用SCLC法研究低k多孔SiO2:F薄膜的隙态密度

用溶胶-凝胶法制备了低k多孔SiO2:F薄膜,用空间电荷限制电流法(SCLC)研究了多孔SiO2:F薄膜中的隙态密度以及掺F量对隙态密度的影响,得到了平衡费米能级附近的隙态密度约为7×1015 cm-3·eV-1,以及带隙中隙态随能量的分布.并对造成隙态的主要原因也进行了讨论.     

Chemiluminescence enzyme immunoassay using magnetic nanoparticles for detection of neuron specific enolase in human serum

To detect a biomarker for small cell lung carcinoma, neuron specific enolase (NSE), a sensitive and specific chemiluminescence enzyme immunoassay was developed. Fluorescein isothiocyanate (FITC) labeled NSE capture antibody connected with NSE and alkaline phosphatase (ALP) labeled NSE detection antibody in a sandwich-type detection manner. This immune complex was further reacted with anti-FITC coated magnetic beads. In a magnetic field, the complex was enriched, and the sensitivity was thus enhanced. The limit of detection (LOD) of this method was <0.2 ng mL⁻¹. The proposed immunoassay was highly selective, and not interfered by hook effect. The recovery was >83.0% and the coefficient of variation was <10.0%. Human sera from 120 patients were tested with the presented and traditional chemiluminescence enzyme immunoassay. An excellent linear relationship was obtained between two techniques. Overall, this immunoassay offers a promising alternative for NSE detection than traditional clinical examinations.     

Solution growth of single crystals of 4-hydroxycyanobenzene (4HCB) suitable for electronic applications

Squared, platelet-like single crystals of 4-hydroxycyanobenzene (4HCB) have been grown from solutions based on ethylic ether and petroleum ether. Properly modifying the growth conditions, in terms of both solvent used for the growth and concentration of 4HCB in the starting solution, allowed one to tune the planar dimensions of the platelets in the range 2–6 mm, and their thickness in the range 150–600 μm. In this way samples well suited for desired practical manipulation and electronic measurements may be obtained. Moreover, lowering the growth temperature resulted in larger but still thin 4HCB crystals. The ability to tailor crystal thickness has allowed one to study their Space-Charge Limited Current (SCLC) behaviour along that dimension, showing that the so-contacted samples exhibit intrinsic-like bulk conduction behaviour, and are hence well suitable for electronic studies and applications.     

Heterojunction between crystalline silicon and nanocomposite coupled ZnO·SnO2 and optimization of its photovoltaic performance

In this work coupled ZnO·SnO₂ nanocomposite has been used as heterojunction partner to Si for photovoltaic application and its performance is optimized. The interface defect more than 10¹² cm⁻² reduces the short circuit current density, fill factor and efficiency of the device. In addition, the best device performance is observed at the vicinity of 280K. The junction of the device has a dark saturation current density and ideality factor of the order of 10⁻⁴ Acm⁻² and 21 respectively. In addition, four different organic materials are used as back surface field layer (BSL) to the same device and performance is improved. The best conversion efficiency and open circuit voltage as high as 4.1% and 0.591 V respectively are obtained for the device with CuSCN as BSL. Consequently, a range of combined values of the energy band gap and electron affinity of the BSL materials are examined for optimal device performance.     

Study of density of localized states in Cd4Se96−xSx (x=0, 4, 8, 12) chalcogenide semiconductor

Thin films of Cd₄Se_96−xS_x (x=0, 4, 8, 12) chalcogenide semiconductor were deposited by the thermal evaporation technique on glass substrates. XRD pattern of CdSeS alloys show that the grain size decreases with the concentration of Sulfur (S). The surface morphology changes due to the addition of sulfur content. The effect of sulfur on the DC conductivity has been investigated, which show that the DC conductivity is a thermally activated process. The Mott parameter shows that dominate conduction is in the localized states, also the addition of sulfur in Cd–Se results an increase in electrical conductivity, which may be due to shift of Fermi level. Current–voltage (I–V) measurements at different fixed temperatures show two regions; Ohmic conduction at low bias having a unit slope, and non ohmic conduction at high bias. Observation of the data shows that conduction is dominated by trap limited space charge limited conduction (SCLC), from where the density of state has been calculated using SCLC measurement data. The increase in the density of states with sulfur concentration may be due to the increase in the defect states.     

Side chain liquid crystal polyurethanes with azobenzene mesogenic moieties: Influence of spacer length on hydrogen bonding at different temperatures

A series of side chain liquid crystal polyurethanes (CnCNPs), in which the spacer length was varied from 2 to 12 methylene units, were synthesized by the addition polymerization of α-[bis(2-hydroxyethyl)amino]-ω-(4-cyanoazobenzene-4′-oxy)alkanes (CnCN-diols) with hexamethylene diisocyanate. The liquid crystalline properties of CnCNPs were characterized by means of differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. Polyurethanes with spacer length 4 or higher exhibited mesomophic properties. C4CNP and C5CNP exhibited an enantiotropic nematic mesophase, while C6-C12CNPs exhibited enantiotropic bilayer smectic mesophases. CnCNPs have a high tendency to crystallize; crystallization is kinetically controlled. Polyurethane's backbone crystallization is closely related to hydrogen bonding. To establish the role of hydrogen bonding in mesophase formation as well as crystallization, Fourier transform infrared spectroscopy studies of CnCNPs were carried out at different temperatures focusing on H-bonds between the N H and CO groups of the urethane backbone. With increasing temperature, CO and N H stretching bands were evenly shifted to higher wavenumbers, with two exceptions (C4CNP and C5CNP) discussed in detail in the text. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2135–2146, 1998     

阻变式存储器存储机理

阻变式存储器（resistive random access memory, RRAM）是以材料的电阻在外加电场作用下可在高阻态和低阻态之间实现可逆转换为基础的一类前瞻性下一代非挥发存储器.它具有在32nm节点及以下取代现有主流Flash存储器的潜力,成为目前新型存储器的一个重要研究方向.但阻变式存储器的电阴转变机理不明确,制约它的进一步研发与应用.文章对阻变式存储器的体材料中几种基本电荷输运机制进行了归纳,总结了目前对阻变式存储器存储机理的理论模型.     

Synthesis and photovoltaic properties of a furan-diketopyrrolopyrrole-fluorene terpolymer

We report the synthesis of two solution-processable reduced band gap donor–acceptor conjugated polymers p(C8-DPP-F) and p(C12-DPP-F), composed from 9,9-dioctylfluorene as the donor moiety, diketopyrrolopyrrole (DPP) moiety as the acceptor moiety and furan bridges. Two different alkyl chains, n-dodecyl and n-octyl were used on the DPP moiety and the impact of this structural modification evaluated in detail. Both polymers exhibited similar optical and electrochemical properties with optical band gap of around 1.75 eV as result of LUMO levels near −3.4 eV and high-lying HOMO levels of ∼5.2 eV. Bulk heterojunction photovoltaic devices using these polymers electron donors along with PC₇₀BM as the electron acceptor, gave power conversion efficiency of 1.60% and 0.75% for p(C12-DPP-F) and p(C8-DPP-F) respectively.     

Space charge limited current conduction in p-N,N-dimethylaminobenzylidenemalononitrile (DBM) thin films

The electrical conduction properties of DBM thin films with different thicknesses, sandwiched between gold (Au) electrodes were investigated at the temperature range 291-353 K. At the low-voltage region the current conduction in Au/DBM/Au device is ohmic type. The charge transport phenomenon appears to be space charge limited current (SCLC) at higher-voltage regions, dominated by a discrete deep trapping level having trap density of 1.31 × 10⁻²¹ cm⁻³. Various electrical parameters were determined from J-V analysis.     

Electrical Methods to Elucidate Charge Transport in Hybrid Perovskites Thin Films and Devices

The panchromatic light absorption and excellent charge carrier transport properties in organo lead halide perovskites allowed to achieve an unprecedented power conversion efficiency in excess of 25 % for thin film photovoltaics fabrication. To understand the underlying phenomena, various comprehensive set of optical and electrical techniques have been employed to investigate the charge carrier dynamics in such devices. In this perspective, we aim to summarize the electrical transport properties of perovskite thin films by using (i) impedance spectroscopy (IS), (ii) space charge limited current (SCLC), (iii) field‐effect transistors (FETs) and (iv) time‐of‐flight (TOF) methods. We have deliberated various equivalent circuit used to model the perovskite solar cells by means of IS. The SCLC technique provide vital electrical parameters such as mobility, activation energy, traps density and distribution, carrier concentration, density of states, etc. The TOF technique measures mobility as a primary parameter while the FETs configuration provide a valuable insight into the in‐plane charge transport in perovskites thin films. We believe that these notable understanding will provide insights into charge carrier dynamics in perovskite materials and devices.