Parameter analysis for gate metal-oxide-semiconductor structures of ion-implanted 4H silicon carbide metal-semiconductor field-effect transistors

From the theoretical analysis of the thermionic emission model of current-voltage characteristics, this paper extracts the parameters for the gate Schottky contact of two ion-implanted 4H-SiC metal-semiconductor field-effect transistors (sample A and sample B for three and four times multiple ion-implantation channel region respectively) fabricated in the experiment, including the ideality factor, the series resistance, the zero-field barrier height, the interface oxide capacitance, the interface state density distribution, the neutral level of interface states and the fixed space charge density. The methods to improve the interface of the ion-implanted Schottky contact are given at last.     

Many-particle decays of α-chain structures in24Mg

We have searched for evidence of exotic cluster configurations in²⁴Mg resembling a linear chain of α particles in various many-particle final states of the¹²C+¹²C system, including¹²C(O ₂ ⁺ )+¹²C(O ₂ ⁺ ) and⁸Be+¹⁶O^*(4α). Such configurations are predicted to occur by a number of different theoretical models of the structure of²⁴Mg. An array of highly segmented double-sided silicon strip detectors permits detailed, high resolution reconstruction of these many-charged-particle final states.     

β-tin→Imma→sh phase transitions of germanium

New paths were designed for the investigations of the β-tin→Imma→sh phase transitions in nanocrystalline Ge under conditions of hydrostatic stress. A second-order transition between the β-tin and Imma phases was identified at 66 GPa, and a first-order transition between the Imma and sh phases was determined at 90 GPa. Superconductivity was obtained up to 190 GPa using the acquired structural data in first-principles calculations. This provides evidence that the standard electron-phonon coupling mechanism is responsible for superconductivity in Ge, as evidenced by the good agreement between the calculations and existing experiments.     

The deformation texture of β-tin I. Compression texture

The compression texture of -tin, produced by compressing the sample at temperatures of 20° C, –80° Cand –180° C,was measured. Measurement was carried out by the reflection method on a Schulz diffractometer by measuring the pole f'gures of the (200)and (101)planes. The results of the measurements show the produced, texture to be considerably dependent on the temperature.     

The deformation texture of β-tin II. Rolling texture

Measurements were made of the rolling texture of -tin which is produced by rolling the sample at a temperature of 20 °C and in the temperature interval –80°C–60 °C and –180 °C–110 °C.     

Study of the Defect Structure and Crystal-Field Parameters of α-Al2O3:Yb3+

The methods currently used for studying the defect structure of laser host crystals doped with transition metal or rare-earth ions have several drawbacks or limitations. This study proposes an alternative approach for obtaining optimized impurity structures using molecular dynamics calculation in conjunction with the superposition model. This new approach is specifically applied to a system named α-Al₂O₃:Yb³⁺, in which the simulated defect structure is used to fit the superposition model parameters directly onto the observed energy levels. Such an approach provides predicted values of crystal-field parameters, Zeeman splitting g-factor, and hyperfine structure constants. Moreover, the C_3v site symmetry is found to be a good approximation for the actual C₃ site of Yb³⁺, as doped in an α-Al₂O₃ crystal.     

Reorientation of Defect Dipoles in Ferroelectric Ceramics

We investigate the frequency, temperature, tetragonality and quenched temperature dependences of the hysteresis loops in Pb[(Zr0.52 Ti0.48)0.95 (Mn1/3Nb2/3)0.05]O3 (PMnN-PZT) ceramics. It has been demonstrated that the polarization-field hysteresis curves show “pinched” shapes when tested at room temperature, higher frequency or using the large-tetragonality specimen. While normal square-like loops are observed at 200℃ and 0.01 Hz or using the small-tetragonality one. Meanwhile, close relations between the P-E loops and the applied frequency,temperature or tetragonality reveal that there exists a typical relaxation time corresponding to the reorientation of the defect dipoles. It can be seen further from the quenched temperature dependences of the loops that the reorientation of the defect dipoles may influence the pinching. Compared to the intrinsic depinning procedure induced by changes of the distribution of defect dipoles, we provide new evidence for extrinsic depinning mechanism of the defect dipoles in the ferroelectric ceramics.     

“Defect” states of channeling electrons

We develop a theory of quantum states caused by defects of the crystal lattice during planar channeling of electrons. Points defects are considered. We obtain expressions for the wave function and the transverse energy of the defect states and make estimates for {110} planar channeling in silicon by electrons with energies of 1–10 MeV. Substitutional, interstitial, and vacancy impurity atoms are examined. We propose using properties of the electromagnetic radiation of electrons in defect states for diagnostics of single crystals.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp.68–72, April, 1990.     

The realization of ion-implanted Hg1−xCdxTe photovoltaic arrays

A review of the main aspects of the realization of PV Hg_1−xCd_xTe arrays is presented. Results obtained on coating this material are reported and related to the carrier concentration of the bulk. Changes in the electrical properties, produced by ion implantation, are also reported and discussed.     

Electronic band structures of the alkali metals and of the noble metals and their α-phase alloys

In the monovalent metals the electronic band structure is strongly affected by the size of the band gap E _s-E _p at the Brillouin zone faces, a large gap implying a large distortion of the Fermi surface. Here E _s and E _p are the energies of the purely s-like and p-like states on the zone faces. We have made crude estimates of E _s-E _p for the alkali and noble metals, in terms of the s-p excitation energy Δ_sp of the free atoms. These suggest a single model which correlates most of the experimental information about the band structures of these metals. In particular the Fermi surface of lithium appears to make considerable contact with the zone faces. In the α-phase alloys of the noble metals, the solute always has a larger value of Δ_sp than the solvent, which raises the energy E _p relative to E _s. The Fermi surface becomes more nearly spherical in copper alloys than in copper, since E _p<E _s, whereas it distorts further in the gold alloys (E _p>E _s). This accounts for many Knight shift, electronic specific heat, magnetic susceptibility and other data on these alloys. Furthermore it provides the extension of Jones' explanation of the Hume-Rothery rule demanded by the non-spherical Fermi surface in pure copper and gold.     

Peptide arrays with designed α-helical structures for characterization of proteins from FRET fingerprint patterns

A practical high-throughput protein detection system is described, based on synthetic peptide arrays consisting of designed alpha-helical peptides, detected by fluorescence resonance energy transfer (FRET). Initially a model alpha-helical peptide known to interact with a structured protein, calmodulin, was selected to establish the strategy for high-throughput detection. In comparison to peptides with a single probe, a much higher FRET response has been observed with two fluorescent probes (7-diethylaminocoumarin-3-carboxylic acid and 5(6)-carboxy-fluorescein) at both termini of the synthetic peptides. To establish a reproducible high-throughput detection system, peptides were also immobilized onto a solid surface for detection of the target proteins. A small library of 112 different peptides was constructed, based on a model of the alpha-helical peptide with systematic replacement of residues carrying specific charges and/or hydrophobicities. The library was used to effectively characterize various proteins, giving their own 'protein fingerprint' patterns. The resulting 'protein fingerprints' correlate with the recognition properties of the proteins. The present microarray with designed synthetic peptides as the capturing agents is promising for the development of protein detection chips.     

Defect and electrical properties of nanocrystalline tungsten trioxide

Nanocrystalline tungsten trioxide particles were prepared by a wet-chemical method. Transmission electron microscope (TEM) analysis shows that the average grain size is about 15nm. The oxygen deficiency of nanometre-sized sample is higher than that of ordinary tungsten trioxide. The electric conductivity increases because of high oxygen deficiency. Ironic relaxation polarization and crystallographic shear (CS) planes theory were used to explain the unusual dielectric characteristic of nanocrystalline tungsten trioxide.     

Determination of activation energy of ion-implanted deuterium release from W–Y_2O_3

The retention and release of deuterium in W–2%Y_2O_3 composite materials and commercially pure tungsten after they have been implanted by deuterium plasma(flux ～ 3.71 × 10~(21) D/m~2·s, energy ～ 25 eV, and fluence up to 1.3 × 10~(26)D/m~2)are studied. The results show that the total amount of deuterium released from W–2%Y_2O_3 is 5.23 × 10~(20) D/m~2(2.5 K/min),about 2.5 times higher than that from the pure tungsten. Thermal desorption spectra(TDS) at different heating rates(2.5 K/min–20 K/min) reveal that both W and W–2%Y_2O_3 have two main deuterium trapped sites. For the low temperature trap, the deuterium desorption activation energy is 0.85 eV(grain boundary) in W, while for high temperature trap, the desorption activation energy is 1.57 eV(vacancy) in W and 1.73 eV(vacancy) in W–2%Y_2O_3.     

Enhanced molecular dynamics simulation of the transformation between α-helix and β-hairpin structures for peptide

ABSTRACT

Here, we investigated the secondary structure transformation for a design peptide, which has both the α-helix (PDB ID code 2DX3) and β-hairpin (PDB ID code 2DX4) structures in aqueous solution. We show that the transformation between α-helix and β-hairpin structures can be sampled efficiently using the enhanced sampling method based on integrated tempering without the definition of reaction coordinates. The reliable and smooth two-dimensional potential of mean force surfaces of the conformation space can be obtained efficiently, which has been used to propose the probable pathways for the transformation of the α-helix and β-hairpin structures. Our simulation results revealed the efficiency, and further suggested the general applicability of integrated tempering sampling method into complex biomolecule processes without prior structure knowledge.     

Passive Q-switching of diode-pumped Yb:YAG microchip laser with ion-implanted GaAs

We reported a passive Q-switched diode laser pumped Yb: YAG microchip laser with an ion-implanted semi-insulating GaAs wafer. The wafer was implanted with 400-keV As+ in the concentration of 1016 ions/cm2. To decrease the non-saturable loss, we annealed the ion-implanted GaAs at 500℃ for 5 minutes and coated both sides of the ion-implanted GaAs with antireflection (AR) and high reflection (HR) films, respectively. Using GaAs wafer as an absorber and an output coupler, we obtained 52-ns pulse duration of single pulse.     

Degeneracy and Split of Defect States in Photonic Crystals

One-dimensional photonic crystals with two or more structural defects are studied. We observed an interesting characteristic of transmission band structure of photonic crystals with defects using the transmission-matrix-method simulation. The transmission states in the wide photonlc band gap caused by defects reveal degeneracy and split in certain conditions. Every split state is contributed by coupling of all defects in a photonic crystal.Using the tight-binding method, we obtain an approximate analytic expression for the split frequency of photonic crystals with two structural defects.     

Modelling Analysis of Influence of Substrate Surface Defect on Optical Characteristics of Single-Layer Coating

A simple and practical model is used to analyse the influence of substrate surface defect on the optical characteristics of a single-layer coating. A single-layer coating is prepared and its optical properties are fitted. Some explanations for the origin of the transition layer are presented. It is concluded that there is a transition layer forming between the substrate and coating, which is attributed to substrate surface defects, and its refractive index change is nearly of linearity.     

Influence of Defect Particles on Configuration of a Two-Dimensionally Confined Dusty Plasma

The behaviour of defect particles in a two-dimensional （2D） confined dusty plasma system is investigated by molecular dynamics （MD） simulations. The mean square displacement （MSD） and the pair correlation function g（r） are used to characterize the structural and dynamical properties of the system. The influences of the number and the charge （mass） of the defect particles on the system configurations are simulated. All the defect particles with charges （masses） larger than the normal particles have the trend to move towards the system centre. The moving speed of the defect particles towards the centre increases with the increasing number and charge （mass） of defect particles and with the system temperature.     

Lowest energy structures of self-interstitial atom clusters in α-iron from a combination of Langevin molecular dynamics and the basin-hopping technique

A combination of simulated annealing with Langevin molecular dynamics and the basin-hopping with occasional jumping (BHOJ) technique was used to systematically determine the most stable configurations of self-interstitial atom (SIA) clusters I _n (n = 1–38) in α-iron. In addition to the original BHOJ technique, we introduced an additional long jumping process in which a randomly selected less-bounded atom is moved to a neighbouring site of another SIA in the cluster to enhance the probability of locating the global minimum structure. With the obtained putative lowest energy structures, the binding energies as a function of cluster size were estimated. We also determined the sizes of particular stable clusters based on their geometrical symmetry. Furthermore, the values were extrapolated based on accurately determined formation energies, and are available for immediate use in kinetic Monte Carlo or rate theory models.