Sideband Absorption and its Effects on Temperature Dependence of Local Vibrational Mode Main Absorption Band for Carbon Acceptor in Gallium Arsenide

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INTERACTION AMONG Si IN LEC GaAs AND B_2O_3 AND H_2O IN THE ENCAPSULANT

本文利用文献报道的LEC法GaAs晶体中的Si,B的红外LVM吸收光谱和SIMS分析数据,作出三条lg[Si]-lg[B]直线,其斜率分别接近于4/3,2/3,1/2.本文结合晶体生长的不同工艺条件试用熔体中Si与B_2O_3,H_2O间的相互作用,解释斜率的差异.     

A tetrathiafulvalene-based conjugated donor-acceptor-donor system

Unique donor-acceptor-donor systems possessing tetrathiafulvalene (TTF) and benzoquinone moieties have been prepared. The soluble, fully defined title systems show a charge-transfer absorption in solution and in the solid state. According to UV-transmission spectroscopy, the charge-transfer absorption in solution is an intramolecular process. In order to increase the acceptor ability of the quinone subunit, 1a has been protonated to a dication. Cyclic voltammetry shows the existence of two discrete oxidation states. It is thus possible to form charged species by either proton or electron transfer.     

Photorefractive properties of composites based on polyvinyl alcohol,single-wall carbon nanotubes,and fullerene

Composites with photoelectrical, nonlinear optical, and photorefractive properties have been prepared. The composites consist of polyvinyl alcohol, single-wall carbon nanotubes, and fullerene C₆₀. Addition of C₆₀ with a long wavelength boundary near 630 nm resulted in an eight- to tenfold increase in both the quantum efficiency of generation of mobile hole charges and the photorefractive two beam gain coefficient measured at wavelengths exceeding 1000 nm (over an area of optical absorption of nanotubes). This is attributed to electron trapping by acceptor fullerene, which limits the regeneration of photogenerated charges and provides an increase in mobile hole charges.     

Photoluminescence of donor–acceptor carbazole chromophores

Absorption and emission features of various chromophores both in the solid amorphous state and in solution are presented. These 1-(N-ethyl-carbazolyl)-2-substituted-2-cyanovinylene molecules contain in their structure the electron-donor carbazole nucleus and cyanovinylene bearing different acceptor moieties such as either another nitrile function, a methylester, a phenyl, or a para-nitro-phenyl group. It is shown that depending on the strength of the donor–acceptor internal charge transfer, both the absorption and emission spectra are more or less red-shifted. It is found that the methylester derivative displays the best relative photoluminescence efficiency among all the samples. From solvatochromic studies we showed that the remarkable luminescence of the cyanoester derivative can be attributed to a strong dipole moment in the excited state. Furthermore, cyanoester microcrystallites exhibited spectral narrowing which was attributed to an amplified spontaneous emission.     

Protonation and charge transfer in polyaniline: an optical absorption study of the mixed solutions

Interaction of polyaniline (PANI) with a protonating dopant, dodecylbenzenesulfonic acid (DBSA), and an organic electron acceptor, pentadecyltetracyanoquinodimethane (C₁₅TCNQ), is studied in DMSO solutions, using optical absorption spectroscopy. Each of the two agents alone induces an absorption band at 417 nm, attributable to cation-radicals of PANI. Free carrier absorbance in the near-infrared is absent in the case of C₁₅TCNQ. Moreover, the charge-transfer interaction between PANI and C₁₅TCNQ suppresses a transition to the conductive state. When PANI/C₁₅TCNQ mixtures are aged, a new band near 500 nm appears that can be attributed to an adduct of PANI and C₁₅TCNQ.     

Effect of surface state of carbon fiber electrode on copper electroplating from sulfate solutions

The effect of the fiber surface state of a carbon fiber fabric on the parameters of copper electro-plating from a sulfate solution (the copper current efficiency, the electroplating rate, and the deposit distribution in the depth of electrode) is studied. The surface state of fibers was changed by preliminarily polarizing the carbon fiber fabric in electrolyte solutions. The change in the specific conductivity and weight of the carbon fiber fabric, as well as the surface state of oxides and the morphology of the copper deposit, depending on the conditions of electrode polarization was studied.     

Nonlinear absorption in an azo-containing ion liquid crystal polymer in the different excitation regimes

The nonlinear absorption of an azo-containing ion liquid crystal polymer, in dimethylformamide solution or solid thin film, has been investigated using Z-scan technique. Under the excitation of nanosecond or picosecond pulses at 532 nm, the film presents large saturable absorption (SA), while the solution shows reverse saturable absorption. The alteration of nonlinear absorption behavior is due to the change of excited state cross-section and the time of intersystem crossing in solution and film. Irradiated by a continuous wave laser, SA is observed in both solution and film due to the low excitation optical intensity and thermal effect.     

硼酸缓冲溶液中pH值和腐蚀产物对低碳钢活化/钝化敏感性的影响

研究了在pH值分别为8,9和10的除氧硼酸缓冲溶液中,低碳钢腐蚀产物对其活化/钝化敏感性的影响.实验结果表明,在pH值为8时,低碳钢一直处于活性溶解状态,不受腐蚀产物影响;在pH值为9和10时,表面腐蚀产物使低碳钢钝化,其腐蚀电位最后稳定于钝化区间.XPS和XRD等分析结果表明,腐蚀产物由FeB(OH)12B4O7和γ...     

Possibility to Use Hydrothermally Synthesized CuFeS<Subscript>2</Subscript> Nanocomposite as an Acceptor in Hybrid Solar Cell

Here we have approached the plausible use of CuFeS₂ nanocomposite as an acceptor in organic–inorganic hybrid solar cell. To produce CuFeS₂ nanocomposite, hydrothermal strategy was employed. The room-temperature XRD pattern approves the synthesized material as CuFeS₂ with no phase impurity (JCPDS Card no: 37-0471). The elemental composition of the material was analyzed from the TEM-EDX data. The obtained selected area electron diffraction (SAED) planes harmonized with the XRD pattern of the synthesized product. Optical band gap (4.14 eV) of the composite from UV–Vis analysis depicts that the synthesized material is belonging to wide band gap semiconductor family. The HOMO (? 6.97 eV) and LUMO (? 2.93 eV) positions from electrochemical study reveal that there is a possibility of electron transfer from MEH-PPV to CuFeS₂. The optical absorption and photoluminescence spectra of MEH-PPV:CuFeS₂ (donor:acceptor) composite were recorded sequentially by varying weight ratios. The monotonic blue shifting of the absorption peak position indicated the interaction between donor and acceptor materials. The possibility of electron transfer from donor (MEH-PPV) to acceptor (CuFeS₂) was approved with photoluminescence analysis. Subsequently, we have fabricated a hybrid solar cell by incorporating CuFeS₂ nanocomposite with MEH-PPV in open atmosphere and obtained 0.3% power conversion efficiency.     

Synthesis,photophysical and electroluminescent properties of donor–acceptor–donor molecules based on α-cinnamoyl cyclic ketene dithioacetals

New symmetrical π-conjugated donor–acceptor–donor functionalized molecules consisting of different electron-donating moieties but same α-cinnamoyl cyclic ketene dithioacetals (CCKDA) acceptor have been synthesized. The photophysical properties of these compounds indicate that the absorption and emission result from the intramolecular charge-transfer between the donor and the acceptor. Cyclic voltammetry data show that the band gaps of the compounds vary by introducing different donor moieties. Density functional theory calculations provide an insight into the electronic structure of the molecules. The double-layer electroluminescent devices are fabricated by using these molecular materials as light emitting layer. The electroluminescent performance of the device suggests that these donor–acceptor–donor molecules can be good candidates for the application in organic light-emitting diodes.     

Interpretation of current noise generation by a simple model

The corrosion process of low carbon steel in natural aerated sulphuric acid was examined by electrochemical noise. Noise was interpreted in the time domain in terms of current fluctuations and amplitude distribution. A simple electrochemical model was used to analyse the electrochemical state of steel surface. Stochastic behaviour of the metal‐electrolyte interface in the model was based upon the assumption that the elementary fluctuation sources were related to fluxes of electrons that pass from a metal to electron‐acceptor ions in solution. The probability that in a certain time a number of successful electron transfers occur, obeyed the Gaussian distribution. At the corrosion potential, it was possible to estimate the corrosion current density (i_corr) from the number of successful electron transfers.     

MLCROSTRUCTURE AND PROPERTIES OF C-Cu NANOSTRUCTURE THIN FILM

1. IntroductionTlle filnls of dial11ol1d-Iike carboll (DLC) llave a smooth, chemically inert sllrface withhigh hardness, a sluall fri.ti.,1 coefficiellt, and a low threshold fOr electron emissioll. Theyllaxv lIlall}' applicatioIls ill differellt fields. T…     

碳掺杂氧化钛薄膜可见光催化性能及机制研究

以四异丙醇钛为原料,用大气开放式MOCVD装置通过控制工艺参数制备不同含碳量的氧化钛薄膜.分别采用EDS、XRD、SEM、UV-VIS、罗丹明B光催化降解的方法对不同碳含量的碳掺杂氧化钛薄膜的光吸收性能以及可见光下的光催化活性进行研究.研究结果表明,随着碳掺杂量的增加,薄膜的可见光吸收和可见光催化活性均增强.     

TZM材料热吸收率的分析与研究

钛镐钼合金(TZM)作为面对等离子体材料(PFM)将会继续在EAST中大量使用。研究和分析TZM材料的热吸收率对未来PFM的选择具有很高的价值。本文利用深圳大学的电子枪设备分别对轧制态及锻造态的TZM进行了热吸收率的测试并对相关结果进行了分析。结果显示,轧制态及锻造态的TZM的热吸收率均在0.7左右,并且这个数值不会受到冷却效果及材料温度的影响而产生变化。这项结果将对判断TZM在使用中的安全性有巨大帮助,同时对EAST的远期升级及CFETR的建设都具有重要的参考价值。     

Crystallinity dependence of electrochemical properties for LiFePO_4

Li Fe PO4 composites were prepared by solid state reactions at different temperatures and time. The crystalline structure and morphology of the composites were analyzed by X-ray diffraction(XRD) and scanning electron microscopy(SEM), while X-ray absorption spectroscopy(XAS) was employed to characterize the crystallinity. Experimental results show that the electrochemical properties do not monotonously get better with the decrease of particle size and the traditional long reaction time is needless. Moreover, XAS is an effective technique to discover the change in crystallinity.     

Hydrogen absorption and desorption in metallic glass and nanocrystalline Zr52.5Cu17.9Ni14.6Ti5Al10 alloy

To illuminate the intrinsic surface activity of Zr52.5Cu17.9Ni14.6Ti5Al10 alloy in its glass and nanocrystalline states, hydrogen absorption and desorption in both states was investigated by gas chromatographic analysis. The results show that the Zr52.5Cu17.9Ni14.6Ti5Al10 alloy in the nanocrystalline state can absorb a larger amount of hydrogen than that in glass state at room temperature after activation. According to the desorption process and surface state, the significant change in absorption induced by crystallization is proposed to result from that the glassy alloy has a higher desorption energy, which can adsorb gas physically and nonselectively, and is difficult to activate, while the nanocrystalline alloy can absorb much hydrogen due to the inter-atomic or intra-atomic electron transfer, which accelerates the kinetics of the catalytic reaction for the dissociation of molecular hydrogen into atomic hydrogen.     

Change in carbon state by low-temperature aging in heavily drawn pearlitic steel wires

Atom probe tomography analysis of heavily drawn pearlitic steel wires was performed with and without low-temperature aging. In the as-drawn wire, the lamellar cementite hardly decomposed and remained in a sufficient amount. By contrast, almost homogeneous carbon atomic distribution of the concentration near the average carbon content was observed in the wire with maximum tensile strength aged at 150 °C for 30 min. In the 200 °C × 30 min aging, carbon atoms were enriched at the boundary (prior lamellar cementite) and the carbon concentration in the lamellar ferrite was lower. The change in carbon state was explained by the presence of the high number density of vacancies that was introduced by heavy drawing. These results indicate that cementite decomposition occurred during the thermal aging after, and not during, drawing. The mechanism of the change in strength by low-temperature aging was discussed.     

A new donor–acceptor carbazole derivative: Electrochemical polymerization and photo-induced charge transfer properties

A new donor–acceptor carbazole derivative containing N-2-(2-ethylhexyl)-1,8-napthalimide as acceptor pendant was synthesized at three steps and directly coated on to ITO glass surface by using electrochemical process. Subsequently, electrochemical co-polymerization of this monomer was carried out by using 3,4-ethylenedioxythiophene (EDOT) as co-monomer to give electrochromic polymer film. Spectro-electrochemical studies indicated that co-polymer films exhibit relatively lower band gap than that of homo-polymer. Consequently, photo-induced energy and charge transfer properties from the donor-carbazole to naphthalimide-acceptor were studied by using cyclic voltammetry, UV–vis absorption and emission spectroscopy.     

Effect of acceptor substituents on photophysical and photovoltaic properties of triphenylamine–carbazole alternating copolymers

Three alternative copolymers of carbazole (Cz) and triphenylamine (TPA) with substituent containing acceptor group of aldehyde (PCzTPA-CHO), mono-cyano (PCzTPA-CN) or di-cyano (PCzTPA-DCN), were designed and synthesized. Through manipulating the acceptor group attached to TPA unit, the electronic properties and energy levels of the copolymers were effectively tuned. The presence of pendant cyano groups leads to a decrease in the LUMO levels, but influences the HOMO levels very little, so that results in a lower bandgap and red-shift of its absorption spectrum. These results suggest a simple and effective approach for tuning the bandgap in a conjugated polymer through modification of the pendant acceptor groups. Their optoelectronic properties are largely determined by the nature of pendant substituent. Polymer solar cell based on PCzTPA-CN as donor and PC₇₀BM as acceptor demonstrates a power conversion efficiency of 0.81% with a high V_oc of 0.93 V.