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Ge1−xSnx and Si1−x−yGeySnx alloys are promising materials for future opto- and nanoelectronics applications. These alloys enable effective bandgap engineering, broad adjustability of their lattice parameter, exhibit much higher carrier mobility than pure Si, and are compatible with the complementary metal-oxide-semiconductor technology. Unfortunately, the equilibrium solid solubility of Sn in Si1−xGex is less than 1% and the pseudomorphic growth of Si1−x−yGeySnx on Ge or Si can cause in-plane compressive strain in the grown layer, degrading the superior properties of these alloys. Therefore, post-growth strain engineering by ultrafast non-equilibrium thermal treatments like pulse laser annealing (PLA) is needed to improve the layer quality. In this article, Ge0.94Sn0.06 and Si0.14Ge0.8Sn0.06 thin films grown on silicon-on-insulator substrates by molecular beam epitaxy were post-growth thermally treated by PLA. The material is analyzed before and after the thermal treatments by transmission electron microscopy, x-ray diffraction (XRD), Rutherford backscattering spectrometry, secondary ion mass spectrometry, and Hall-effect measurements. It is shown that after annealing, the material is single-crystalline with improved crystallinity than the as-grown layer. This is reflected in a significantly increased XRD reflection intensity, well-ordered atomic pillars, and increased active carrier concentrations up to 4 × 1019 cm−3. [ABSTRACT FROM AUTHOR]

We have attained low leakage current, low interfacial traps, and low border traps by effectively passivating both p- and n-In0.53Ga0.47As (InGaAs) surfaces using the same gate dielectrics of ultra-high-vacuum deposited Al2O3/Y2O3. Gate leakage currents below 2 × 10−7 A/cm2 at gate fields of ±4 MV/cm were obtained after 800 °C rapid thermal annealing, demonstrating the intactness of the interface and heterostructure. Negligibly small frequency dispersions in the capacitance–voltage (C–V) characteristics of p- and n-type metal-oxide-semiconductor capacitors (MOSCAPs) were obtained from accumulation, flatband, to depletion as measured from 300 K to 77 K, indicative of low border and interfacial trap density; the C–V frequency dispersions in the accumulation region are 1.5%/dec (300 K) and 0.19%/dec (77 K) for p-InGaAs, and 2.2%/dec (300 K) and 0.97%/dec (77 K) for n-InGaAs. Very low interfacial trap densities (Dit's) of (1.7–3.2) × 1011 eV−1cm−2 and (6.7–8.5) × 1010 eV−1cm−2, as extracted from the conductance method, were achieved on p- and n-InGaAs MOSCAPs, respectively. [ABSTRACT FROM AUTHOR]

InAs quantum-dot structures were grown using a GaAs1-xSbx matrix on a GaAs(001) substrate. The use of GaAs1-xSbx for the buffer and cap layers effectively suppressed coalescence between dots and significantly increased the dot density. The highest density (~3.5 x 1011/cm²) was obtained for a nominal 3.0 monolayer deposition of InAs with an Sb composition of x = 13-14% in the GaAs1-xSbx matrix. When the Sb composition was increased to 18%, the resulting large photoluminescent red shift (~90 meV) indicated the release of compressive strain inside the quantum dots. For x > 13%, we observed a significant decrease in photoluminescence intensity and an increase in the carrier lifetime (≥4.0 ns). This is attributed to the type-II band alignment between the quantum dots and matrix material. [ABSTRACT FROM AUTHOR]

The melting curves and structural properties of tantalum (Ta) are investigated by molecular dynamics simulations combining with potential model developed by Ravelo et al. [Phys. Rev. B 88, 134101 (2013)]. Before calculations, five potentials are systematically compared with their abilities of producing reasonable compressional and equilibrium mechanical properties of Ta. We have improved the modified-Z method introduced by Wang et al. [J. Appl. Phys. 114, 163514 (2013)] by increasing the sizes in Lx and Ly of the rectangular parallelepiped box (Lx=Ly « Lz). The influences of size and aspect ratio of the simulation box to melting curves are also fully tested. The structural differences between solid and liquid are detected by number density and local-order parameters Q6. Moreover, the atoms' diffusion with simulation time, defects, and vacancies formations in the sample are all studied by comparing situations in solid, solid-liquid coexistence, and liquid state. [ABSTRACT FROM AUTHOR]

The influence of Co thickness on the microstructural characteristics of Pt/Co multilayered thin films was investigated using high resolution electron microscopy. The results showed that increased Co thickness resulted in the degradation of coherence and increased surface roughness. In addition, there was an observed increase in the incidence of twining and reflection plane defects.

The optical properties of a simple metallic nanomatryushka (nanosphere-in-a-nanoshell) with gain have been investigated theoretically. The spaser (surface plasmon amplification by stimulated emission of radiation) phenomena can be observed at two critical wavelengths in the active metallic nanomatryushkas. With increasing the gain coefficient of the middle layer, a similar super surface plasmon (SP) resonance is first found at the ω-+∣1 mode of the active nanoparticles and then breaks down. With further increasing the gain coefficient, another similar super-resonance occurs at the ω--∣1 mode. The near-field enhancements in the active nanomatryushkas also have been greatly amplified at the critical wavelengths for ω-+∣1 and ω--∣1 modes. It is further found that the amplifications of SPs in the active Ag-SiO2-Au nanoshell are strongest in four kinds of nanoshells and hence the largest near fields. The giant near-field enhancement can greatly enhance the Raman excitation and emission. [ABSTRACT FROM AUTHOR]

Research into the switching dynamics of 50 nano-m diameter epitaxial Fe(100) disks is presented. It was possible to demonstrate complex reversal behaviour. This work demonstrates the utility of real time-resolved scanning Kerr microscopy.

The effects of biaxial tensile strain on the structure, electronic states, and mechanical properties of silicene are studied by ab-initio calculations. Our results show that up to 5% strain the Dirac cone remains essentially at the Fermi level, while higher strain induces hole doped Dirac states because of weakened Si-Si bonds. We demonstrate that the silicene lattice is stable up to 17% strain. It is noted that the buckling first decreases with the strain (up to 10%) and then increases again, which is accompanied by a band gap variation. We also calculate the Grüneisen parameter and demonstrate a strain dependence similar to that of graphene. [ABSTRACT FROM AUTHOR]

The atomic structures of four Ca40+XMg25Cu35-X (X = 0, 5, 10, and 20 at. %) ternary metallic glasses have been determined using a synergistic combination of neutron diffraction, ab initio molecular dynamics (MD) simulation, and constrained reverse Monte Carlo modeling. It is described as close-packing of efficiently packed Cu-centered clusters that have Ca, Mg, and Cu atoms in the first coordination shell. The close-packed arrangement of the clusters provides a characteristic medium range order in these alloys. An average coordination number (CN) of 10 (with about 5-7 Ca, 2-3 Mg, and 1-2 Cu atoms) is most common for the Cu-centered clusters. The average coordination numbers around Mg and Ca are 12-13 (∼6-8 Ca, 3 Mg, and 1-4 Cu) and 13-15 (7-9 Ca, 3-4 Mg, and 2-5 Cu), respectively, and they are composition dependent. Strong interaction of Cu with Mg and Ca results in pair bond shortening. Icosahedral short range order does not dominate in these amorphous alloys, although polytetrahedral packing and five-fold bond configurations resulting in pentagonal bi-pyramids have been found to be the most common nearest atom configurations. [ABSTRACT FROM AUTHOR]

In this study, we report the characterization of thin-film GaAs grown on germanium-on-insulator (GeOI) on Si substrate. A GaAs/GeOI diode with a 600 nm buffer layer showed a rectification of 1.0 × 107 at ±2 V and had an electrical performance similar to that of the reference sample grown on GaAs substrate. We demonstrate two thin diodes (<350 nm in thickness) that still showed high forward densities and rectification properties. The electrical performances of the diodes degraded as the diode active regions were grown closer to the GaAs/Ge interface due to the increase of defects propagating into the active regions. The experimental results were fitted with the thermionic emission equation and the Frenkel-Poole model. [ABSTRACT FROM AUTHOR]

This study investigates the propagation of Lamb waves in a phononic crystal plate in the form of a staggered-layer structure. Using the analyses of the band structures and the transmission spectra, a significant modulation to the lower-order Lamb modes is demonstrated due to the staggered arrangement. The modulation leads to remarkable changes in the location and width of the phononic band gaps. We further identify the physical mechanism for the effects of the staggered-layer through the particle displacement fields of the eigenmodes. The symmetric mode converts to the antisymmetric mode and vice versa with the existence of the staggered arrangement. In addition, we find that the phononic band gaps are very sensitive to the degree of stagger, which could be indispensable to practical applications such as band gap tuning. [ABSTRACT FROM AUTHOR]

We have conducted an experimental and theoretical study on first- and second-order Raman scattering of zinc blende and wurtzite ZnS. Based on the calculated phonon band structure, phonon density of states, and symmetry selection rules, we have clearly identified for the first time the origins of these vibration modes in the second-order Raman spectra from these two polymorphs. For zinc blende ZnS, it is found that the previously estimated frequency of the LA mode at X point in the Brillouin-zone boundary is much smaller than the value obtained from other experiments and our calculation. Considering the involvement of LA phonon at X point, we reassign the second-order Raman active modes and some other modes which have not yet been understood so far. This work clarifies some of the controversial Raman mode assignments in zinc blende and wurtzite ZnS. [ABSTRACT FROM AUTHOR]

The optical and vibrational properties of 2H-, 4H-, and 6H-AlN are studied based on the ab initio pseudopotential density functional theory. Three polymorphs have similar electronic and optical properties implying that 4H- and 6H-AlN are also of importance to optoelectronics. Infrared spectra of the three polymorphs show two main modes at 660 and 690 cm-1 and an additional mode at 570 cm-1 can only be observed from 4H- and 6H-AlN. The Raman spectra of 4H- and 6H-AlN show more active modes than that of 2H-AlN. These infrared and Raman features can be used as the fingerprints to distinguish the three polymorphs. [ABSTRACT FROM AUTHOR]

We have simulated the variance in the diffracted electron intensity as a function of scattering vector in fluctuation electron microscopy for a range of fully amorphous and nanocrystal-containing metallic glass models. Variance peaks are obvious for glasses that contain well-developed short-to-medium range order but absent for their parent liquids. The variance peaks are very sensitive to the presence and especially the size of the nanocrystal embryos or nuclei embedded in the glass matrix but much less so to the variations in the type or degree of the cluster ordering developed in fully amorphous materials. [ABSTRACT FROM AUTHOR]

A series of TiN/Ti multilayer coatings with fixed TiN layer thickness and different Ti layer thicknesses were deposited using a large area filtered arc deposition technique. X-ray diffraction was used to investigate the crystalline structure, lattice strain, and crystallinity of the deposited coatings. A substrate curvature method was used to measure the internal stress in the multilayer coatings. The influence of the Ti interlayer thickness on the crystalline structure and internal stress in the coatings was systematically studied. It was found that a cubic TiN phase and hexagonal Ti phase exist in all the multilayer coatings. The TiN and Ti layers in the multilayer coatings exhibit a strong (111) and (002) preferred orientation, respectively. With the increase in the Ti layer thickness, the d-spacing decreases and the peak width increases for both TiN (111) and Ti (002) peaks, indicating a decrease in the lattice strain and an increase in the crystallinity of both TiN and Ti phases. It is suggested, that the reduction in the defect density in both TiN and Ti layers and the relaxation of the stain by the diffusion of the Ti atoms in the underneath Ti layer contribute to the decrease in the total internal stress with increasing Ti layer thickness. [ABSTRACT FROM AUTHOR]

In this study, the viscous flow behavior and thermomechanical properties of Mg65Cu25-xBxGd10 (x=0 and 3 at. %) bulk metallic glasses (BMGs) in the supercooled liquid region have been investigated by using differential scanning calorimetry and thermomechanical analyzer. It has been found that the fragility of the supercooled liquid is reduced by the boron addition, thus, degrading the deformability. This conclusion is supported by the many other extracted parameters. Thus, even with much higher hardness, the B-additive Mg based BMG will be more difficult to be formed, which appears to be a negative factor in applying in the microforming or nanoimprinting industry. [ABSTRACT FROM AUTHOR]

We investigate the electronic structures and optical properties of the wurtzite, zinc blende, and rocksalt AlN phases at their structural phase transition pressures by the ultrasoft pseudopotential density functional method. We employ the Perdew–Burke–Eruzerhof form of the generalized gradient approximation available in the CASTEP code with the plane-wave basis sets to expand the periodic electron density. The dielectric function and optical properties such as reflectivity, absorption coefficient, refractive index, and electron energy-loss function are presented in a wide energy range between 0 and 50 eV. Our results reveal that for rocksalt AlN phase, the intensity of N 2p orbitals in the conduction bands obviously decreases when the pressure increases from 15 to 17 GPa. The calculated optical properties indicate that the zinc blende and wurtzite AlN phases have some similar features but the rocksalt AlN phase has other characteristics. [ABSTRACT FROM AUTHOR]

The morphology and the size-dependent photoluminescence (PL) spectra of the type-II ZnTe quantum dots (QDs) grown in a ZnSe matrix were obtained. The coverage of ZnTe varied from 2.5 to 3.5 monolayers (MLs). The PL peak energy decreased as the dot size increased. Excitation power and temperature-dependent PL spectra are used to characterize the optical properties of the ZnTe quantum dots. For 2.5- and 3.0-ML samples, the PL peak energy decreased monotonically as the temperature increased. However, for the 3.5-ML sample, the PL peak energy was initially blueshifted and then redshifted as the temperature increased above 40 K. Carrier thermalization and carrier transfer between QDs are used to explain the experimental data. A model of temperature-dependent linewidth broadening is employed to fit the high-temperature data. The activation energy, which was found by the simple PL intensity quenching model, of the 2.5, 3.0, and 3.5 MLs were determined to be 6.35, 9.40, and 18.87 meV, respectively. [ABSTRACT FROM AUTHOR]

Electrical properties of damascene silver wires with widths between ≈60 and 840 nm and heights between ≈100 nm and 300 nm are presented. The superconformal electrodeposition process by which the seam-free and void-free metallizations were fabricated is summarized. The chemical-mechanical polishing plus oblique ion sputtering process by which metal overburden was removed from the field adjacent to the wires is detailed. The size-dependent resistivity of the wires is obtained and interpreted in terms of intrinsic resistivity, grain boundary reflection, and surface scattering. Quantitative analysis of the last is accomplished using a different implementation of the Fuchs-Sondheimer formalism for wires of rectangular geometry and nonzero surface specularity that is derived herein. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

MgO films were deposited by using a pulsed mid-frequency magnetron sputtering technique. X-ray diffraction, atomic force microscopy, Rutherford backscattering, and a diode discharge device were used to characterize crystalline structure, surface morphology, oxygen content, and secondary electron emission (γ) coefficient of the films, respectively. The influence of the duty cycle on the structure and secondary electron emission properties of the films was systematically studied. No remarkable change in the oxygen content in the films with duty cycle can be observed, but crystalline structure, surface morphology, and secondary electron emission properties of the films are significantly affected by the duty cycle. All films exhibit a strong (220) preferred orientation growth, but the increase of the duty cycle results in a continuous decrease in grain size, surface roughness, and γ coefficient, as well as an increase in the defect density. The increase of the defect density with increasing duty cycle is the main reason for the reduction of the γ coefficient. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A pulsed mid-frequency magnetron sputtering technique was used to deposit MgO films. Atomic force microscopy, Rutherford backscattering, x-ray diffraction, and a diode discharge device were used to characterize surface morphology, oxygen content, crystalline structure, and the secondary electron emission (γ) coefficient of the films, respectively. The oxygen content (56 at. %) in all the films remained constant. However, surface morphology, crystalline structure, and the secondary electron emission properties of the films are strongly dependent on the O[sub 2] flow rate. As the O[sub 2] flow rate is increased from 3 to 10 sccm, a sudden decrease in the grain size and the y coefficient of the films can be observed, and the crystalline orientation evolves from a strong (200) preferred orientation continuously to a fully (220) preferred orientation. Further increase of O[sub 2] flow rate results in a slight change in the grain size and the crystalline orientation, but a considerable increase in the full width at half maximum of the x-ray diffraction peaks and a significant decrease in the y coefficient of the films. We found that preferred orientation and crystalline quality are the main factors that influence the secondary electron emission properties of the MgO films. [ABSTRACT FROM AUTHOR]

Raman spectroscopy was used to characterize TiN films deposited by using an off-plane double bend filtered cathodic vacuum arc technique. The influence of substrate bias on the Raman spectra was systematically studied. Four peaks at 235, 320, 440, and 570 cm[sup -1], related to transverse acoustic (TA), longitudinal acoustic (LA), second-order acoustic (2A), and transverse optical (TO) modes of TiN, respectively, were observed in the Raman spectra of TiN films. The intensity of all four peaks and the area fraction as well as the full width at half maximum (FWHM) of the TO peak increase drastically with increasing substrate bias, reaching a maximum at -100 V, and then decrease greatly. However, the area fraction of TA, LA, and 2A peaks, the FWHM of TA and 2A peaks, as well as the frequency of all four peaks decrease rapidly with increasing substrate bias to -100 V, and then increase greatly. At a bias above -200 V, only a slight change in the Raman spectra of TiN films were observed. The change in the N/Ti ratio is the main reason for the evolution in the Raman spectra of TiN films with increasing substrate bias. The internal stress and the crystal size play only a minor role in the Raman spectra of TiN films in the present study. [ABSTRACT FROM AUTHOR]

(Ti,Al)N films were deposited by an off-plane double bend filtered cathodic vacuum arc technique in N[sub 2] ambient at room temperature. X-ray diffraction (XRD) and Raman spectroscopy were used to characterize the film structure. The influence of deposition pressure and the substrate bias on the XRD patterns and Raman spectra were systematically studied. As deposition pressure is increased, the film structure evolves from metallic, to metal rich (Ti,Al)[sub 2]N, and finally to a single face-centered cubic (Ti,Al)N. As substrate bias is increased, the structure evolves from amorphous to crystalline (Ti,Al)N for bias at 200 V. Further increase of substrate bias results in the decrease of the crystalline size and increase of disorder phase. Four peaks at 238, 326, 442, and 679 cm-1, arisen from the transverse acoustic, longitudinal acoustic, transverse acoustic optical, and longitudinal acoustic modes of (Ti,Al)N phase, respectively, can be observed in the Raman spectra. ! The variation of the Raman spectra with the deposition pressure and substrate bias are in good agreement with that of the XRD measurements. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Data on oxidation kinetics, oxide structure and oxide morphology of AlAs0.1Sb0.9 in order to determine the optimal oxidation conditions are presented. A physical explanation as to how self-limiting oxidation occurs in the material is suggested.

Presents information on a study on the methods for reducing and enhancing the intensity of the spontaneous ordering in the growth of (InP)2/(GAP)2 short-period superlattice (SPS) quantum wells using solid source molecular beam epitaxy. Various studies on spontaneous ordering; Methodology used in conducting the study; Results of the study.

Focuses on a study that reported the conduction enhancement characteristics and the conduction mechanism in nitroxide. Sample preparation and measurements; Results; Discussion; Conclusions.

Presents a study which aimed to characterize the silicon-silica interface traps in p-metal-oxide-semiconductor structures with very thin gate oxides by conductance and quasistatic techniques. Review of the theory of the conductance technique; Description of the hole capture cross section; Discussion on dispersion parameters as a function of the surface potential.

Presents a study which derived a closed-form analytical expression to predict the threshold voltage of a narrow-gate metal-oxide-semiconductor field-effect transistor with a fully recessed field-isolation structure. Calculation using depletion approximation; Discussion of threshold-voltage variations under the influence of various physical parameters.

Suggests a model which attempts to explain the entire dielectric breakdown procedure. Mathematical relationship accounting for the effects of oxide thickness, defects, mobile positive ions and the width of the band gap on the dielectric strength and breakdown mechanism; Correlation of dielectric strength and the breakdown phenomenon with processing conditions; Main mechanisms which are influenced by the geomorphic and physical parameters and the examination conditions.

Presents a study that fabricated metal-oxide-semiconductor field-effect transistors with very thin gate oxides. Inverse relation between the fixed oxide charge density and the oxide thickness; Surface mobilities at both room temperature and 77 Kelvin; Correlation of oxide thickness, growth condition and physical parameters.

Presents a study which investigated surface mobility in thin-gate oxide metal-oxide-semiconductor field-effect transistors. Method of the study; Results and discussion; Conclusion.

Presents information on a study wherein theoretical expressions for the hot-electron induced interface state generation and threshold-voltage shift are developed, by considering the decomposition of water-related bonds at the silicon-oxide interfaces. Methods; Results; Discussion.

Presents a study which examined the instabilities of the metal-oxide-semiconductor (MOS) transistors with nitrided oxides as gate insulators. Materials and methods used; Discussion on the electrical characteristics of MOS capacitors; Behaviors of channel hot-electron stressing; Results of flicker noise for different gate-oxide preparation techniques.

Provides information on a study which observed the antiferromagnetic coupling of iron layers in epitaxial cobalt chromium sandwiches or multilayers (MLF). Hysteresis curves; Characterization of the MLF through x-ray scattering and high-resolution electron microscopy; Magnetoresistance of the MLF.

Presents the low-frequency noise measurements on n-channel metal-oxide-semiconductor (MOS) transistors with trichoroethylene, dry, thermally nitrided, or reoxidized nitrided oxides as gate dielectrics. Devices used in the experiment; Nitridation of as-grown oxide; Plot of total oxide-trap density and frequency index of noise spectrum versus gate vias for MOS transistor with gate oxide grown by dry oxidation.

Presents the first attempt in correlating the low-frequency noise with the surface characteristics of metal films prepared by sputtering of copper onto oxidized-silicon and sapphire substrates. Noise behaviors and the surface physics of metal films on the substrates; Dependence of the spectral slope of noise spectrum on the thickness and surface area of the metal films; Basic mechanism of the surface noise in metal film.

Presents a study which described a growth kinetic model for thermal oxidation of silicon in dry oxygen. Parallel oxidizing species that are assumed to be transported during oxidation; Description of the proposed oxidation kinetic model; Results and discussion; Conclusions.

Determines the threshold voltage degradation of metal-oxide-semiconductor field-effect transistors with thermally nitrided oxide or pure oxide as gate dielectric under Fowler-Nordheim stressing. Observation of typical threshold votage turnaround behavior for both kinds of devices; Shift of substrate current peak; Field-effect electron mobility.

Presents information on a study which investigated the effect of elevated temperature on the structural stability and performance of molybdenum-silicon multilayer (ML) mirrors. Characterization using small angle x-ray scattering; Characterization by large-angle x-ray scattering; Determination of ML structural parameters; Relation between optical stability of an ML x-ray mirror and structural stability.

Investigates the interface and oxide-charge trapping characteristics of bombarded metal-oxide-semiconductor field-effect transistors. Interface state density decreases; Oxide charge trapping properties; Stress compensation.

Examines the drain leakage in n-channel metal-oxide-semiconductor field-effect transistors (MOSFET) under off-state conditions. Correlation between current density and electric field characteristics for metal-oxide-semiconductor capacitors; Causes of shallow trap sites responsible for the leakage in n-MOSFET; Application of a trap-assisted tunneling model for explaining the low-field gate current.

Proposes a simple method for determining the energy level and spatial density of traps in insulators. Analysis of metal-oxide-semiconductor capacitors and transistors; Significance of nitridation techniques for ultrathin dielectrics; Conditions required for applying nitridation using a low-partial-pressure process.

Reports on the application of the simplified closed-form trap-assisted tunneling model to nitrided oxide dielectric capacitors. Problem associated with the nitridation process; Electrical characteristics of capacitors fabricated by a low-partial-pressure nitridation procedure; Energy-band diagram of the metal oxide semiconductor capacitor under a negative gate bias.