不同手性单壁碳纳米管分离及其场效应晶体管性能研究

高纯度的单手性单壁碳纳米管对于下一代碳基电子器件的发展具有重要意义。利用聚[(9,9-二辛基芴-2,7-二基)-共-联吡啶](PFO-BPy)、聚(9,9－二辛基芴－2,7－二基)(PFO)和聚(9,9－二辛基芴－共苯并噻二唑)(PFO-BT)三种聚合物在有机相中分别分选出(6,5),(7,5)和(10,5)三种手性单壁碳纳米管,具有较高纯度以及浓度,并去除了超过99%的残留分散剂。使用上述溶液沉积获得高均匀性和高密度的碳纳米管薄膜,以此作为器件沟道材料,制备了手性单壁碳纳米管场效应晶体管阵列。结果显示,大直径的(10,5)手性碳纳米管晶体管器件具有较好的电学性能,其迁移率最高达16cm²·V-1·s-1,开关比达10⁷。     

Cu/SiO2逐层沉积增强无杂质空位诱导InGaAsP/InGaAsP量子阱混杂

研究了Cu/SiO_2逐层沉积增强的无杂质空位诱导InGaAsP/InGaAsP多量子阱混杂(QWI)行为。在多量子阱(MQW)外延片表面,采用等离子体增强的化学气相沉积(PECVD)不同厚度的SiO_2,然后溅射5 nm Cu,在不同温度下进行快速热退火(RTA)诱发量子阱混杂。通过光荧光(PL)谱表征样品在QWI前后的变化。实验结果表明,当RTA温度小于700℃时,PL谱峰值波长只有微移,且变化与其他参数关系不大;当RTA温度大于700℃时,PL谱峰值波长移动与介质层厚度和RTA时间都密切相关,当SiO_2厚度为200 nm,退火温度为750℃,时间为200 s时,可获得54.3 nm的最大波长蓝移。该种QWI方法能够诱导InGaAsP MQW带隙移动,QWI效果与InGaAsP MQW中原子互扩散激活能、互扩散原子密度以及在RTA过程中热应力有关。     

基于阳极键合的环形静电谐振器的制作与测试

设计了一种基于阳极键合的环形谐振器的制作方法,用以简化环形静电陀螺谐振器的制作工艺。采用(100)及(111)顶层硅的SOI,分别通过阳极键合工艺制作了硅基环形陀螺谐振器。分析了不同晶向下频率裂解的产生及对陀螺谐振的影响,同时通过仿真分析了晶向对双波腹与三波腹振型的影响程度。利用网络分析仪在真空腔内对器件进行扫频测试实验,得到了两种器件的幅频响应特性,讨论了双波腹与三波腹工作模态与晶向的关系。双波腹相对于三波腹更易受加工条件的影响,而相对的振动幅值更大。同时设计静电调谐的方法,解决了(111)晶向硅基双波腹存在的频率裂解较大的问题。     

太赫兹扫描成像在高通量测量铜合金薄膜电导中的应用（特邀）

高通量制备与表征对将材料基因组方法应用于先进材料研发制造实践起着关键作用。针对基于材料基因工程的高通量实验技术应用,采用透射式太赫兹扫描成像方法,对样品密度为144个/片的铜合金薄膜材料芯片进行了高通量电导的快速、微区检测。基于Tinkham薄膜透射方程及Fresnel公式的太赫兹光谱成像表征技术,对不同组分含量铜合金薄膜的太赫兹测量结果与四探针测量数据比较,具有一致的趋势。通过太赫兹成像可以进行同一基底上 144个高通量组合铜合金样品点电导的半定量比较。对代表性样品点的电导变化趋势与合金组分含量变化趋势,以及微观组织形貌进行分析比较得到相关对应关系,显示出太赫兹检测方法用于微区高通量金属薄膜电导表征方面的巨大潜力,显著提升研发效率。     

Preparation and characterization of triangular hollow porous polyacrylonitrile fiber made by coaxial wet spinning

Hollow porous fiber with both hollow and mesoporous structural characteristics can play an important role in storage, adsorption, and other fields. Triangular hollow porous fiber was prepared by coaxial wet spinning in this paper. Polyacrylonitrile (PAN) and N-N dimethylformamide (DMF) were blended to get cortical solution. Polyvinylpyrrolidone (PVP) and DMF were blended to get core solution. Subsequently, coaxial triangular spinneret was adopted to inject solution into coagulation bath for double diffusion and obtain primary fiber. Then PAN-based triangular fiber with high porosity was prepared after washing and drying. Scanning electron microscopy, nitrogen physical adsorption instrument, thermogravimetric analyzer, and other instruments were used to test and characterize. The results show that the cross-section of the fiber is triangular and has a sense of luster. The hollow degree of the fiber is as high as 84.17%, and the sheath has three-level structure with multi-scale pore diameters, including micropores (200 μm), submicron pores (200 nm), and nanopores (20 nm). Through the range analysis of orthogonal experiment, it is found that the concentration of cortical solution is the main factor affecting the fiber tensile strength. When the concentration of cortical solution is 17%, the concentration of core solution is 10%, the flow rate ratio of cortical solution to core solution is 10:1, and the concentration of coagulation bath is 10%, the fiber tensile strength reaches 1.43 N/mm². The thermal insulation performance of fiber is better than that of silk, cotton and polyester. The results in this paper will provide an experimental foundation for the design and application of hollow porous profiled fibers.     

Highly efficient phosphorescent organic light-emitting diodes using a homoleptic iridium(III) complex as a sky-blue dopant

Homoleptic triscyclometalated iridium(III) complex Ir(dbi)₃ was used as a dopant for sky blue phosphorescent organic light-emitting diodes (PHOLEDs). Its photophysical, thermal, electrochemical properties as well as the device performances were investigated. Ir(dbi)₃ exhibited high quantum yield of 0.52 in solution at room temperature. A maximum current efficiency and external quantum efficiency (EQE) of 61.5 cd A⁻¹ and 23.1% were obtained, which are the highest ever reported for blue homoleptic iridium complexes. High efficiencies of 53.5 cd A⁻¹ and 20.1% EQE were achieved even at the luminance of 1000 cd m⁻².     

An integrated low temperature approach to highly photoactive nanocrystalline mesostructured titania

A new type of nanocrystalline mesostructured TiO₂ (NMT) predominantly in the anatase phase with a high specific surface area up to 269 m² g⁻¹ was prepared by a novel integrated nonhydrolytic sol–gel/UV-illumination technique at low temperature. During the gaseous phase photocatalytic degradation of acetone, the material exhibited excellent photoactivity, much higher than commercial Degussa P-25, which closely related to the markedly enhanced crystallization degree and the beneficial formation of surface Ti–OH groups on the NMT sample during the post UV-illumination process.     

Influence of GaInP ordering on the performance of GaInP solar cells

CuPt-type ordering with undesirable properties always occurs in GaInP at growth conditions that are very close to those leading to the highest quality material in metal organic chemical vapor deposition. In this work, highly disordered GaInP with high crystalline quality was obtained by optimizing growth conditions. Room-temperature and low-temperature photoluminescence (PL) spectra of AlGaInP/GaInP/AlGaInP double heterostructures (DHs) reveal that the band edge emission intensity is enhanced by optimizing growth temperature, V/III ratio, and reactor pressure at the expense of low energy peak originating from spatially indirect recombination due to the ordering-related defects. The DH sample with less ordering-related defects demonstrates a longer effective minority carrier lifetime, consequently, the GaInP solar cell shows a significant improvement in the performance.     

All-inkjet printed organic transistors: Dielectric surface passivation techniques for improved operational stability and lifetime

We report about the use of a printed pentafluorothiophenol layer on top of the dielectric surface as a passivation coating to improve the operational stability of all-ink-jet printed transistors. Transistors with bottom-gate structure were fabricated using cross-linked poly-4-vinylphenol (c-PVP) as dielectric layer and an ink formulation of an amorphous triarylamine polymer as semiconductor. The resulting TFTs had low turn-on voltage (V_th < |5 V|) and a mobility ≈0.1 cm²/(V s). A comparison of identically fabricated transistors shows that devices with coated dielectric have a higher operational stability than those using bare c-PVP. This conclusion is supported by a quantitative study of the threshold voltage shift with time under continuous operation. Long exposure to the ambient atmosphere causes an increase in the threshold voltage strongly dependent on the used semiconducting ink formulation.     

On the manufacturing and electrical and mechanical properties of ultra-high wt.% fraction aligned MWCNT and randomly oriented CNT epoxy composites

The effect of CNT orientation on electrical and mechanical properties is presented on the example of an ultra-high filler loaded multi-walled carbon nanotube (68 wt.% MWCNTs) epoxy-based nanocomposite. A novel manufacturing method based on hot-press infiltration through a semi-permeable membrane allows to obtain both, nanocomposites with aligned and randomly oriented CNTs (APNCs and RPNCs) over a broad filler loading range of ≈10–68 wt.%. APNCs are based on low-defected, mm-long aligned MWCNT arrays grown in chemical vapour deposition (CVD) process. Electrical conductivity and mechanical properties were measured parallel and perpendicular to the direction of CNTs. RPNCs are based on both, aligned mm-long MWCNTs and randomly oriented commercial μm-long and entangled MWCNTs (Baytube C150P, and exemplarily Arkema Graphistrength C100). The piezoresistive strain sensing capability of these high-wt.% APNCs and RPNCs had been investigated towards the influence of CNT orientations. For the highest CNT fraction of 68 wt.% of unidirectional aligned CNTs a Young’s modulus of E_|| ≈ 36 GPa and maximum electrical conductivity of σ_|| ≈ 37·10⁴ S/m were achieved.