mm from the filament (1.04×1014molecules/cm3). Methyl radicals decay rapidly as a function of a distance from the filament and disappear about 2 cm from the filament within our present detection sensitivity (3×1012molecules/cm3). ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115475

出版商:AIP    

年代:1995

数据来源: AIP