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Both dynamic and static approaches are proposed and investigated for controlling the optical phase of a p-polarized light wave guided through a surface-patterned metallic structure with subwavelength features. For dynamic control, the important role of photo-excited electrons in a slit-embedded atomic system with field-induced transparency (FIT) is discovered within a narrow frequency window for modulating the intensity of focused transmitted light in the near-field region. This is facilitated by electromagnetic coupling to surface plasmons between the two FIT-atom embedded slits. The near-field distribution can be adjusted by employing a symmetric (or asymmetric) slit configuration and by a small (or large) slit separation. In addition, the cross-transmission of a light beam is also predicted as a result of this strong coupling between optical transitions in embedded FIT atoms and surface plasmons. For static control, the role of surface curvature is found for focused transmitted light passing through a Gaussian-shaped metallic microlens embedded with a linear array of slits. A negative light-refraction pattern, which is associated with higher-order diffraction modes, was also found for large angles of incidence in the near-field region. This anomalous negative refraction can be suppressed when higher-order waveguide modes of light leak through a very thin film. In addition, this negative refraction can also be suppressed with a reinforced reflection at the left foothill of a Gaussian-shaped slit array of the forward-propagating surface-plasmon wave at large angles of incidence. A prediction is given of near-field focusing of light with its sharpness dynamically controlled by the frequency of the light in a very narrow window. Moreover, a different scheme based on Green's second integral identity is proposed for overcoming a difficulty in calculating the near-field distribution very close to a metallic surface by means of a finite-difference-time-domain method. © 2013 AIP Publishing LLC.

A giant negative electrocaloric (EC) effect in a PbZrO3/(0.88BaTiO3-0.12 Bi(Mg1/2,Ti1/2)O3) (PZ/(BT-BMT)) multilayered composite ferroelectric (MCFE) thin film which is grown on Pt(111)/Ti/SiO2/Si(100) substrates by the sol-gel method is investigated in this work. The negative EC effect in the PZ/(BMT-BT) MCFE thin film is greatly higher than that in the PZ AFE thin film with an adiabatic temperature change (ATC) ΔT = 1.5 K. The ATC ΔT of the PZ/(BMT-BT) MCFE thin film is -32 K under the applied electric field change ΔE = 1151 kV/cm. The result is conducive to enhance the EC refrigeration efficiency greatly. [ABSTRACT FROM AUTHOR]

The electrocaloric (EC) effect in PbTiO3 ferroelectric thin films (FETFs) with an array of partially compensated head-to-head (HH) and tail-to-tail (TT) 90° charged domain walls (CDWs) has been studied by using a phase field method. The calculation results indicate that the magnitude of the adiabatic temperature change ΔT increases with the diminution of the charge density (ρ*), in which ρ* is provided by charged defects or band bending. In particular, a negative EC effect caused by the direction difference between the applied electric field and the dipole is found near the HH and TT domain walls when ρ*>2.0. The EC strength |ΔT|/|ΔE| is 0.020 K cm kV-1 with the positive ΔT = 2.03 K at the external dimensionless electric field Eb*=0.08 (ΔE=104kV cm-1). These results indicate that the CDWs can provide an efficient way to adjust the EC effect of FETFs for refrigeration applications at room temperature. [ABSTRACT FROM AUTHOR]

Research was conducted to study intersubband transitions in GaAs/GaAIAs multiquantum wells under hydrostatic pressure. Weak indirect transitions were improved by using modulated transmission measurements while several phonon-assisted indirect transitions were resolved on the photo-transmission spectra. Results indicated that phonon-assisted indirect transitions can be significantly improved by the use of the photomodulation technique in transmitting geometry.

We have studied the electronic structure of Fe-doped ZnO nanoparticles, which have been reported to show ferromagnetism at room temperature, by x-ray photoemission spectroscopy, resonant photoemission spectroscopy, x-ray absorption spectroscopy, and x-ray magnetic circular dichroism (XMCD). From the experimental and cluster-model calculation results, we find that Fe atoms are predominantly in the Fe3+ ionic state with mixture of a small amount of Fe2+ and that Fe3+ ions are dominant in the surface region of the nanoparticles. It is shown that the room temperature ferromagnetism in the Fe-doped ZnO nanoparticles primarily originated from the antiferromagnetic coupling between unequal amounts of Fe3+ ions occupying two sets of nonequivalent positions in the region of the XMCD probing depth of ∼2–3 nm. [ABSTRACT FROM AUTHOR]

We present resonant soft x-ray scattering studies of Ti 3d and O 2p states at the interfaces of SrTiO3/LaAlO3 superlattices. From reflectivity analyses, focusing on the (003) peak which is forbidden for our “ideal” superlattice structure, we concluded that the LaO|TiO2/SrO and the SrO|AlO2/LaO interfaces have distinct reconstructions, breaking the heterostructure symmetry. [ABSTRACT FROM AUTHOR]

Under ultrahigh vacuum conditions, extremely small Ge nanodots embedded in SiO2, i.e., Ge–SiO2 quantum dot composites, have been formed by ion implantation of 74Ge+ isotope into (0001) Z-cut quartz at a low kinetic energy of 9 keV using varying implantation temperatures. Transmission electron microscopy (TEM) images and micro-Raman scattering show that amorphous Ge nanodots are formed at all temperatures. The formation of amorphous Ge nanodots is different from reported crystalline Ge nanodot formation by high energy ion implantation followed by a necessary high temperature annealing process. At room temperature, a confined spatial distribution of the amorphous Ge nanodots can be obtained. Ge inward diffusion was found to be significantly enhanced by a synergetic effect of high implantation temperature and preferential sputtering of surface oxygen, which induced a much wider and deeper Ge nanodot distribution at elevated implantation temperature. The bimodal size distribution that is often observed in high energy implantation was not observed in the present study. Cross-sectional TEM observation and the depth profile of Ge atoms in SiO2 obtained from x-ray photoelectron spectra revealed a critical Ge concentration for observable amorphous nanodot formation. The mechanism of formation of amorphous Ge nanodots and the change in spatial distribution with implantation temperature are discussed. [ABSTRACT FROM AUTHOR]

Organized extremely small Ti–Sn alloy nanodots have been formed in the subsurface of SiO2 by dynamic coimplantation of isotopic 48Ti+ and 120Sn+ at a low kinetic energy of 9 keV into (0001) Z-cut quartz at different substrate temperatures. Transmission electron microscopy images show that the Ti–Sn alloy nanodots are single crystal and have been formed uniformly at room temperature. They are distributed in a two-dimensional array with similar size of ∼4 nm and constant interdot spacing between each dot. The regions beyond and below the two-dimensional array are depleted of detectable nanodots. At high temperature, the distribution and crystallinity were destroyed with much smaller amorphous nanodots in a slightly deeper region. The implantation was carried out by dynamic coimplantation, rather than the commonly used sequential implantation. These results indicate that dynamic low energy coimplantation is capable of forming well-ordered two-dimensional array of alloy nanodots. [ABSTRACT FROM AUTHOR]

The influence of a nano-nitride-layer (NNL) doped at different interfaces in the structure of Cu/Co/Cu/Co/Cu on magnetoresistance (MR) is investigated. As the NNL is doped at the inner interfaces of the core Co/Cu/Co sandwich, an inverse MR is observed. This contrasts sharply with that doping at the two outer interfaces between the core sandwich (Co/Cu/Co) and the buffer or/and the capping layers. The result arises from the negative spin asymmetry induced by the NNL doping under different interfacial circumstances. Moreover, the MR value increases in magnitude as temperature is decreased from room temperature to 4.2 K. [ABSTRACT FROM AUTHOR]

Gadolinium-doped ceria (Ce0.8Gd0.2O2-δ) thin films were grown on single-crystal (001) LaAlO3 (LAO) substrates by a pulsed laser ablation. The transmission electron microscope observation reveals a unique type of periodic film distortion along the film/substrate interface. Each distorted film area is associated with a few substrate-surface steps and the spacing between these distorted areas is about 50 μm. The distortion starts at the substrate-surface steps and extends into the film along one of the {111} planes at the step-forward direction. The {111} planar defects induced by the nearby steps can interact with each other to form a planar defect network. The structure of the (001) LAO surface, the structure of the film/substrate interface, and the mechanism of the formation of these {111} planar defects have been analyzed using a high-resolution electron microscopy. Structural models for these planar defects and their interaction are suggested. [ABSTRACT FROM AUTHOR]

A series of sharp intense peaks was observed in the low-temperature photoluminescence spectrum of unintentionally doped GaN in the photon energy range between 3.0 and 3.46 eV. We attributed the majority of these peaks to excitons bound to unidentified structural and surface defects. Most of the structural- and surface-related peaks (at 3.21, 3.32, 3.34, 3.35, 3.38, and 3.42 eV) were observed in Ga polar films. In N polar GaN, we often observed the 3.45 eV peak attributed to excitons bound to the inversion domain interfaces. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

MnBiSi films subjected to favorable doping indicate a structural distortion. The structure and magneto-optical properties of the effect of Al doping on these films are analyzed. The structural distortion is caused by the doping of Al and an increase in the Kerr rotation angle.

The microstructural and magnetic characteristics of Bi/Al/Mn/SiO multilayered structures were investigated using magnetic measurements. A new type of domain structure which was characterized by increasing ramified branches and conspicuous circular envelopes was reported. The results showed that these branches were associated with the magnetization orientations of the films.

Provides information on a study which investigated the lattice damage and the nature of the atomic intermixing of aluminum and gallium induced by As[sup++] implantation and thermal annealing in AlAs/GaAs multiple quantum-well structures. Basis for the photoluminescence spectra; Way that the depth profiles of intermixing were obtained; Techniques that introduce defects; Cause of the reduction of the radiation damage.

Focuses on a study which measured the dielectric function of YBa[sub2]Cu[sub3]O[sub7-δ] by spectroscopic polarization modulation ellipsometry. Properties of superconductor yttrium-barium-copper-oxygen; Effect of critical or plasma energy in crystal orientation; Magnitude of the dialectric functions.

Presents a study on diamond particles that were produced by microwave-assisted combustion of acetylene in oxygen. Experimental procedures; Results and discussion.

Presents a study which examined the oscillations in the photoreflectance spectra in the energy range below band gap of gallium arsenide on samples containing gallium arsenide/aluminum gallium arsenide quantum wells and other multilayers grown on silicon-doped gallium arsenide substrates.

Focuses on a study which analyzed the properties of undoped and lightly silicon-doped gallium arsenide[sub1-x] antimony [subx] bulk layers that was molecularly beam epitaxy-grown on gallium arsenide substrates with antimony (Sb) composition. Findings from photoluminescence and absorption measurements; Observations in absorption spectra; Effect of higher quality epilayers.

Presents information on a study which analyzed the photoreflectance (PR) spectra of bulk aluminum[subx] gallium (Ga)[sub1-x] arsenide (As) alloys. Advantages of PR over other techniques; Experimental procedures; Absoprtion spectrum of pure bulk Ga As; Depth profiling by the nuclear resonant reaction analysis technique; Factors determining PR line shape.

Provides information on the measurement of low-temperature optical transmission spectra of several indium-gallium-arsenic/gallium arsenide strained multiple quantum wells. Transitions related to the nth conduction and mth valence heavy hole subbands; Application of standard single-band Kronig-Penney model; Energy band configuration for light holes.

Reports the homogeneous nucleation of diamond powder in the gas phase. Description of the experimental setup; Details of the operating conditions of the successful experiments; Discussion of results.

Presents a study which calculated the recombination lifetimes for donor-acceptor (D-A) pairs in gallium arsenide (GaAs). Observation of a group of photoluminescent lines in the energy in GaAs; Characteristics of the lifetimes D-A recombinations in GaAs; Activation of energies of D-A pairs.

Presents a motor design that efficiently reduces magnetic flux leakage by using a pair of yokes on the rotor magnet. Reason that a small direct current spindle motor with small magnetic flux leakage must be used for a CD-ROM drive application; Magnetic field profile and flux density of a single rotor magnet; Description of a good shielding design for a motor application.

Describes the magnetic field splitting and strain splitting of the emission lines in the 1.5040-1.5110 electronvolt range in GaAs. Information on the shallow donor-acceptor pair model; Description of the splitting patterns for shallow donor-acceptor centers in a zinc-blende lattice; Analysis of nine lines for hole g values.