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We report the electronic and thermal properties of scandium monoantimonide ScSb by means of the Seebeck coefficient, thermal conductivity, specific heat, and nuclear magnetic resonance measurements. The experimental Seebeck coefficient exhibits a strong temperature dependence, and the theoretical calculation based on the two-band model provides a realistic description of the observed feature. The analysis of the thermal conductivity reveals that the lattice thermal conductivity dominates at low temperatures while electronic thermal conductivity makes a major contribution at high temperatures. A small value of the Sommerfeld coefficient of $0.38\phantom{\rule{0.16em}{0ex}}\mathrm{mJ}\phantom{\rule{0.16em}{0ex}}\mathrm{mo}{\mathrm{l}}^{\text{--}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\text{--}2}$ was extracted from the low-temperature specific heat measurement, indicative of a low electronic Fermi-level density of states (DOS) in ScSb. Furthermore, we have deduced the Sc $3d$ and Sb $5s$ partial Fermi-level DOSs based on the Korringa behavior in the $^{45}\mathrm{Sc}$ and $^{121}\mathrm{Sb}$ NMR spin-lattice relaxation rates. The determined values of the DOS are quite low, giving strong evidence for the semimetallic character in ScSb.

The adsorptions of CO molecule on various fcc(111) surfaces (Rh, Ir, Pt, and Cu) have been studied by diffusion quantum Monte Carlo (DMC) calculations, and the results show that the top site is the...

This study is aimed to carry out an experimental verification for the finite element model and to propose a design scheme for using a dual-mass blankholder in a stamping process to increase the press ram speed without raising the impact force, in part by generating the response surface of the process parameters, whose ranges in the finite element analysis are extended. As a result, the impact has no significant relationship to the preload and the coefficient of the springs used to connect plates, but it has a significant positive correlation with the mass of the plates and the press speed. Thus an empirical equation is found by linear regression to design a dual-mass blankholder for a stamping process. With two examples, it shows that the design scheme is indeed feasible, which could become a reference for industrial applications.

In the present communication, the effect of Ba substitution on the structural, mechanical, electrical transport and thermal properties of La0.65Ca0.35� xBaxMnO3 (0.00 6 x 6 0.25) manganites have been investigated. Rietveld refinement of XRD data reveals that all samples are single phase. With increasing Ba content, a transformation of crystal structure from rhombohedral (x = 0.00–0.15) to cubic symmetry (x = 0.25) is observed. In the micro-hardness study, a correlation between the average grain size and micro-hardness is concluded. It is found that all samples exhibit a clear metal–insulator transition, and the transition temperature (TMI) shifts monotonically towards higher temperature. The Seebeck coefficient (S) of the pristine sample is negative in the entire temperature range, whereas for all doped samples the measured S exhibits a crossover from positive to negative values. The analysis of Seebeck coefficient data indicates that the small polaron hopping model is operative in the high temperature region. The room-temperature magnitude of thermal conductivity, j of the studied samples is in the range of 20–35 mW/cm K and such low value is presumably attributed to the Jahn Teller (J-T) effect. An analysis of j using Wiedemann–Franz’s (W–F) law confirms that the total thermal conductivity is mainly associated with the lattice phonons rather than charge carriers. The change in entropy associated with the transition evaluated from the specific heat measurements is found to decrease with increasing x, most likely due to the enhancement of magnetic inhomogeneity in these manganites.

We reported the first hybrid Ill-V/Si integrated QPSK wavelength-tunable transmitter based on high-speed ring modulators (BW∼23GHz). 80 Gbit/s PDM-QPSK signal transmission over 100 km with said integrated hybrid transmitter as well as a fully packaged silicon-based coherent receiver is demonstrated.

We review recent advances on hybrid III-V/Silicon devices using edge coupling. Design of external silicon cavities enables the realization of a broad range of on-chip functionalities as well as advanced hybrid transmitters.

The ZnO nanorod arrays are grown on the sol–gel-derived seed layer through aqueous chemical growth, and then assembled as gas sensors for detecting carbon monoxide (CO). It is found that the structural and photoluminescent properties of the ZnO nanorod arrays are different as they are grown on seed layers annealed at different temperature (300–700 °C), which is ascribed to distinct growth kinetics of nanorods on the annealed seed layer. Moreover, the correlation between the exposed surface area and the defect density of those ZnO nanorod arrays points out the intrinsic (interior) defects can dominate the green emission instead of surface defects in the present study. Furthermore, the quantities of chemisorbed oxygen on ZnO nanorod arrays can be estimated through XPS analysis. Consequently, the influence of intrinsic defects and chemisorbed oxygen on the electrical properties and gas sensitivities of ZnO nanorod arrays has been clearly elucidated. It is demonstrated that the more adsorbed oxygen and an appropriate amount of intrinsic defects is advantageous to obtain superior CO gas sensitivity for ZnO nanorod arrays.

We designed and fabricated a fast-wavelength-tunable hybrid laser diode using two selectable silicon photonic Vernier ring-based cavities. Single mode operation (SMSR > 30 dB) over more than 35 nm and switching speed of 35 ns are demonstrated.

A trilevel resist system was employed to fabricate self-aligned, submicron emitter finger In0.52Al0.48As/In0.42Ga0.58As0.77Sb0.23/ In0.53Ga0.47As double heterojunction bipolar transistors (DHBTs). Selective wet-etchants were used to define the emitter fingers and to form an InGaAs guard-ring around the emitter fingers. Due to the low energy bandgap of the InGaAsSb base layer and type II base-collector junction, a low turn-on voltage of 0.38 V at 1 A/cm2 and a high dc current gain of 123.8 for a DHBT with a 0.65 x 8.65 µm2 emitter area were obtained. A unity gain cut-off frequency (fT) of 260 GHz and a maximum oscillation frequency (fmax) of 485 GHz at JC = 302 kA/cm2 were achieved.

We report the results of yttrium substitution on the electrical resistivity (r), the thermal conductivity (k), as well as the Seebeck coefficient (S) of the Sr1� xYxAl2Si2 alloys with 0 � x � 0.20. Both r(T) and S(T) data suggest that SrAl2Si2 is a semimetallic, low charge carrier density system with a pseudogap at the Fermi level density of states (DOS). Upon substituting Y onto the Sr sites, the electrical resistivity and the absolute value of the Seebeck coefficient decrease significantly. Such an observation can be associated with the modification of the electronic band structure due to electron doping via Y substitution. Analysis of the thermal conductivity reveals the contribution of various thermal scattering mechanisms through chemical substitution. Theoretical studies with density functional theory are also employed to investigate the electronic band structure of Sr1�x YxAl2Si2. It is revealed that SrAl2Si2 possesses a shallow DOS at the Fermi level with both n-type and p-type charge carriers. Upon Y substitution a shift in the Femi level occurs such that the Sr1�x YxAl2Si2 system becomes more metallic with increasing x, being consistent with the experimental findings.

Nitride-based p-i-n ultraviolet (UV) photodetectors with a low-temperature (LT) GaN interlayer were proposed and fabricated. Compared with a conventional GaN p-i-n photodetector, it was found that both the dark current and ideality factor of the p-i-n photodetector with an LT-GaN interlayer became larger whereas the UV-to-visible rejection ratio became smaller because of the poor crystal quality of the LT-GaN interlayer. However, the responsivity of the GaN p-i-n photodetector with an LT-GaN interlayer was larger than that of the conventional GaN p-i-n photodetector under a high reverse bias because of the carrier multiplication effect and/or internal gain that originated from the defect levels.

A novel 16-channel digitally wavelength-tunable laser is proposed and experimentally demonstrated using a semiconductor optical amplifier and silicon photonic integrated circuit. The device exhibits a laser threshold below 45 mA, SMSR around 20–25 dB and nanosecond switching time.

International audience; We propose a novel cost efficient node architecture for a wavelength division multiplexed packet-switched network based on reflective integrated device. We demonstrate a 16-channel, silicon-on-insulator, reflective monolithic integrated slot-blocker that integrates one arrayed waveguide grating, 16 variable optical attenuators, 16 Bragg grating mirrors and one vertical fiber coupler. Small-form factor device, improved extinction ratio and fast switching speed are presented.

Amorphous (ZrO 2 ) x –(SiO 2 ) 1− x and (Al 2 O 3 ) x –(ZrO 2 ) y –(SiO 2 ) 1− x − y composite films were prepared using r.f. unbalanced magnetron sputtering in an atmosphere of argon and oxygen at room temperature. The (ZrO 2 ) x –(SiO 2 ) 1− x and (Al 2 O 3 ) x –(ZrO 2 ) y –(SiO 2 ) 1− x − y composite films were completely oxidized when an O 2 /Ar flow rate ratio of 2.0 was used. The optical constants of these thin films depend linearly on the mole fraction of corresponding films. By tuning the ( x , y ) mole fractions of (Al 2 O 3 , ZrO 2 ) in the (Al 2 O 3 ) x –(ZrO 2 ) y –(SiO 2 ) 1− x − y composite films, the optical constants can meet the optical requirements for a high transmittance attenuated phase shift mask (HT-AttPSM) blank. The n – k values in the quadrangular area in the ( x , y ) plane, where x and y represent the mole fractions of Al 2 O 3 and ZrO 2 , respectively, meet the optical requirements for an HT-AttPSM blank with an optimized transmittance of 20 ± 5% in ArF lithography. It is noted that the quadrangular area is bounded by (0, 0.31), (0, 0.62), (0.26, 0) and (0.57, 0). All the films also met the chemical and adhesion requirements for an HT-AttPSM application. One (Al 2 O 3 ) 0.1 –(ZrO 2 ) 0.52 –(SiO 2 ) 0.38 composite film was fabricated with optical properties that meet the optimized optical requirements of ArF-line HT-AttPSM blanks. Combined with these HT-AttPSMs, ArF-line (immersion) lithography may have the potential of reaching 65-, 45-nm and possibly the 32-nm technology nodes for the next three generations.

Homoepitaxial ZnSe metal–semiconductor–metal (MSM) photodetectors with ITO, TiW and Ni/Au contact electrodes were fabricated. It was found that barrier heights for electrons were 0.66, 0.695 and 0.715 eV for ITO, TiW and Ni/Au on the homoepitaxial ZnSe, respectively. With an incident wavelength of 448 nm, it was found that the maximum responsivities for the homoepitaxial ZnSe MSM photodetectors with ITO, TiW and Ni/Au contact electrodes were 120, 50.6 and 28.1 mA/W, which corresponds to quantum efficiencies of 33.5, 14 and 8%, respectively. For a given bandwidth of 100 Hz and a given bias of 1 V, it was found that the corresponding noise equivalent power of our homoepitaxial ZnSe MSM photodetectors with ITO, TiW and Ni/Au electrodes were 8.14 × 10 −13 , 1.73 × 10 −12 and 9.25 × 10 −13 W, respectively. Furthermore, it was found that the corresponding D * were 8.7 × 10 11 , 4.09 × 10 11 and 7.65 × 10 11 cm Hz 0.5 W −1 , respectively.

Homoepitaxial and heteroepitaxial ZnSe metal–semiconductor–metal (MSM) photodetectors were both fabricated and characterized. It was found that homoepitaxial ZnSe MSM photodetector could provide us smaller dark current and large photocurrent. With an incident wavelength of 448 nm, it was found that the maximum responsivities for the homoepitaxial and heteroepitaxial ZnSe photodetectors were 0.128 and 0.045 A/W, which corresponds to a quantum efficiency of 36 and 12%, respectively. Furthermore, it was found that we achieved the minimum noise equivalent power (NEP) of 7.6 × 10 −13 W and the maximum normalized detectivity ( D * ) of 9.3 × 10 11 cm Hz 0.5 W −1 from our homoepitaxial ZnSe photodetector. In contrast, NEP and D * of the heteroepitaxial ZnSe photodetector were 2.9 × 10 −12 W and 2.44 × 10 11 cm Hz 0.5 W −1 , respectively.

Ultra-thin Cr2O3 well-crystallized thin films are deposited on UV grade fused sifica substrates and Si wafers by using r.f. reactive unbalanced magnetron sputtering from a Cr metal target in an atmosphere of Ar and O2 at 350 °C. The optical constants of such thin films were found to be a sensitive function of oxygen-to-argon flow rate ratio. At the ratio of 0.2, a Cr2O3 well-crystallized thin film with appropriate refractive index and extinction coefficient at a wavelength of 365 nm can be used as attenuated phase-shifting mask (APSM) blank as well as being good for inspection. The simulated thickness range of a Cr2O3 well-crystallized thin film was found to be between 28.2 and 30.3 nm. This meets the optical requirements for high transmittance APSM (HT-APSM) with a transmittance of 18-20% at 193 nm for the pattern fabrication and with transmittance less than 50% at 365 nm for the mask inspection. One such Cr2O3 well-crystallized thin film that satisfies the optical requirements was fabricated.

Optical and electrical properties of InGaN/GaN multi-quantum-well (MQW) structure light-emitting diodes (LED) are systematically studied as a function of barrier thickness and Si doping of barriers. The emission energy of photoluminescence (PL) and electroluminescence (EL) of MQW-LEDs decrease with barrier thickness increased, but with Si doping of barriers decreased. The electrical characteristics of MQW-LEDs strongly depend on barrier thickness and Si-doped content in barriers. With increasing barrier thickness, forward voltages of MQW-LEDs dramatically reduce as well as the barriers are increasingly doped with Si. Reverse currents of MQW-LEDs measured at reverse bias 6 V present a similar behavior that Ir increase with increasing barrier thickness as well as increasing Si doped content in barriers. The experimental results imply an optimized quality of MQW-LED fabrication by an appropriate combination of barrier thickness and carrier concentration.

A novel method was proposed to glue an AlGaInP-GaAs light-emitting diode (LED) onto a transparent sapphire substrate. The absorbing GaAs was subsequently removed by selective wet etching. It was found that the emission efficiency could reach 401 m/W under 20-mA current injection for the 622-nm glue bonded (GB) AlGaInP-sapphire LED. It was also found that these GB LEDs are highly reliable, with small variations in operation voltage and luminescence intensity during the life test.

The joint strength and fracture surface of Pb/Sn and Au/Sn solders in laser-diode packages after thermal-aging testing were studied experimentally. Specimens were aged at 150°C for up to 49 days. The joint strength decreased as aging time increased. The microstructure and fracture surface of the Pb/Sn and Au/Sn solder joints showed that the joint strength decrease was caused by both the enlargement of the initial voids and an increase in the number of voids as aging time increased. The formation of Kirkendall voids with intermetallic-compound (IMC) growth of the Pn/Sn solder as aging time increased was also a possible mechanism for the joint-strength reduction. Finite-element method (FEM) simulations were performed on the joint-strength estimation of Pb/Sn and Au/Sn solders in thermal-aging tests. The coupled thermal-elasticity-plasticity model was used to simulate distributions of the thermal and residual stresses, creep deformation, and joint-strength variations in the solder joints under various thermal-aging tests. Simulation results were in good agreement with the experimental measurements that the solder-joint strength decreased as aging time increased. The result suggests that the FEM is an effective method for analyzing and predicting the solder-joint strength in laser-diode packages.

This UV LED lighting technology developed in this study is expected to be applied to photolithography industry. Since the accuracy of the degree of cross linking and sidewall profile could be affected by intensity of UV light dosage, this research proposes optical design and fabrication of free-curved lens for light source element of UV LED for exposure machines. In this study, the optical intensity distributions of the lens with TFMG were determined by using commercial optical simulation FRED software. Based on the design, the lenses were fabricated using thermoforming of optical glass and PMMA, respectively. Then the lens is selectively coated with thin film metallic glasses (TFMG, Ag 30 Mg 45 Al 25 ). For the TFMG coating, multi-target sputtering system is applied to sputter TFMG reflecting film on the surface of lens with thickness of 100 nm to 300 nm. With the both design of TFMG selective deposition and lens curve, the optical field of Lambertian emission patterns of UV LED can be transformed to uniform profile. Through this design of reflection of UV LED light source, the intensity and uniformity could be enhanced. UV LED light source with 360 to 390 nm in wavelength was chosen as light source to simulate the effects of I-line and G-line. The specific wavelength of UV light is measured by spectrometer (USB2000+VIS-NIR, Ocean Optics) and BM7.

The polymer dispensing technology used for a lens type LED package had been revealed in [1]. The ring type micro structure is adopted to confine the dispensed silicone encapsulant so as to form the packaged lens. To use the dispensing technology, the deviations in lens geometry are larger as comparing to that as using the silicone lens molding process. In this study herein, the dome-type UV LED and White LED packages are selected to verify the variations in the spatial radiation induced by the collimation between lens and LED chip, the height of lens and the collimation between lens and LED chip increases to 100µm, the phosphor application. Comparing to the collimating ones, as the shape of radiation pattern changes from a mountain type to a slope type at the spatial range of −75° to 75°. Furthermore, the view angle also increases 4°∼7°. The diffusive character from phosphor significantly reduces the variation in radiation pattern causing by the collimation. The view angle could reach 150° in white LED package. The view angles are 149°and 141° for the packages with the lens height of 1.3 mm and 1.5 mm, respectively. However, the radiation patterns are similar to each other in these two conditions of lens height.

We use ab initio density-functional theory supplemented with the embedded-atom method to study the self-diffusion of small clusters on the (111) surface of eight fcc metals. A zigzag motion is found to be important in the dimer and tetramer diffusions. The dimer diffuses by a zigzag and concerted motion. The trimer diffuses by a concerted three-atom motion. The tetramer diffuses through a zigzag motion where only two atoms move simultaneously in each step. Thus, instead of increasing, the migration energy is lowered (or stays constant) for the tetramer as compared to that for the trimer. This novel break of the upwards trend in migration energy is predicted to be a general phenomenon.

In GaN/GaN multiple quantum wells (MQW) and blue MQW light-emitting diodes (LEDs) were grown by metal-organic vapor phase epitaxy (MOVPE). Band-gap narrowing of the PL spectra for the InGaN/GaN MQW LEDs can be observed at room temperature. In addition, the emission wavelength of EL and PL spectra for the MQW blue LEDs exhibit a blue-shift phenomenon while increasing the injection current and laser power, respectively. This luminescence behavior can tentatively be understood as a competition between a spectral red-shift mechanism of piezoelectricity-induced quantum-confined Stark effect (PQCSE) and a blue-shift mechanism of band-filling and charge screening effects.

The inability to economically separate Fe3+(aq) from a variety of liquid effluents is a major concern for the primary metals industry. A unique solvent extraction process, galvanic stripping, has been developed to address this problem. The galvanic stripping of iron from D2EHPA using only a 5≈10 g/L H2SO4 solution is achieved after Fe3+ is directly reduced to Fe2+ in the organic phase using zinc metal additions. To date, the primary focus of the laboratory research has been on optimizing the parameters that control iron removal. The results from these studies have now been used to make a preliminary design for a continuous flow process that is envisioned for zinc industrial applications. Specific quantitative data are shown for the use of a Zn-Pb alloy in the iron-removal process. Some introductory results on electrochemical potential measurements and impurity distribution with solution cycling are also given.

In this letter, AlGaInP-GaP-based light-emitting diodes (LEDs) were fabricated with an Si substrate and an SiO2-ITO-Ag omni-directional reflector using a metal-to-metal bonding technique. To enhance light extraction efficiency, a periodic texture was applied to the (Al0.5Ga0.5)0.5In0.5P surface layer of AlGaInP-Si LEDs by photolithography and a wet etching process. The exterior of the etched texture consists of a series of bowl-shaped recesses. With a 350-mA current injection, the typical output power of the AlGaInP-Si LEDs with and without the textured surface (LED-I and LED-II, respectively) were measured at approximately 118 and 81 mW, respectively, when the LED chips were bonded on the TO 46 without resin encapsulation. The enhancement of output power in LED-I can be attributed to a multitude of bowl-shaped notches on the surface, which resulted in a reduction of the reabsorption probability of the photons due to the fact that the photon path length in LED-I is shorter than in LED-II before the photons escape into the free space.

ZnSe-based white light emitting diodes (LEDs) were homoepitaxially prepared on ZnSe substrates by molecular beam epitaxy. It was found to be possible to simultaneously observe the greenish-blue emission at 483 nm originating from the epitaxial layer and the weaker ZnSe substrate-related orange emission centred at around 595 nm. It was found that the emission wavelength of the LED and the measured chromaticity coordinate were almost independent of the injected current. It was also found that the turn-on voltage and the 20 mA operation voltage of the fabricated LED were 2.25 and 4 V, respectively

Photon stimulated desorption from aluminum surfaces was studied by irradiating an aluminum chamber in the 1.3 GeV electron storage ring at the Synchrotron Radiation Research Center. Experiments on aluminum samples were also performed in an experimental station. The behavior of water vapor, the main concern in this work, was quite different from that of the other gases. A time delay between the peak of the H2O signal and the starting time of irradiation was observed. Effects due to different conditions such as beam current, pumping speed, and beam dose of the storage ring were investigated.

Prober testers have been widely used by the semiconductor industry to determine whether the individual Integrated Circuits (IC) meet specifications of design. In this paper, probe contact tests are developed with different testing overdrive distance by using a microforce tester. The probe tests are subsequently applied to a single tungsten needle probe to examine the relationships between contact force and scrub mark size on aluminum pads at various overdrive levels. A FE base simulation model was built and the simulation results were compared with testing output. The changing of the friction coefficient between pad and needle were studied, the results shown that it might be a key factor to control the scrubbing mark size bend angle was 103°. The probe diameter was 10mils. The probe length was 4 mm. The tip length was 11mils. The probe tip diameter was 25µm. The testing pads were made from an 8 inch diameter silicon wafer, onto which 0.7µm thick aluminum layers and intermediate Ti layer had been deposited. The wafer was then divided up into separate testing samples with diameter 12mm × 18mm × 0.7µm using a diamond saw. Figure 1 shows the testing dummy wafer and aluminum pad. Six needle overdrive settings, 10, 20, 30, 40, 50 and 60µm, were selected.

Due to the light weight and electromagnetic interference shielding capabilities in magnesium alloy material, it is widely utilized in 3C electronic components and automobile parts. However, its formability is very poor due to the phenomenon of negative strain hardening rate appearing in large strain deformation range, so it is usually formed as die casting or casting styles leads to much scrap, and manufacturing cost is thus increased. The objective of this study is to investigate the process parameters effect on a rectangular tube hydro-forming with magnesium alloy. AZ31 magnesium alloy circular tube is used as the billet material for hydroforming with hydraulic pressure as the main forming power combined with the mechanically auxiliary force from the punch to fabricate the rectangular tube products. A finite element based software is utilized to investigate the forming characteristics of the rectangular tube hydro-forming, by changing process parameters such as punch velocity, hydraulic pressure and tool-workpiece interface friction etc. to investigate the material flow of tube filling, wall thickness variations, and stress and strain distributions. And the abductive network is then applied to synthesize the data sets obtained from the numerical simulations and a prediction model is established. From the prediction model, product dimensions of corner radius and minimum tube thickness may be estimated in advance when the process variables have been set. The results show that proper mechanical force can help material flow, prevent large strain deformation from falling into the area of negative strain hardening rate, enhance magnesium alloy to become easy in forming and make tube may be formed successfully.

In this work indium tin oxide (ITO) films were prepared using electron beam evaporation to form Schottky contacts on n-type GaN films. The thermal stability of ITO on n-type GaN was also investigated by annealing the samples at various temperatures. In addition, current–voltage (I–V) measurements were taken to deduce the Schottky barrier heights. Owing to the large series resistance, the Norde method was used to plot the F(V)–V curves and the effective Schottky barrier heights were determined as well. The effective Schottky barrier heights were 0.68, 0.88, 0.94, and 0.95 eV for nonannealed, 400, 500, and 600 °C annealed samples, respectively. Results presented herein indicate that an increase of the barrier heights may be attributed to the formation of an interfacial layer at the ITO/GaN interface after annealing.

We report a novel Au-Ag alloy catalyst supported on mesoporous aluminosilicate Au-Ag@MCM prepared by a one-pot synthesis procedure, which is very active for low-temperature CO oxidation. The activity was highly dependent on the hydrogen pretreatment conditions. Reduction at 550-650 degrees C led to high activity at room temperature, whereas as-synthesized or calcined samples did not show any activity at the same temperature. Using various characterization techniques, such as XRD, UV-vis, XPS, and EXAFS, we elucidated the structure and surface composition change during calcination and the reduction process. The XRD patterns show that particle size increased only during the calcination process on those Ag-containing samples. XPS and EXAFS data demonstrate that calcination led to complete phase segregation of the Au-Ag alloy and the catalyst surface is greatly enriched with AgBr after the calcination process. However, subsequent reduction treatment removed Br- completely and the Au-Ag alloy was formed again. The surface composition of the reduced Au-Ag@MCM (nominal Au/Ag = 3/1) was more enriched with Ag, with the surface Au/Ag ratio being 0.75. ESR spectra show that superoxides are formed on the surface of the catalyst and its intensity change correlates well with the trend of catalytic activity. A DFT calculation shows that CO and O2 coadsorption on neighboring sites on the Au-Ag alloy was stronger than that on either Au or Ag. The strong synergism in the coadsorption of CO and O2 on the Au-Ag nanoparticle can thus explain the observed synergetic effect in catalysis.

Understanding the behavior and energetics of oxygen atoms on the silicon surface is important, and therefore water molecules dissociatively adsorbed on the $\mathrm{Si}(111)\text{\ensuremath{-}}7\ifmmode\times\else\texttimes\fi{}7$ surface were studied. At elevated temperatures, complete decomposition of a water molecule into two hydrogen atoms and one oxygen atom was directly observed by scanning tunneling microscopy. The methodology employed in this study provided an opportunity to examine the dynamic behavior of single oxygen atoms. We found that an oxygen atom has at least four bonding states between 290 and $340\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. The majority state appeared as an intensely bright spot located at an adatom site. At room temperature, this state can also be formed by stimulation of tunneling electrons at a water-reacted site. The hopping barriers between equivalent surface sites were determined from Arrhenius plots to be in the range of $1.8--2.0\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, indicating that the diffusion barrier for oxygen atoms into the bulk of Si(111) was higher than $2.0\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$.

The atomic geometry, electronic structure, and magnetic moment of 4d transition-metal clusters with 13 atoms are studied by pseudopotential density-functional calculations. We find a new buckled biplanar structure with a C(2v) symmetry stabilized by enhanced s-d hybridization. It has a lower energy than the close-packed icosahedral or cuboctahedral structure for elements with more than half-filled d shells. The magnetic moments of this buckled biplanar structure are found to be smaller than those of the icosahedral structure and closer to available experimental results.

We present first-principles calculations that provide a detailed diffusion picture of an adsorbed Si atom on the Si( 111)-(7X 7) surface. Several diffusion paths for the adsorbed Si atom are established by mapping out thetotal energy as a function of its positions on the surface. For diffusion between the faulted and unfaulted halves, the energy barriers range from 0.96 to 1.21 eV, while remarkable low-energy barriers from 0.3 to 0.7 eV are discovered within the faulted and unfaulted regions.

We used the embedded-atom method potential to study the structures, adsorption energies, binding energies, migration paths, and energy barriers of the Ir adatom and small clusters on fcc Ir (100), (110), and (111) surfaces. We found that the barrier for single-adatom diffusion is lowest on the (111) surface, higher on the (110) surface, and highest on the (100) surface. The exchange mechanisms of adatom diffusion on (100) and (110) surfaces are energetically favored. On all three Ir surfaces, ${\mathrm{Ir}}_{2}$ dimers with nearest-neighbor spacing are the most stable. On the (110) surface, the ${\mathrm{Ir}}_{2}$ dimer diffuses collectively along the 〈110〉 channel, while motion perpendicular to the channel walls is achieved by successive one-atom and correlated jumps. On (111) surface, the ${\mathrm{Ir}}_{2}$ dimer diffuses in a zigzag motion on hcp and fcc sites without breaking into two single atoms. On the (100) surface, diffusion of the ${\mathrm{Ir}}_{2}$ dimer is achieved by successive one-atom exchange with the substrate atom accompanying by a 90\ifmmode^\circ\else\textdegree\fi{} rotation of the ${\mathrm{Ir}}_{2}$ dimer. This mechanism has a surprisingly low activation energy of 0.65 eV, which is 0.14 eV lower than the energy for single adatom exchange on the (100) surface. Trimers were found to have a one-dimensional (1D) structure on (100) and (110) surfaces, and a 2D structure on the (111) surface. The observed abrupt drop of the diffusion barrier of tetramer, ${\mathit{I}}_{{\ensuremath{\gamma}}_{4}}$ on the Ir (111) surface was confirmed theoretically. \textcopyright{} 1996 The American Physical Society.

The emitter size effect of a series InGaAsSb base series of InP/InGaAsSb/InGaAs heterojunction bipolar transistors (HBTs) with different emitter sizes is investigated. Compared to the InGaAs base HBTs, these devices exhibit much lower base surface recombination current. This is attributed to the surface Fermi level pinning near the valence band of the antimonide base. The effect of Sb composition and doping concentration of the base on the surface recombination current is well explained by the postulate.

We explore the structural, electronic, photoluminescent, metallic, and semiconducting characteristics of 2D pure Zn-metal nanoplates. The 2D pure Zn-metal nanoplates are synthesized by the hot-filament metal-oxide vapor deposition (HFMOVD) technique. They have an average diameter and thickness of ∼520 and ∼144 nm, respectively. The results of the electronic and crystalline structure studies reveal the 2D nanoplates to be pure Zn hexagonal crystals, which can provide a wide-range photoluminescence from ultraviolet (UV) to red light emissions at room temperature. The measured valence-band and the calculated band-structure of the 2D pure Zn-metal nanoplates verify that the UV and blue light arise from the 3d–sp interband transitions, while the green, yellow, and red lights come from the valence-conduction interband transitions at a bandgap that is only present in the 2D nanoplates. Therefore, the 2D pure Zn-metal nanoplates possess not only metallic, but also semiconducting characteristics.

A trilevel resist system was employed to fabricate self-aligned, submicron emitter finger In0.52Al0.48As/In0.42Ga0.58As0.77Sb0.23/In0.53Ga0.47As double heterojunction bipolar transistors (DHBTs). Selective wet-etchants were used to define the emitter fingers and to form an InGaAs guard-ring around the emitter fingers. Due to the low energy bandgap of the InGaAsSb base layer and type II base-collector junction, a low turn-on voltage of 0.38 V at 1 A/cm2 and a high dc current gain of 123.8 for a DHBT with a 0.65×8.65 μm2 emitter area were obtained. A unity gain cutoff frequency (fT) of 260 GHz and a maximum oscillation frequency (fmax) of 485 GHz at JC=302 kA/cm2 were achieved.

The structures and performances of surface emitting AlGaInP green light emitting diodes (LEDs) with emission wavelength around 565 nm were studied. The AlGaInP green LEDs with epitaxial structure grown on P-type GaAs substrate showed the best performance. This is the first paper ever reported for the fabrication of AlGaInP LEDs using P-type GaAs as a substrate. In AlGaInP LED structure using P-type GaAs substrate, the highly conductive n- type AlInP was consequently used as a top confining layer and the current crowding problem was significantly improved. Therefore, the green electroluminescence (EL) was uniformly emitted from the surface of LED dice.

In this paper, the trapping/detrapping in high-k gate dielectrics has been analyzed by gate current random telegraph noise (IG) measurement. Gate current is suppressed when traps capture electrons and recovers for empty traps. By statistically extracting capture and emission times, we can understand the trap properties. Besides, the influence will be understood by observing the variation of Gate current fluctuation. Through the analysis of the device after soft-breakdown (SBD), the deterioration of the dielectric will change the capture cross section. Moreover, the traps in the SBD path have been identified as the cause of a huge increase in the gate leakage.

Carbon nanotubes have been considered as an alternative material for next generation nanoelectronic devices, such as the carbon nanotube field-effect transistor (CNT-FET) or nanosensor. Large-scale growth of single-walled carbon nanotubes (SWNTs) is particularly essential to the fabrication of the CNT-FET on a full wafer. In this study, SWNTs grown at designated positions on broken pieces in a conventional thermal furnace chemical vapor deposition (CVD) system and on a 4-in. full size silicon wafer in a cold-wall thermal CVD were compared. The distinct characteristics of SWNTs grown by the two systems are explained by the differences in the temperature distribution and the gas flow pattern, and their interplay with the catalysis and the feedstock gas decomposition. The adoption of cold-wall CVD process provides a simple method, but an essential step, toward commercial applications of SWNT-based devices.

Ultrathin TiO2 amorphous films are deposited on ultraviolet grade fused silica substrates and CaF2 by using rf reactive unbalanced magnetron sputtering from a Ti metal target in atmosphere of Ar and O2. For an O2/Ar flow rate ratio of more than 1.5, the deposited TiO2 thin films are stoichiometric. TiO2 thin films that meet the optical requirements of a high transmittance attenuated phase-shifting mask (HTAPSM) at 157 and 193 nm wavelengths can also be properly inspected since the transmittance at 257 nm wavelength is less than 28%. The simulated thickness range of such a TiO2 thin film is found to be between 16 and 20 nm. A TiO2 amorphous thin film with thickness of 23.5 nm, transmittance of 24.9% and reflectance of 15.0% at wavelength of 193 nm, transmittance of 16.3% at 157 nm wavelength and transmittance of 23.0% at 257 nm wavelength is shown to be able to serve as an absorber layer for HTAPSM blanks at 157 and 193 nm wavelength.

Indium-tin oxide (ITO) transparent conducting films with a low resistivity of 2–3 × 10-4 Ω·cm have been introduced as a window layer in (Al0.7Ga0.7)0.5In0.5P/(Al0.1Ga0.9)0.5In0.5P double-heterostructure orange light-emitting diodes to obtain a uniform spatial distribution of the emission light, a good device performance and high reliability. An output power of 450 µW at 20 mA corresponding to an external quantum efficiency of 1.1% for the 620 nm emission can be achieved.

High temperature, low threshold current, and transverse mode stabilised operation is achieved in a separate confinement heterostructure AlGaInP/Ga/sub 0.4/In/sub 0.6/P compressively strained multiquantum-well structure which was fabricated from an epitaxial wafer grown on misoriented

In this study, the mechanism for ohmic contact of Ti/Al bilayer formation on as-grown, etched and postetch annealed GaN surfaces were investigated. A nonalloyed Ti/Al ohmic contact to etched GaN surface, with postetch annealing prior to metal deposition, was obtained. The specific contact resistance of 2.3×10−4 Ω cm2 was obtained. The nonalloyed ohmic contact may be attributed to the postetch annealing which generates nitrogen vacancies that result in a heavily n-type surface thereby forming a tunneling junction. On the other hand, the nonalloyed Ti/Al contact on as-grown and as-etched GaN surfaces exhibits non-ohmic behavior. After alloying at 500 °C for 5 min, Ti/Al contacts on as-grown, as-etched and postetched annealing GaN surfaces have specific contact resistances around 9.8×10−5, 1×10−4, and 7.2×10−5 Ω cm2, respectively. Nonalloyed Ti/Al ohmic contacts would be especially useful for fabricating high breakdown, recessed-gate field effect transistors on GaN since the moderate postannealing condition converts only the near surface layer to heavily n type.In this study, the mechanism for ohmic contact of Ti/Al bilayer formation on as-grown, etched and postetch annealed GaN surfaces were investigated. A nonalloyed Ti/Al ohmic contact to etched GaN surface, with postetch annealing prior to metal deposition, was obtained. The specific contact resistance of 2.3×10−4 Ω cm2 was obtained. The nonalloyed ohmic contact may be attributed to the postetch annealing which generates nitrogen vacancies that result in a heavily n-type surface thereby forming a tunneling junction. On the other hand, the nonalloyed Ti/Al contact on as-grown and as-etched GaN surfaces exhibits non-ohmic behavior. After alloying at 500 °C for 5 min, Ti/Al contacts on as-grown, as-etched and postetched annealing GaN surfaces have specific contact resistances around 9.8×10−5, 1×10−4, and 7.2×10−5 Ω cm2, respectively. Nonalloyed Ti/Al ohmic contacts would be especially useful for fabricating high breakdown, recessed-gate field effect transistors on GaN since the moderate postannealing condition ...

Visible light-emitting diodes (LEDs) emitting at 615 nm and employing the AlGaInP/GaInP double heterostructure (DH) grown on a lattice-matched GaAs/sub 0.7/P/sub 0.3/ substrate have been fabricated for the first. The external quantum efficiency of 0.156% for the orange LEDs can be achieved by introducing the GaP material as the current spreader and window layer for the DH LEDs. >