高速原子力显微术研究进展

自1986年发明原子力显微镜以来,它已成为材料、生物以及纳米科技等许多领域的重要工具。由于常规原子力显微镜成像速度缓慢,在动态过程观测、工业生产线原位测量以及高密度信息存储等领域的应用受到限制,因此发展高速原子力显微术近年来已引起国内外的高度关注。本文综述了高速原子力显微术关键技术(包括:微小探针、高速扫描器设计和控制方法)以及应用等方面的最近进展。     

On simulation of resist profiles in electron beam lithography

Resist profiles in electron beam exposed PMMA have been simulated before and after proximity exposure compensation (correction) for isolated and closely spaced line patterns. Edge slope of the resist profiles obtained in the two cases (before and after proximity exposure compensation) indicate the effectiveness of the compensation technique. Along with the edge slopes the line width variations are also determined.     

Thermal detection of device failure by atomic force microscopy

Device and interconnect electrical failures often occur in the form of short or open circuits which produce hot or cold spots under voltage bias. With the minimum device feature size shrinking to 0.25 μm and less, it is impossible to locate the exact position of defects by traditional thermal or optical techniques such as infra-red emission thermometry, liquid crystals or optical beam induced current. We have used a temperature-sensing probe in an atomic force microscope to locate a hot spot created by a short-circuit defect between the gate and the drain of a Si MOSFET with a spatial resolution of about 0.5 μm. The technique has the potential to produce spatial resolutions in the range of 0.05 μm and efforts are underway to reach this goal     

POLYMETHYLMETHACRYLATE LANGMUIR-BLODGETT FILMS FOR HIGH RESOLUTION ELECTRON BEAM RESIST

Ultra-thin (20-100nm) polymethylmethacrylate(PMMA) films prepared by Langmuir-Blodgett techniques have been explored as high resolution electron beam resists. A Hitachi S-450 Scanning Electron Microscope (SEM) has been refitted for a high resolution electron beam exposure system. The lithographic properties and exposure conditions of LB PMMA films were investigated. 0.15μm lines-and-spaces patterns were achieved by using the SEM as the exposure tool. The results demonstrate that the etch resistance of such films is sufficiently good to allow patterning of a 20 nm aluminum film suitable for mask fabrication.     

Local oxidation of titanium films by non-contact atomic force microscopy

Characteristics of local nanolithography on oxidative titanium dots and wires were studied using an amplitude modulation atomic force microscopy in the non-contact mode. Nanolithographic experiments were conducted to investigate the influence that different experimental parameters had on the height, the width, the growth rate, the morphology, and the composition of the nanostructures using Auger electron spectroscopy. The results indicate that anodization time, applied voltage, and tip-sample distance are proportional to the heights and widths of the dots. When the tip-sample distance was too close during continued anodization, concave dots appeared because the oxide that enclosed the tip. Carbon nanotube probe fabricated dots are also presented and compared.     

原子力显微镜激光光路调整方法

ＣＳＰＭ 930ｂ型多功能扫描探针显微镜经常需要进行手动激光光路调整。该仪器使用说明书[1] 介绍的调整方法可操作性差、手续繁琐、过程冗长 ,且难以判断激光束是否准确照射到微悬臂针尖背面的镀金层上 ,往往造成误判而导致微悬臂针尖被撞断裂。而且 ,按照原有方法操作者需要长时间全神贯注观察激光斑 ,使用者眼睛极易疲劳甚至造成损伤。笔者使用该仪器过程中 ,对光路调整方法进行了大量试验 ,摸索出了一套操作方便 ,容易准确判断针尖位置的有效方法。现总结交流如下。调整方法ＣＳＰＭ 930ｂ扫描探针显微镜ＡＦＭ部分激光光路如图 1所示。…     

Control of interaction force in constant-height contact mode atomic force microscopy

Contact mode is a versatile and widely used technique for imaging samples using the Atomic Force Microscope (AFM). When contact mode imaging is performed in constant-height mode, it enables linear and faster response but leads to uncontrolled tip-sample forces. Here, a control strategy based on magnetic actuation is proposed to achieve high-bandwidth control of the tip-sample forces in constant-height contact mode AFM. A magnetic particle attached to the AFM probe is actuated by an external solenoid and employed for force regulation. A quasi-static model has been proposed and employed to develop the control strategy. Likewise, the contact natural-frequency, which decides the limit of achievable speed, has been shown to be significantly higher relative to the free probe and to be relatively insensitive to the particle size. Subsequently, a setup is developed to validate the control strategy and demonstrate reduction of tip-sample force variation by over a factor of 12 compared to conventional constant-height mode operation. Likewise, in comparison with conventional contact mode AFM, an improvement of linearity by over a factor of 9 and improvement in response speed by a factor of 100 have been demonstrated while imaging hard samples. The system has been shown to image topography at speeds of 2.44 frames per second while regulating the interaction force. Finally, the stiffness of a sample has also been characterized using the developed system and simultaneous estimation of topography has also been demonstrated. They are shown to agree well with theoretical expectations.     

碳纳米管原子力显微镜针尖的研究

本文研究了制作碳纳米管原子力显微镜针尖的方法和过程。在光学显微镜下，通过两个微工作台操纵将纯化后的多壁碳纳米管粘结在传统的原子力显微镜的Si针尖上。运用电蚀的方法优化碳管针尖的长度使其达到高分辨率的要求。我们运用制作的碳纳米管针尖在敲击模式下时G型免疫球蛋白进行扫描成像，结果显示了其典型的Y形结构，这是传统AFM的Si针尖无法获得的。     

Observations of xenon gas-treated barley cells in solution by atomic force microscopy

Barley cells cut from a sprout were exposed to either air or high-pressure xenon gas for 3 days and the surface of those cells was observed by atomic force microscopy (AFM) to examine the effect of the gas treatment. This method enabled the direct observation of the fresh surface of the barley cells in solution at high resolution. The cuticle layer was preserved on the primary cell wall of 0.48 MPa xenon gas-treated barley cells, while air-treated barley cells lost the cuticle layer from the primary cell wall. These findings indicate that the high-pressure xenon gas treatment is effective to preserve the cuticle layer attached to the primary cell wall. AFM is a powerful tool for the observation of the surface structure of living plant cells in solution.     

纳米颗粒填充的PTFE微结构的原子力显微镜测量

本文报道了用原子力显微镜(AFM)研究多种纳米微粒填充的聚四氟乙烯(PTFE)材料的结构组成，观察了在纳米颗粒填充的PTFE中，纳米微粒的分散不均匀性以及纳米粉末在与PTFE混合、压制后发生的团聚现象。     

利用原子力显微镜鉴别相变诱发塑性钢的显微组织

相变诱发塑性（TRIP）钢比双相钢具有更高强度和塑性，因此TRIP钢在汽车工业中的应用对于汽车轻量化有重要的经济意义。TRIP钢的高强度和高延展性主要来源于钢中复杂的显微组织以及应变条件下亚稳态的残余奥氏体（A1）向马氏全（M）的转变，即相变诱发塑性。钢中各相组织的正确鉴别显得尤为重要，特别是钢中残余奥氏体的含量、分布及其稳定性直接关系到TRIP钢性能的好坏。根据目前使用的常规鉴别方法、     

原子力显微镜对不同条件下果胶微粒的表面形态学观察

果胶是由D-半乳糖醛酸残基经α(1→4)键相连接聚合而成的酸性大分子多糖，并且半乳糖醛酸C6上的羧基有许多是甲酯化形式，根据酯化度DE值可将果胶分为高甲酯果胶(DE值高于50％)和低甲酯果胶(DE值低于50％)。果胶在食品工业中的作用主要表现在增稠、胶凝和稳定。     

海藻酸薄膜表面超微结构的原子力显微镜研究

本文采用原子力显微镜（ＡＦＭ）对海藻酸生物薄膜表面的超微结构进行了实验研究,选择出最佳观察方法。结果发现薄膜上分布不规则的微孔,其长短孔径之比大约为３：２,微孔的中心距为孔径的２倍。     

乙酰胆碱酯酶分子的原子力显微成像

本文研究了用原子力显微技术对乙酰胆碱酯酶进行成像的方法。在新鲜裂解的云一表面镀一层金膜,金膜与疏基丙酸（ＭＰＡ）的疏基形成Ｓ－Ａｕ键。使ＭＰＡ的游离羧基再通过碳二亚胺反应与ＡＣｈＥ的碱性氨基酸的氨基形成肽键连接,ＡＣｈＥ因而被固定于支持物表面,这样固定的ＡＣｈＥ可获得清晰成像而不脱落。     

激光光路跟踪型原子力显微镜研究

提出和发展了一种激光光路跟踪型原子力显微镜(AFM)技术及系统。研制了新型AFM探头,设 计了与XY扫描器联动的跟踪透镜及扫描跟踪光路,实现激光束对微探针(微悬 臂)的XY扫描的实时跟踪;研 究设计了独特的反馈跟踪光路,既可实现微悬臂偏转量的精确检测,又可巧妙地消除因微探 针的Z向反馈运动 造成的干扰噪声。利用研发的AFM系统对多孔氧化铝纳米孔等具有不同横向与 纵向结构尺寸的微纳米样品进行了扫 描成像,得到了理想的实验结果,表明研发的系统具有优良的XY扫描跟踪特性 和Z向反馈跟踪性能。本文研发的 AFM系统原理新颖、方法巧妙、扫描成像性能好和分辨率高,克服了常规样品 扫描型AFM的局限性,能够以 微探针扫描的方式实现不同大小、不同重量的样品的AFM扫描成像,可望在微纳米技术领 域获得广泛应用。     

Metal lift-off using a trilevel resist system for electron beam lithography

Multilayer resist optical lithography is transposed into trilevel resist electron beam lithography. A thin electron-sensitive multilayer resist is exposed in a dedicated scanning transmission electron microscope. The upper resist layer is chemically developed, the underlying layers are patterned by reactive ion etching. Very fine titanium lines (1 μm to 30 nm) are obtained after evaporation and lift-off process.     

In-situ etching observation of human teeth in acid agent by atomic force microscopy

Atomic force microscopy was applied to the in-situ observation of the etching process of human teeth by acid agents. The change of surface morphology was observed consecutively before and during etching for the same area in the same specimen. The course of the etching process in enamel from dissolution of smear layer just after injection of acid agent, appearance of enamel prisms and progress of demineralization were quantitatively analysed for three fundamental acid agents of 2% phosphoric acid, 10% citric acid and 10% polyacrylic acid. Then the depth profile, etching amount, etching rate and thickness of smear layer were evaluated. Observation by scanning electron microscopy was also done and compared with the results by atomic force microscopy.     

基于原子力显微镜技术的单个生物大分子压弹性研究

单个生物大分子力学性质已经成为一个新兴的研究领域,近几年来由于单分子技术的不断发展,这个领域取得了很多突破性的进展。本文介绍了基于原子力显微镜技术的几种单分子压弹性测量技术及这些技术的具体应用,同时也简要阐述了这些技术的局限性。另外对这个领域的发展也进行了初步地探讨。