PREPARATION AND PROPERTIES OF COATED SEMICONDUCTOR CdS/ZnS NANOPARTICLES

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Theoretical investigation of sulfur defects on structural, electronic,and elastic properties of ZnSe semiconductor

The structural, electronic, and elastic properties of ZnSe1-xSx for the zinc blende structures have been studied by using the density functional theory. The calculations were performed using the plane wave pseudopotential method, as implemented in Quantum ESPRESSO. The exchange-correlation potential is treated with the local density approximation pz-LDA for these properties. Moreover, LDA＋U approximation is employed to treat the ＂d＂ orbital electrons properly. A comparative study of the band gap calculated within both LDA and LDA＋U schemes is presented. The analysis of results show considerable improvement in the calculation of band gap. The inclusion of compositional disorder increases the values of all elastic constants. In this study, it is found that elastic constants C11, C12, and C44 are mainly influenced by the compositional disorder. The obtained results are in good agreement with literature.

Study of magnetic and optical properties of Zn1-xTMxTe(TM = Mn,Fe,Co,Ni) diluted magnetic semiconductors：First principle approach

We present structural,magnetic and optical characteristics of Zn_（1-x）TM_xTe（TM = Mn,Fe,Co,Ni and x = 6.25%）,calculated through Wien2 k code,by using full potential linearized augmented plane wave（FP-LAPW） technique.The optimization of the crystal structures have been done to compare the ferromagnetic（FM） and antiferromagnetic（AFM） ground state energies,to elucidate the ferromagnetic phase stability,which further has been verified through the formation and cohesive energies.Moreover,the estimated Curie temperatures T_c have demonstrated above room temperature ferromagnetism（RTFM） in Zn_（1-x）TM_xTe（TM =Mn,Fe,Co,Ni and x= 6.25%）.The calculated electronic properties have depicted that Mn- and Co-doped ZnTe behave as ferromagnetic semiconductors,while half-metallic ferromagnetic behaviors are observed in Fe- and Ni-doped ZnTe.The presence of ferromagnetism is also demonstrated to be due to both the p-d and s-d hybridizations between the host lattice cations and TM impurities.The calculated band gaps and static real dielectric constants have been observed to vary according to Penn＇s model.The evaluated band gaps lie in near visible and ultraviolet regions,which make these materials suitable for various important device applications in optoelectronic and spintronic.

Characterization of structural and electrical properties of ZnO tetrapods

ZnO tetrapods were synthesized by a typical thermal vapor-solid deposition method in a horizontal tube furnace.Structural characterization was carried out by transmission electron microscopy （TEM） and select-area electron diffraction （SAED）,which shows the presence of zinc blende nucleus in the center of tetrapods while the four branches taking hexagonal wurtzite structure.The electrical transport property of ZnO tetrapods was investigated through an in-situ nanoprobe system.The three branches of a tetrapod serve as source,drain,and ＂gate＂,respectively;while the fourth branch pointing upward works as the force trigger by vertically applying external force downward.The conductivity of each branch of ZnO-tetrapods increases 3-4 times under pressure.In such situation,the electrical current through the branches of ZnO tetrapods can be tuned by external force,and therefore a simple force sensor based on ZnO tetrapods has been demonstrated for the first time.

Effects of edge hydrogenation and Si doping on spin-dependent electronic transport properties of armchair boron–phosphorous nanoribbons

In this article, the spin-dependent electronic and transport properties of the armchair boron–phosphorous nanoribbons（ABPNRs） are mainly studied by using the non-equilibrium Green function method combined with the spin-polarized density function theory. Our calculated electronic structures indicate that the edge hydrogenated ABPNRs exhibit a ferromagnetic bipolar magnetic semiconductor property, and that the Si atom doping can make ABPNRs convert into up-spin dominated half metal. The spin-resolved transport property results show that the doped devices can realize 100% spinfiltering function, and that the interesting negative differential resistance phenomenon can be observed. Our calculations suggest that the ABPNRs can be constructed as a spin heterojunction by introducing Si doping partially, and it would be used as a spin-diode for nano-spintronics in future.

Theoretical calculations of structural, electronic, and elastic properties of CdSe_(1-x)Te_x:A first principles study

The plane wave pseudo-potential method was used to investigate the structural, electronic, and elastic properties of Cd Se_（1-x）Te_x in the zinc blende phase. It is observed that the electronic properties are improved considerably by using LDA ＋ U as compared to the LDA approach. The calculated lattice constants and bulk moduli are also comparable to the experimental results. The cohesive energies for pure Cd Se and Cd Te binary and their mixed alloys are calculated. The second-order elastic constants are also calculated by the Lagrangian theory of elasticity. The elastic properties show that the studied material has a ductile nature.

Synthesis and optoelectronic properties of a novel molecular semiconductor of dithieno[5,6-b:11,12-b']coronene-2,3,8,9-tetracarboxylic tetraester

A facile procedure for the synthesis ofdithieno[5,6-b：11,12-b＇]coronene-2,3,8,9-tetracarboxylic tetra（2- ethylhexyl）ester （DTCTI＇E-EH） from readily available perylene-3,4,9,10-tetracaroboxylic dianhydride is described. The electronic properties of DTCTTE-EH were elucidated on the basis of UV-vis spectra, emission spectrum and electrochemical measurement, which demonstrate that DTCTTE is a new class of components for promising semiconducting materials.

Ab-initio investigation of AGeO_3(A=Ca, Sr) compounds via Tran Blaha-modified Becke Johnson exchange potential

We employ ab-initio calculations to analyze the mechanical, electronic, optical and also thermoelectric properties associated with AGeO3（A = Ca, Sr） compounds. The full-potential linearized augmented plane wave（FP-LAPW） technique in the generalized gradient approximation（GGA-PBEsol） and the lately designed Tran-Blaha-modified Becke-Johnson exchange potential are utilized to examine the mechanical and optoelectronic properties respectively. To explore the thermoelectric quality, we use the semi-classical Boltzmann transport theory. The particular structural stabilities regarding AGeO3（A = Ca, Sr） materials are validated simply by computations from the elastic constants. The energy band structural framework and the density of states are displayed to indicate indirect bandgap under ambient conditions. The particular computed optical attributes that reveal prospective optoelectronic applications are usually elucidated simply by studying ε1（0） and also Eg, which can be connected by means of Penn＇s design. The optical details uncover the actual suitability to power ranging products. Finally, the Boltz Tra P code is executed to analyze the actual thermoelectric properties, which usually presents that the increase of internal temperatures can enhance the electric conductivity, thermal conductivity and also the power factor, whilst Seebeck coefficient decreases. Therefore, the studied materials will also be ideal for thermoelectric products to understand helpful option for alternative energy resources.

Transport and magnetoresistance effect in an oxygen-deficient SrTiO_3/La_(0.67)Sr_(0.33)MnO_3 heterojunction

An oxygen-deficient SrTiO3/La0.67Sr0.33MnO3 heterojunction is fabricated on an SrTiO3 （001） substrate by a pulsed laser deposition method. The electrical characteristics of the heterojunction are studied systematically in a temperature range from 80 K to 300 K. The transport mechanism follows I ∝ exp （eV/nkT） under small forward bias, while it becomes space charge limited and follows I ∝ Vm（T） with 1.49〈 m 〈1.99 under high bias. Such a heterojunction also exhibits magnetoresistance （MR） effect. The absolute value of negative MR monotonically increases with temperature decreasing and reaches 26.7% at 80 K under H=0.7 T. Various factors, such as strain and oxygen deficiency play dominant roles in the characteristics.

Nonlinear properties of quantum dot semiconductor optical amplifiers at 1.3 μm:errata

The authors regret that one of the coauthors was inadvertently omitted in the previous paper. E. Varene was a member of the Institut fur Festk6rperphysik at the Technische Universitat Berlin and contributed to the results on cross-phase modulation.

Research Advances of Ferroelectric Semiconductors of 2D Hybrid Perovskites toward Photoelectronic Applications

Ferroelectric materials, characterized by the switchable spontaneous polarization(Ps) through reversing the directions of external electric field, exhibit versatile physical attributes that have been extensively used for practical device applications. Two-dimensional(2D) organic-inorganic hybrid perovskites are recently emerging as a robust family of candidate ferroelectrics, termed ferroelectric semiconductors. In particular, the coexistence and/or coupling of ferroelectric polarization with their semiconducting properties enables new physical concepts, thus providing a potential platform for the development of new multifunctional optoelectronic devices. This review primarily describes the structural origin of symmetry breaking for generating ferroelectric orders in 2D hybrid perovskites, and then presents the combination of ferroelectric Ps with other semiconducting optoelectronic activities. Regarding the emergence of new photoelectric behaviors, the prospects for this 2D family of ferroelectric semiconductors are further discussed, along with their development tendency for the future photoelectronic device applications.

Semiconductor performance of rare earth gadolinium-doped aluminum–zinc oxide thin film

Rare earth element gadolinium-doped aluminum–zinc oxide（Gd–AZO） semiconductor thin film material was deposited on both silicon and glass substrate by radio frequency（RF） sputtering at room temperature.Electrical properties and microstructure of Gd–AZO thin film were mainly modulated by altering O2 partial pressure（OPP） during the RF sputtering process.Scanning electron microscope（SEM） and X-ray diffraction（XRD） test were carried out to uncover the microstructure variation trend with the sputtering OPP,and amorphous structure which is beneficial to large mass industry manufacture was also demonstrated by the XRD pattern.Transmittance in visible light spectrum implies the potential application for Gd–AZO to be used in transparent material field.Finally,bottom gate,top contact device structure thin film transistors（TFTs） with Gd–AZO thin film as the active channel layer were fabricated to verify the semiconductor availability of Gd–AZO thin film material.Besides,the Gd–AZO TFTs exhibit preferable transfer and output characteristics.

Fluorinated 1,8-naphthalimides:Synthesis,solid structure and properties

Three fluorinated 1,8-napthalimides were synthesized from acenaphthene.Their structures were characterized by NMR and EI-MS analyses.The structures of compounds 1b and 1c were also confirmed by X-ray diffraction analysis,which showed that they possessed different packing models.Their optoelectronic properties were investigated.The results indicated that all of the naphthalimides possess good solubility and low LUMO energy level,which make them good solution processing candidates in n-type semiconductor.

Electronic structure and optical properties of F-doped β-Ga_2O_3 from first principles calculations

The effects of F-doping concentration on geometric structure, electronic structure and optical property of β-GaOwere investigated. All F-doped β-GaOwith different concentrations are easy to be formed under Ga-rich conditions, the stability and lattice parameters increase with the F-doping concentration. F-doped β-GaOmaterials display characteristics of the n-type semiconductor, occupied states contributed from Ga 4s, Ga 4p and O 2p states in the conduction band increase with an increase in F-doping concentration. The increase of F concentration leads to the narrowing of the band gap and the broadening of the occupied states. F-doped β-GaOexhibits the sharp band edge absorption and a broad absorption band. Absorption edges are blue-shifted, and the intensity of broad band absorption has been enhanced with respect to the fluorine content. The broad band absorption is ascribed to the intra-band transitions from occupied states to empty states in the conduction band.

Structural, Optical, and Electrical Properties of Zn-Doped CdO Thin Films Fabricated by a Simplified Spray Pyrolysis Technique

Thin films of zinc-doped cadmium oxide with different Zn-doping levels（0, 2, 4, 6, and 8 at%） were deposited on glass substrates by employing an inexpensive, simplified spray technique using perfume atomizer at relatively low substrate temperature（375 °C） compared with the conventional spray method. The effect of Zn doping on the structural,morphological, optical, and electrical properties of the films was investigated. XRD patterns revealed that all the films are polycrystalline in nature having cubic crystal structure with a preferential orientation along the（1 1 1） plane irrespective of Zn-doping level. Zn-doping level causes a slight shift in the（1 1 1） diffraction peak toward higher angle. The crystallite size of the films was found to be in the range of 28–37 nm. The band gap value increases with Zn doping and reaches a maximum of 2.65 eV for the film coated with 6 at% Zn doping and for further higher doping concentration it decreases.Electrical studies indicate that Zn doping causes a reduction in the resistivity of the films and a minimum resistivity of15.69 X cm is observed for the film coated with 6 at% Zn.

First-principles study on electronic structure and conductivity of Sn-doped Ga_(1:375)In_(0:625)O_3

The structural properties, band structures and densities of states of Sn-doped Ga1.375In0.625O3 with a Sn atom substituting for the Ga atom or a Sn atom substituting for the In atom are calculated by using the firstprinciples method. The substitution of the Sn atom for the Ga atom in Ga1.375In0.625O3（Ga1.25In0.625Sn0.125O3/has larger lattice parameters and stronger Sn–O ionic bonds than that of the substitutional doping of the Sn atom for the In atom in Ga1.375In0.625O3（Ga1.375In0.5Sn0.125O3/. Results show that the Sn atom is preferentially substituted for the In atom in Sn-doped Ga1.375In0.625O3. Sn-doped Ga1.375In0.625O3 exhibits n-type metallic conductivity,and the impurity bands are mainly provided by the Sn 5s states. The optical band gap of Ga1.375In0.5Sn0.125O3is larger than that of Ga1.25In0.625Sn0.125O3. Ga1.25In0.625Sn0.125O3 has a smaller electron effective mass and a slightly larger mobility. However, Ga1.375In0.5Sn0.125O3 has a larger relative electron number and a slightly higher conductivity.