Nanofabrication of grid-patterned substrate by holographic lithography

The two-dimensional grid patterns on Si(001) in nanometer scale have been fabricated by holographic lithography and reactive ion etching, which can be used as a substrate for positioning Ge islands during self-assembled epitaxy to obtain an ordered Ge quantum dots matrix. By changing the configuration of the holographic lithography and the etching rate and time, we can control the grid period, the shape of the pattern cell, and the orientation of those shapes, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.

微纳光学结构及应用

简短回顾微纳光学的几个重要研究方向,包括光子晶体、表面等离子体光学、奇异材料、负折射、隐身以及亚波长光栅等。微纳光学不仅成为当前科学的热点研究领域,更重要的是,微纳光学是新型光电子产业的发展方向,在光通信、光存储、激光核聚变工程、激光武器、太阳能利用、半导体激光、光学防伪技术等诸多领域,起到了不可替代的作用。

Three-dimensional micro- and nano-fabrication in transparent materials by femtosecond laser

Femtosecond pulsed lasers have been widely used for materials microprocessing. Due to their ultrashort pulse width and ultrahigh light intensity, the process is generally characterized by the nonthermal diffusion process. We observed various induced microstructures such as refractive-index-changed structures, color center defects, microvoids and microcracks in transparent materials (e.g., glasses after the femtosecond laser irradiation), and discussed the possible applications of the microstructures in the fabrication of various micro optical devices [e.g., optical waveguides, microgratings, microlenses, fiber attenuators, and three-dimensional (3D) optical memory]. In this paper, we review our recent research developments on single femtosecond-laser-induced nanostructures. We introduce the space-selective valence state manipulation of active ions, precipitation and control of metal nanoparticles and light polarization-dependent permanent nanostructures, and discuss the mechanisms and possible applications of the observed phenomena.

Structure, magnetization, and low-temperature spin dynamic behavior of zincblende Mn-rich Mn(Ga)As nanoclusters embedded in GaAs

We have fabricated a set of samples of zincblende Mn-rich Mn(Ga)As clusters embedded in GaAs matrices by annealing (Ga,Mn)As films with different nominal Mn content at 650 degrees C. For the samples with Mn content no more than 4.5%, the Curie temperature reaches nearly 360 K. However, when Mn content is higher than 5.4%, the samples exhibit a spin-glass-like behavior. We suggest that these different magnetic properties are caused by the competing result of dipolar and Ruderman-Kittel-Kasuya-Yosida interaction among clusters. The low-temperature spin dynamic behavior, especially the relaxation effect, shows the extreme creeping effect which is reflected by the time constant tau of similar to 10(11) s at 10 K. We explain this phenomenon by the hierarchical model based on the mean-field approach. We also explain the memory effect by the relationship between the correlation function and the susceptibility.

Applications of scanning probe microscopy in intrinsically conducting polymer research

The applications of scanning probe microscopy (SPM) in intrinsically conducting polymer research is briefly reviewed, including morphology observation, nanofabrication, microcosmic electrical property measurements, electrochemistry researches, in-situ measurements of film thickness change, and so on. At the same time, some important variations of SPM and the related techniques are briefly introduced. Finally, the future development of SPM in the study of intrinsically conducting polymers is prospected.

Direct patterning of rhodamine 6G molecules on mica by dip-pen nanolithography

Dip-pen nanolithography (DPN) has been developed to pattern monolayer film of various molecules on suitable substrate through the controlled movement of ink-coated atomic force microscopy (AFM) tip, which makes DPN a potentially powerful tool for making the functional nanoscale devices. In this paper, the direct patterning of rhodamine 6G on mica by dip-pen nanolithography was demonstrated. R6G features patterned on the mica was successfully achieved with different tip movement which can be programmed by Nanoscript(TM) language. From the AFM image of R6G patterns, we know that R6G molecule is flatly binding to the mica surface through electrostatic interaction, thus stable R6G nanostructures could be formed on mica. The influence of translation speed and contact time on DPN was discussed. The method can be extended to direct patterning of many other organic molecules, and should open many opportunities for miniaturized optical device and site-specific biological staining.

Direct patterning of negative nanostructures on self-assembled monolayers of 16-mercaptohexadecanoic acid on Au(111) substrate via dip-pen nanolithography

Both bare and self-assembled monolayer (SAM) protected gold substrate could be etched by allyl bromide according to atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometric (ICPMS) analysis results. With this allyl bromide ink material, negative nanopatterns could be fabricated directly by dip-pen nanolithography (DPN) on SAMs of 16-mercaptohexadecanoic acid (MHA) on Au(111) substrate. A tip-promoted etching mechanism was proposed where the gold-reactive ink could penetrate the MHA resist film through tip-induced defects resulting in local corrosive removal of the gold substrate. The fabrication mechanism was also confirmed by electrochemical characterization, energy dispersive spectroscopy (EDS) analysis and fabrication of positive nanopatterns via a used DPN tip.

基于机械力与电场的AFM纳米操作/加工研究

纳米技术是在纳米尺度上研究物质的特性和相互作用，以及利用这些特性的多学科交叉的新兴科学技术。纳米加工技术是对纳米技术的重要应用，它使人类在纳米尺度上进行结构和器件的制造成为可能。基于原子力显微镜(AFM)的纳米加工是近20年来发展的技术，由于AFM具有许多新颖的技术特点(如高分辨率，可操控等)，因而基于AFM的纳米加工技术成为纳米科学研究的新热点。 本论文以纳米制造为背景，围绕基于AFM的纳米加工技术所涉及的科学问题，重点开展了基于机械力的AFM纳米操作和基于电场的AFM纳米加工的理论方法和实现技术研究。在这些研究的基础上，开展了基于纳观机械力的刻划、纳米颗粒的排列、碳纳米管的装配实验研究，开展了基于微观电场的氧化点、氧化线、氧化文字的加工实验研究，以及微观电场氧化切割、焊接加工方法的研究。 本文的主要内容包括：交互式纳米操作系统的构建，基于机械力的AFM纳米操作研究，基于电场的AFM纳米加工研究，基于机械力与电场的AFM纳米操作/加工实验研究。具体如下： 在商用AFM的基础上，研究并搭建了具有力觉与视觉反馈的交互式纳米操作系统。通过该系统操作者可以实时感觉到操作中作用在AFM针尖的纳观力并控制针尖的运动，还可以实时观察到模拟出的针尖操作过程，因而显著提高了纳米操作的直观性、可靠性及效率。 在基于机械力的AFM纳米操作研究方面，为了理解纳观环境下普遍存在的黏附力特性，对AFM的力曲线进行了分析并给出了详细解释；通过研究探针悬臂的形变，提出了探针所受三维作用力的建模方法，以此模型获得了操作中的纳观力信息；基于多刚体动力学理论提出了碳纳米管的二连杆动力学建模方法，并对碳纳米管在操作中的弯曲特性进行了仿真分析。这些研究为基于机械力的AFM纳米操作提供了理论指导。 在基于电场的AFM纳米加工方面，研究了微观电场在样本表面的分布，建立了电场氧化加工中电场分布模型，以此模型分析了氧化物特性与电场分布的关系；对氧化加工中氧化物生长过程进行了动力学分析，得到了氧化物生长的理论模型；系统地研究了氧化加工中各因素(偏压，加工速度，针尖－样本距离等)对氧化结构生成的影响，总结了氧化物的生成与各因素的关系，验证了理论分析的结果，提高了电场氧化加工的重复性及可控性。这些研究为基于电场的AFM纳米加工提供了理论及实验依据。 在基于机械力与电场的AFM纳米操作/加工理论研究的基础上，进行了相关的实验研究。通过基于机械力的AFM纳米操作方法实现了在样本表面刻划文字，纳米颗粒的排列，碳纳米管的操作及装配；通过基于电场的AFM纳米加工方法实现了在样本表面加工氧化点，氧化线及氧化文字等纳米结构。利用电场氧化加工方法还实现了对碳纳米管的定点切割与焊接，拓展了AFM纳米加工的应用领域。这些实验研究验证了系统的操作及装配性能，证明了电场加工的有效性及具有潜在的应用前景。 本文的研究工作为制造纳米结构、纳米器件提供了一条可行的技术途径，对AFM纳米加工技术的进一步发展具有一定的理论参考及实践指导意义。