基于原子力显微镜的PMMA飞秒激光纳米加工

介绍了一种基于原子力显微镜（AFM）的激光近场增强纳米加工方法。探讨了作为主要影响因素的激光场增强效应，用时域有限差分法对AFM探针下光场的空间分布进行了数值分析。研究了飞秒激光入射到AFM探针的PMMA材料的图形化，在PMMA材料表面加工了不同宽度的线条和字母。利用AFM对所得纳米图形进行了原位测试。在激光参数未经优化的情况下，其线宽可达100nm，超过了实验室飞秒激光远场加工的分辨能力（200nm）。     

纳结构的连续激光复合微纳探针刻划加工

为了加工形貌稳定且尺寸尽可能小的纳结构,建立了一套连续激光复合微纳探针的加工系统,并研究了光纤探针导光的连续激光辐照微纳探针的近场增强效应以及该系统的加工性能。首先,根据表面等离子体激元理论仿真分析了激光辐照原子力显微镜(AFM)探针的近场增强因子,并研究了微纳探针的针尖温度场和针尖热膨胀。接着,搭建了基于光纤探针导光的连续激光复合微纳探针的纳结构加工系统。最后,对聚乙烯片状材料样品进行了纳结构加工。结果显示:加工得到的纳米点尺度为200nm左右;纳米线的尺度为30~40nm。结果表明:光纤探针导光连续激光复合微纳探针系统避免了复杂的空间光路结构,是一种成本低廉,结构简单的系统,能够实现纳结构的加工。     

采用AFM研究单晶硅纳米加工特性

为获得AFM金刚石微探针在纳米尺度上加工脆性材料的加工特性,在AFM系统上对单晶硅表面进行了刻划、加工实验.实验结果与宏观车削加工结果进行了对比,得出在纳米尺度上进行的加工属塑性域加工.采用AFM金刚石微探针加工硅表面的加工质量主要受材料残留高度和形成的切屑在已加工表面的粘结两个因素影响.验证了AFM作为一种加工工具,受其刻划方向的影响,可以很容易地实现纳米量级材料的去除,得到厚度为数个纳米的切屑.     

基于AFM纳米机械刻蚀的分子动力学模拟研究

基于原子力显微镜AFM(atomic force microscope)的纳米机械刻蚀加工是扫描探针刻蚀加工技术( scanning probe lithography, SPL)的一个重要组成,目前已取得较大进展.但由于纳米机械刻蚀涉及原子的结构与运动,其加工机理尚有待于进一步研究.分子动力学模拟技术是近年来发展的继实验和理论研究后的又一重要研究方法.文章综述采用分子动力学模拟技术,研究基于AFM的纳米机械刻蚀加工的进展, 分析纳米尺度的加工机理,评述探针、刻蚀工艺、工件材料等因素对纳米机械加工过程的影响.文章最后指出今后研究的方向.     

基于原子力显微镜的纳米加工研究

以原子力显微镜(AFM)作为加工工具对单晶硅进行了基于金刚石针尖的纳米加工试验,运用不同的方法对纳米加工区域的特性、材料在不同垂直载荷下的去除机理及切屑形成特征进行了系统的研究和分析,提出了一种在纳米尺度下研究加工机理的新方法。在此基础上,应用有限元法对AFM纳米加工中存在于金刚石针尖和被加工材料之间的接触作用机制进行了计算仿真。     

水凝胶支架的飞秒激光全息加工

为了实现以水凝胶为材料的细胞支架快速加工,将计算全息法引入传统的飞秒激光双光子加工中,并对全息图的生成方法和全息图对加工结构的影响进行了研究。首先,根据贝塞尔光波动方程和其透射函数生成贝塞尔光束全息图,分析两种参数对环形结构大小和质量的影响。然后利用生成的全息图加工得到壁厚800nm、直径为8~15μm不等的水凝胶(PEGDA)圆管结构。最后,实现了基于圆管道的水凝胶细胞支架高效快速加工,支架中圆管道壁厚800nm、直径为8μm。本文首次将飞秒激光全息加工技术应用于水凝胶三维支架加工,解决了飞秒激光单点加工效率的问题。该技术在生物医学中具有广阔的应用前景。     

基于 LSTM 的矩形纳米光栅 AFM 图像复原方法

原子力显微镜(AFM)利用探针与待测物之间的交互作用力进行成像,通过获取矩形纳米光栅计量标准器具的高分辨率成像得到相关的几何量参数并进行标定,实现从标准计量器具到工作计量器具的量值传递。在AFM扫描过程中,由于针尖的影响作用,使得扫描所获图像是探针和样品共同作用的结果,而不是样品形貌的真实描述。针对这一现象,本文提出了一种基于长短期记忆网络(LSTM)的AFM图像复原方法,该方法对通过膨胀法获得的仿真图像各扫描行进行训练,进而获得适用于矩形纳米光栅AFM图像复原模型。实验结果表明,针对线宽20 nm,高40 nm的矩形纳米光栅,经过该方法复原后光栅线宽的相对误差为7.40%,相较于传统的复原方法进一步提高了测量准确度。     

海外科技

飞秒激光切削加工技术将进入实用阶段日本财团法人激光技术综合研究所激光环境应用测量研究小组正在进行多项基于飞秒(千万亿分之一秒,10-15秒)激光的加工工艺基础研究,并充分利用研究成果、探讨具有纳米周期结构的挖槽切削加工技术的实用化事宜。目前已着手与多家制造商共同制     

飞秒激光加工及其应用

综述了激光短脉冲化的飞秒激光发展史,重点论述了飞秒激光的加工机理和特点.飞秒激光独特的光束特性决定了他是一种理想的微细加工工具,可以实现聚合物的制备,可以对各种透明材料内部进行三维加工和改性,另外在生物学领域也有着独特的应用.本文最后还展望了飞秒激光加工未来的发展方向.     

基于飞秒激光诱发前向转移技术的研究

在激光诱导的作用下实现微量物质的转移技术即为激光诱发前向转移技术。飞秒激光具有激光脉宽极短、峰值功率极高的特点,其在与材料作用过程中的特性不同于长脉冲激光。在利用传统长脉冲激光对材料进行加工时,材料是通过固相、液相和气相这3个热熔过程而逐层剥离的,从而导致热扩散十分严重,进而对加工质量产生了很大的影响。飞秒激光烧蚀材料时间非常短,基体内的热传导可以被忽略,这就从根源上避免了长脉冲激光加工过程中产生的冲击波、热影响区和熔融区等不利影响,从而在一定意义上使冷加工得以实现。针对飞秒激光的特点、飞秒激光加工机理和飞秒诱发向前转移技术的优点进行了研究,希望对飞秒激光诱发前向转移技术有一个全面的了解。     

Nanometer edge profile measurement of diamond cutting tools by atomic force microscope with optical alignment sensor

This paper describes an atomic force microscope (AFM) based instrument for nanometer edge profile measurements of diamond cutting tools. The instrument is combined with an AFM unit and an optical sensor for alignment of the AFM probe tip with the top of the diamond cutting tool edge in the submicrometer range. In the optical sensor, a laser beam from a laser diode is focused to generate a small beam spot with a diameter of approximately 10 μm at the beam waist, and then received by a photodiode. The tool edge top and the AFM probe tip are brought to the center of the beam waist, respectively, through monitoring the variation of the photodiode output. To reduce the influence of the electronic noise on the photodiode output so that the positioning resolution can be improved, a modulation technique is employed that modulates the photodiode output to an AC signal by driving the laser diode with a sinusoidal current. Alignment experiments and edge profile measurements are carried out.     

Application of evanescent wave optics to the determination of absolute distance in surface force measurements using the atomic force microscope

A combined scanning near field optical/atomic force microscope (AFM) is used to obtain surface force measurements between a near field sensing tip and a tapered optical fibre surface, whilst simultaneously detecting the intensity of the evanescent field emanating from the fibre. The tapered optical fibre acts as a compliant sample to demonstrate the possible use of the near field intensity measurement system in determining 'real' surface separations from normal AFM surface force measurements at sub-nanometer resolution between deformable surfaces.     

Optical microcantilever consisting of channel waveguide for scanning near-field optical microscopy controlled by atomic force

We develop a novel optical microcantilever for scanning near-field optical microscopy controlled by atomic force mode (SNOM/AFM). The optical microcantilever has the bent channel waveguide, the corner of which acts as aperture with a large tip angle. The resonance frequency of the optical microcantilever is 9 kHz, and the spring constant is estimated to be 0.59 N/m. The optical microcantilever can be operated in contact mode of SNOM/AFM and we obtain the optical resolution of about 200 nm, which is as same size as the diameter of aperture. We confirm that the throughput of optical microcantilever with an aperture of 170 nm diameter would be improved to be more than 10(-5).     

A compact CCD‐monitored atomic force microscope with optical vision and improved performances

A novel CCD‐monitored atomic force microscope (AFM) with optical vision and improved performances has been developed. Compact optical paths are specifically devised for both tip‐sample microscopic monitoring and cantilever's deflection detecting with minimized volume and optimal light‐amplifying ratio. The ingeniously designed AFM probe with such optical paths enables quick and safe tip‐sample approaching, convenient and effective tip‐sample positioning, and high quality image scanning. An image stitching method is also developed to build a wider‐range AFM image under monitoring. Experiments show that this AFM system can offer real‐time optical vision for tip‐sample monitoring with wide visual field and/or high lateral optical resolution by simply switching the objective; meanwhile, it has the elegant performances of nanometer resolution, high stability, and high scan speed. Furthermore, it is capable of conducting wider‐range image measurement while keeping nanometer resolution. Microsc. Res. Tech. 76:931–935, 2013. © 2013 Wiley Periodicals, Inc.     

Adhesion and Friction Studies of Nano-textured Surfaces Produced by Self-Assembling Au Nanoparticles on Silicon Wafers

This article presents the results of nanoscale friction and adhesion of nanoparticle-textured surfaces (NPTS) using atomic force microscope (AFM). The effects of coverage ratio, texture height, and packing density on the adhesion and friction of the NPTS were investigated. The nano-textured surfaces were produced by self-assembling Au nanoparticles (NPs) with diameters of 20 nm and 50 nm on the silicon (100) surfaces, respectively. Surface morphology of the NPTS was characterized by field emission scanning electron microscopy and AFM. The results show that the NPTS significantly reduced the adhesive force compared to the smooth surface. The adhesion of NPTS is mainly dependent on the coverage ratio of NPs rather than the texture height and higher coverage ratio resulted in smaller adhesive force. The reduced adhesion of textured surfaces was attributed to the reduced real area of contact. The friction of NPTS is mainly dependent on the spacing between asperities. The lowered frictional force was obtained when the spacing between asperities is less than the size of AFM tip, because of the effectively reduced real area of contact between the AFM tip and the NPTS surface.     

散射式太赫兹扫描近场光学显微技术研究

基于散射式近场探测原理,设计并搭建了散射式太赫兹扫描近场光学显微系统(THz s-SNOM),实现了纳米量级空间分辨率的太赫兹近场显微成像测量。该系统以输出频率范围为0.1~0.3THz的太赫兹倍频模块为发射源,通过纳米探针的针尖产生纳米光源与样品相互作用,并将样品表面的倏逝波转化为可在远场测量的辐射波。通过探针逐点扫描样品表面,同时获得了样品表面的形貌图和太赫兹近场显微图。该系统的显微分辨率取决于探针针尖的曲率半径,而与太赫兹波的波长无关。使用该系统测量了金薄膜/硅衬底样品和石墨烯样品的近场显微图,结果表明,近场显微的空间分辨率优于60nm,波长与空间分辨率之比高达λ/26000。     

Optical microcantilever consisting of channel waveguide for scanning near-field optical microscopy controlled by atomic force

We develop a novel optical microcantilever for scanning near-field optical microscopy controlled by atomic force mode (SNOM/AFM). The optical microcantilever has the bent channel waveguide, the corner of which acts as aperture with a large tip angle. The resonance frequency of the optical microcantilever is 9 kHz, and the spring constant is estimated to be 0.59 N/m. The optical microcantilever can be operated in contact mode of SNOM/AFM and we obtain the optical resolution of about 200 nm, which is as same size as the diameter of aperture. We confirm that the throughput of optical microcantilever with an aperture of 170 nm diameter would be improved to be more than 10⁻⁵.     

Resolution enhancing using cantilevered tip-on-aperture silicon probe in scanning near-field optical microscopy

Scanning near-field optical microscopy (SNOM) achieves a resolution beyond the diffraction limit of conventional optical microscopy systems by utilizing subwavelength aperture probe scanning. A problem associated with SNOM is that the light throughput decreases markedly as the aperture diameter decreases. Apertureless scanning near-field optical microscopes obtain a much better resolution by concentrating the light field near the tip apex. However, a far-field illumination by a focused laser beam generates a large background scattering signal. Both disadvantages are overcome using the tip-on-aperture (TOA) approach, as presented in previous works. In this study, a finite difference time domain analysis of the degree of electromagnetic field enhancement is performed to verify the efficiency of TOA probes. For plasmon enhancement, silver is deposited on commercially available cantilevered SNOM tips with 20nm thicknesses. To form the aperture and TOA in the probes, electron beam-induced deposition and focused ion beam machining were applied at the end of the sharpened tip. The results show that cantilevered TOA probes were highly efficient for improvements of the resolution of optical and topological measurement of nanostructures.     

High-resolution constant-height imaging with apertured silicon cantilever probes

We present high-resolution aperture probes based on non-contact silicon atomic force microscopy (AFM) cantilevers for simultaneous AFM and near-infrared scanning near-field optical microscopy (SNOM). For use in near-field optical microscopy, conventional AFM cantilevers are modified by covering their tip side with an opaque aluminium layer. To fabricate an aperture, this metal layer is opened at the end of the polyhedral probe using focused ion beams (FIB). Here we show that apertures of less than 50 nm can be obtained using this technique, which actually yield a resolution of about 50 nm, corresponding to λ/20 at the wavelength used. To exclude artefacts induced by distance control, we work in constant-height mode. Our attention is particularly focused on the distance dependence of resolution and to the influence of slight cantilever bending on the optical images when scanning at such low scan heights, where first small attractive forces exerted on the cantilever become detectable.