摘要:

Bimetal ‘‘T‐gate’’ structures have been obtained by selective Ti‐Al plasma etching. These structures have been used as self‐aligned masks for ohmic contact metallizations. Titanium Schottky diodes exhibit a barrier height of 720 mV with an ideality factor of 1.17. By using only the optical lithographic process, normally on GaAs metal Schottky field‐effect transistors (MESFET) of 1.3‐&mgr;m gate length have been fabricated. Transconductance up to 142 mS mm−1and pinchoff voltage around −2 V have been measured.

ISSN:0021-8979    

DOI:10.1063/1.336865

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The thermal stability of sputtered TbFeCo thin films in magneto‐optic quadrilayer structures containing Si3N4, SiO, and SiO2dielectrics has been examined. The observed changes in coercivity upon annealing are attributed to two parallel mechanisms: structural relaxation in the amorphous magnetic alloy and preferential oxidation of Tb at the TbFeCo/SiO and TbFeCo/SiO2interfaces. Kinetic modeling has revealed that a spectrum of activation energies is required to explain the relaxation data, whereas a single activation energy of 1.65 eV describes the oxidation process.

ISSN:0021-8979    

DOI:10.1063/1.336866

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The phenomenological propagation loss theory based on the Gilbert form of the equation of motion for the magnetization is clarified for surface wave modes and extended to include volume wave modes. For small numbers, the expression 76.4&Dgr;H(dB/&mgr;s) is found to accurately give forward volume wave losses, but to underestimate both surface and backward volume wave losses at low frequencies. Here &Dgr;His the full ferromagnetic resonance linewidth. As an example, the surface and backward volume wave losses at 3 GHz in yttrium iron garnet are more accurately given by 99.3&Dgr;H(dB/&mgr;s) for small wave numbers. For a fixed bias field, surface wave losses per unit time are shown to be constant with frequency across the passband, whereas volume wave losses per unit time have a quadratic frequency dependence. After a review of existing experimental results, it is concluded that further data is necessary for a definitive test of the theory.

ISSN:0021-8979    

DOI:10.1063/1.336867

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A time‐dependent model is presented for the periodically excited crossed‐beam thermal lens. In order to obtain good agreement between the theory and data for chopped excitation, it is necessary to consider the finite time required to block and unblock the pump beam. Unfortunately, a closed form expression has not been developed which considers the excitation waveform for a chopped Gaussian beam. On the other hand, a useful approximation has been developed based on a trapezoidal excitation function. This model is verified with respect to time, absorbance, alignment, and thermal diffusivity.

ISSN:0021-8979    

DOI:10.1063/1.336868

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Raman scattering by coupled plasmon‐phonon modes in Ga0.75Al0.25As epitaxial layers grown by molecular beam epitaxy and metalorganic chemical vapor deposition was studied. Good agreement between predicted and observed behavior was found. It was concluded that Raman scattering can be conveniently used for nondestructive and fast evaluation of free electron concentration in these materials.

ISSN:0021-8979    

DOI:10.1063/1.336869

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We report new results obtained for thermal‐wave nondestructive evaluation applied to composite material using the mirage effect. We have thermally characterized a composite of woven carbon fibers and epoxy consisting of both opaque and transparent parts. We have measured the thermal diffusivity in the different regions of the composite. An anisotropy was found in the thermal diffusivity of the fibers and an effective diffusivity of the epoxy was calculated. From these experimental values we have been able to determine the thickness of the epoxy which coats, in many parts, the fibers. Subsurface cuts made perpendicular to the fibers were easily detected.

ISSN:0021-8979    

DOI:10.1063/1.336870

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Negative ion formation on a W(110) surface which is covered with a coadsorbed layer of cesium and hydrogen is studied by scattering a proton beam from such a surface. The primary energy is 400 eV. The angle of incidence is 70° with respect to the surface normal. The hydrogen exposure ranges from 0 to 3000 L. The negative ion formation probability on a surface with 0.6 times the saturation cesium coverage is reduced by a factor of 4 by a hydrogen exposure of 3000 L. At small coverage the reduction is found to be proportional to the number of adsorbed hydrogen atoms. The formation probability on a surface which is covered with a thick cesium layer is hardly affected by a similar exposure. These phenomena are attributed to resonant electron transfer between a negative ion and an adsorbed hydrogen atom.

ISSN:0021-8979    

DOI:10.1063/1.336871

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Hydrogenated amorphous silicon films are made by atmospheric pressure chemical vapor deposition from polysilanes between 430 and 480 °C. The films have hole diffusion lengths up to 0.4 &mgr;m, as measured by the surface photovoltage technique. Oxygen impurities are shown to reduce the diffusion length. Stainless‐steel and crystalline silicon substrates give slightly different results, implying that contamination is introduced by the substrates.

ISSN:0021-8979    

DOI:10.1063/1.336872

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Mechanically polished molybdenum samples have been irradiated with 150 keV molybdenum ions at fluences from zero to 16×1015ions/cm2to study the effects on surface smoothing. Both fluence and substrate temperature during irradiation (25, 250, and 500 °C) had considerable effects on the optical properties. Ellipsometry, profilometry, and Nomarski photography were used to characterize the surfaces. Multiple wavelength, multiple angle of incidence ellipsometry results were analyzed using effective medium approximation models, with molybdenum, molybdenum oxide, and voids as the principal constituents. Generally, we find that the reflectance calculated from the ellipsometric measurements increases continuously as a function of fluence. However, for high substrate temperature and short wavelength the reflectance as a function of fluence reaches a maximum and then decreases. Effective medium calculations indicate that there is a corresponding change in the surface roughness with fluence, and that effects due to oxides are minimal.

ISSN:0021-8979    

DOI:10.1063/1.336873

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Variable distances of the transitional, defect‐free, seeded crystallization of thin‐film silicon on insulating substrates have been investigated using energy beams of Gaussian intensity distribution. Phenomenologically, defect‐free crystals from the seed have been found to form Gaussianlike contours with respect to sub‐boundary‐laced crystals. The results are attributed to the thermal gradient effect upon the crystallization stability. This study bears a significant implication in the current efforts to increase the sub‐boundary‐free crystalline region over extended distances.

ISSN:0021-8979    

DOI:10.1063/1.336874

出版商:AIP    

年代:1986

数据来源: AIP