摘要:

We performed scanning tunneling microscope experiments with GaAs tips under illumination by circularly polarized light in ultrahigh vacuum at room temperature. Ferromagnetic ultrathin cobalt layers with perpendicular magnetization were employed as test samples. The spin-polarized tunneling current was shown to exhibit a magnetic sensitive component, changing its sign from one place to another on the sample surface. Reproducible images exhibiting magnetic domains of a 300–500 nm characteristic size were obtained. These results agree with magnetic force microscope measurements performed on a typical sample. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120274

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Scattering of He ions off a magnetic surface results in the emission of circularly polarized light from a triplet transition. From the light polarization the spin polarization of the surface electrons can be deduced. We show that this electron capture spectroscopy (ECS) in the grazing incidence mode is an inherently surface sensitive method capable of measuring magnetic hystereses. The temperature dependence of the signal gives clear evidence that ECS is sensitive to the outermost atomic layer only. The signal follows a Bloch law with a surface prefactor ofAsurf=3.33×10−5 K−3/2. The signal as a function of the applied magnetic field results in a hysteresis which is compared to a hysteresis obtained by means of the magneto-optical Kerr effect. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120275

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Novel field emission devices with electron path lengths an order of magnitude less than the elastic mean free path of electrons in air have been fabricated and tested at atmospheric pressure. The nanoscale-tip field emission system consisted of multiple emitter tips of radii about 1 nm within an extractor aperture of diameter 50 nm. The extractor turn-on voltage was approximately 7.5 V; field-emitted currents of up to 10 nA were collected at extractor voltages of less than 10 V. Maximum current densities of over1011 A m−2have been observed, and the emission stability in air at atmospheric pressure is better than 3&percent;. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120276

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The delicate interplay between the effects of mechanical rubbing and subsequent photo-induced chemical reactions on polyimide films has been studied for aligning liquid crystals. Exposure to linearly polarized ultraviolet (LPUV) light was found to profoundly alter the direction and the degree of molecular orientations obtained by rubbing. A simple model is presented to describe the observed changes in the director orientation. The results show that LPUV exposure can be very effectively used to control and fine-tune liquid crystal alignment. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120277

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have studied microdefects and interfaces ofAl2O3films on iron and nickel aluminide substrates using variable-energy positron lifetime spectroscopy. Di-vacancies, vacancy clusters, and microvoids were observed in the oxide scales. Their sizes and distributions were determined by the nature of the process used to synthesize the alumina film, and influenced by the composition of the alloy substrates. For oxide–iron aluminide interfaces, positron lifetimes are longer than those for the alumina layer itself, suggesting a greater defect concentration at such sites. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120278

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The cold neutron transmission through a monolithic polycapillary lens is studied by scanning a pinhole beam across the entrance cross section of the lens. The relative transmission as a function of bending radius of a tapered channel is obtained. The results are explained in terms of a reduced critical angle for total reflection for the tapered channels. A technique for qualitative examination of monolithic lenses is proposed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120449

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Electromigration-induced stress in near bamboo structure interconnects has been simulated by the finite element method. The maximum stress at the juncture of polygranular clusters and bamboo segments increases when the stress profile interacts with the line end. The maximum stress at final steady state depends on the relative location of the polygranular cluster in the line under the constant source boundary condition. Under the blocking boundary condition, the steady state stress profile (if it exists) is determined only by current density and total line length and is independent of the microstructure of the line. Finally, the ratio of effective diffusivity of the cluster to that of bamboo segments affects the magnitude of maximum stress at quasi-steady state. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120279

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Nano-compact disks (Nano-CDs) with400 Gbit/in2topographical bit density (nearly three orders of magnitude higher than commercial CDs) have been fabricated using nanoimprint lithography. The reading and wearing of such Nano-CDs have been studied using scanning proximal probe methods. Using a tapping mode, a Nano-CD was read 1000 times without any detectable degradation of the disk or the silicon probe tip. In accelerated wear tests with a contact mode, the damage threshold was found to be 19 &mgr;N. This indicates that in a tapping mode, both the Nano-CD and silicon probe tip should have a lifetime that is at least four orders of magnitude longer than that at the damage threshold. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120280

出版商:AIP    

年代:1997

数据来源: AIP