The interaction of a single-cycle THz electric field with the topological insulator $\mathrm{MnBi}_2\mathrm{Te}_4$ triggers strongly anharmonic lattice dynamics, promoting fully coherent energy transfer between the otherwise non-interacting Raman-active $E_g$ and infrared (IR)-active $E_u$ phononic modes. Two-dimensional (2D) THz spectroscopy combined with modeling based on the classical equations of motion and symmetry analysis reveals the multi-stage process underlying the excitation of the Raman-active $E_g$ phonon. In this process, the THz electric field first prepares a coherent IR-active $E_u$ phononic state and subsequently interacts with this state to efficiently excite the $E_g$ phonon.

A total of 17 low-cost single-frequency L1 global positioning system (GPS) receivers with real-time internet transmission have been set up to intensify the pre-existing network of continuously operating reference stations (CORS) in southeastern Taiwan since 2008. The main objective of this study is to investigate the validity and uncertainty of the L1 stations in southeastern Taiwan. It is well known that the main error source of single-frequency GPS relative positioning in low latitude areas comes from an atmospheric delay, even if the relative distance is only a few kilometres. In this study, two methods of correction algorithms, including adopting local ionospheric models and applying correction terms from local CORS, are tested to estimate the long-period accuracy of station positioning. Our results indicate that the standard deviation of calibrated relative positioning is in a linear trend with respect to the baseline length. The derived positioning accuracies from applying correction terms from CORS provide satisfactory results with the linear ratios of standard deviation/baseline of 0.11 +/- 0.02, 0.12 +/- 0.02, 0.44 +/- 0.06 mm km(-1) in the north, east and up component, respectively for relative distances under 30 km. The corresponding positioning scatterings amount to 3, 3 and 13 mm, in the north, east and up component, respectively. Although the use of a local ionospheric model algorithm can significantly reduce positioning variation, especially in the north component, the use of the correction terms method yields the best positioning results for three components, horizontal and vertical.

Long-range electronic interaction between Bismuth (Bi) adatoms on graphene formed on a 4H-SiC (0001) substrate are clearly observed at room temperature (T=300K). Using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations, we have demonstrated that such oscillatory interaction results mainly from the mediation of graphene Dirac-like electrons and the effect of the corrugated surface of SiC substrate. These two factors cause the observed oscillatory interaction with characteristic distribution distances and linear arrangements of Bi adatoms. The present study sheds light on understanding and controlling the nucleation of adatoms and subsequent growth of nanostructures on graphene surface.

To improve graphene-based multifunctional devices at nanoscale, a stepwise and controllable fabrication procedure must be elucidated. Here, a series of structural transition of bismuth (Bi) adatoms, adsorbed on monolayer epitaxial graphene (MEG), is explored at room temperature. Bi adatoms undergo a structural transition from one-dimensional (1D) linear structures to two-dimensional (2D) triangular islands and such 2D growth mode is affected by the corrugated substrate. Upon Bi deposition, a little charge transfer occurs and a characteristic peak can be observed in the tunneling spectrum, reflecting the distinctive electronic structure of the Bi adatoms. When annealed to ~500 K, 2D triangular Bi islands aggregate into Bi nanoclusters (NCs) of uniform size. A well-controlled fabrication method is thus demonstrated. The approaches adopted herein provide perspectives for fabricating and characterizing periodic networks on MEG and related systems, which are useful in realizing graphene-based electronic, energy, sensor and spintronic devices.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The simple α,β-unsaturated ketones and 2-pyrones are readily available and synthetically important dienophiles and dienes, respectively, for Diels−Alder reactions. However, both prove to be challenging substrates for catalytic asymmetric Diels−Alder reactions. By exploring a new catalysis strategy featuring cooperative catalysis with readily available cinchona catalysts, an unprecedented asymmetric Diels−Alder reaction of simple α,β-unsaturated ketones with 2-pyrones has been successfully developed. With broad scopes for both reactants, the reaction provides a direct and versatile asymmetric access to a wide range of structurally novel bicyclic chiral building blocks amenable for further synthetic elaborations.

Experiments are preformed to demonstrate enhancement of the heat transfer around a horizontal heated cylinder due to presence of acoustic excitation. The cylinder is placed inside a wind tunnel and the wall temperatures around the cylinder are measured and are reduced to the local heat transfer. A loud speaker that is placed downstream of the cylinder is used as the acoustic generator. The frequency of the sound F-e is set equal to the natural frequency F-n of the shedding vortex in the wake or its multiples. Therefore, synchronization of vortex shedding with the acoustic wave can be expected. The excitation frequencies selected are at F-e/F-n = 1, 2, 3, and up to 8. Other frequencies at F-e/F-n = 1.5, 2.5, 3.5 and up to 7.5 are also selected for comparison. During the experiments, the sound pressure varies from 0 to 100 dB and the Reynolds number varies from 2938 to 8814. The heat transfer around the cylinder is found significantly enhanced by the acoustic waves. More detailed measurements for the energy spectrum of the acoustic waves generated by the current speaker are made. This provides a better understanding for the physical process. Flow visualization is also made to demonstrate synchronization of vortex shedding with the acoustic excitation. The effect of the sound pressure levels and the Reynolds numbers on the wall heat transfer will be presented and discussed.

The structure and surface morphology of self-assembly vicinal surfaces (SAVSs) of Mo epitaxially grown on Al2O3(1 (1) over bar 02) substrates have been investigated by reflective high energy electron diffraction and scanning tunneling microscopy. The terrace edges for the Mo(001) SAVS are mainly arranged along [1 (1) over bar0](Mo)parallel to[11 (2) over bar0](Al2)O-3 with a narrow distribution terrace width. The structural analyses show that the formation of the SAVS is due to a tilt growth of Mo(001) plane with respect to Al2O3(1 (1) over bar 02) substrate. By a simple geometric model, the tilt growth and SAVS of Mo(001) can be attributed to the asymmetric lattice mismatch between Mo(001) and Al2O3(1 (1) over bar 02) surfaces.

The structure and surface morphology of self-assembly vicinal surfaces (SAVSs) of Mo epitaxially grown on Al2O3(11¯02) substrates have been investigated by reflective high energy electron diffraction and scanning tunneling microscopy. The terrace edges for the Mo(001) SAVS are mainly arranged along [11¯0]Mo‖[112¯0]Al2O3 with a narrow distribution terrace width. The structural analyses show that the formation of the SAVS is due to a tilt growth of Mo(001) plane with respect to Al2O3(11¯02) substrate. By a simple geometric model, the tilt growth and SAVS of Mo(001) can be attributed to the asymmetric lattice mismatch between Mo(001) and Al2O3(11¯02) surfaces.

A reduction of Ni/Au ohmic contact on p-type GaN is obtained by surface treatment using Cl2 inductively coupled plasma (ICP).

Experiments are performed to study the flow structure and heat transfer over a heated cylinder oscillating radially with small amplitude in streamwise direction. Both flow visualization using a smoke wire in the upstream and the local heat transfer measurements based on wall temperatures around the cylinder were made. The excitation frequencies of the cylinder are selected at Fe/Fn=0, 0.5, 1, 1.5, 2, 2.5, and 3. The oscillation amplitude selected is less than a threshold value of A/D=0.06 where synchronization of vortex shedding with the cylinder excitation was not expected. However, experiments indicate that synchronization still occurs which stimulates a great interest to study its enhancement in the heat transfer. Synchronization occurred at Fe/Fn=2 is antisymmetric vortex formation while synchronization at Fe/Fn=2.5 and 3 is symmetric type. The forward motion (advancing into the cross flow) of the cylinder during one cycle of oscillation has an effect to suppress the instability and the vortex formation. This leads to the occurrence of a smaller and symmetric vortex formation and a less enhancement of heat transfer than the case of antisymmetric type Fe/Fn=2. For excitations at lower frequencies Fe/Fn⩽1.5, all the vortex formations occurred are mostly antisymmetric. The dominant mode of the instability in the shear layer is actually the natural shedding frequency Fn of the vortex. A closer excitation frequency to 2Fn causes a greater enhancement in the heat transfer. During the experiments, the Reynolds numbers varies from 1600 to 3200, the dimensionless amplitude A/D from 0.048 to 0.016.

ZnS epitaxial layers grown using metalorganic vapor phase epitaxy were etched by reactive ion etching (RIE) employing a gas mixture of CH4, H2 and Ar. The etching rates were investigated as functions of the plasma parameters: rf power density, the relative composition and the total flow rate of reactive gases. It was determined that the amount of CH4 in CH4/H2 gas discharge decides whether a polymer will be produced. The optimum composition of the mixed gas was 1CH4/7H2/4Ar, when the pressure, rf power density and total flow rate were 30 mTorr, 0.4 W/cm2 and 30 sccm, respectively. The quality of the etched surfaces under these conditions was examined using X-ray photoelectron spectroscopy and photoluminescence. It was determined that the etching process does not damage the ZnS film based upon the results of photoluminescence spectra.

High-efficiency diffractive optical elements can be achieved by an increase in the number of phase levels. We present a technique for laser direct-write gray-level masks on high-energy-beam-sensitive glass and one-step etching on the gray-level mask plate for the production of high-efficiency diffractive optical elements. Sixteen-phase-level diffractive microlenses and microlens arrays with a focusing efficiency of approximately 94% have been realized by use of the one-step nonphotolithographic fabrication technique.

The objective of this study was to compare the physicochemical properties of starch and bean paste products and to relate to the sensory properties of the finished products made from Great Northern, navy, mung, adzuki, red kidney, and pinto beans. Mung beans had the smallest and adzuki beans the largest starch granule size. Amylose content ranged from 279–415 g/kg of the starch. The starch content of the bean paste ranged from 610–710 g/kg on dry basis. The pasting viscosity of the bean paste had strong correlations with smoothness (+0.93,P< 0.05) and grittiness (−0.92,P< 0.05). Amylose content also had strong correlations with smoothness (+0.88,P< 0.05) and grittiness (−0.89,P< 0.05). The smoothness of the sweetened paste was not related to the granule size and shape of the starch granules, starch gelatinization temperatures tested by differential scanning calorimetry and raw bean pasting viscosity.

A new technique of laser-assisted single-step chemical etching for diffractive microlens fabrication upon high-energy-beam sensitive glass is reported. Laser direct writing with calibrated writing parameters results in gray-level mask patterns upon the ion-exchanged layer of the glass. The transmittance-dependent chemical etching upon the glass is then effectively utilized to yield suitable surface relief structures for multiple-phase-level diffractive optical elements. The one-step nonphotolithographic fabrication technique has been successfully applied for the realization of an eight-phase-level diffractive microlens.

Reactive ion etching (RIE), employing CH4/H2/Ar plasmas, of ZnS films grown by metalorganic chemical vapor deposition (MOCVD) is reported. The etching rates are investigated as functions of the plasma parameters: pressure, RF power and relative composition of reactive gases. It is found that the amount of CH4 in a CH4/H2/Ar gas discharge will decide whether the polymer will be produced. The optimum composition of the mixed gas is 1CH4/7H2/4Ar, when the pressure, RF power and total flow rate are 30 mTorr, 245 W and 30 sccm, respectively. The etching mechanism is also proposed. The quality of the etched surfaces under these conditions is examined by X-ray photoelectron spectroscopy. It is found that the amount of overt damage is small under these etching conditions. A dot-matrix thin-film electroluminescent device employing a ZnS:Mn phosphor layer is also fabricated by this etching process.

This article examines the feasibility of fabricating polycrystalline ZnS and ZnS:Mn films with a size of 9 in. diagonal (190 mm x 130 mm) for use in thin film electroluminescent display via low pressure metallorganic chemical vapor deposition. The uniformities of film thickness and crystallinity are studied as functions of H-2 flow rate, the slit width of inlet nozzles, and the manganese concentration. Uniform polycrystalline ZnS and ZnS:Mn films are also obtained. Film thickness Variance is controlled below +/-3%. Less than +/-5% variation in x-ray full width at half maximum is obtained in the ZnS film as well. The atomic ratio of S/Zn is close to unity value, as estimated by the measurement of electron probe microanalyzer. In addition, the distribution of manganese dopant concentration in ZnS:Mn films is also uniform. The uniform counts of Zn, S, and Mn atoms persist throughout the ZnS:Mn films, as demonstrated by the secondary ion mass spectrometry. Moreover, atomic force microscopy image root-mean-square roughness of film's surface is measured to be 93 Angstrom.

Abstract— In order to improve the characteristics of thin‐film electroluminescent (TFEL) devices, the dependence of crystallinity on deposition conditions of ZnS:TbOF thin films deposited by rf‐magnetron sputtering have been studied. The optimal deposition conditions obtained are: rf power density, 1.54 W/cm2; substrate temperature, 175°C; pressure, 5 mTorr; and sputtering gas, pure Ar. Several types of ZnS:TbOF green ACTFEL devices with different stacked insulating‐layer structures were prepared and compared. The ACTFEL device obtained with the superior structure is ITO/SiO2/Ta2O5/ZnS:TbOF/SiO2/Ta2O5/Al. This result suggests that a high‐resistivity dielectric can be used as the second insulating layer adjacent to the phosphor layer and can improve the luminous characteristics of ACTFEL devices in this study.

We report the successful use of di-n-cyclopentadienyl manganese [(C5H5)(2)Mn] as a manganese dopant for ZnS films, fabricated by low-pressure metallorganic chemical vapor deposition onto an indium-tin oxide coated glass substrate. The substrate temperature was 225 degrees C. The concentration of manganese in the films was studied as a function of a (C5H5)(2)Mn bubbler temperature. The crystallinity and morphology of the films were examined by x-ray diffraction and atomic force microscopy. The grain size was 43 nm, as evaluated by the Debye-Scherrer relation. ZnS:Mn ac thin film electroluminescent devices with a double insulating layer structure were prepared. The luminance exceeded 1500 cd/m(2), which is higher than the previously reported value of 680 cd/m(2), employing the same Mn source.