缺陷对坡莫合金薄膜磁畴翻转钉扎影响的洛伦兹透射电镜显微研究

利用磁控溅射法,在具有孔洞缺陷的铜网碳膜上成功地溅射了一层厚度100 nm,具有圆形缺陷的坡莫合金薄膜。结合常规透射电镜分析测试,研究了此类缺陷的形成机理及结构性质。利用洛伦兹透射电镜观察缺陷对周围磁矩的影响,以及在磁化反转过程中,缺陷对畴壁运动的影响。结果表明,此类缺陷是不同于膜本身的第二相弱磁性材料,它对畴壁的运动有着先排斥后吸引的钉扎作用。     

利用MFM研究薄膜厚度对Co60Fe20B20薄膜磁畴结构的影响

本文利用磁力显微镜(MFM)主要研究了由磁控溅射法制备的Co60Fe20B20软磁薄膜的厚度变化(2.5nm～400nm)对薄膜磁畴结构的影响.在室温下观察到垂直各向异性随薄膜厚度的增大而增大.从薄膜的表面形貌像观察到在溅射过程中薄膜温度随薄膜厚度增大而升高.当薄膜厚度小于20nm时,磁畴尺寸随薄膜厚度的增大而增大;当薄膜厚度大于20nm时,磁畴尺寸随薄膜厚度的增大而减小;厚度在20nm附近时,畴壁尺寸达到一个最小值.     

Development of a magnetizing stage for in situ observations with electron holography and Lorentz microscopy

A magnetizing stage, by which approximately horizontal magnetic fields can be applied to thin-foiled specimens, has been developed so that magnetization process can be observed in situ with electron holography and Lorentz microscopy. It is possible to apply magnetic field up to 200 Oe without serious image distortion by utilizing the magnetizing stage, beam-deflection-back coils and a magnetically shielded objective lens. The devised system can be used to studies of magnetization processes in many soft magnets.     

扫描电镜中纳米线弹性模量的原位测量方法

弹性性能是材料最基本的力学性能之一.随着样品尺寸减小,纳米材料(如纳米线)的弹性模量可能偏离块体材料的值,而其准确测量是认识这一尺寸效应的前提.本文基于自行设计制作的纳米操纵台和纳米压电马达,讨论了在扫描电镜中原位测量纳米线弹性模量的两种主要方法,即电致振动和单轴拉伸方法.通过分析电致振动模式,确立了纳米线固有频率的判...     

In Situ Observation of Point-Defect-Induced Unit-Cell-Wise Energy Storage Pathway in Antiferroelectric PbZrO3

Phase transition is established to govern electrostatic energy storage for antiferroelectric (AFE)-type dielectric capacitors. However, the source of inducing the phase transition and the pathway of storing the energy remains elusive so far given the ultrafast charging/discharging process under normal working conditions. Here, by slowing down the phase-transition speed using electron-beam irradiation as an external stimulus, the in situ dynamic energy-storage process in AFE PbZrO₃ is captured by using atomic-resolution transmission electron microscopy. Specifically, it is found that oxygen-lead-vacancy-induced defect core acts as a seed to initiate the antiferrodistortive-to-ferrodistortive transition in antiparallel-Pb-based structural frames. Associated with polarity evolution of the compressively strained defect core, the ferroelectric (FE)–ferrodistortive state expands bilaterally along the b-axis direction and then develops into charged domain configurations during the energy-storage process, which is further evidenced by observations at the ordinary FE states. With filling the gap of perception, the findings here provide a straightforward approach of unveiling the unit-cell-wise energy storage pathway in chemical defect-engineered dielectric ceramics.     

A revew of in situ transmission electron microscopy study on the switching mechanism and packaging reliability in non-volatile memory

Non-volatile memory(NVM)devices with non-volatility and low power consumption properties are important in the data storage field.The switching mechanism and packaging reliability issues in NVMs are of great research interest.The switch-ing process in NVM devices accompanied by the evolution of microstructure and composition is fast and subtle.Transmission electron microscopy(TEM)with high spatial resolution and versatile external fields is widely used in analyzing the evolution of morphology,structures and chemical compositions at atomic scale.The various external stimuli,such as thermal,electrical,mechanical,optical and magnetic fields,provide a platform to probe and engineer NVM devices inside TEM in real-time.Such ad-vanced technologies make it possible for an in situ and interactive manipulation of NVM devices without sacrificing the resolu-tion.This technology facilitates the exploration of the intrinsic structure-switching mechanism of NVMs and the reliability is-sues in the memory package.In this review,the evolution of the functional layers in NVM devices characterized by the ad-vanced in situTEM technology is introduced,with intermetallic compounds forming and degradation process investigated.The principles and challenges of TEM technology on NVM device study are also discussed.     

扫描电镜在无源外科植入物检测中的应用综述

超微结构技术与无源外科植入等生物医学的交叉融合,使得相关研究的尺度向更直观和更微观的方向延伸.无源外科植入物的安全性能及与人体接触部分的生物相容性和生物稳定性受其原料和结构组成特点的影响.扫描电子显微技术将植入物的超微界面体系可视化,是当今无源外科植入等生命科学研究的前沿方向之一.本文介绍了扫描电子显微技术结合能谱分析...     

Investigation of field-emitted electron beam behaviors using a line collector in a triode electron gun system

The performance of a field-emission scanning electron microscope (SEM) is primarily dependent on the characteristics of the electron source. Field-emission electron sources provide a high current density, which can be used to produce a beam that can be focused through an electrostatic lens. Using a single 〈1 1 1〉 crystalline tungsten tip, we fabricated and tested a field emitter having a 91 nm radius and a stability under 14%. In this electron source, two electrostatic lenses consisting of 1st and 2nd anodes were designed and implemented and their performance dependence on variations in electrode shape, position, and applied voltage was investigated using a first-order finite-element method simulation. We also developed a line collector capable of measuring beam distribution and quantifying shifts in the electrical optical axis to characterize the behavior of a field-emitted electron beam as focused by an electrostatic optical system.