【作者】 张华丽；

【导师】 张飞虎；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 纳米技术是当代科学发展的一个新兴领域,它的最终目标就是在纳米尺度上制造出具有特定功能的产品。纳米技术的核心是纳米加工技术。纳米加工技术水平的提高将对微型机械、信息存储、微电子技术、生物科学等技术领域产生巨大的影响。扫描探针显微镜(包括扫描隧道显微镜(STM)和原子力显微镜(AFM))因其具有原子和纳米尺度的检测和加工能力,在纳米加工技术的发展中占有极其重要的地位。纳米加工机理是纳米加工技术研究的重要内容。目前基于SPM的纳米加工技术虽已能实现纳米级厚度的材料去除,得到具有纳米级加工精度的被加工表面,但是对纳米加工过程机理的研究还有许多亟待解决的问题。在纳米加工的尺度范围内,SPM针尖-样品相互作用区域存在的量子效应不能被忽略,继续使用宏观经典理论来描述加工过程中的微观机理已不再合适,必须依靠量子物理学等理论来研究加工过程中的相互作用,进而深入描述纳米加工过程中的微观物理机制。此外,对于切削过程中的材料变形和剥离机理、表面与亚表面材料性能以及切削刀具与工件之间的相互作用等方面还缺乏深入的了解。对于纳米加工最终可达到的精度和纳米切削机理,如切屑的去除机理和加工表面的形成机理等问题还有待深入研究。本文针对现有的纳米加工微观机理研究的不足,采用密度泛函理论的第一性原理计算研究纳米加工表面形成过程中的内部微观输运机制,进一步揭示纳米加工过程的本质和基本规律。在此基础上,利用扫描探针显微镜等纳米加工设备进行了纳米级加工实验。研究结果对纳米加工过程的微观机理做出新的解释,为现有的纳米加工技术方法提供理论解释,并为进一步探索新的纳米加工技术手段提供理论依据,具体研究内容包括如下几个方面:为了从原子尺度研究纳米加工过程的本质,在充分阐述纳米物理体系的基本特征和纳米尺度的表征手段的基础上,结合密度泛函理论的第一性原理计算,在纳米加工机理中考虑了量子效应的影响,从针尖、样品表面原子的微观形貌和电子云分布特征出发,对SPM扫描、加工过程中针尖-样品相互作用的微观机制进行了研究,揭示了SPM纳米加工过程的本质和基本规律,为今后的实验奠定了理论基础。为了研究纳米加工过程中针尖原子和样品表面原子间的相互作用,构建了适用于电场加工的STM纳米加工系统,在该系统上对金薄膜和单晶硅材料进行了纳米级结构的微细加工,研究了大气状态下STM纳米加工时探针与试件表面间的相互作用机理,分析了脉冲个数、电流反馈环的开关、隧道间隙等参数在SPM电场加工中的作用机制。为了研究纳米级材料去除过程,本文应用AFM和纳米压痕仪(Nanoindenter)进行了材料的纳米刻划实验,分析了材料从弹性变形到塑性变形的过程,得出了划痕产生的刻划临界载荷值以及最小极限切削厚度。在研究纳米划痕形成过程的基础上,重点探讨了加载速率、最大加载值对划痕形成、刻划临界载荷值的影响规律。为了进一步研究SPM纳米刻划过程,以典型的一维纳米材料-碳纳米管为研究对象,采用纳米压痕仪刻划模式对多壁碳纳米管的径向结构稳定性进行了实验研究。通过分析划入过程摩擦系数随施加载荷值的变化趋势,证明了多壁碳纳米管受机械刻划作用,从发生弹性变形、进而发生塑性变形,最终导致断裂的过程,给出了碳纳米管径向断裂的临界载荷值,为碳纳米管力学性能研究提供了一种实验研究的方法,拓宽了扫描探针显微技术在纳米技术研究中的应用范围。在系统地研究了基于SPM的纳米刻划过程的基础上,应用AFM金刚石针尖对金属材料进行了纳米级凹坑的加工试验,研究了纳米尺度加工中切屑形成的过程。通过SEM和AFM分析了被加工表面质量和切屑形态,较为系统地研究了垂直载荷、刻划速度、横向进给量、加工次数、针尖进给方向、材料的力学性能等因素对材料去除过程、切屑形成的影响,为在纳米尺度上实现稳定、可控的材料去除提供了实验依据。更多还原

【Abstract】 Nanotechnique is one of the novel fields among current techniques, which aims to manufacture products with specific functions in nanometer. Advances in nanomachining technique can lead to significantly improvements in research fields such as micromachine, information storage, microelectronic technique and biotechnique. Scanning probe microscope (including Scanning Tunneling Microscope (STM) and Atomic Force Microscope (AFM)) are becoming regarded as the manipulation technique in nanomachining technique due to its atomic and nanoscaled analytical and nanomachining efficient.Nanomachining mechanism is the key issue in nanomachining technique.Existing results of nanomachining studies based on SPM could fulfill both nanoscaled material removal and nanoscaled machining accuracy, however, there are still problems about the instinct principle of nanomachining mechanism. When the objects are scaled down to the nanometer scale, there are many significant changes in the physics and properties of nanomachining process. It’s inaccuracy using the continuum mechanics to describe the nanomachining mechanism ignoring the quantum effect of SPM probe-sample interaction. Quantum physics approach is advantageous to disclosure the nature of nanomachining mechanism. In addition, studyies on material deformation, surface-sbusurface properties and cutting tool-sample interaction of nanomachining process are scarce. To better understand the nanomachined surface accuracy and nanomechanism, more investigations on chip formation and nanomachined surface formation mechanisms are necessary. To solve these problems, density-functional theory is used to simulate the transport mechanism in nanoscale process with first-principle calculation, to disclosure the basic principle of nanomachining process. In addition, nanomachining experiments using scanning probe microscope have been carried out to study the nanomachining mechanism, give theoretical explanation of current namomachining tehnciques, and provide theoretical promotion of novel naomachining methods. The detailed contents of this thesis contain:First-principle calculation of density-functional theory was carried out to simulate SPM scanning process and probe-sample interaction during nanomachining process. The simulations took into account the quantum efforts and analyzed the probe-sample micro-pattern and distributions of their electron clouds. The results provide a basic principle of SPM nanomachining process, and theorticial foundation for future experimental studies.To study the interaction of probe-sample atomics during nanomachining process, STM nanofabrication system using electric-field method was established. And nanofabrication experiments were conducted on Au thin film and crystal silicon to study the STM probe-sample interaction mechanism in the state of atmosphere, to investigate the influences of impulse quantities, current feedback control, current distance on stability of nanofabricated microstructures.Nanoscratching experiments were performed using AFM and Nanoindenter to obtain minimum thickness of scratching data and to determine the critical loads at which scratching tracks initiated. The influences of loading rate and maximum normal load on scratching process and critical load were studied by analyzing the scratching process from elastic recovery to plastic deformation.To further stuy nanoscratching process, scratch resistance of carbon nanotube-typical one-dimension material, was studied using Nanoindenter scratching mode. The radial structure of carbon nanotube was proved to be scratched breakage. The revolution of friction coefficient as a function of normal load helped in identifying the deformation process of carbon nanotubes, from elastic recovery, plastic deformation and finally scratched breakage, and helped in determine the scratch critical load of carbon nanotube. This experimental study brings a new method to study carbon nanotube mechanical properties.Nanomachining experiments using AFM diamond probe were conducted furrowed surfaces to investigate the influences of normal loads, speed, lateral feed, multiple scratching, probe feed direction, sample mechanical properties on removal material, chip formation. The nanomachined surface roughness and chip behaivour were detected by SEM and AFM. The experiment results helped a better understanding to increase the reliability, stability and controllability of this nanomachining technique.更多还原