Fluorescence enhancement of single-phase red-blue emit-ting Ba_3MgSi_2O_8:Eu~(2 ),Mn~(2 ) phosphors via Dy~(3 ) addition for plant cultivation

Fluorescence enhancement of red and blue concurrently emitting Ba3MgSi2O8:Eu2 ,Mn2 phosphors for plant cultivation has been investigated by Dy3 addition.The Ba3MgSi2O8:Eu2 ,Mn2 ,Dy3 (BMS-EMD) phosphors have two-color emissions at the wavelength peak values of 437 nm and 620 nm at the excitation of 350 nm.The two emission bands are coincident with the absorption spectrum for photosynthesis of plants.An obvious enhancement effect has been observed upon addition of Dy3 with amount of 0.03 mol%,in which the intensities of both blue and red bands reach a maximum.The origin of red and blue emission bands is analysed.The photochromic parameters of the samples at the nearly UV excitation are tested.This fluoresence enhancement is of great significance for special solid state lighting equipment used in plant cultivation.     

Monte-Carlo simulation studies of the effect of temperature and diameter variation on spin transport in Ⅱ-Ⅵ semiconductor nanowires

We have analyzed the spin transport behaviour of four Ⅱ–Ⅵ semiconductor nanowires by simulating spin polarized transport using a semi-classical Monte-Carlo approach. The different scattering mechanisms considered are acoustic phonon scattering, surface roughness scattering, polar optical phonon scattering, and spin flip scattering. The Ⅱ–Ⅵ materials used in our study are CdS, CdSe, ZnO and ZnS. The spin transport behaviour is first studied by varying the temperature(4–500 K) at a fixed diameter of 10 nm and also by varying the diameter(8–12 nm) at a fixed temperature of 300 K. For Ⅱ–Ⅵ compounds, the dominant mechanism is for spin relaxation;D’yakonov Perel and Elliot Yafet have been actively employed in the first order model to simulate the spin transport.The dependence of the spin relaxation length(SRL) on the diameter and temperature has been analyzed.     

Monte-Carlo simulation studies of the effect of temperature and diameter variation on spin transport in II-VI semiconductor nanowires

We have analyzed the spin transport behaviour of four II—VI semiconductor nanowires by simulating spin polarized transport using a semi-classical Monte-Carlo approach. The different scattering mechanisms considered are acoustic phonon scattering, surface roughness scattering, polar optical phonon scattering, and spin flip scattering. The II—VI materials used in our study are CdS, CdSe, ZnO and ZnS. The spin transport behaviour is first studied by varying the temperature (4—500 K) at a fixed diameter of 10 nm and also by varying the diameter (8—12 nm) at a fixed temperature of 300 K. For II—VI compounds, the dominant mechanism is for spin relaxation; D'yakonovPerel and Elliot Yafet have been actively employed in the first order model to simulate the spin transport. The dependence of the spin relaxation length (SRL) on the diameter and temperature has been analyzed.     

Synthesis and characterization of ZnO-CuO nanocomposites powder by modified perfume spray pyrolysis method and its antimicrobial investigation

Pure ZnO,ZnO-CuO nanocomposites can be synthesized by using a modified perfume spray pyrolysis method (MSP).The crystallite size of the nanoparticles (NPs) has been observed by X-ray diffraction pattern and is nearly 36 nm.Morphological studies have been analyzed by using Field Emission Scanning Electron Microscopy (FESEM) and its elemental analysis was reported by Elemental X-ray Analysis (EDX);these studies confirmed that ZnO and CuO have hexagonal structure and monoclinic structure respectively.Fourier Transform Infrared (FTIR) spectra revealed that the presence of functional frequencies of ZnO and CuO were observed at 443 and 616 cm-1.The average bandgap value at 3.25 eV using UV-vis spectra for the entitled composite has described a blue shift that has been observed here.The antibacterial study against both gram positive and negative bacteria has been studied by the disc diffusion method.To the best of our knowledge,it is the first report on ZnO-CuO nanocomposite synthesized by a modified perfume spray pyrolysis method.     

Effects of Doping Mn on Nd_(1.85)Ce_(0.15)CuO_4 System

Nd1.85Ce0.15Cu1-xMnxO4 samples with doping level up to 20% have been synthesized by solid-state reaction method. The influence of Mn on their normal-state transport, crystal structure, superconductivity and magnetic properties has been investigated. For the samples with x〉0.03, magnetization under zero-field cooling indicates that the magnetic state changes from ferromagnetic to paramagnetic at T≈100 K, which can be explained with the interaction between Mn4＋and Mn3＋. The electrical resistivity p of samples increases with Mn doping. For the samples with doping level lower than 0.20, p initially increases with the decrease of temperature, i.e., dp/dt〈0, and then shows superconductivity transition at ≈20 K. The results suggest the coexistence of superconductivity and ferromagnetic ordering in Mn doped Nd1.85Ce0.15CuO4.     

Double humps and radiation effects of SOI NMOSFET

Radiation experiments have been carried out with a SOI NMOSFET.The behavior of double humps was studied under irradiation.The characterization of the hump was demonstrated.The results have shown that the shape of the hump changed along with the total dose and the reason for this was analyzed.In addition,the coupling effect of the back-gate transistor was more important for the main transistor than the parasitic transistor.     

Q-switched and Mode-locked Characteristics of Cr~(4+)∶YAG Crystal

The passively Q-switched and mode-locked(QML) characteristics in a diode-pumped Nd∶GdVO_4 laser with Cr~(4+)∶YAG saturable absorbers have been demonstrated. A maximum average output power of 710mW has been obtained in the QML laser. The maximum energy of a single Q-switched pulse is 52.5μJ, with the corresponding pulse width of 30ns and the peak power of 1.75kW, at the incident pump power of 7.75W. The repetition rates of the Q-switched envelope and the mode-locked laser pulse are 16.7kHz and 680MHz, respectively.     

MnQ2（Q=S,Se,Te）and [Mn（en）3]Te4 Structures and Their Semiconductor Properties

The solvo-thermal technique is used for the synthesis of [Mn(en)3]Te4 (I).The crystal structure has been determined by single crystal X-ray diffraction techniques.The crystal belongs to the monoclinic, space group p21/c with unit cell:a=0.8461(1),b=1.5653(2), c=1.4269(2)nm, α=90°,β=91.37(1) (3)°, γ=90°,V=1.8893(4)nm3,and Z=4.The results show that the structure contains a linear chain Zintl anion,[Te4]2-and a complex cation,[Mn(en)3]2+. Optical studies have been performed on the powder sample of I, suggesting that the compound is a semiconductor with a band gap of 0.73eV. The semiconductor properties for MnQ2(Q=S,Se,Te) and [Mn(en)3]Te4 have been discussed by molecular orbital theory.     

The structure and magnetic properties of β-(Ga0.96Mn0.04)2O3 thin film

High quality epitaxial single phase (Ga0.96Mn0.04)2O3 and Ga2O3 thin films have been prepared on sapphire substrates by using laser molecular beam epitaxy (L-MBE).X-ray diffraction results indicate that the thin films have the monoclinic structure with a (-201) preferable orientation.Room temperature (RT) ferromagnetism appears and the magnetic properties of β-(Ga0.96Mn0.04)2O3 thin film are enhanced compared with our previous works.Experiments as well as the first principle method are used to explain the role of Mn dopant on the structure and magnetic properties of the thin films.The ferromagnetic properties are explained based on the concentration of transition element and the defects in the thin films.     

Oxygen-doped ZnTe phosphors for synchrotron X-ray imaging detectors

ZnTe:O powder phosphors were successfully prepared by a dry synthesis process using gaseous doping and etching media. It was found that dry doping by O₂ through ball-milling was an effective way to synthesize ZnTe:O powder phosphors and produced a red emission centered at 680 nm with a decay time of 1.1 μs. The emission intensity of dry O₂-doped samples was three times more intense than from ZnO-doped samples, possibly due to a more uniform distribution of oxygen substitution on tellurium sites. The samples annealed in a 95% N₂/5% H₂ forming gas atmosphere exhibited a x-ray luminescent efficiency five times higher than did powders annealed in vacuum or N₂ atmosphere. This enhancement was attributed to the removal of surface tellurium oxides. ZnTe:O phosphor screens were prepared with x-ray luminescence efficiencies equivalent to 56% of ZnSe:Cu,Ce,Cl and 76% of Gd₂O₂S:Tb screens under 17-keV radiation. An x-ray imaging resolution of 2.5 lines/mm was resolved, the same as that measured for commercial ZnSe:Cu,Ce,Cl and Gd₂O₂S:Tb screens. These results indicate that ZnTe:O is a promising phosphor candidate for synchrotron x-ray imaging applications.     

Study on optical compund films

Using the compound materials and double e-gun evaporation ,the compound optical films have been successfully deposited on K9 glass substrate.The refractive index of optical compound films deposited in diffeent parameters have been measured and theoretical formula for calculation refractive index of compound films have been derived.Tt is shown that the experimental curve for the variation of re-fractive index with wavelength in 0.4-1.4цm region and the theoretical one agree very well.Using these films,the laser reflecting mirror has been successfully coat-ed.     

Fabication of Organic／Polymeric Superlattice Structure and Its Use for Electroluminescent Device^①②

Superlattices consisting of alternating layers of organic/polymeric materials have been fabricated from tris(8-hydroxyquinoline) aluminum(Alq3) and poly(N-vinylcarbazole)(PVK) by a multisource-type high-vacuum organic molecular deposition.The characteristics of superlattice structures are determined by the smallangle X-ray diffraction,optical adsorption and photoluminescence.The electroluminescent devices with the superlattice structure have also been fabricated and the emission characteristics are discussed.     

CuPc based organic--inorganic hetero-junction with Au electrodes

In present work, a hetero-junction of n-silicon (n-Si) with copper phthalocyanine (CuPc) has been fabricated. The current-voltage characteristics were investigated to explain the rectification and conduction mechanism. The effect of temperature and humidity on electrical properties of n-Si/CuPc hetero-junction has also been investigated. The characteristics of the junction have been observed to be temperature and humidity dependent so it is suggested that this junction can be used as temperature and humidity sensor.     

Optical Properties of Silicon—doped InGaN and GaN Layers

The optical properties of Silicon—doped InGaN and GaN grown on sapphire by MOCVD have been investigated by photoluminescence (PL) method. At room temperature, the band—gap peak of InGaN is 437.0 nm and its full width of half—maximum (FWHM) is about 14.3 nm. The band—gap peak and FWHM for GaN are 364.4 nm and 9.5 nm, respectively. By changing the temperature from 20 K to 293 K, it is found that the PL intensity of samples decreases but the FWHM broadens with the increasing of the temperature.GaN sample shows red—shift, InGaN sample shows red—blue—red—shift. The temperature dependence of peak energy shift is studied and explained.     

THE STUDY OF LATTICE MATCH IN GaInAsP/InP HETEROJUNCTION LPE LAYERS

The effects of the growth conditions of two-phase solution liquid phase epitaxy(LPE)(i.e.growth temperature,cooling rates and solution composition)on lattice mismatch and band-gapwavelength in GaInAsP/InP heterojunction LPE layers have been investigated by X-ray double-crystal diffractometry and double-beam spectrophotometry.The stress in the grown interface freeof misfit dislocations and lattice mismatch at growth temperature have been calculated.     

975 nm multimode semiconductor lasers with high-order Bragg diffraction gratings

The 975 nm multimode diode lasers with high-order surface Bragg diffraction gratings have been simulated and calculated using the 2D finite difference time domain(FDTD) algorithm and the scattering matrix method(SMM).The periods and etch depth of the grating parameters have been optimized.A board area laser diode(BA-LD) with high-order diffraction gratings has been designed and fabricated.At output powers up to 10.5 W,the measured spectral width of full width at half maximum(FWHM) is less than 0...     

The determination of the interface-state density distribution from the capacitance-frequency measurements in Au/n-Si schottky barrier diodes

The Au/n-Si Schottky barrier diodes (SBDs) with 200-μm (sample D200) and 400-μm (sample D400) bulk thicknesses have been fabricated. The ideality factor and the barrier height have been calculated from the forward-bias current-voltage (I-V) characteristics of D200 and D400 SBDs. The energy distribution of the interface states and relaxation time are found from the capacitance-frequency (C-f) characteristics. The density of interface state and relaxation times have a (nearly constant) slow exponential rise with bias in the range of E_c −0.77 and E_c −0.47 eV from the midgap toward the bottom of the conductance band. Furthermore, the energy distribution of the interface states obtained from C-f characteristics has been compared with that obtained from the forward-bias I-V characteristics.     

MBE Growth of High Electron Mobility InP Epilayers

The molecular beam epitaxial growth of high quality epilayers on (100) InP substrate using a valve phosphorous cracker cell over a wide range of P/In BEP ratio (2.0～7.0) and growth rate (0.437 and 0.791μm/h).Experimental results show that electrical properties exhibit a pronounced dependence on growth parameters,which are growth rate,P/In BEP ratio,cracker zone temperature，and growth temperature.The parameters have been optimized carefully via the results of Hall measurements.For a typical sample,77K electron mobility of 4.57e4cm2/（V·s） and electron concentration of 1.55e15cm－3 have been achieved with an epilayer thickness of 2.35μm at a growth temperature of 370℃ by using a cracking zone temperature of 850℃.     

Optical Characterization of GaN Grown by Plasma Source MBE

By using spectroscopic photoconductance, transmittance and luminescence methods, the optical characterization of GaN grown by plasma source MBE have been evaluated.The imperfection of the epitaxial layer deduced from the measured results have been discussed.The transient responses of the photoconductive detectors have been measured .Two time constants of 0.17ms and 6.85 ms at room temperature are deduced from the measured results.The origins have also been discussed.     

Metal-organic vapor-phase epitaxial growth of HgCdTe device heterostructures on three-inch-diameter substrates

A new metal-organic vapor-phase epitaxial (MOVPE) reactor-cell design has been developed to grow on 3-in.-diameter substrates. This was required to produce uniform, fully doped heterostructures needed for array producibility and wafer-scale processing compatibility. The reactor has demonstrated epitaxial growth of HgCdTe (MCT) with good morphology onto both GaAs and GaAs on Si wafers. The density of surface-growth defects, typical of MOVPE growth, has been reduced to <5 cm⁻² at a sufficient yield to make the production of low cluster-defect, two-dimensional (2-D) arrays possible. The new horizontal reactor cell uses substrate rotation to achieve improved uniformity and is able to incorporate substrates up to 4-in. diameter. Good compositional and thickness uniformity was achieved on epilayers grown on 3-in.-diameter, low-cost GaAs and GaAs on Si wafers. Sufficient uniformity has been achieved to produce 12 sites of full-TV format 2-D arrays per slice. To yield the benefits of heterostructure design, the MCT epilayers also needed to demonstrate efficient and uniform activation of both arsenic (acceptor) and iodine (donor) dopants. Secondary ion mass spectrometry (SIMS) and Hall assessment showed that the uniformity of As and I doping was ±10%. Fully doped heterostructures have been grown to investigate the device performance in the 3–5 μm and 8–12 μm infrared bands. The 2-D array performance has shown that at 180 K near-background-limited performance (BLIP) diodes have been produced in the 3–5 μm band.