Realization of aligned three-dimensional single-crystal chromium nanostructures by thermal evaporation

Aligned three-dimensional single-crystal chromium nanostructures are fabricated onto a silicon substrate by thermal evaporation in a conventional thermal evaporator, where the incident angle of Cr vapor flux with respect to the substrate surface normal is fixed at 88°. The effects of the deposition time and incident angle on the morphology of the resulting nanostructures are investigated. The achieved Cr nanostructures are characterized by scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and surface area measurement. This study provides a convenient way to fabricate three-dimensional single-crystal Cr nanostructures, which is suitable for batch fabrication and mass production. Finally, the same technique is employed to fabricate the nanostructures of other metals such as Ag, Au, Pd, and Ni.     

Development of laser deposited multilayer zone plate structures for soft X-ray radiation

As a novel approach, the combination of pulsed laser deposition and focused ion beam was applied to fabricate different types of multilayer zone plate structures for soft X-ray applications. For this purpose, high quality non-periodic ZrO₂/Ti multilayers were deposited by pulsed laser deposition on planar Si substrates and on rotating steel wires with layer thicknesses according to the Fresnel zone plate law. Linear focusing optics were fabricated by cutting slices out of the multilayers by focused ion beam and placing them directly over pinholes within Si₃N₄ substrates. Additionally, it was shown that laser deposition of depth-graded multilayers on a wire is also a promising way for building up multilayer zone plates with point focus. First experiments using a table-top X-ray source based on a laser-induced plasma show that the determined focal length and spatial resolution of the fabricated multilayer Laue lens corresponds to the designed optic.     

Dependence on substrate topography of growth of nanosized dendritic structures in an electron-beam-induced deposition process

Nanometer-sized W-dendrites are fabricated on Al₂O₃ substrates with an electron-beam-induced deposition process. Dependence of growth of nanodendrite on surface topography is investigated with transmission electron microscopy. It is confirmed that the nanodendrite grows on convex surfaces but not around a hole on a substrate. These are attributed to different distribution of charges on surfaces with different topographies during electron beam irradiation when charges are produced on the surface due to emission of second electrons. The charges accumulate on convex surface and do not distribute around a hole. Therefore, the nanodendrite grows on the former and not on the latter.     

圆锥磁绝缘传输线的横向空间电荷流

根据电磁场基本理论及电子运动守恒方程，导出圆锥传输线横向空间电荷流的数值模型和磁绝缘临界条件。通过数值计算，讨论了电压及圆锥几何结构参数等对横向空间电荷流和磁绝缘性能的影响。电压较高时,无磁场的空间电荷流较大，而磁绝缘性能更好。在传输线的三个几何参数中，几何因子对传输性能影响最大。     

Growth and characterization of branched carbon nanostructures arrays in nano-patterned surfaces from porous silicon substrates

A method to grow branched carbon nanostructures arrays is presented. We employ the electron-beam-induced deposition method using a transmission electron microscope in poor vacuum conditions where hydrocarbons are present in the chamber. The hydrocarbons are attracted to the substrates by the local electric fields. Saw-tooth nano-patterns were made with a focused ion beam in porous silicon substrates with high porosity in order to create sites with high-local electric fields. We found that the adequate ion dose to create well-defined saw-tooth nano-patterns was between 8 and 10 nC/microm(2). Raman and electron energy-loss spectroscopy on the branched carbon nanostructures show a high concentration of sp(2) sites suggesting that they are made of graphite-like hydrogenated amorphous carbon. Selected area electron diffraction, high-resolution images and energy dispersive X-ray analysis (EDS) are also presented.     

Profile calculation of gold nanostructures by dispersed-nanosphere lithography through oblique etching for LSPR applications

Nanosphere lithography is an inexpensive method used to fabricate gold nanostructures on a substrate. Using dispersed-nanosphere lithography, in which the nanospheres are dispersed on a substrate, 2D or 3D nanostructures can be fabricated by obliquely depositing a gold film on the nanospheres and etching the gold film afterward. These nanostructures are tunable and acute, and are thus good emitting elements for the localized surface plasmon resonance applications. So far, for the fabrication of nanostructures on a substrate with dispersed nanospheres, only 2D nanostructures have been reported through perpendicular etching. We report in this paper that the 3D nanostructures fabricated by dispersed-nanosphere lithography are rigid non-conformal structures, and perpendicular gold etching can be expanded to oblique etching, which provides more possibilities for fabricating the gold nanostructures in various shapes. The profiles of gold nanostructures after several varying angle depositions, and their final profiles after perpendicular or oblique etching, are calculated in this paper. Our profile simulations are applicable for nanospheres (or microspheres) within the range of tens of nanometers to tens of micrometers, and are consistent with our fabricated nanostructures observed using scanning electron and atomic force microscopy. Electronic Supplementary Material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Dispersion of nanospheres on large glass substrate by amorphous or polycrystalline silicon deposition for localized surface plasmon resonance

Nanosphere lithography is a cost-effective way to fabricate noble metal nanostructures for plasmonics. However, dispersing nanospheres on a large area of glass substrate is a difficulty encountered when transparent substrate is required in applications such as localized surface plasmon resonance or surface enhanced Raman spectroscopy. Because poly(diallyldimethyl ammonium chloride) (PDDA) on silicon surface introduces a force that can disperse nanospheres on silicon, in this article, we modify the glass surface through amorphous or polycrystalline silicon deposition and thus well disperse polystyrene or silica nanospheres over a glass area of more than 2 cm × 2 cm. Transmission loss of the glass substrate caused by amorphous or polycrystalline silicon deposition is analyzed with good agreement to experimental spectra, and localized surface plasmon resonance signals generated from the gold nanostructures fabricated on these substrates are measured and yield a sensitivity of 317 nm/RIU, which prove the feasibility and effectiveness of our method.     

΢�����ӻ�������������廯ѧ����������Ʊ��ྦྷ�象Ĥ

利用微波电子回旋共振等离子体增强型化学气相沉积(ECR-PECVD)采用一步法直接在K9玻璃上低温沉积制备了多晶硅薄膜.研究了不同实验参数对薄膜沉积的影响,采用X射线衍射(XRD)、拉曼光谱、扫描电子显微镜(SEM)等实验分析方法对不同条件下制备的样品进行了晶体结构和表面形貌分析,并讨论了多晶硅薄膜沉积的最佳条件.实验结果表明,玻璃衬底上多晶硅薄膜呈柱状生长,并有一定厚度的非晶孵化层;较高氢气比例和衬底温度有利于结晶,薄膜的结晶率达到了62％;晶粒团簇的最大尺寸约为500nm.     

Effect of accelerating voltage on crystallization of self-standing W-nanodendrites fabricated on SiO2 substrate with electron-beam-induced deposition

Self-standing W-nanodendrite structures were grown on SiO₂ substrate using an electron-beam-induced deposition (EBID) process with various accelerating voltages from 400 to 1000 kV. Effect of accelerating voltage on crystallization of the nanodendrites was investigated. The nanodendrites consisted of nano-sized grains and amorphous structures. The nano-sized grains were determined to be W crystal in BCC structure. The higher was electron beam accelerating voltage, the higher was crystallinity of the as-fabricated nanodendrites. It is suggested that high-energy electron irradiation enhances diffusion of W atoms in the nanodendrites, promotes crystallization of W grains.     

TEM study of annealed Pt nanostructures grown by electron beam-induced deposition

In this paper we report on the microstructural characterization of Pt nanostructures fabricated by electron beam-induced deposition in a dual beam system and subsequently annealed in furnace. The as-deposited nanostructures are made of a mixture of nanocrystalline Pt and amorphous carbon. We show by transmission electron microscopy and electron energy loss spectroscopy that the annealing in presence of oxygen at 550 °C for 30 min is able to remove the amorphous carbon from the nanostructure, leaving polycrystalline Pt grains.     

The resistance of single atomic steps in ultrathin Pb nanowires on Si(557)

We studied the local electronic transport properties of a monolayer thick Pb wire by local potentiometry with the tip of a tunneling microscope. 50-nm-wide wires on bare Si(557) were generated by direct writing with an electron beam in an ultrathin film of SiO₂ using the process of electron-beam-induced selective stimulated thermal desorption of oxygen (EBSTD) in combination with a shadow-mask technique and macroscopic TiSi₂ contacts. The resistivity of this wire agrees well with expectations derived from anisotropic monolayer thick Pb films on Si(557). Although small Pb clusters nucleated during annealing and desorption of excess Pb, they had a negligible effect on the local resistive properties of the wire. Steps in the substrate of atomic height apparently do not interrupt the conducting path, but due to local scattering at step edge states increase the local resistivity by more than one order of magnitude.     

Application of a focused ion beam to prepare electron microscopy samples of surface nanostructures

Carbon nanotubes grown on a silicon substrate with an array of FeNiCo₂₀ catalyst islands are studied using focused ion beam and transmission electron microscopy. A method for preparing cross-sectional samples is proposed, which makes it possible to exclude the destructive effect of the ion beam on surface nanostructures during sample preparation using a microscopic three-dimensional protective barrier.     

Characterization and optimization of AuNPs labeled by Raman reporters on glass based on silver enhancement

In this report, gold nanoparticles (AuNPs) labeled by Raman reporters (AuNPs‐R6G) were assembled on glass and used as the seeds to in situ grow silver‐coated nanostructures based on silver enhancer solution, forming the nanostructures of AuNPs‐R6G@Ag, which were characterized by scanning electron microscopy (SEM) and UV‐visible spectroscopy. More importantly, the obtained silver‐coated nanostructures can be used as a surface enhancement Raman scattering (SERS) substrate. The different SERS activities can be controlled by the silver deposition time and assembly time of AuNPs‐R6G on glass. The results indicate that the maximum SERS activity could be obtained on AuNPs‐R6G when these nanostructures were assembled on glass for 2 h with silver deposition for 2 min. In addition, the reproducibility of SERS signal on the fabricated nanostructures is very high with the intensity error lower than 15%, which has great promise as a probe for application in bioanalysis. Copyright © 2008 John Wiley & Sons, Ltd.     

利用电子束蒸发制备铝隧道结工艺研究

采用电子束蒸发的方法在Si片上制备超导铝(Al)薄膜。利用X射线衍射和直流四电极电阻法分别测试了厚度从100埃到5000埃的Al薄膜物向组成,超导转变温度(Tc)和临界电流密度(Jc)。当Al薄膜厚度大于500埃时,超导转变温度Tc=1.2K。电子束蒸发制备的Al薄膜性能良好,具有较高的结晶质量,为制备Al超导隧道结奠定了良好基础。对小面积的Al超导隧道结工艺进行了研究,该超导隧道结两层的超导体材料为Al薄膜,中间势垒层材料为Al2O3。其中Al薄膜利用电子束蒸发制备,势垒层通过直接氧化Al薄膜表面实现,该工艺和采用直接蒸发氧化物薄膜工艺相比不仅简单而且能有效防止势垒层不连续造成的弱连接。     

Realization of silicon quantum wires by selective chemical etching and thermal oxidation

Ultra-fine silicon quantum wires with SiO₂ boundaries were successfully fabricated by combining SiGe/Si heteroepitaxy, selective chemical etching and subsequent thermal oxidation. The results are observed by scanning electron microscopy. The present method provides a very controllable way to fabricate ultra-fine silicon quantum wires, which is fully compatible with silicon microelectronic technology. As one of the key processes of controlling the lateral dimensions of silicon quantum wires, the wet oxidation of silicon wires has been investigated, self-limiting wet oxidation phenomenon in silicon wires is observed. The characteristic of the oxidation retardation of silicon wires is discussed.     

FIB快速加工纳米孔点阵的新方法

纳米尺度的点阵在纳米器件和基础科学研究方面都具有非常重要的应用.目前普遍采用的聚焦离子束和电子束曝光技术可以很方便的在衬底上加工纳米量级的微细结构，但大面积的图形加工过程需要花费太多的机时.介绍一种利用设计图形BMP文件的像素点阵和实际加工区域之间的匹配关系，通过聚焦离子束加工获得所需要的纳米孔点阵的新方法.采用这种方法可以在短时间内获得大面积的纳米点阵结构. 关键词： 聚焦离子束 电子束曝光 纳米孔点阵     

Selective tungsten deposition into ordered nanohole arrays of anodic porous alumina by electron-beam-induced deposition

The selective deposition of a metal (tungsten) into ordered nanohole arrays of an anodic porous alumina membrane was performed using an electron-beam-induced deposition process. After deposition, the membrane was observed and analyzed using electron microscopy and energy-dispersive X-ray spectroscopy. It is shown that the deposition was preferentially conducted in the holes in the irradiated area of the electron beam. A calculation of the electron-beam intensity explains the reason for the preferential deposition in the holes. PACS 81.07.-b; 81.16.Rf; 61.46.+w     

Fabrication of CoPt magnetic nanodot arrays by electrodeposition process

We attempted to fabricate patterned media using the electrochemical deposition process along with nanopatterned substrates prepared by the electron beam lithography (EBL), UV nanoimprint lithography (UV-NIL), and spin-on-glass nanoimprint lithography (SOG-NIL) approaches. CoPt was electrodeposited into the nanopatterned substrates and chemical mechanical polishing was carried out to planarize the surface. It was clarified that CoPt nanodot arrays were successfully deposited into the patterned nanopores fabricated by UV-NIL and SOG-NIL as well as by EBL with high area selectivity and uniformity. The density of the CoPt nanodot arrays deposited into the nanopores fabricated by EBL was equal up to an areal recording density of 250 Gbit/in².     

Fabrication of self-standing nanowires, nanodendrites, and nanofractal-like trees on insulator substrates with an electron-beam-induced deposition

Self-standing tungsten nanowires, nanodendrites, and nanofractal-like trees were fabricated on insulator (Al₂O₃) substrates with a process of electron-beam-induced decomposition in a transmission electron microscope. The conditions for fabricating different morphologies are described. The fabricated structures are characterized with high-resolution transmission electron microscopy and X-ray energy-dispersive spectroscopy. A high concentration of tungsten and a high crystallinity of the structure are confirmed. The growth process is discussed, involving charges produced on the surface of the substrate and the behavior of precursor molecules under electron-beam irradiation. The formation of these structures is considered to relate to nanoscaled unevenness of the charge distribution on the surface of the substrate, movement of charges to the convex surface of the substrate, and accumulation of charges at the tips of the grown structures. PACS 81.07.-b; 07.78.+s; 81.15.Gh; 81.16.-c     

Spatial chemistry evolution during focused electron beam-induced deposition: origins and workarounds

The successful application of functional nanostructures, fabricated via focused electron-beam-induced deposition (FEBID), is known to depend crucially on its chemistry as FEBID tends to strong incorporation of carbon. Hence, it is essential to understand the underlying mechanisms which finally determine the elemental composition after fabrication. In this study we focus on these processes from a fundamental point of view by means of (1) varying electron emission on the deposit surface; and (2) changing replenishment mechanism, both driven by the growing deposit itself. First, we revisit previous results concerning chemical variations in nanopillars (with a quasi-1D footprint) depending on the process parameters. In a second step we expand the investigations to deposits with a 3D footprint which are more relevant in the context of applications. Then, we demonstrate how technical setups and directional gas fluxes influence final chemistries. Finally, we put the findings in a bigger context with respect to functionalities which demonstrates the crucial importance of carefully set up fabrication processes to achieve controllable, predictable and reproducible chemistries for FEBID deposits as a key element for industrially oriented applications.