基于AFM力曲线的纳米梁厚度的非破坏测量方法

本文阐述了基于原子力显微镜(AFM)的弯曲测试测量纳米梁厚度的理论和方法,并界定了基于AFM的厚度测量方法的适用条件,对基于AFM的厚度测量的两个典型应用进行了介绍.对硅纳米梁进行了厚度测量,并进行了重复性实验,梁的平均测量度为160.36nm.     

一种适用于原位纳米力学测试的AFM测头

设计并制作了一种适用于原位纳米力学测试的原子力显微镜(AFM)测头.测头由光学检测系统和Z向压电陶瓷微位移机构组成.其中光学检测系统采用光杠杆与显微镜同轴光路检测探针形变,压电位移机构内置电容传感器可实现探针进给量的闭环控制.标定实验表明该测头闭环位移分辨力优于10 nm,在标定范围内具有很好的线性.利用该测头对某型微悬臂梁法向弹性常数进行了测量,测得值与采用具有溯源性的标定方法所得结果一致.     

AFM扫描图像重构算法的改进

针对原子力显微镜（AFM）纳米成像中存在的失真问题,研究了通过探针建模实现AFM扫描图像重构方法.目前探针盲建模算法在重构AFM图像时存在较大误差,因此提出基于探针模型预估计的AFM扫描图像重构方法.该方法采用分区探针针尖建模,并通过基于该探针模型的反卷积运算实现AFM扫描图像重构,获得比较接近真实形貌的AFM扫描图像.文中介绍了算法的具体步骤,通过仿真和实验结果证明,该方法能够有效降低AFM图像重构时引入的误差,得到的图像更能反映样品表面真实的形貌.     

硅纳米板杨氏模量的尺度效应

硅微机械加工的梁、桥和板是微纳器件的基本结构;杨氏模量是描述力学性能的基本参数．用半连续方法计算了不同厚度的（001）硅纳米板沿[100]方向和[110]方向的应变能,并由此得到了两个方向上的杨氏模量．结果表明,沿[100]和[110]方向的硅纳米板杨氏模量均随着板厚度的减小而减小,并且减小的趋势随着板厚度的减小越来越明显,当板厚度逐渐增加超过50nm时,两个方向上的杨氏模量均趋于定值,且都接近体硅的值．     

基于AFM硅表面局域阳极氧化的特性研究及纳米计量标准样板的制作

基于原子力显微镜(AFM)在硅(Si)表面进行局域阳极氧化的技术,以其成本低、易加工等优势被广泛应用于各种纳米元器件的制造.本文基于AFM在Si表面进行局域阳极氧化来制作纳米计量标准样板,首先分别在接触模式和轻敲模式下进行实验,定量分析了偏置电压、移动速率和刻蚀方向等主要参数对所得纳米线尺寸的影响,从而得到标准样板制作的最佳加工参数:在探针针尖电压为-7 V、移动速率为0.3μm/s、Z Distance值为-45 nm时,可以产生稳定的标准样板结构;同时两种模式下对纳米氧化线的影响趋势相同.最后在此最佳参数下,利用AFM在Si表面进行局域阳极氧化,加工得到了一维线光栅、二维光栅和圆形光栅结构.     

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.     

一种FIB刻蚀结合KOH腐蚀的制造纳米梁的新方法

常规的通过干法刻蚀制作纳米梁的方法会不可避免地在梁上引入晶格损伤层。本文提出一种制造无晶格损伤层纳米梁的新工艺方法。在常规光刻后,辅助利用FIB(聚焦离子束)刻蚀修改硅梁中部上方的SiO2掩模。根据单晶硅的材料和工艺特点,通过KOH各向异性腐蚀,硅梁两侧壁与硅片表面垂直,并自停止为(111)面。自停止面自校正地沿112晶向自硅梁中部向两端扩展,直至硅梁成型。经过冷冻干燥,最终在(110)SOI硅片上制得了宽度为112nm的单晶硅纳米梁。自校正的腐蚀方式提升了工艺稳定性,并且由于结合利用了湿法腐蚀和FIB技术,此工艺方法具有无晶格损伤层、工艺重复性好、加工精度高等优点。     

复合持续时间对P2O5-Al2O3异相复合玻璃结构和力学性能的影响

近年来,分相玻璃以其独特的结构以及优异的物理化学性质引起了广泛关注。本研究结合气动雾化加料和机械搅拌,采用熔融冷却法制备了纳米SiO₂-Na₂O高硅玻璃颗粒增强的P₂O₅-Al₂O₃玻璃。通过改变复合持续时间,研究了玻璃的结构与力学性能之间的关系。结果表明,异相复合玻璃的杨氏模量高于P₂O₅-Al₂O₃玻璃,并且随着复合持续时间由10s增大到8min,玻璃的杨氏模量呈现先升高后降低的趋势,在复合持续时间为6min时,杨氏模量达到最大值80.7GPa。相比于P₂O₅-Al₂O₃玻璃,杨氏模量提高了18%。引入SiO₂-Na₂O高硅玻璃颗粒不仅能够在基体玻璃中形成第二相,而且会改变P₂O₅-Al     

采用防Footing效应工艺加工的SOI微加速度计

为了解决深刻蚀绝缘体上硅(silicon on insulator,SOI)材料时存在的横向刻蚀(Footing)效应,在背腔释放SOI微机电系统(micro electro mechanical system,MEMS)工艺基础上,提出并实现了一种改进的利用背面保护电极抑制Footing效应的工艺方案.在SOI圆片上生长SiO2和Si3N4掩模材料并图形化后,背面腐蚀支撑层Si至掩埋层SiO2.去除掩埋层SiO2后,完成正面Al电极和背面保护Al电极的溅射.深反应离子干法刻蚀SOI圆片形成结构,再腐蚀背面Al薄膜完成结构释放.基于该工艺,对结构层厚度为80μm的采用双端固支梁的SOI微加速度计的结构进行设计与仿真、器件加工和最终的性能测试.加速度计在±1 g(g=9.8 m/s2)范围内的灵敏度和非线性度分别为106.7 mV/g和0.1%.实验结果表明,该改进工艺方案可以有效抑制Footing效应对器件结构的损伤,提高加工的可靠性.     

PECVD法生长氮化硅薄膜及其微结构梁特性的研究

采用化学气相沉积法(PECVD)在石英基片上制备氮化硅薄膜,应用MEMS工艺将氮化硅薄膜制作成双端固定的微结构梁,纳米压痕仪测量氮化硅薄膜的杨氏模量表明其值在136～172 Gpa之间,用曲率半径法测试薄膜的残余应力,并对微结构梁的弹性系数进行计算,结果表明弹性系数值在11.4～57 N/m.之间,根据实验所得弹性系数对微结构梁的驱动电压进行计算,其驱动电压在32.8～73V之间,微结构梁的实际驱动电压测得为34～60V。     

铝纳米梁的电学特性测试

对铝纳米梁进行了力学和电学特性测试．力学测试结果表明,铝纳米梁处于弹性形变区,具有张应力、电学测试结果表明,纳米梁电阻随着扫描次数增加而增加．通过分析电学实验结果可知,扫描次数增加使纳米梁发生塑性形变,并使纳米梁上张应力减小．研究结果表明,纳米梁电阻随着纳米梁张应力增大而减小．     

Determination of mechanical properties of electroplated Ni thin film using the resonance method

This paper addresses a relatively simple method of measuring the mechanical properties such as Young's modulus and residual stress of electroplated Ni thin film using the resonance method of Atomic Force Microscope. Thin layer of nickel to be measured is electroplated onto the tip side of AFM silicon cantilever and plating thicknesses were measured at the end of each plating step. The measured Young's modulus of nickel at the end of each plating step ranged from 148.04 GPa to 159.90 GPa with the maximum standard deviation of 3.47. The end deflection of electroplated AFM cantilever is also measured as a function of the plated Ni thickness, which is converted into the film stress by appropriate mechanics.     

Measurement of Young''s modulus and residual stress of copper film electroplated on silicon wafer

The Young's modulus and residual stresses of electroplated copper film microbridges were measured. Special ceramic shaft structure was designed to solve the problem of getting the load-deflection curves of the microbridges from a nanoindentation system equipped with a normal Berkovich probe. Theoretical analysis of the load-deflection curves of the microbridges is proposed to evaluate the Young's modulus and residual stress of the copper films simultaneously. The calculated results based on the experimental measurements showed that the average Young's modulus and residual stress of the electroplated copper films are 115.2 GPa and 19.3 MPa, respectively, while the Young's modulus measured by the nanoindenter for the same copper film with silicon substrate is 110±1.67 GPa.     

Nanoindentation of Ni-Ti Thin Films

Ni-Ti thin films of various compositions were sputtered-deposited on silicon substrates. Their mechanical properties (hardness and Young's modulus) were then determined using a nanoindenter equipped with a Berkovich tip. This paper examines the effects of composition on the mechanical properties (hardness and Young's modulus) of the sputter deposited Ni-Ti thin films. This is of particular interest since the actuation properties of these shape memory alloy films are compositionally sensitive. The surface-induced deformation is revealed via Atomic Force Microscopy (AFM) images of the indented surfaces. Which show evidence of material pile-up that increases with increasing load. The measured Young's moduli are also shown to provide qualitative measures of the extent of stress-induced phase transformation in small volumes of Ni-Ti films.     

Evaluation of Young''''s Modulus and Residual Stress of NiFe Film by Microbridge Testing

Microbridge testing was used to measure the Young's modulus and residual stress of metallic films. Samples of freestanding NiFe film microbridge were fabricated by microelectromechanical systems. Special ceramic shaft structure was designed to solve the problem of getting the load-deflection curve of NiFe film microbridge by the Nanoindenter XP system with normal Berkovich probe. Theoretical analysis of load-deflection curves of the microbridges was proposed to evaluate the Young's modulus and residual stress of the films simultaneously. The calculated results based on experimental measurements show that the average Young's modulus and residual stress for the electroplated NiFe films are 203.2 GPa and 333.0 MPa, respectively, while the Young's modulus measured by the Nano-hardness method is 209.6±11.8 GPa for the thick NiFe film with silicon substrate.     

Feasibility of Estimation Methods for Measuring Young's Modulus of Wood by Three-Point Bending Test

We examined the feasibility of estimation methods for measuring Young's modulus of wood by the three-point bending test using spruce specimens (Picea sitchensis Carr.). By measuring the deflections at the midspan and at the midpoint between the loading and supporting points, Young's moduli were determined according to elementary and Timoshenko's beam theory. Additionally, longitudinal strain at the midspan was measured independently of measuring the deflections, and Young's modulus was also determined from the load-strain relation. The values of Young's modulus obtained by the different procedures were compared with each other, and the following results were obtained: (1) Measurement of two-point deflections was effective for obtaining Young's modulus while reducing the influence of shear deformation when the specimen had a small depth. (2) In the measurement of two-point deflections, the specimen configuration should be regarded as more important than the contact at the loading and supporting points. (3) The use of strain gauges should be taken into account as a standardized method for measuring Young's modulus by bending.     

Electrical actuation and readout in a nanoelectromechanical resonator based on a laterally suspended zinc oxide nanowire

In this paper, we present experimental results describing enhanced readout of the vibratory response of a doubly clamped zinc oxide (ZnO) nanowire employing a purely electrical actuation and detection scheme. The measured response suggests that the piezoelectric and semiconducting properties of ZnO effectively enhance the motional current for electromechanical transduction. For a doubly clamped ZnO nanowire resonator with radius ~10 nm and length ~1.91 μm, a resonant frequency around 21.4 MHz is observed with a quality factor (Q) of ~358 in vacuum. A comparison with the Q obtained in air (~242) shows that these nano-scale devices may be operated in fluid as viscous damping is less significant at these length scales. Additionally, the suspended nanowire bridges show field effect transistor (FET) characteristics when the underlying silicon substrate is used as a gate electrode or using a lithographically patterned in-plane gate electrode. Moreover, the Young's modulus of ZnO nanowires is extracted from a static bending test performed on a nanowire cantilever using an AFM and the value is compared to that obtained from resonant frequency measurements of electrically addressed clamped–clamped beam nanowire resonators.     

Evaluation of Young＇s Modulus and Residual Stress of NiFe Film by Microbridge Testing

Microbridge testing was used to measure the Young＇s modulus and residual stress of metallic films. Samples of freestanding NiFe film microbridge were fabricated by microelectromechanical systems. Special ceramic shaft structure was designed to solve the problem of getting the load-deflection curve of NiFe film microbridge by the Nanoindenter XP system with normal Berkovich probe. Theoretical analysis of load-deflection curves of the microbridges was proposed to evaluate the Young＇s modulus and residual stress of the films simultaneously. The calculated results based on experimental measurements show that the average Young＇s modulus and residual stress for the electroplated NiFe films are 203.2 GPa and 333.0 MPa, respectively, while the Young＇s modulus measured by the Nano-hardness method is 209.6：1：11.8 GPa for the thick NiFe film with silicon substrate.     

超薄硅纳米谐振梁的制作及谐振特性的测量

利用氧化、光刻、刻蚀、溅射等传统MEMS加工工艺,在绝缘衬底上的硅（SOI）基片上制作出一种厚度只有50nm的双端固支结构的硅纳米谐振梁;在实验室条件下,针对实验中谐振梁的结构特点,提出了静电激励与感生电动势检测（EMF）的测量方法,并利用专业的Conventorware MEMS仿真软件及ANSYS有限元分析软件,定量地给出合适的静电驱动电压,同时初步估算了梁谐振时将会产生的感生电动势的大小,并对此分析结果提出了相应的测试电路,为下一步对这种超薄纳米梁的实际测试工作提供了可行性的理论参考．     

Accuracy of the spring constant of atomic force microscopy cantilevers by finite element method

Atomic force microscopy (AFM) probe with different functions can be used to measure the bonding force between atoms or molecules. In order to have accurate results, AFM cantilevers must be calibrated precisely before use. The AFM cantilever's spring constant is usually provided by the manufacturer, and it is calculated from simple equations or some other calibration methods. The spring constant may have some uncertainty, which may cause large errors in force measurement. In this paper, finite element analysis was used to obtain the deformation behavior of the AFM cantilever and to calculate its spring constant. The influence of prestress, ignored by other methods, is discussed in this paper. The variations of Young's modulus, Poisson's ratio, cantilever geometries, tilt angle, and the influence of image tip mass were evaluated to find their effects on the cantilever's characteristics. The results were compared with those obtained from other methods.