Temperature dependent carrier induced ferromagnetism in Zn(Fe)O and Zn(FeAl)O thin films

Epitaxial films of ZnO doped with magnetic ion Fe and, in some cases, with 1% Al show clear evidence of room temperature ferromagnetic ordering but containing huge amount of paramagnetic moment in it. The total ferromagnetic and paramagnetic contributions have been extracted from the low temperature SQUID measurements. A clear correlation between the magnetization per transition metal ion and the ratio of the number of carriers and number of donors have been found in these films and established the theory of carrier induced ferromagnetism. The experimental data has been best explained through the modification of electronic structure of oxide semiconductors with impurity states.     

基于Lab VIEW的半导体光源P-I特性测试系统

采用PCI-6251数据采集卡和LahVIEW平台。设计了一套半导体光源的P-I特性测试系统。该系统通过软件驱动数据采集卡为发光器件提供合适的驱动电压,采集发光器件的光功率和驱动电流,实现了P-I特性曲线的测量、分析和存储等功能。测试结果表明该系统设计成本低、测量效率高、人机界面友好、操作简单、扩展性强,适用于教学、实验及科研等领域。     

Investigation of electron delay in the base on noise performance in InGaP heterojunction bipolar transistors

The DC, RF and noise characteristics of InGaP/GaAs heterojunction bipolar transistors (HBTs) with different base layer widths and δ‐doped layer in the collector were investigated. Analysis of the RF and noise characteristics revealed that the high frequency noise of these HBTs is reduced due to cross‐correlation of shot noise sources and Coulomb blockade from accumulated charge. The measured noise performance is in a good agreement with the HICUM L2 compact model [M. Schroter, IEICE Trans. Electron. E88‐C , 1098 (2005)] when correlated shot noise sources with Fano factor for collector shot noise are included.

     

Capacitive and Charge Transfer Effects of Single-Walled Carbon Nanotubes in TiO2 Electrodes

The transfer of nanoscale properties from single-walled carbon nanotubes (SWCNTs) to macroscopic systems is a topic of intense research. In particular, inorganic composites of SWCNTs and metal oxide semiconductors are being investigated for applications in electronics, energy devices, photocatalysis, and electroanalysis. In this work, a commercial SWCNT material is separated into fractions containing different conformations. The liquid fractions show clear variations in their optical absorbance spectra, indicating differences in the metallic/semiconducting character and the diameter of the SWCNTs. Also, changes in the surface chemistry and the electrical resistance are evidenced in SWCNT solid films. The starting SWCNT sample and the fractions as well are used to prepare hybrid electrodes with titanium dioxide (SWCNT/TiO₂). Raman spectroscopy reflects the optoelectronic properties of SWCNTs in the SWCNT/TiO₂ electrodes, while the electrochemical behavior is studied by cyclic voltammetry. A selective development of charge transfer characteristics and double-layer behavior is achieved through the suitable choice of SWCNT fractions.     

二维半导体材料纳米电子器件和光电器件

近年来,随着各领域对微电子器件集成度及性能要求的不断提高,发展基于二维半导体材料的新型高性能功能性器件成为了突破当前技术瓶颈的重要环节和关键方向。目前,作为新型二维半导体材料的代表,二维过渡金属二硫化物、二维黑磷以及范德瓦尔斯异质结凭借其在电学、热学、机械、光学等方面的优异性能已经成为了发展高性能纳米电子器件和光电器件的最具潜力的材料之一。在本综述中,首先概述了几种用于纳米器件的常见二维材料,分析了材料的结构、性能及其在纳米器件中的应用,其次重点对基于过渡金属二硫化物、黑磷以及由其衍生的范德瓦尔斯异质结的纳米电子器件和光电器件的最新研究进展进行讨论,最后对目前二维半导体纳米器件所面临的挑战以及未来的发展方向进行总结及分析,从而为未来发展高性能功能性纳米器件提供支持。     

一种2-甲基-3-羟基喹啉-4-甲酸单核铜(Ⅱ)配合物的合成、晶体结构、理论计算与性质

以2-甲基-3-羟基喹啉-4-甲酸和1,10-菲咯啉为原料,经溶剂热法合成了一种新颖的Cu(Ⅱ)配合物,[Cu(L)(Phen)(H_2O)]·CH_3OH(1,HL=2-甲基-3-羟基喹啉-4-甲酸,Phen=1,10-菲咯啉),并通过红外光谱、元素分析、单晶衍射、固态漫反射、光致发光及理论计算对其结构和性质进行了研究。单晶结构分析表明配合物1的晶体属于单斜晶系,P2_1/c空间群,是一种零维(0D)结构的单核体。固态光致发光表明其为蓝紫色光发射体。时间密度泛函理论(TDDFT)计算表明其发射归属于配体-配体电荷转移(LLCT)。固态漫反射测量显示该化合物存在1.91 eV的窄带能隙。     

Four isostructural lanthanide(III) coordination compounds based on a new N‐oxydic pyridyl naphthalenediimide ligand: synthesis and characterization

Naphthalenediimides, an attractive class of electron‐deficient organic dyes with rich redox and photoredox properties, have been investigated extensively as building blocks for coordination networks or metal–organic frameworks in recent decades. However, most of the available work has focused on d‐block metal cations rather than f‐block lanthanide ions, whose complexes exhibit a large variability in coordination numbers. In this article, four coordination polymers composed of naphthalenediimides and lanthanide cations, namely catena‐poly[[[tris(nitrato‐κ²O,O′)lanthanide]‐bis{μ‐N,N′‐bis[(1‐oxidopyridin‐1‐ium‐3‐yl)methyl]‐1,8:4,5‐naphthalenetetracarboxdiimide‐κ²O:O′}‐[tris(nitrato‐κ²O,O′)lanthanide]‐μ‐N,N′‐bis[(1‐oxidopyridin‐1‐ium‐3‐yl)methyl]‐1,8:4,5‐naphthalenetetracarboxdiimide‐κ²O:O′] methanol disolvate], {[Ln(C₂₆H₁₆N₄O₄)_1.5(NO₃)₃]·CH₃OH}_n, with Ln = Eu, 1 , Gd, 2 , Dy, 3 , and Er, 4 , have been successfully synthesized under hydrothermal conditions. Single‐crystal X‐ray diffraction analyses revealed that the four compounds are isomorphic and that each asymmetric unit contains one nine‐coordinated Ln centre, one and a half diimide ligands, three nitrate anions and one uncoordinated methanol molecule. In addition, each metal centre is surrounded by nine O atoms in a distorted tricapped trigonal–prismatic geometry. Two centres are bridged by two cis ligands to form a ring, which is further bridged by trans ligands to generate one‐dimensional chains. Neighbouring chains are stacked via π–π interactions between pyridine rings to give a two‐dimensional structure, which is stabilized by π–π interactions between naphthalene rings, forming the final three‐dimensional supermolecular network. Solid‐state optical diffuse‐reflectance spectral studies indicate that compound 4 is a potential wide band gap semiconductor.     

Ferromagnetism in GaN doped with transition metals and rare-earth elements: A review

Gallium nitride is a wide band gap semiconductor material that has drawn significant interest due to its potential applications in opto-electronics and spin-tronics devices that can be operated above room temperature. First principle calculations by density functional theory have a key role in the field of materials science research. Theoretical findings on gallium nitride revealed that it shows ferromagnetic behavior doped by transition metals (i.e. 3d and 4d metals) and rare-earth elements. Ferromagnetism developed in gallium nitride by doping 3d (Ti, Cr, Mn, Fe, Co, Ni, and Cu), 4d metals (Ag and Pd), and rare-earth elements (Eu, Gd, and Ce) is discussed in this review. Effect of concentration on magnetic moment is also discussed. The origin of magnetism and exchange interaction that play a vital role in ferromagnetic and anti-ferromagnetic behavior is also explained. P-d exchange mechanism, s-d hybridization, and exchange mechanism are also explained in detail.     

Pressure-sensitive Transistor Fabricated from an OrganicSemiconductor 1,1'-Dibutyl-4,4'-bipyridinium Diiodide

Although organic semiconductors have attracted extensive interest and been utilized to fabricate a variety of optoelectronic devices, their electrical transportation characteristics under high pressure have rarely been investigated. However, the weak intermolecular interaction of organic semiconductors endows them with a pre- ssure-sensitive crystal structure and electrical transportation performance, especially the latter. Herein, a new pre- ssure-sensitive transistor was fabricated from an organic semiconductor 1,1'-dibutyl-4,4'-bipyridinium diiodide. It was found that this transistor exhibited increasing resistance as the pressure gradually increased and that it eventually shut off under a pressure of 288 MPa. Such a characteristic makes this organic semiconductor a potential candidate for the use in the fabrication of pressure-sensitive switches and regulators. In addition, these results shed light on the electrical performance of flexible organic optoelectronic devices working under high pressure levels resulted from the bending force.     

Optoelectronic and conductivity of ᴫ‐conjugated polymers based on phenylenevinylene, 1,3,4‐thiadiazole and thiophene: Suitable candidates for n‐type organic semiconductors

New poly‐phenylenevinylenes PPVs containing 1,3,4‐thiadiazole as candidates for organic semiconductors have been theoretically studied at density functional theory (DFT) and time‐dependent DFT levels. This study has been conducted in order to investigate the geometrical and electronic properties as well as the conductivity of a series of PPV–thiophene–1,3,4–thiadiazole–thiophene (H–PhTAT–H) containing –CHO, –CH₂–P(=O)(OCH₃)₂, and phenyl–CHO (PhCHO) terminal groups. The impact of terminal groups on the optical bandgaps, electron affinity, LUMO energy, and intramolecular reorganization energy was studied for different oligomers and for a limit polymer. The incorporation of terminal groups did not affect the chain length evolution and the vertical transition energy E_vert value for a polymer limit compared with the unsubstituted oligomer (H–PhTAT–H). All studied properties showed that CHO–PhTAT–PhCHO and H–PhTAT–H oligomers can be considered as n‐type semiconductors.