纳米线阵列的电化学优化光吸收增强研究

通过在自生长的半导体Cu2S纳米线阵列表面进一步应用电化学表面沉积处理,在纳米线表面形成尺寸更小的Cu2S纳米颗粒结构,实现了在不减小纳米线直径或增加纳米线长度的情况下,有效提高了纳米线阵列光吸收性能。利用I-V循环扫描曲线研究了以Cu2S纳米线阵列为工作电极的Cu2S沉积电位,利用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见-近红外分光光度计,对纳米阵列的相结构、微观表面形貌、晶体结构及光吸收能力进行了表征和分析。研究表明:沉积于单斜晶系Cu2S纳米线阵列上的纳米颗粒为斜方晶系Cu2S,沉积后纳米线表面结构改变,粗糙度明显增加,起到了减少纳米线的光反射、优化原纳米线阵列光吸收综合能力的作用。     

SiO2纳米球的粒径均一性研究及其在硅光学共振纳米柱阵列中的应用

近年来, 半导体纳米结构材料的光学共振效应作为一种重要的光调控手段被广泛应用于各类光电子器件。本文用改进的两步Stober法制备了粒径在270~330 nm之间的单分散二氧化硅纳米球, 通过优化工艺参数有效改善了纳米球的粒径均一性。采用恒温加热蒸发引诱自组装方法将纳米球在硅半导体上自组装成单层膜作为掩膜, 采用感应耦合等离子体技术刻蚀制备了硅纳米柱阵列并测试了其光反射谱。光谱结果表明直径在300~325 nm之间的硅纳米柱阵列可以激发四极子Mie光学共振, 其在可见光波段的最低反射率低于5%, 具有良好的光调控性能。     

嵌段共聚物/纳米粒子自组装杂化结构的光吸收性能

结合耗散粒子动力学模拟和时域有限差分方法,研究了两嵌段共聚物(AB)/纳米粒子共混体系的自组装行为及其光吸收性能,分析了纳米粒子与嵌段之间的相互作用参数、纳米粒子大小和共聚物结构对纳米粒子在杂化结构中的分布及其光吸收性能的影响。结果表明,AB/纳米粒子共混体系可形成层状杂化结构,并且调节相互作用参数、纳米粒子大小可以控制纳米粒子分布在A、B相界面或B相,另外共聚物结构也会影响纳米粒子在B相中的分布。当杂化结构中纳米粒子分布不同时,其光吸收率存在显著差异。在可见光范围内,纳米粒子聚集在B相的杂化结构的光吸收率显著高于纳米粒子分布在A、B相界面处的光吸收率,最高可提升75%。改变纳米粒子的分布调控杂化结构的光吸收率,为设计具有优异光吸收性能的杂化材料提供了指导。     

CdSe/CdS纳米颗粒共敏化ZnO光电极的制备及光电化学性能研究

采用电沉积法将CdS和CdSe纳米颗粒沉积在ZnO纳米线阵列上得到CdSe/CdS纳米颗粒共敏化ZnO光电极。利用X射线衍射、扫描电镜、透射电镜和能谱仪等对所得样品结构和形貌进行表征,并通过紫外-可见分光光度计和电化学工作站测试其光吸收性能和光电化学性能。结果发现,相对纳米颗粒单敏化CdS/ZnO光电极而言,纳米颗粒共敏化CdSe/CdS/ZnO光电极具有更好的可见光吸收性能,进而提高短路电流密度和光电转换效率分别到9.56mA/cm2和1.89%。     

微米铜粉/纳米TiO_2复合粒子的低温制备及光吸收性能

利用仿生合成的方法在温和条件下制备了微米铜粉/纳米TiO2复合粒子.选择有机胺对Cu粉进行表面处理,XPS分析表明有机胺通过N原子与表面Cu2+络合形成功能层,在Cu粉表面引入NH2和OH等功能基团,对比实验证实功能基团能够诱导无机氧化物的仿生沉积.XRD结果表明铜粉表面包覆的纳米TiO2呈现锐钛矿晶型,漫反射光谱(DRS)分析表明,Cu粉经过有机胺处理后在716.5nm处出现了由Cu2+离子与N配位产生的弱吸收.复合粒子的光吸收性能介于TiO2和Cu粉之间,Cu负载后样品的光吸收阀值从397.5nm红移至448.9nm,红移的原因可归于Cu负载后TiO2导带下出现新能级,光生电子经过这些中间能级发生跃迁,所需激发能量降低至可见光范围.448.9nm处吸收边的存在表明复合粒子具备可见光催化活性.     

我国纳米分子功能材料研究取得系列创新成果

据媒体近日报道,我国“纳米分子功能材料研发”研究课题,通过一年半的攻关,取得了系列创新性成果,开发出硼硫化法和无溶剂法合成纳米材料的新方法,并成功合成出具有荧光性能的稀土硫氧化物纳米线、具有吸附性能的Cu2与Cu2S核壳结构，以及具有光电转化性能的高温稳定性CulnS2半导体材料；     

Cu0.4In（0.4）Zn1.2S2纳米线的催化生长

采用液相法制备了Cu0.4In0.4Zn1.2S2固溶半导体纳米线。对纳米线生长过程的分析表明,纳米线生长遵循溶液-固态-固相机理。前驱体首先受热分解形成Cu1.75S纳米晶,利用其结构中存在的Cu+空位溶解In3+和Zn2+,达到饱和后析出晶体形成Cu0.4In0.4Zn1.2S2固溶半导体纳米线。X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)分析表明,纳米线呈曲折Z形,长度为5μm,具有纤锌矿结构。     

一维α-Bi_2O_3纳米线的合成及光性能

采用溶液沉淀法,以丙酮-水为复合溶剂、正庚烷为油相,在油酸为封端剂的辅助下,在常温常压下高效便捷地合成出了一维α-Bi_2O_3纳米线。采用X射线衍射(XRD)和场发射扫描电子显微镜(FE-SEM)对产物进行了表征。合成的纳米线直径为50~100nm,长约10μm,长径比为100~200,表面清晰光滑。机理分析表明,油酸在纳米线的形成过程中起着至关重要的作用。紫外-可见光(UV-Vis)吸收光谱表明其在小于455nm的紫外-可见光波段具有明显的光吸收,荧光(PL)光谱表明其在400~600nm具有宽的发射谱带。     

单晶TiO_2纳米线束阵列的合成及光电转换性能研究

采用水热合成技术,以盐酸、去离子水和钛酸丁酯为反应前驱物,在透明导电玻璃(FTO)衬底上合成TiO2纳米线束阵列.采用X射线衍射(XRD)、扫描电子显微镜(SEM)和高分辨透射电镜(TEM)对其结构和形貌进行了分析.结果表明:在FTO衬底上形成了垂直排列的具有金红石结构的单晶TiO2纳米线束阵列,TiO2纳米线束由φ4～6nm的几十条纳米线聚集在一起,形成宽度约110～210nm、长度约3μm的四方柱状结构.研究了以TiO2纳米线束阵列为光阳极制备的染料敏化太阳能电池的光电性能,其开路电压为0.72V,短路电流密度为2.9mA/cm2,填充因子为0.42,转换效率为0.88%.     

纳米阵列结构光吸收性能研究进展

分别介绍了近年来国内外对硅纳米线阵列、碳纳米管阵列和金属钠米阵列这几种典型的纳米阵列结构的研究,从理论和实验研究的角度综述了其光吸收性能的研究进展并提出了今后可能的研究方向.     

Cu Diffusion in Co/Cu/TiN Films for Cu Metallization

Some information on how to use in-situ determined diffusion coefficient of Cu to make barrier layer of Cu metallization in ultra large scale integrations （ULSIs） was provided. Diffusion coefficients of Cu in Co at low temperature were determined to analyze Cu migration to Co surface layer. The diffusion depths were analyzed using X-ray photoelectron spectroscopy （XPS） depth profile to investigate the diffusion effect of Cu in Co at different temperatures. The possible pretreatment temperature and time of barrier layer can be predicted according to the diffusion coefficients of Cu in Co.     

Cu surface segregation in Ni/Cu system

We report experimental evidence of Cu surface segregation in Ni/Cu system, during deposition of Ni film onto Cu substrate at room temperature and during heat treatment in vacuum. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) by Tougaard's analysis results show that surface segregation defeats in competition with increase in Ni thickness and terminates when thickness of Ni increase to more than 4 nm. Surface energy and concentration were calculated using contact angle measurements and the results confirm that segregation reduces the surface energy. Surface segregation during heat treatment at 150-220 °C range as a function of time initially shows linear mass transfer. By solving Fick's equation and taking empirical diffusion coefficient, 125 ± 20 kJ/mol is obtained for activation enthalpy of effective diffusion.     

Development of Cu particles and Cu core-shell particles reinforced Al composite

Copper particles were incorporated and retained in elemental state in an aluminium matrix by friction stir processing thereby producing a non-equilibrium particulate composite. The processed Al–Cu_p composite exhibited improved strength with significantly high ductility. The composite was stable up to a temperature of more than 300°C. Thermal exposure at 350°C for more than 10 min led to diffusion of Cu atoms into the Al matrix forming a core-shell type structure in the Cu particles and thus producing an Al–Cu core-shell composite. The shell consists of multiple layers, the thickness of which was controllable.     

Direct bonding of Cu to oxidized silicon nitride by wetting of molten Cu and Cu(O)

When pressureless sintered silicon nitride with the main additives Y₂O₃ and Al₂O₃, having a thermal conductivity K = 20 W/m K, was oxidized at 1240–1360 °C in still air, the resulting surface oxide layer easily bonded to a copper plate in the temperature region between 1065 and 1083 °C, and in the oxygen concentration range of 0.008–0.39 wt%, as shown in a Cu–O phase diagram. The oxide on the silicon nitride was characterized as Y₂O₃·2SiO₂ and mixed silicate glass with additives and impurities that diffused through the grain boundary. The bonding strength of Cu/Si₃N₄ depends on the amount or layer thickness of silicate glass and reaches as high as 100 MPa by shear at room temperature. Detailed analysis of the oxidation layer and the peeled-off surfaces of directly bonded Si₃N₄/Cu reveal that the main mechanism of bonding is wetting to glassy silicate phase by mixtures of molten Cu and α-solid solution Cu(O), which solidify to α + Cu₂O below 1065 °C by a eutectic reaction. The direct reactive wetting of molten Cu, supplied from the grain boundary of a Cu plate, on the glassy phase enables very tight chemical bonding via oxygen atoms.     

Solid state spreading in the Cu/Cu system

Solid state spreading of copper particles on a copper polycrystalline substrate was analysed at 1050^°C. A specific procedure was settled to produce pure monocrystalline and nearly spherical copper particles. Spreading dynamics were analysed from SEM images and preferential particle/substrate orientations were identified by EBSD. The effect of a preferential orientation on the spreading kinetics is limited, if any. A general agreement is found between the kinetic results and numerical calculations of Mullins [1] for mass transport by surface diffusion under the action of surface curvature gradients. The experimental kinetics are however significantly more rapid, due to the contribution of other mechanisms like volume diffusion.     

Precipitation of Cu in Fe–Cu alloys by high-speed deformation

The differences between defect structures in Fe–Cu alloys deformed at the high (4.3×10⁵ s⁻¹) and the low strain rate (67 s⁻¹) were studied. Positron lifetime and coincidence Doppler broadening (CDB) measurements were carried out to investigate the formation of vacancy clusters and Cu precipitates. Both the size of vacancy clusters and the total amount of vacancy-type defects were larger after high-speed deformation at room temperature. Cu precipitation in the specimen deformed at the high-speed stopped for 10 h after annealing at 400 °C, while that in the specimen deformed at the low-speed continued for 100 h. Transmission electron microscopy (TEM) observations showed a heterogeneous distribution of dislocations in the case of low-speed deformation but a homogeneous distribution in the case of high-speed deformation. These results suggested that the sink efficiency for defects was higher in the specimen deformed at the high-speed.