bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved morphology for ohmic contacts to AlGaN/GaN high electron mobility transistors using WSix- or W-based metallization
Authors: Luo B. , Ren F. , Fitch R. C. , Gillespie J. K. , Jenkins T. , Sewell J. , Via D. , Crespo A. , Baca A. G. , Briggs R. D. , Gotthold D. , Birkhahn R. , Peres B. , Pearton S. J.
Published: May 2003

A comparison was made of specific contact resistivity and morphology of Ti/Al/Pt/WSi/Ti/Au and Ti/Al/Pt/W/Ti/Au ohmic contacts to AlGaN/GaN heterostructures relative to the standard Ti/Al/Pt/Au metallization. The W- and WSi-based contacts show comparable specific resistivities to that of the standard contact on similar layer structures, reaching minimum values of ∼10−5 Ω cm2 after annealing in the range 850–900 °C. However, the W- and WSi-based contacts exhibit much smoother surface morphologies, even after 950 °C annealing. For example, the root-mean-square roughness of the Ti/Al/Pt/WSi/Ti/Au contact annealed at 950 °C was unchanged from the as-deposited values whereas the Ti/Al/Pt/Au contact shows significant deterioration of the morphology under these conditions. The improved thermal stability of the W- and WSix-based contacts is important for maintaining edge acuity during high-temperature operation.
Mutual pulse injection-seeding scheme by the use of two Fabry–Pérot laser diodes for tunable dual-wavelength optical short-pulse generation
Authors: Wang D. N. , Fang Xiaohui
Published: May 2003

Two Fabry–Pérot laser diodes, one being gain switched and the other dc biased, are used in a mutual pulse injection-seeding scheme for tunable dual-wavelength optical short-pulse generation. Wavelength selection and tuning are achieved by adjusting two fiber Bragg gratings and optical delay lines while a constant repetition frequency of 1.5053 GHz is maintained. An erbium-doped fiber amplifier is employed to enhance light intensity injected to the laser diode. The sidemode suppression ratio of the output pulses achieved is better than 25 dB over the wavelength-tuning range of 12.1 nm. The system is robust, flexible, and convenient for wavelength tuning.
Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene-containing polymer films
Authors: Kang Jae-Wook , Kim Mi-Jeong , Kim Jae-Pil , Yoo Seong-Jong , Lee Jae-Suk , Kim Dong Yu , Kim Jang-Joo
Published: May 2003

Polymeric wavelength filters with Bragg gratings have been fabricated using holographic surface relief gratings on azobenzene polymer films. In order to fabricate Bragg gratings on polymer waveguides, we used holographic surface relief gratings on the azobenzene polymer film as an etch mask and the grating patterns were transferred to the polymer waveguides by O2 reactive ion etching. The grating period was ∼500 nm and the depth was ∼30 nm with a 10-mm-long Bragg grating length. A transmission dip of −15 dB at the Bragg wavelength and a 3-dB-transmission bandwidth of ∼0.2 nm were obtained from the device.
Single-pass gain in a chirped quasi-phase-matched optical parametric oscillator
Authors: Baker K. L.
Published: May 2003

In this letter, the single-pass gain of a quasi-phase-matched optical parametric oscillator with chirped poling is calculated. Specifically, the single-pass gain from optical parametric oscillators containing a zn chirped profile of their periodically poled grating wavelength is derived. Using the calculated gain, the parametric oscillator threshold is determined. Both the gain and threshold condition for a chirped device contain an increased power scaling in the pump intensity over a uniformly poled device due to the pump power dependence in the interaction length. The chirped poling structure exhibits a lower gain, a higher threshold, and a larger bandwidth at threshold than uniformly chirped devices with the same overall crystal length.
Beam shaping by a periodic structure with negative refraction
Authors: Shadrivov Ilya V. , Sukhorukov Andrey A. , Kivshar Yuri S.
Published: May 2003

We analyze transmission of a layered photonic structure (a one-dimensional photonic crystal) consisting of alternating slabs of two materials with positive and negative refractive index. For the periodic structure with zero averaged refractive index, we demonstrate a number of unique properties of the beam transmission observed in strong beam modification and reshaping.
Al
2
O
3
/
Si
3
N
4
stacked insulators for 0.1 μm gate metal–oxide–semiconductor transistors realized by high-density Si3N4 buffer layers
Authors: Fujisaki Yoshihisa , Iseki Kunie , Ishiwara Hiroshi , Mao Ming , Bubber Randhir
Published: May 2003

We developed Al2O3/Si3N4 stacked insulators suitable for the advanced metal–oxide–semiconductor (MOS) devices. Ultrathin Si3N4 was prepared by direct nitridation of Si substrate using atomic nitrogen radicals. With this process, the film obtained was less defective compared to conventional Si3N4. Al2O3 was then deposited by atomic layer deposition on Si3N4 and oxidized to eliminate defects in the film. Since the buffer Si3N4 does not contain a large amount of hydrogen, we could perform high-temperature oxidation without any additional interfacial layer formation in the Si substrate. We achieved high capacitance density and low leakage current that are acceptable for the gate insulator in advanced MOS devices with a 0.1 μm gate length by exploiting this buffering technique.
Nonlocal resonant interaction between coupled quantum wires
Authors: Morimoto T. , Iwase Y. , Aoki N. , Sasaki T. , Ochiai Y. , Shailos A. , Bird J. P. , Lilly M. P. , Reno J. L. , Simmons J. A.
Published: May 2003

We study the transport in a system of coupled quantum wires and show evidence for a resonant interaction that occurs whenever one of them is biased close to pinch off. Measuring the conductance of one of the wires, as the width of the other is varied, we observe a resonant peak in the conductance that is correlated to the point at which the other wire pinches off. The origin of this interaction remains undetermined at present, although its characteristics appear consistent with predictions that a correlated many-body state should form in narrow wires as their conductance vanishes.
Mechanism of the reverse gate leakage in AlGaN/GaN high electron mobility transistors
Authors: Karmalkar Shreepad , Sathaiya D. Mahaveer , Shur M. S.
Published: May 2003

The off-state gate current in AlGaN/GaN high electron mobility transistors is shown to arise from two parallel gate to substrate tunneling paths: a direct path, and a path via deep traps, which are distributed throughout the AlGaN layer and spread over an energy band. A model to calculate this current is given, which shows that trap-assisted tunneling dominates below T∼500 K, and direct tunneling (thermionic field emission) dominates at higher temperatures. A model fit to experimental results yields the following fabrication process sensitive parameters: trap concentration of ∼1013–1015 cm−3, and trap bandwidth of ∼50%–70% of the barrier height located 0.4–0.55 V below the conduction band edge.
Cyclotron resonance of terahertz photoresponse in two-dimensional polar semiconductors at high temperatures
Authors: Lei X. L. , Liu S. Y.
Published: May 2003

Far infrared photoresponse of magnetoresistivity ΔRxx of two-dimensional electron systems is investigated theoretically at high temperatures. Photon-assisted impurity and phonon scatterings, rather than the electron heating, are shown to be the dominant mechanisms for high-temperature photoresponse at cyclotron resonance. Based on the theory developed for electron magnetotransport driven by intense terahertz radiations, we have calculated the far infrared photoresistivity of a GaAs/AlGaAs heterostructure at temperature T=150 K, predicting notable cyclotron resonance of ΔRxx, in agreement with the experimental finding. Contrary to low temperature case, where the electron heating is almost solely responsible for the cyclotron resonance of ΔRxx, at T=150 K electron-heating contribute at most a small fraction of the total response.
Electroluminescence of a quantum dot cascade structure
Authors: Anders S. , Rebohle L. , Schrey F. F. , Schrenk W. , Unterrainer K. , Strasser G.
Published: May 2003

We present electroluminescence and photocurrent measurements on InAs quantum dots that are embedded into a cascaded GaAs/AlAs structure. Compared to a quantum cascade laser, population inversion in a quantum dot cascade laser should potentially occur at a lower threshold. The electroluminescence spectra of our device peak in the midinfrared at about 150 meV. From the polarization behavior of the electroluminescence, we conclude that quantum dots are the origin of the optical transition.
Determination of the electron capture time in quantum-well infrared photodetectors using time-resolved photocurrent measurements
Authors: Steinkogler S. , Schneider H. , Walther M. , Koidl P.
Published: May 2003

We have investigated the transport properties of optically excited electrons in a 100 period InGaAs/GaAs-quantum well infrared photodetector. The electrons were excited by femtosecond-infrared laser pulses and the transient photocurrent was recorded in the picosecond regime. We have carefully analyzed the measured photocurrent transients taking into account both the capture time τc and the transit time τtrans. Our experimental results allow us to determine τc, which increases from 10 ps at 5 kV/cm to about 20 ps at 20 kV/cm. We have also measured the noise gain in order to determine the transit time and the drift velocity. The dynamic parameters extracted from our measurements are consistent with values from the literature.
Spatially resolved Poisson strain and anticlastic curvature measurements in Si under large deflection bending
Authors: Yang Wenge , Larson B. C. , Ice G. E. , Tischler J. Z. , Budai J. D. , Chung K.-S. , Lowe W. P.
Published: May 2003

A scanning-monochromatic form of differential-aperture x-ray microscopy (DAXM) has been developed that provides micron-resolution depth-resolved dilatational strain measurements. This scanning-monochromatic DAXM technique is applied to measurements of Poisson dilatational strain in 25-μm-thick Si bent into an arch with an apex radius of R=3 mm. Poisson strain measurements agree with anisotropic linear elasticity calculations for a Searle parameter as large as β=1009. Local anticlastic bend radii were shown to oscillate across the arch and reach the R/ν limit for distances less than the plate thickness from the edges, where ν is the anisotropic Poisson’s ratio.
Optical peristalsis
Authors: Koss Brian A. , Grier David G.
Published: May 2003

We describe an efficient method for transporting and rearranging mesoscopic objects in three dimensions using short repetitive sequences of holographic optical trapping patterns. Material transport in this process is analogous to peristaltic pumping, with the configurations of optical traps mimicking the states of a physical peristaltic pump. Optical peristalsis can transport large numbers of small particles rapidly and determinstically through complex three-dimensional patterns. The same system also can be used to study transport in a variety of model thermal ratchets.
Nonlinear optical susceptibility measurements of solutions using third-harmonic generation on the interface
Authors: Shcheslavskiy Vladislav , Petrov Georgi , Yakovlev Vladislav V.
Published: May 2003

By simultaneous measurements of the third-harmonic intensity on two interfaces, it is possible to make precise and fast measurements of the third-order nonlinear optical susceptibility of solutions. We propose a simple nonlinear optical technique that eliminates the effects of both scattering and absorption, thus allowing for characterization of colloidal solutions with possible aggregation. The proposed technique is experimentally demonstrated for a variety of solutions, both transparent and scattering, and shows very good agreement with data obtained by other means.
Time-resolved energy dispersive x-ray reflectometry measurements on ruthenium phthalocyanine gas sensing films
Authors: Rossi Albertini V. , Generosi A. , Paci B. , Perfetti P. , Rossi G. , Capobianchi A. , Paoletti A. M. , Caminiti R.
Published: May 2003

The energy dispersive (ED) variant of the conventional x-ray reflectivity (XR) provides an atomic scale determination of the morphological characteristics of thin films, such as their thickness and surface roughness. We report on the in situ EDXR measurements of the (minimal) morphological changes of ruthenium phthalocyanine gas sensing thin films. A series of reflectivity spectra have been collected, during the exposure of the films to a gas flux of nitrogen oxides (NOx) molecules. The measurements allowed a very high density time sampling of the evolution of the two morphological parameters, providing important information on the gas-film interaction.
Li
2
CsSb
:
A highly-efficient photocathode material
Authors: Ettema A. R. H. F.
Published: May 2003

The electronic band structure of the alkali antimonide Li2CsSb has been calculated. Based on this calculation, estimates are given for the absorption coefficient and the radiative lifetime of the photoelectron. The optical generation of photoelectrons in this material proceeds via a direct optical transition, but after relaxation of the photoelectron it is prohibited to recombine with a valence band hole due to the indirect band gap. The photoelectron lifetime and the diffusion lengths are compared with other photocathode materials. The results suggest that for Li2CsSb the photocathode can be made significantly thicker and therefore more efficient.
Electronic structure of GaN nanowire studied by x-ray-absorption spectroscopy and scanning photoelectron microscopy
Authors: Chiou J. W. , Jan J. C. , Tsai H. M. , Pong W. F. , Tsai M.-H. , Hong I.-H. , Klauser R. , Lee J. F. , Hsu C. W. , Lin H. M. , Chen C. C. , Shen C. H. , Chen L. C. , Chen K. H.
Published: May 2003

X-ray absorption near edge structure (XANES) and scanning photoelectron microscopy (SPEM) measurements have been employed to obtain information on the electronic structures of the GaN nanowires and thin film. The comparison of the XANES spectra revealed that the nanowires have a smaller (larger) N (Ga) K edge XANES intensity than that of the thin film, which suggests an increase (decrease) of the occupation of N 2p (Ga 4p) orbitals and an increase of the N (Ga) negative (positive) effective charge in the nanowires. The SPEM spectra showed that the Ga 3d band for the nanowires lies about 20.8 eV below the Fermi level and has a chemical shift of about −0.9 eV relative to that of the thin film.
Photonic crystal structure with square symmetry within each layer and a three-dimensional band gap
Authors: Roundy David , Joannopoulos John
Published: May 2003

We present a layered photonic crystal structure having a connectivity that is different from diamond which possesses square symmetry within each layer. This structure has a complete photonic band gap of 18% of the midgap frequency with a dielectric contrast of 12:1, and is a structure with layered square symmetry having a gap greater than 10%. We demonstrate a waveguide in this crystal created by removing a row of rods from a single layer.
Polarized total-reflection x-ray absorption fine structure for self-assembled monolayer of zinc porphyrin at air–water interface
Authors: Tanida Hajime , Nagatani Hirohisa , Watanabe Iwao
Published: May 2003

A new x-ray absorption fine structure (XAFS) method is applied to the air–solution interface. Under the total reflection condition, the XAFS method becomes surface sensitive, enabling the self-assembled monolayer of a metal complex at the solution surface to analyze in situ. Furthermore the introduction of two types of linearly polarized x rays allows us to determine the selective orientation of a planar metal complex at the surface. We obtain spectra for a square planar complex, 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrinato zinc(II) (ZnTPPC) adsorbed on the aqueous solution surface forming a monolayer with two polarized x rays and compared them with spectra of the same compound in a bulk solution and in solid powder. The polarized XAFS spectra exhibit different features leading to the unambiguous conclusion that the plane of the ZnTPPC molecule is oriented parallel to the air–water interface and that there is no coordination to the axial sites of the zinc atom.
Single-electron charging of a self-assembled II–VI quantum dot
Authors: Seufert J. , Rambach M. , Bacher G. , Forchel A. , Passow T. , Hommel D.
Published: May 2003

We have studied single-electron injection into individual self-assembled CdSe/ZnSe quantum dots. Using nanostructured contacts to apply a vertical electric field, excess electrons are promoted to the single-quantum-dot ground state in a controlled fashion. Spatially-resolved photoluminescence spectroscopy is applied to demonstrate single-quantum-dot charging via the formation of single zero-dimensional charged excitons with a binding energy on the order of 10 meV.
A 33% efficient chemical oxygen–iodine laser with supersonic mixing of iodine and oxygen
Authors: Rybalkin V. , Katz A. , Barmashenko B. D. , Rosenwaks S.
Published: May 2003

We report on a highly efficient supersonic chemical oxygen–iodine laser (COIL), with supersonic mixing of iodine and oxygen. Output power exceeding 0.5 kW with chemical efficiency of ∼33% was obtained in a 5-cm gain length for Cl2 flow rate of 17 mmole/s. A 33% efficiency is the highest reported chemical efficiency of any supersonic COIL. Comparison between different mixing schemes shows that, for supersonic mixing, the output power and chemical efficiency are about 20% higher than for transonic mixing scheme. The optimal conditions for the efficient operation are investigated.
Polymeric amorphous carbon as p-type window within amorphous silicon solar cells
Authors: Khan R. U. A. , Silva S. R. P. , van Swaaij R. A. C. M. M.
Published: May 2003

Amorphous carbon (a-C) has been shown to be intrinsically p-type, and polymeric a-C (PAC) possesses a wide Tauc band gap of 2.6 eV. We have replaced the p-type amorphous silicon carbide layer of a standard amorphous silicon solar cell with an intrinsic ultrathin layer of PAC. The thickness of the p layer had to be reduced from 9 to 2.5 nm in order to ensure sufficient conduction through the PAC film. Although the resulting external parameters suggest a decrease in the device efficiency from 9.2% to 3.8% due to a reduced value of open-circuit voltage, the spectral response shows an improvement in the 400–500-nm wavelength range, as a consequence of the wider band gap of the PAC layer.
Effects of pulsed potential on address electrode in a surface-discharge alternating-current plasma display panel
Authors: Ahn Jeong Chull , Shintani Youichi , Tachibana Kunihide , Sakai Tetsuo , Kosugi Naoki
Published: May 2003

The influence of pulsed potential application onto the address electrode of an ac-type plasma display panel was investigated from the observation of front and side views of Xe atom densities in the metastable (1s5) and excited (2p) states in a unit discharge cell by using microscopic laser absorption spectroscopy and optical emission spectroscopy. It was seen that a predischarge occurs between the address electrode and one of the sustain electrode worked as a preceding anode, which is a similar effect found previously by applying a higher sustain voltage. The predischarge partially erases the surface charge accumulated in the preceding pulse, but it induces a faster main sustain discharge, bowing towards the address electrode, and enhances the production efficiency of Xe(1s5) atoms, if the applied potential is within an optimal range.
Electrically active defects in silicon produced by ion channeling
Authors: Kortegaard Nielsen H. , Svensson B. G. , Goubet J.-J. , Nylandsted Larsen A.
Published: May 2003

Low-dose implantations with 65 Si and 150 keV Ge ions into the n+ top layer of Si n+p diodes have been carried out. The defects produced in deeper-lying layers were studied by deep level transient spectroscopy. Results were compared to crystal-TRIM calculations and results from 2 MeV electron irradiations. Previously, ion channeling was disregarded in studies on point defect migration at room temperature using ion implantation in surface layers. In our studies, ion channeling is dominant and it overwhelms any contribution from point defect diffusion.
Bottom-contact organic field-effect transistors having low-dielectric layer under source and drain electrodes
Authors: Yuan Jianfeng , Zhang Jian , Wang Jun , Yan Xuanjun , Yan Donghang , Xu Wu
Published: May 2003

An organic thin-film transistor (OTFT) having a low-dielectric polymer layer between gate insulator and source/drain electrodes is investigated. Copper phthalocyanine (CuPc), a well-known organic semiconductor, is used as an active layer to test performance of the device. Compared with bottom-contact devices, leakage current is reduced by roughly one order of magnitude, and on-state current is enhanced by almost one order of magnitude. The performance of the device is almost the same as that of a top-contact device. The low-dielectric polymer may play two roles to improve OTFT performance. One is that this structure influences electric-field distribution between source/drain electrodes and semiconductor and enhances charge injection. The other is that the polymer influences growth behavior of CuPc thin films and enhances physical connection between source/drain electrodes and semiconductor channel. Advantages of the OTFT having bottom-contact structure make it useful for integrated plastic electronic devices.
High-temperature ferroelastic phase transitions in Li–Na niobate compounds
Authors: Jiménez B. , Castro A. , Pardo L.
Published: May 2003

Measurements of mechanoelastic properties as a function of the temperature of (LixNa1−x)NbO3 (x⩽0.12) ceramics in the paraelectric phase show a sequence of anomalies in the complex Young’s modulus Y*. These anomalies are associated with structural phase transitions of the ferro–ferroelastic and ferro–paraelastic type, where strong elastic softening due to the order-parameter–spontaneous-strain coupling of linear quadratic character takes place. The existence of NbO6 octahedra tilts and the lack of significant volume change in the phase transition temperatures of the studied compositions allows considering the order parameters in the same way as that invoked in the case of the strontium titanate.
High-color-rendering light sources consisting of a 350-nm ultraviolet light-emitting diode and three-basal-color phosphors
Authors: Nishida Toshio , Ban Tomoyuki , Kobayashi Naoki
Published: May 2003

The high-color-rendering (HCR) potential of the light sources consisting of 350-nm ultraviolet light-emitting diodes (UV-LED) and three-basal-color phosphors was simulated and experimentally confirmed. By using an AlGaN-based UV-LED as an excitation source at the 350-nm wavelength, we measured fluorescence spectra of three-basal-color phosphors, and simulated the optimum phosphor mixture based on the Commission Internationale de l’Eclairage standard light sources D75, D65, D55, D50, C, and A, with HCR indexes (Ra) over 92. We confirmed the potential of HCR of this light source consisting of 350-nm UV-LED and three-basal-color phosphors, by obtaining Ra=86∼89 of the incandescent type of standard light source A experimentally. Such high Ra are due to the highly monochromatic UV-LED emission and the wide spectral separation between the UV excitation (350 nm) and visible fluorescences. This combination also provides a diffusive, nonglare light source with highly steady color independent of the emission orientation. We also examined the importance of the separation between the excitation wavelength and the fluorescence emission wavelength for practical lighting applications.
Magnetism induced by the organization of self-assembled monolayers
Authors: Carmeli I. , Leitus G. , Naaman R. , Reich S. , Vager Z.
Published: May 2003

Unique occurrence of magnetism is shown, in which magnetism appears ex nihilo, when organic molecules are self-assembled as monolayers on gold substrate. The molecules as well as the substrate, when they stand alone, are diamagnetic. Using a superconducting quantum interference device type magnetometer we obtained direct evidence that close-packed organized thio-organic films adsorbed on gold substrates possess magnetic properties at room temperature. The films studied show very high specific magnetization, up to many tens Bohr magnetons per adsorbed molecule, with a very small hysteresis. It is highly anisotropic and shows almost no temperature dependence. The magnetism observed is related to charge transfer between the organic layer and the metal substrate. Yet, the uniqueness here is that many spins are polarized per adsorbed molecules. The magnetic effect is related to the two dimensional organization of the organic molecules on the metal substrate which might explain the high anisotropy.
Temperature dependence of photoreflectance in InAs/GaAs quantum dots
Authors: Lai C. M. , Chang F. Y. , Chang C. W. , Kao C. H. , Lin H. H. , Jan G. J. , Lee Johnson
Published: May 2003

Temperature dependent photoreflectance (PR) and photoluminescence experiments of the InAs/GaAs quantum dot (QD) structures were performed. At 20 K, effective band-gap transitions due to the InAs QDs, wetting layers, and GaAs buffer and cap layers were identified. Transition energies of the ground state and four excited states with nearly equal interlevel spacings (75–80 meV) were observed. The linewidth of the ground-state transition decreased as the temperature increased from 20 K to 100 K while the linewidth became broader at temperatures above 100 K. Energy features of the PR spectra originating from QDs and relating to the in-plane parabolic potentials were discussed.
Thickness-dependent stress effect in p-type metal–oxide–semiconductor structure investigated by substrate injection current
Authors: Hong Chao-Chi , Liao Wei-Jian , Hwu Jenn-Gwo
Published: May 2003

The effects of oxide, Si wafer, and gate Al thicknesses on the substrate injection currents (Jsub) of p-type metal–oxide–semiconductor structures with ultrathin oxides are studied. Jsub is reported to be both trap-related (interface and Si bulk) and Si band gap-related (intrinsic carrier concentration). Both mechanisms have given rise to the stress near the Si/SiO2 interface. Current–voltage and capacitance–voltage characterizations reveal that Jsub increases with oxide thickness, which is suggested to be dominated by the trap-related mechanism. A stronger dependence of Jsub on a change in oxide thickness is observed for a thicker Si wafer, which is proposed to be mainly caused by the band gap-related mechanism. Furthermore, a thicker gate Al introduces a higher Jsub, which is proposed to be due to both the trap-related and the band gap-related mechanisms.
Structure and optical anisotropy of vertically correlated submonolayer InAs/GaAs quantum dots
Authors: Xu Zhangcheng , Birkedal Dan , Hvam Jørn M. , Zhao Zongyan , Liu Yanmei , Yang Kuntang , Kanjilal Aloke , Sadowski Janusz
Published: May 2003

A vertically correlated submonolayer (VCSML) InAs/GaAs quantum-dot (QD) heterostructure was studied using transmission electron microscopy, high-resolution x-ray diffraction (HRXRD) and polarization-dependent photoluminescence. The HRXRD (004) rocking curve was simulated using the Tagaki–Taupin equations. Excellent agreement between the experimental curve and the simulation is achieved assuming that indium-rich VCSML QDs are embedded in a quantum well (QW) with lower indium content and an observed QD coverage of 10%. In the VCSML QDs, the vertical lattice mismatch of the InAs monolayer with respect to GaAs is around 1.4%, while the lattice mismatch in the QW is negligible. The photoluminescence is transverse magnetic—polarized in the edge geometry.
Void nucleation in thin HfO2 layer on Si
Authors: Miyata Noriyuki , Nabatame Toshihide , Horikawa Tsuyoshi , Ichikawa Masakazu , Toriumi Akira
Published: May 2003

We examined void nucleation in a thin HfO2 film on Si at 820–920 °C in an ultrahigh vacuum. The clustering of mobile species on the HfO2 surface led to the opening of micron-scale voids containing Hf silicide. The incubation period observed for void nucleation exhibited transition of decomposition process with activation energies of 2.3 eV (<890 °C) and 11 eV (>890 °C). We propose that the former energy corresponds to the creation of mobile species and the latter to the decomposition of the HfO2 film under the cluster.
The effect of the surface layer of tetrahedral amorphous carbon films on their tribological and electron emission properties investigated by atomic force microscopy
Authors: Liu Dongping , Benstetter Günther , Frammelsberger Werner
Published: May 2003

The nanowear resistance, tribological, and field emission properties of tetrahedral amorphous carbon (ta-C) films have been analyzed by atomic force microscope (AFM)-based wear testing technique, lateral force microscope, and conducting AFM. The ta-C films grown by filtered pulsed cathodic arc discharge were found to have soft surface layers, 1.1±0.1 nm thick, which contribute to an improvement of their field emission properties. The low friction coefficient between the nanotip and film surface is correlated to one or two graphite-like atomic layers at the ta-C film surfaces. The analysis of Fowler–Nordheim tunneling currents indicates the formation of filament-like emission channels in amorphous carbon films.
GaAs film on Si substrate transplanted from GaAs/Ge structure by direct bonding
Authors: Chandrasekaran N. , Soga T. , Jimbo T.
Published: May 2003

A process to transplant GaAs film from a Ge substrate to Si substrate using a direct bonding method is proposed. The scanning electron microscopy picture shows that the GaAs film is uniformly transplanted from Ge to Si. The high-resolution transmission electron microscopy image shows that GaAs is connected to Si by the covalent bonds. The stress of the bonded GaAs on Si is compared with GaAs/GaAs and heteroepitaxially grown GaAs/Ge(before bonding) by a 4.2 K photoluminescence method. The difference in the residual stress between the bonded GaAs/Si sample and GaAs/Si grown by two-step growth is explained by a thermal stress relaxation mechanism during the cooling process.
Observation of self-organized superlattice in AlGaInAsSb pentanary alloys
Authors: Jaw D. H. , Chang J. R. , Su Y. K.
Published: May 2003

An unexpected self-organized superlattice structure has been observed in the AlGaInAsSb pentanary alloys grown by metalorganic vapor-phase epitaxy. The samples were studied by transmission electron microscopy, double-crystal x-ray diffraction, and secondary ion mass spectrometry measurements. The modulation strength and period of the self-organized superlattice are correlated to the alloy composition.
Band gap of GaAs1−xBix, 0<x<3.6%
Authors: Francoeur S. , Seong M.-J. , Mascarenhas A. , Tixier S. , Adamcyk M. , Tiedje T.
Published: May 2003

The band gap of GaAsBi epitaxial layers as a function of bismuth concentration up to 3.6% is determined. The optical transitions were measured by modulated electroreflectance. The energy of the band gap decreases at a linearized rate of 88 meV/% Bi, or 83 meV/% Bi for the heavy hole to conduction band transition for GaAsBi strained to GaAs. The valence-band splitting increases faster than that of GaAs under similar compressive strain whereas the temperature dependence of the observed GaAsBi transitions is similar to that of GaAs.
Photovoltaic effect on differential capacitance profiles of low-energy-BF2+-implanted silicon wafers
Authors: Chang M. N. , Chen C. Y. , Pan F. M. , Lai J. H. , Wan W. W. , Liang J. H.
Published: May 2003

Using scanning capacitance microscopy (SCM), we have studied the photovoltaic effect on differential capacitance (dC/dV) signals of low-energy-BF2+-implanted silicon wafers. The surface photovoltage induced by the stray light of the atomic force microscope laser beam leads to distorted dC/dV profiles and hence perturbs the contrast of SCM images. Due to the photovoltaic effect on the junction region, the observed junction image also exhibits a narrower junction width. According to this study, the photovoltaic effect not only significantly affects the dC/dV signals but also deteriorates the accuracy of junction characterization, in particular for ultrashallow junctions and lower band-gap semiconductors.
Consumer-Oriented Monitoring and Environmental Reform
Authors: van den Burg Sander W K , Mol Arthur P J , Spaargaren Gert
Published: June 2003

The monitoring of environmental flows is usually considered an important first step in realising environmental reform of production and consumption. When citizen-consumers are involved, monitoring is frequently associated with surveillance and social control by the powerful (governmental and nongovernmental) providers of goods and services. The authors investigate the future perspectives for monitoring that empowers citizen-consumers. Post-Fordism, chain inversion, and liberalisation allow for consumer-oriented monitoring, which increases the countervailing power of end-users and strengthens the potentials of citizen-consumers to change the infrastructures of consumption. Several monitoring projects, for example eco-teams and Scorecard, are dealt with in some detail. It is concluded that consumer-oriented monitoring schemes do seem to be of considerable importance.
Carbon Dioxide Reduction in Housing: Experiences in Urban Renewal Projects in the Netherlands
Authors: van der Waals Jochem F M , Vermeulen Walter J V , Glasbergen Pieter
Published: June 2003

It is increasingly being recognised that the housing sector can contribute to reductions in the levels of carbon dioxide (CO2). The renewal of existing residential areas offers opportunities to reduce CO2 emissions. However, technical options for CO2-reduction, such as insulation, solar energy, and combined heat and power, often fail to materialise. For a better understanding of why options for CO2-reduction are applied or rejected, it is insufficient to consider only the economic and technical features of these options themselves: factors related to planning processes play an important role as well. Experiences in urban renewal projects suggest that a combination of local process management and national top-down strategies is needed to go beyond conventional building practices.
Information Used in Detecting Upcoming Collision
Authors: Bootsma Reinoud J , Craig Cathy M
Published: June 2003

In four experiments we examined the nature of the information used in judging whether events would or would not give rise to a collision in the near future. Observers were tested in situations depicting approaches between two objects (lateral approaches) and approaches between an object and the point of observation (head-on approaches), with objects moving according to constant deceleration or sinusoidal deceleration patterns. Judgments were found to be based, to a large extent, on the (in)sufficiency of current deceleration to avoid upcoming collision, as specified optically by tau-dot (τ̇). However, the information specified by tau (τ), that is the current (first-order) time remaining until contact, was also found to play a significant role. We deduce that judgment of upcoming collision is based on the detection of τ and its evolution over time, suggesting that observers are sensitive to Δτ rather than to τ̇ itself.
The Lasting Impression of Chairman Mao: Hyperfidelity of Familiar-Face Memory
Authors: Ge Liezhong , Luo Jing , Nishimura Mayu , Lee Kang
Published: June 2003

We examined the accuracy of a highly-familiar-face representation in memory. In experiment 1, a famous portrait of Chairman Mao was digitally altered in terms of the distance between his two eyes, two pixels at a time. Mainland Chinese adults were shown the original or altered photos, one at a time, and asked to determine whether each was that of Chairman Mao or altered. Eastern Asian and Caucasian participants, who were unfamiliar with Mao's photo, were shown simultaneously the original face paired with the altered ones and asked to determine whether the photos were identical. The Mainland Chinese participants' memory threshold approximated the perceptual discrimination threshold of the Eastern Asian and Caucasian participants. Experiments 2 and 3 ruled out that the result of experiment 1 was due to artifacts of photographic alteration. The findings of the present study suggest that our memory of a very familiar face is highly accurate, at least in terms of the interocular configuration. The accuracy is perhaps only limited by the perceptual resolution capacity of our visual system.
A Comparison of Visual and Nonvisual Sensory Inputs to Walked Distance in a Blind-Walking Task
Authors: Ellard Colin G , Shaughnessy Sarah C
Published: June 2003

Two experiments were conducted in order to assess the contribution of locomotor information to estimates of egocentric distance in a walking task. In the first experiment, participants were either shown, or led blind to, a target located at a distance ranging from 4 to 10 m and were then asked to indicate the distance to the target by walking to the location previously occupied by the target. Participants in both the visual and locomotor conditions were very accurate in this task and there was no significant difference between conditions. In the second experiment, a cue-conflict paradigm was used in which, without the knowledge of the participants, the visual and locomotor targets (the targets they were asked to walk to) were at two different distances. Most participants did not notice the conflict, but despite this their responses showed evidence that they had averaged the visual and locomotor inputs to arrive at a walked estimate of distance. Together, these experiments demonstrate that, although they showed poor awareness of their position in space without vision, in some conditions participants were able to use such nonvisual information to arrive at distance estimates as accurate as those given by vision.
History of Chinese science on‐line
Authors: Ka Wai Fan
Published: May 2003

The study of the history of Chinese science has attracted further attention over the past 50 years, with an increasing number of scholars, influenced by Joseph Needham and his project “Science and Civilization in China”, developing ideas in this field. There are a range of Web sites which have been produced and are available to the scholar of the history of Chinese science, and some of these are collected together and evaluated in this article.
A model for inter‐institutional collaboration: the GAELS project document delivery trials
Authors: Ashworth Susan , Joint Nicholas
Published: May 2003

Glasgow and Strathclyde Universities received funding from the Scottish Higher Education Funding Council to investigate the collaborative provision of library services between the two institiutions. The investigation was, initially, in the area of engineering. The GAELS Project (Glasgow Allied Electronically with Strathclyde) ran between June 1999 and June 2001. An audit of existing information services which demonstrated that perceived information needs of researchers in both engineering faculties did not match the actual needs. Engineering researchers had low use of traditional library services and preferred electronic services. An overlap study of periodicals holdings between the two institutions found duplication in periodicals holdings of around £70,000 per annum. A series of document delivery trials was initiated, including local document delivery between the two sites, a commerical document delivery service for one research group, and a wholly electronic service to the desktop for bioengineers at Strathclyde University. The trials’ findings are presented along with outcomes, both actual and projected, for future collaboration.
The digital marketplace and library and information education in the GCC member nations: a critical review
Authors: ur Rehman Sajjad , Al‐Ansari Husain
Published: May 2003

A study was conducted to assess the potential of six library and information education programs in preparing manpower for the digital environment. The situation of six schools in the member nations of the Gulf Cooperation Council has been analyzed by collecting data from the schools heads and 49 faculty members, focusing on: curricular changes; faculty size and its research and publication record; hardware equipment and software packages available for instruction; use of digital resources such as databases, online services, and electronic utilities for instruction; and availability of periodicals, books, and electronic resources for instructional activity. This study has brought forth a number of crucial issues related to these factors. Unless these schools take significant developmental or remedial initiatives, they cannot fare well in coping with the changes wrought by the digital imperatives.
The ERIC database: a comparison of four versions
Authors: Dagenais Brown Janet
Published: May 2003

Today’s librarians are faced with the need to constantly reevaluate database purchases in order to find the most cost‐effective means of supplying these resources to users. When a database is available from more than one provider, it may be necessary to make a detailed comparison of features and search engines to determine the best version for a particular library. This article compares 48 features of four versions of the ERIC database (SilverPlatter, FirstSearch, AskERIC, and SearchERIC.org), and discusses the relative merits of some of the more important features. Also included is an overview of the results of a survey given to Education majors which provides information on user preferences for versions of the ERIC database.
Keeping up with Africa: a selective annotated bibliography
Authors: Mason‐Middleton Cheryl J.
Published: May 2003

Awareness of developments taking place in Africa is essential for non‐African economies, commercial interests, and investors; and also for governmental, diplomatic, and political interests. Reference librarians may find themselves faced with more and varied questions concerning African affairs and current events, and may be asked to supply more than just general answers about Africa. This article presents resources for developing an understanding of African affairs, and keeping up‐to‐date with African economics, governance, and development issues on a day‐to‐day basis.
Fun in the workplace
Authors: Rockman Ilene F.
Published: May 2003

Explores the ways in which the working environment in libraries can be made to be more fun. Among the methods discussed are: sports tournaments, dress‐up days, award ceremonies, contests, recreational activities, food‐related events and learn‐at‐lunch sessions. Highlights the ways in which fun, and laughter in particular, can add to a sense of wellbeing, relaxation and a positive outlook in the workplace.
Perceptions and perplexities of the faculty‐librarian partnership: an Australian perspective
Authors: Doskatsch Irene
Published: May 2003

Many Australian universities have identified information literacy as a required graduate quality. As the scope of resources on which student learning is based expands, the definition of educator is broadening and requires the involvement of a range of non‐academic professional staff in the educational process. Information literacy‐related activities largely define the educative role of the librarian and forge faculty‐librarian partnerships. The paper is based on the premise that collaboration between librarians and other educators is the key to the integration of information literacy within the total educational process. The author draws on both personal experience and that of Australian colleagues to examine the faculty‐librarian relationship, explore the contentious territories of professional credibility and identity, and analyze changes in Australian higher education that impact on the educative role of librarians.
New roles and opportunities for academic library liaisons: a survey and recommendations
Authors: Glynn Tom , Wu Connie
Published: May 2003

A task force at Rutgers University Libraries was charged with exploring ways to develop more effective liaison relations with teaching departments. As a preliminary step the working group surveyed Rutgers liaisons to identify preferred practices and to solicit comments on trends in liaisonship in academic libraries. Based on this survey, we examine changes in the information profession and how they have effected the reference and instruction that departmental liaisons provide to faculty and students. Particular emphasis is placed on the impact of the Internet. Generally, electronic resources have made faculty and students less reliant on liaisons for help with their research, while electronic communication, especially via e‐mail, has the potential to make liaisonship more efficient and effective. We offer a number of recommendations for effective liaisonship, including concise and purposeful e‐mail messages and making direct and personal contact with faculty and students whenever possible.
Information literacy program assessment: one small college takes the big plunge
Authors: Flaspohler Molly R.
Published: May 2003

Managing a library instruction program at a small liberal‐arts college has many challenges. Programs at such institutions often have limited financial resources and are maintained under difficult staffing conditions. This study examines the effectiveness of an instruction program offered at a four‐year liberal‐arts college with fewer than 3,000 students. The research was designed to assess the effectiveness of the current program and measure it against a pilot group of students exposed to enhanced information literacy opportunities based on the Association of College and Research Libraries (ACRL)Information Literacy Competency Standards for Higher Education.Working with five faculty members, information literacy goals were clearly articulated and implemented into nine sections of first‐year writing and speaking courses. Bibliographic analysis, an information literacy questionnaire, and an in‐class writing exercise were used to determine whether students in the pilot groups performed better than students receiving the program’s customary library training.
Win‐win strategy for the employment of reference graduate assistants in academic libraries
Authors: Wu Qi (Kerry)
Published: May 2003

Discusses the application of win‐win mindsets and strategy in the employment of reference graduate assistants in academic libraries. The strategy covers different stages of the employment including recruitment, training and support, and transition. It focuses on the concept of treating graduate assistants as colleagues and involving them in the whole process. Also compares the differences between the employment of reference graduate assistants who are library school students and those who are non‐library school students, and the differences between graduate assistants in libraries and contingency workers in the business world.
The adoption of family‐friendly HRM policies
Authors: Poelmans Steven A.Y. , Chinchilla Nuria , Cardona Pablo
Published: May 2003

Several authors have tried to explain the variation across firms in the implementation of work‐family programmes in terms of the employment strategy of these firms and institutional pressures. But most of these studies have been done in the US context. This study replicates these studies in Spain, which has a very different legal, cultural, and labour market context and where the diffusion of work‐family programmes has only recently started. Using data from a sample of 131 Spanish, mostly private firms, tests five hypotheses that may explain the adoption of family‐friendly human resources management policies. Finds that even in this particular context both the employment strategy and some institutional pressures play an important role. The size of the firm, the percentage of female employees, the presence of a high‐commitment work system and the tightness of the labour market are associated with the implementation of a work/family programme. With the increasing participation of female workers and the ageing of the population expects that work/family programmes will continue to diffuse in Spain.