准一维纳米结构的电子显微学研究

自从１９９１年，Ｉｉｊｉｍａ发现纳米碳管［１］以来，一系列准一维纳米材料被相继用不同方法合成出来。由于其独特的结构特性和因此而具有的不同于体材料的新颖的物理性质，这些准一维纳米材料有着很大的基础研究价值和潜在的应用价值，因而受到人们的广泛研究和关注。...     

准一维半导体纳米结构的电子显微学研究

本文总结了近年来我们在功能准一维纳米结构材料研究方面所获得的一些有意义的结果。借助于现代电子显微镜技术，不仅研究了硅、氮化稼、氧化锌等一维纳米材料的形貌和显微结构，还研究了其一维择优生长机理及小尺度效应。尤其是利用高能量分辨电子能量损失谱、高角环形暗场探头等先进技术，解决了一个传统X－光等结构分析手段所不能解决的难题，分析了一种SiOx/SiC复合纳米电缆的成份与结构。     

蓝宝石上石墨烯的近程催化生长研究

在半导体或者绝缘衬底上利用化学气相沉积方法生长石墨烯和在金属上生长石墨烯相比具有很明显的优势,它克服了前期转移石墨烯时引入的杂质污染和缺陷产生的问题.本文提出了一种新的近程催化的方法可以在蓝宝石衬底上直接进行石墨烯的生长.该方法利用了金属作为催化剂的优势,又避免了转移石墨烯的过程.该方法能制备出完全覆盖衬底的石墨烯,同时石墨烯畴的大小接近1μm.基于生长过程中石墨烯的成核和畴的生长,本文提出了近程催化的生长机理.     

Transformation from β-Ga2O3 to GaN Nanowires via Nitridation

Element doping is an important way to modify the properties of semiconductor materials. In our previous work, it was found that nitrogen-doping in β-Ga2O3 nanowires can induce a novel luminescence emission （around 740 nm） caused by generation of acceptor levels at the middle of the band gap of the β-Ga2O3 nanowires. Here we report that further heavy doping of nitrogen can transform the β-Ga2O3 nanowires completely into wurtzite structured GaN nanowires. Transmission electron microscopy （TEM）, x-ray diffraction （XRD） and Raman spectrum are used to evaluate the transition process. Both XRD and Raman analysis reveal that the monoclinic β-Ga2O3 nanowires start phase transformation at a temperature around 850℃ towards wurtzite structured GaN. Our results will be very helpful to profound our understanding of the doping induced effects and phase transformation in semiconductor compounds.     

Room Temperature Ferromagnetism and Optical Tunability in Cu Doped GaN Nanowires

GaN nanowires doped with 2at.% and 6at.% Cu ions are synthesized by chemical vapour deposition method. Structural and compositional analyses demonstrate that the as-grown nanowires are of single crystal wurtzite GaN structure. Magnetic characterizations reveal that the doped GaN nanowires exhibit room temperature ferromagnetism. The measured saturation magnetic moments are 0.37ug and 0.47ug per Cu atom at 300 K for Cu 2 at. % and 6 at. %, respectively. The photoluminescence spectra show that Cu dopant can tune the band gap of the GaN, which leads to a red shift of band-edge emission with increasing dopant concentration.     

Mn掺杂ZnO纳米线的制备及其磁学性能

采用气相沉积方法在ZnO纳米线中实现了磁性元素的原位掺杂,获得大量高结晶质量的Zn1-xMnxO纳米线.X射线衍射、光电子能谱和透射电镜结果表明,Mn确实固溶入ZnO中而没有形成杂质相.采用超导量子干涉仪研究了Zn1-xMnxO纳米线的磁学性能,发现其铁磁性与Mn的掺杂含量有关.     

Negative magnetoresistance in Dirac semimetal Cd3As2 with in-plane magnetic field perpendicular to current

Topological insulators and semimetals have exotic surface and bulk states with massless Dirac or Weyl fermions,demonstrating microscopic transport phenomenon based on relativistic theory. Chiral anomaly induced negative magnetoresistance(negative MR) under parallel magnetic field and current has been used as a probable evidence of Weyl fermions in recent years. Here we report a novel negative MR result with mutually perpendicular in-plane magnetic field and current in Cd3As2nanowires. The negati...     

SnO2掺Ag纳米线的制备、结构表征及光学性质研究

用化学气相沉积法在管式炉中制备了SnO2掺Ag纳米线.纳米线直径约50 nm,长几十微米.通过XRD、TEM和Raman谱仪等测量确定SnO2掺Ag纳米线为金红石型结构,XPS谱表明样品中含有Sn、O和Ag元素,Ag的浓度约为1.8 at.%,室温PL谱显示样品在626nm处有很强的红光发射峰.     

Au/SnO_2异质同轴纳米电缆

本文报道了一种新型的Au/SnO2金属-半导体异质同轴纳米电缆结构。通过透射电镜表征,发现其轴心为沿特定方向生长的单晶Au纳米线,而壳层则为沿[100]方向生长的单晶SnO2,整体看来就如同一根单晶Au纳米线外套了一根单晶SnO2纳米管。管的两端是封闭的,而Au轴则几乎贯穿整个管,只在端部与SnO2之间有一定间隙。本文讨论了纳米电缆可能的生长机制,而空隙应该是由于两者的热膨胀系数不同所致。     

Novel Route to Fabrication of Metal-Sandwiched Nanoscale Tapered Structures

Tapered dielectric structures in metal have exhibited extraordinary performance in both surface plasmon polariton （SPP） waveguiding and SPP focusing. This is crucial to plasmonic research and industrial plasmonic device integration. We present a method that facilitates easy fabrication of smooth-surfaced sub-micron tapered structures in large scale simply with electron beam lithography （EBL）. When a PMMA layer is spin-coated on previously-EBL-defined PMMA structures, steep edges can be transformed into a declining slope to form tapered PMMA structures, scaled from 10nm to 1000nm. Despite the simplicity of our method, patterns with PMMA surface smoothness can be well-positioned and replicated in large numbers, which therefore gives scientists easy access to research on the properties of tapered structures.