摘要:

We found that the ferroelectric coercive field of LiTaO3, both in forward and reverse directions, can be increased in large amount by high power multiline argon laser illumination. This phenomenon is especially profound when the coercive field measurement is performed closer in time to the previous domain inversion operation. We also demonstrated that the domain in lithium‐tantalate crystal can be patterned in accordance with the argon laser light distribution on the crystal plate surface. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117110

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A single molecule in an inhomogeneous environment is studied theoretically using phenomenological theory. The molecule is located on a planar glass substrate and a finite sized, three dimensional object is scanned over the molecule at different heights. Lifetime and quantum yield are calculated as a function of the lateral position of the object. The analysis is based on a new field expansion method using Green’s functions of a layered reference system as basis functions. It is found that, near the edges of the object, the molecular lifetime is highly sensitive to the orientation of the transition dipole. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117111

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

High resolution near‐field fluorescence and topology images of intact neurons are reported using a cantilevered near‐field fiber optic probe. A bend is introduced into a normal geometry near‐field tip, allowing the probe to be used in a tapping‐mode arrangement, similar to tapping‐mode atomic force microscopy. Features with a full width at half‐maximum of 140 nm are observed in the near‐field fluorescence image, demonstrating the subdiffraction limit spatial resolution possible with the cantilevered near‐field probe design. Characteristics of the cantilevered tips include resonances between 30 and 60 kHz,Qfactors greater than 100, and measured spring constants of 300 to 400 N/m. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117112

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report the fourth‐harmonic generation of 1.5 ps, 1.053 &mgr;m glass laser pulses, where group velocity mismatch plays a significant role, at intensities up to 100 GW/cm2using newly developed crystal, cesium lithium borate (CsLiB6O10). Type‐I doubler and type‐I quadrupler were used in the fourth harmonic generation experimental scheme. Energy conversion efficiencies of 24% and 53% have been achieved for frequency quadrupling and doubling of the fundamental glass laser pulses, respectively. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117113

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We propose a method to improve the impact energy of ions implanted into the interior sidewalls of cylindrical specimens during plasma immersion ion implantation. Our idea is based on a zero potential conductive auxiliary electrode positioned at the axis of the implanted cylindrical bore. We calculate the structure of the ion‐matrix sheath in an infinitely long cylindrical bore with an auxiliary electrode and analyze the dependence of the radius of the auxiliary electrode on the electric field in the bore. Our results show that the auxiliary electrode improves significantly the distributions of the potential and the electric field inside the cylindrical bore. In addition, because the auxiliary electrode improves the potential drop from axis to sidewalls of the bore and introduces an electric field component which does not vary when the ions are implanted into the sidewalls, the impact energy can be improved in a cylindrical bore during plasma immersion ion implantation. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117114

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The mechanisms of electron heating in low‐pressure bounded rf plasmas are analyzed. These processes are determined by the combined effect of electron interaction with the rf electric field, reflections from the walls and collisions. It is shown that when the discharge gap is small with respect to the electron mean‐free path the finite size of the plasmas is crucial for the stochastic heating. A classification of heating regimes is performed and expressions for the power deposition are derived. In many cases, even though in a semi‐infinite plasma heating exists, in a bounded plasma the electron motion is regular and there is no collisionless heating. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117115

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The kinetics of processes related to the formation of C49 and C54 Ti(Si1−yGey)2germanosilicide phases in the two relaxed and strained Ti/Si1−xGexsystems (x1=0.35 andx2=0.20) in the temperature range 600–800 °C are considered. These processes have been studied through Auger electron spectroscopy, secondary ion mass spectroscopy, x‐ray diffraction, and Raman scattering spectroscopy supported by ion beam etching techniques. Si/Ge ‘‘intergrain’’ alloy has been found between the grains of the C49 or/and C54 phases, with a Ge‐rich part Si1−zGezofz=2x–3xin the upper region. At higher temperatures, the Ge concentration in the Ge‐rich alloy decreases and its volume increases. The temperature required for obtaining similar changes are higher whenx2<x1. A kinetic electron‐related model is proposed to explain the observed phenomena. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117116

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Single crystal 3C–SiC platelets, formed by thermal decomposition of methyltrichlorosilane at 1650–1750 °C, have been characterized in terms of structure and morphology. The platelets are ∼3–5 mm in length and 1–1.5 mm in thickness. The (111) C face of the crystal, which has an effective zero growth rate, presents a large, mirrorlike surface in the as‐grown 3C crystals. Atomic force microscopy indicates that theseas‐grownsurfaces are extraordinarily flat and uniform, with a mean surface roughness of 1–2 A˚. This value is comparable with the roughness of state‐of‐artpolishedSi wafers. X‐ray rocking curves of the ⟨111⟩ peak were obtained with a linewidth of 12.3 arcsec. This is the smallest value reported to date for any polytype of SiC. Raman spectroscopy at 300 K reveals a very sharp TO–phonon peak at 797.8 cm−1, with a linewidth of 2.1 cm−1. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117117

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The elastic properties of organically modified silicates prepared by ultrasonics aided polycondensation of Tetraethoxysilane and Polidimethylsiloxane is studied by means of high resolution Brillouin spectroscopy. Our results evidence the microseparation of the organic and inorganic phases for the systems with high content of polymer. We propose a mechanical model that qualitatively explains the observed variation of the elastic constantc11vs molar fraction of dimethylsiloxane in these vitreous materials and develop a structural model that accounts for the observed dynamical behavior. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117118

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Real‐time stress measurements during Si1−xGex/Si molecular beam epitaxy are used to dynamically monitor Ge surface segregation. Segregation during alloy growth produces a change in the surface stress that offsets the coherency stress in the pseudomorphic film. We outline a method for analyzing the stress evolution kinetics to determine the alloy composition profile resulting from segregation. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117119

出版商:AIP    

年代:1996

数据来源: AIP