基于AFM氮化硅探针刻蚀方法制作聚碳酸酯纳米光栅

基于原子力显微镜(AFM)探针的纳米机械刻蚀技术以其成本低、分辨率高的优势被广泛应用于各种纳米元器件的制造中.为了得到最优的光栅结构,首先通过单次刻蚀实验定量分析了刻蚀方向、加载力和刻蚀速率等3个主要加工参数对所得纳米沟槽形貌和尺寸的影响,给出了普通氮化硅探针对聚碳酸酯(PC)的加工特性及加工效率.然后通过改变沟槽间距(100~500 nm)得到了不同周期的纳米光栅结构,并确定了这种探针与样品的组合对间距的要求及最佳加工参数:沿垂直于微悬臂长轴向右刻蚀,加载力2.3μN,刻蚀速率2.6μm/s.最后利用该技术对实验室已有原子光刻技术所得周期为213 nm的一维Cr原子光栅结构进行了复制加工,得到了均匀的213 nm一维光栅,证明这种基于AFM探针的纳米机械刻蚀技术可被广泛应用于纳米加工.     

Scanning probe microscope lithography at the micro- and nano-scales

Scanning probe microscopy (SPM)-based lithography at the micro- and nano-scales is presented. Our method in SPM local oxidation involves two SPM tips, one having a robust blunt tip, a "micrometer tip," and the other having a sharp tip, a "nanometer tip." In tapping-mode SPM local oxidation experiments, Si oxide wires with sub-10 nm resolution were produced by precisely tuning the dynamic properties of the nanometer tip such as drive amplitude and quality factor. On the other hand, in order to perform large-scale oxidation, SPM tip with a contact area of microm2, which is about 10(4) times larger than that of the conventional nanometer tip, was prepared. We propose and demonstrate a method of performing micrometer-scale SPM local oxidation using the micrometer tip under contact-mode operation. The width of the Si oxide produced was clearly determined by the contact length of the tip. Furthermore, we explore the possibility of performing the sub-20 nm lithography of Si surfaces using SPM scratching with a diamond-coated tip. The influence of various scan parameters on the groove size was investigated. The groove size could be precisely controlled by the applied force, scan direction, and the number of scan cycles. There is no effect of the scan speed on the groove size. It is concluded that high-speed nanolithography can be achieved without the degradation of patterns by SPM scratching. SPM-based lithography has the advantage of being able to fabricate a desired structure at an arbitrary position on a surface and plays an important role for bridging the gap between micro- and nano-scales.     

缓蚀剂对原子力显微镜探针刮擦铜镍合金加速溶解的作用

金属材料在缓蚀剂中受到刮擦会加速溶解,产生相应的腐蚀.采用原子力显微镜(AFM)探针刮伤技术研究了缓蚀剂对探针诱导铜镍合金加速溶解作用的影响.结果表明:在750 nN负载条件下,AFM探针在接触模式下对铜镍合金表面持续扫描,可以加速样品在1.5 mol/L NaCl溶液中的溶解,探针刮擦区域有蚀坑;作为缓蚀剂添加的有机化合物十二胺和无机盐铬酸钠能抑制探针刮擦引起的铜镍合金的加速溶解.     

Fabrication of nanostructure on a polymer film using atomic force microscope

SPM based lithographic techniques have been developed to pattern various substrates such as metals, semiconductors, and organic/polymer films due to its simplicity and high spatial precision nanostructure. Fabrication of nanostructure using polymeric materials is a key technique for the development of nanodevices. Here, we report the fabrication of nanostructures from polyacrylicacid (PAA) and polymethacrylicacid (PMAA) film on a silicon substrate using atomic force microscope (AFM). The formation of the nanopattern from the polymer film was studied using electrostatic nanolithography and the optimization of the conditions for nanopatterning of the polymer film was investigated with respect to the applied potential and translational speed of the AFM tip. The nanostructure of size 28 nm was created using the biased AFM tip on the PMAA film coated on Si(100) substrate and found that this method is a direct and reliable method to produce uniform nanostructures on a polymer film.     

Quantitative Evaluation of SERS-Active Ag Film Nanostructure by Atomic Force Microscopy

The reliability of an image analysis algorithm for atomic force microscopy (AFM) of thin metal films was evaluated by comparison with manual analysis of images and transmission electron micrographs of Ag films deposited on Formvar-coated Cu grids. In order to extract quantitative nanostructural information using the algorithm discussed herein, the optimal fitting parameters were found to be low-pass filtering to reject high-frequency noise, a 5 × 5 point grid for identification of particle maxima, and a linear least-squares fit to a hemispheroidal model of particle shape. Metal particle dimensions were defined from the height and radius of the hemispheroid fit. Due to the close spacing of particles in these Ag films, tip geometry causes the greatest error in the height measurements, rather than width measurements. In addition, the effect of scanning parameters such as scan rate and size, applied load, and humidity on particle count and dimensions was examined. Increasing the scan rate reduced the number of resolvable Ag particles, decreased the apparent particle height, and increased the apparent particle radius. Under conditions of low capillary force, a net repulsive force of ～19 nN resulted in subtle tip-induced changes in the Ag surface morphology. The Ag film surface was damaged at a net repulsive force of ～23 nN. At slow scan rates, the moisture layer did not significantly affect the quality of the AFM images obtained over a broad relative humidity range. Finally, the Ag surface structure was found to be very homogeneous over a relatively large area.     

基于AFM的纳米级表面加工中切屑形成的影响因素

以原子力显微镜（AFM）为加工工具进行了纳米级加工实验,对不同加工条件下的材料去除过程和切屑形态进行了研究．切屑形态通过扫描电子显微镜（SEM）进行观察,分析了不同垂直载荷、循环次数和针尖加工方向下铝铜被加工表面的切屑形成过程．实验结果表明：低栽下切屑呈细小断屑,散布在加工区域周围;随着垂直载荷的增加,切屑逐渐变成连续的带状切屑．不同循环次数、针尖加工面时切屑形成都有很大影响．在此基础上,对比分析了相同实验条件下,不同力学性能材料的切屑形成过程．最后,通过检测被加工表面得出被加工表面质量与切屑的数量和形态之间的关系,提出了改善被加工表面质量的方法,以帮助人们更好地理解基于AFM的纳米级加工技术．     

Investigation of sisal fibers by atomic force microscopy: morphological and adhesive characteristics

Atomic force microscopy (AFM) was used to study the nanoscale surface chemistry and morphological changes caused by chemical treatment of sisal fibers. Scanning Electron Microscopy (SEM) micrographs indicated that sisal in natura (bundle of fibers) is formed by fibers with diameters of approximately 10 microm. AFM images showed that these fibers consist of microfibrils with diameters varying from 250 to 600 nm, which are made up of nanofibrils of ca. 20 nm in diameter. The adhesion force (pull-off force) between the AFM tip and the fibers surface increased after benzylation, pointing to a decrease in the polar groups on the sisal fiber. The adhesion map measured over a scan range of 3 microm was heterogeneous in samples treated with 40% NaOH and the low adhesion sites disappeared after benzylation. Using an established mathematical model, it was possible to evaluate the increase in adhesion work and consequently in the interaction between the AFM tip and sisal fibers. These results indicated that AFM can detect heterogeneity in the wettability of sisal fibers with nanometer resolution and can be applied in the study of fiber-matrix adhesion in polymer composites.     

Surface patterning for brittle amorphous material using nanoindenter-based mechanochemical nanofabrication

This paper demonstrates a micro/nanoscale surface patterning technology for brittle material using mechanical and chemical processes. Fused silica was scratched with a Berkovich tip under various normal loads from several mN to several tens of mN with various tip rotations. The scratched substrate was then chemically etched in hydrofluoric solution to evaluate the chemical properties of the different deformed layers produced under various mechanical scratching conditions. Our results showed that either protruding or depressed patterns could be generated on the scratched surface after chemical etching by controlling the tip rotation, the normal load and the etching condition. In addition, the mask effect of amorphous material after mechanical scratching was controlled by conventional mechanical machining conditions such as contact area, chip formation, plastic flow and material removal.     

Micro/nano surface modification on brittle materials by tribo nanolithography using PCD tool

In this study, brittle materials were mechanically modified under precise normal force control at the mN approximately microN level using PCD tools as a nano tool. The lab-made PCD attached micro cantilevers were customized for tribo nanolithography. The machined patterns were measured under an atomic force microscope (AFM) to obtain the machining characteristics of the samples for each set of conditions. Then the samples were etched using aqueous solution to verify the etch characteristics of the machined surface. Our results showed that either protruding or depressed patterns could be generated on the scratched surface by controlling normal load, scan pitch, and etching condition. The unique mask effect of brittle material after mechanical scratching under PCD tool can be controlled by the conventional mechanical machining conditions such as chip formation, plastic flow, and material removal. We used SEM, TEM, SIMS, and AFM to investigate the etch characteristics and structural change of brittle material under nano scale mechanical machining conditions.     

Influence of sodium chromate and dodecylamine on enhanced dissolution behavior of Cu—Ni alloy induced by AFM tip scratching

The influence of two inhibitors sodium chromate and dodecylamine on enhanced dissolution of Cu–Ni alloy initiated by atomic force microscopy (AFM) tip scratching in 1.5 M NaCl and 0.01 M HCl was investigated. The lateral force traces and force versus distance curves were measured by AFM in distilled water without or with inhibitors to investigate the influence of inhibitors on physical characters of sample surfaces. The results indicated that enhanced dissolution caused by AFM tip scratching was inhibited by adding sodium chromate or dodecylamine into the corrosive solutions, but their inhibition mechanisms are different. The inhibition effect of sodium chromate is due to its oxidation ability to repair the destroyed protection film and the increase of rigidity of metal surface resulted from the formation of oxide film containing Cr elements. On the other hand, the inhibition effect of dodecylamine is due to the organic adsorption film on metal surface to weaken the friction forces between the tip and the sample and to elevate the ionization energy of metal.     

Feature size dependence on hysteresis due to relative humidity ramping and patterning order in dip-pen nanolithography

The water meniscus that forms between an atomic force microscope (AFM) tip and the substrate has been shown to have variable height and width due to relative humidity (RH) hysteresis. The current study investigates the effect of this variability in meniscus shape due to RH on the feature size of patterns written with mercaptohexadecanoic acid on a gold substrate, using dip-pen nanolithography (DPN). The patterns were written under conditions of increasing and decreasing RH cycles with different tip dwell times. The variation in resulting dot sizes during the RH ramping (up and down) cycles was then measured. DPN patterning was also performed with increasing and decreasing order of dwell times at constant RH, in order to quantify whether the order of patterning has an effect on feature size. Significant differences were observed in dot areas patterned over many RH ramping cycles; whereas the order of patterning was observed to have an effect only for dwell times ≤5?s.     

High-rate tunable ultrasonic force regulated nanomachining lithography with an atomic force microscope

This paper describes a high-rate tunable nanomachining-based nanolithography technique using an atomic force microscope (AFM). Controlled vibration between the cantilever tip and the sample is introduced to increase the lithographical speed and controllability of the nanomachining process. In this approach, an ultrasonic z?vibration of the sample and the resulting ultrasonic force from the nonlinear force-distance interaction between the sample and the cantilever tip are utilized to regulate fabrication depth. A high frequency in-plane circular vibration is introduced between the tip and the sample to control the width of the fabricated features, and to improve the speed of nanolithography. Features (e.g.?slots) with dimensions spanning from tens of nanometers to hundreds of nanometers are fabricated in one scan. A lithography speed of tens of microns per second can be achieved, which is significantly higher than other known mechanical-modification-based nanolithography methods. The patterns, that are machined on a thin PMMA film, are transferred to silicon substrate through a reactive ion etching process, which provides a cost-effective tunable approach for the fabrication of nanostructures.     

Observation of Si pattern sidewall using inclination atomic force microscope for evaluation of line edge roughness

Inclination atomic force microscope (AFM) imaging has been studied on the possibility to observe a pattern sidewall in contact mode or digital probing (step-in) mode for a line edge roughness (LER) or line width roughness (LWR). Analysis of the AFM tip bending and slipping indicates that it is serious problem to measure and control very fine patterns within an error of less than 1 nm in contact of the tip on the steep slop of the pattern, and it is very important directly to observe the sidewall at inclination angle. In experiments using pyramidal tip and steep Si pattern with about 90 degrees slop, it has demonstrated that the inclination angle is 35-40 degrees for faithful observation of the sidewall. We have observed the etched strip lines on the sidewall with a width of about 100 nm and a depth of about 6.4 nm. We have demonstrated that the inclination AFM is very useful for evaluation of the LER or LWR.     

Robust optimization of the output voltage of nanogenerators by statistical design of experiments

Nanogenerators were first demonstrated by deflecting aligned ZnO nanowires using a conductive atomic force microscopy (AFM) tip. The output of a nanogenerator is affected by three parameters: tip normal force, tip scanning speed, and tip abrasion. In this work, systematic experimental studies have been carried out to examine the combined effects of these three parameters on the output, using statistical design of experiments. A statistical model has been built to analyze the data and predict the optimal parameter settings. For an AFM tip of cone angle 70° coated with Pt, and ZnO nanowires with a diameter of 50 nm and lengths of 600 nm to 1 μm, the optimized parameters for the nanogenerator were found to be a normal force of 137 nN and scanning speed of 40 μm/s, rather than the conventional settings of 120 nN for the normal force and 30 μm/s for the scanning speed. A nanogenerator with the optimized settings has three times the average output voltage of one with the conventional settings.     

Techniques for imaging human metaphase chromosomes in liquid conditions by atomic force microscopy

The purpose of this study was to obtain three-dimensional images of wet chromosomes by atomic force microscopy (AFM) in liquid conditions. Human metaphase chromosomes-obtained either by chromosome spreads or by an isolation technique-were observed in a dynamic mode by AFM in a buffer solution. Under suitable operating conditions with a soft triangular cantilever (with the spring constant of 0.08-0.4?N?m(-1)), clear images of fixed chromosomes in the chromosome spread were obtained by AFM. For imaging isolated chromosomes with the height of more than 400?nm, a cantilever with a high aspect ratio probing tip was required. The combination of a Q-control system and the sampling intelligent scan (SIS) system in dynamic force mode AFM was useful for obtaining high-quality images of the isolated chromosomes, in which globular or cord-like structures about 50?nm thick were clearly observed on the surface of each chromatid.     

Mono- and multilayer formation by diazonium reduction on carbon surfaces monitored with atomic force microscopy "scratching"

Contact mode atomic force microscopy (AFM) was used to intentionally scratch a monolayer deposited on a pyrolyzed photoresist film (PPF). The force was set to completely remove the monolayer but not to damage the underlying PPF surface. A line profile determined across the scratch with tapping mode AFM permitted determination of the monolayer thickness from the depth of the scratch. A statistical process was devised to avoid user bias in determining the monolayer thickness and was used to determine the thickness as a function of derivatization parameters. PPF surfaces modified by reduction of diazonium ions of stilbene, biphenyl, nitrobiphenyl, terphenyl, and nitroazobenzene (NAB) were scratched and their modification layer thicknesses determined. For single-scan derivatizations of 1 mM diazonium ions to -0.6 V versus Ag+/Ag, the biphenyl and stilbene monolayers exhibited thicknesses close to those expected for true monolayers. However, more extensive derivatization resulted in multilayers up to 6.3 nm thick for the case of NAB. Such multilayers imply that electrons are transmitted through the growing film during diazonium reduction, despite the fact that electron tunneling would not be expected to be operative over such long distances. The results are consistent with a conductance increase in the growing film, which yields a partially conductive layer that can support further diazonium ion reduction and additional layer growth.     

立方碳化硅CMP过程中机械作用分子动力学仿真

为了更好地理解立方碳化硅在化学机械抛光(CMP)过程中原子层面的材料去除机理,利用分子动力学(MD)方法建立了金刚石磨粒刻划碳化硅的原子模型,仿真研究了金刚石磨粒半径、刻划深度和刻划速度对碳化硅表面形貌、晶体结构、摩擦力和原子去除率的影响规律,并与无定型二氧化硅氧化膜的机械刻划作用的仿真结果进行了对比分析.结果发现:碳化硅在机械刻划过程中局部会出现非晶态变化;刻划深度增大会导致切削力和切削温度增大,原子去除率也随之增加;刻划速度的改变会影响温度和原子去除率,而对切削力几乎无影响;磨粒半径的增加会导致切削力和温度的增加,在压入深度相同的情况下对原子去除率影响不大;碳化硅表面生成的二氧化硅膜能大幅度降低切削力,但由于其结构的影响,机械刻划作用仅使氧化膜产生明显的致密化,而不产生磨屑.     

10 micrometer-scale SPM local oxidation lithography

10 micrometer-scale scanning probe microscopy (SPM) local oxidation lithography was performed on Si. In order to realize large-scale oxidation, an SPM tip with a contact length of 15 microm was prepared by focused-ion-beam (FIB) etching. The oxidation was carried out in contact mode operation with the contact force ranging from 0.1 to 2.1 microN. The applied bias voltage was 50 V, and scanning speed was varied from 10 to 200 microm/s. The scan length was 15 microm for one cycle. The influence of contact force on the large-scale oxidation was investigated. At high contact force, the Si oxide with good size uniformity was obtained even with high scanning speed. The SPM tip with larger contact length may increase the spatial dimensions of the water meniscus between the SPM tip and sample surface, resulting in the larger dimensions of the fabricated oxide. Furthermore, the throughput of large-scale oxidation reached about 10(3) microm2/s by controlling the scanning speed and contact force of the SPM tip. It is suggested that SPM local oxidation can be upscaled by using a SPM tip with large contact length.     

PDDA／Au NPs复合分子沉积膜的制备、表征和摩擦学行为

采用小分子柠檬酸钠对金纳米粒子进行包覆改性,紫外光谱分析经改性的金纳米粒子表面共振吸收峰为526iun,激光纳米粒度仪分析表明其平均粒径为8．4nm．改性后的金纳米粒子通过分子沉积技术,与聚二烯丙基二甲基胺盐酸盐（PDDA）组装,制得单层和多层PDDA／Au NPs复合纳米粒子分子沉积（MD）膜（简称PDDA／Au NPs复合MD膜）．采用原子力显微镜（AFM）研究了PDDA／Au NPs复合MD膜的表面形貌以及摩擦、磨损行为．研究结果表明：该复合膜能降低基底的摩擦力,其中以3层膜降低摩擦力的效果最显著．在氮化硅探针扫描行程达到30次后,膜表面才开始出现磨损痕迹．随着扫描次数的增多,膜表面在探针剪切力的作用下逐渐由致密变得疏松,形成颗粒堆积,使表面粗糙度增大,摩擦力、磨损深度也随之增加．通过实验还发现这种复合膜存在两种非正常磨损现象,即磨损负增长和膜的脱落现象.     

用SPM纳米刻蚀方法在Ti表面制备纳米结构的研究

本文用导电原子力显微镜 (AFM)针尖诱导局域氧化反应的方法 ,在Ti膜表面制备了TiO2 纳米结构。实验结果表明 ,Ti膜的氧化阈值为 - 7伏 ,制备的TiO2 纳米线的最小线宽达到 10nm ,TiO2 纳米线的高度和宽度随针尖偏压的增大而增大。在优化的氧化刻蚀条件下 ,通过控制针尖偏压和扫描方式制备出了图形化的TiO2 结构 ,本研究表明基于导电AFM的纳米刻蚀技术将成为构筑纳米电子器件的重要工具