Analyzing the dopant distributions in semiconductors is important because the small amount of impurities (dopants) implanted form electric potential distributions that are responsible for the performance of these devices. However, dopant concentrations are generally as low as 1015cm-3～1019cm-3 (i.e., less than 0.1 atom％), which is below the contrast level of the images obtained by transmission electron microscopes. It is even difficult to map the dopant distribution for such small concentrations using energy dispersive X-ray spectroscopy (EDS) or electron energy loss spectroscopy (EELS). Electron holography enables electric potential distributions to be observed, and thus is a powerful method for profiling dopant distributions. This paper describes the principle, method and typical applications of electron holography for dopant profiling of semiconductors.
We made Au/TiC nano-hetero catalysts by vacuum evaporation method (VE) and characterized the interface structure using high-resolution electron microscopy and electron holography. The mean inner potential of the Au nano particles on TiC exhibit the size dependence. When the size of Au particle was smaller than 3nm, the mean inner potential of Au increased gradually. When the size was smaller than 2nm, the mean inner potential of the Au was over 30V. This tendency is similar to that of Au/TiO2 catalysts prepared by VE which is considered to have Ti rich interfaces.
Electrostatic inner-potentials near the interfaces between Pt and oxide ion-conductor are measured by electron holography. The band bending inferred from the inner-potential distribution inside the proton conductor Strontium-Zirconium Oxide (SZO) supports the experimental result that the composite materials of Pt more than 1.5vol% in SZO show extremely low conductivity. Inner-potentials are also measured with applying external electric field to the model of fuel cell Pt/Gadolinium-doped Ceria (GDC)/Pt. In the result, an inhomogeneous distribution of Oxygen anions and ionic vacancies are detected in the condition no oxygen anions reserved. A new specimen holder has been developed so that specimen is applied external potential at high temperature.
Magnetization dynamics driven by spin current in nano-scaled ferromagnetic materials has attracted much attention in academic and industrial viewpoints because of a wide variety of promising applications in magnetic recording and spintronic devices with higher integration density and lower energy consumption. In the manuscript, basic concepts of spin current and its interaction with magnetization are introduced. TEM in-situ analysis method using Lorentz microscopy and electron holography together with transport measurement has great advantages in microscopically clarifying spintronic properties. Making full use of these advantages, manipulation of magnetic domain states using spin current under small magnetic fields is demonstrated. Its application in spintronic devices and future prospect of spintronic investigation using TEM in-situ analysis method are discussed.
The nucleation and growth mechanism of the ferromagnetic phase inside the charge ordered insulator state of La0.25Pr0.375Ca0.375MnO3, which is a typical manganite showing colossal magnetoresistance, was studied by electron holography and Lorentz microscopy. Cryogenic Lorentz microscopy observations revealed a zig-zag interface that separated the ferromagnetic phase from the non-magnetic mother phase. The results indicated a significant pinning effect for the motion of phase boundary, and the pinning forces originated from the structural antipathy between the ferromagnetic phase and the charge-ordered state. We also determined magnetic parameters, such as the magnetocrystalline anisotropy constant, by using the electron microscopy observations.
Practical techniques of in-situ observation of micro-structural changes by EBSD are explained and their observation results are shown. Heating stage, tensile and heating-tensile stage and specimen bending stage are picked up as in-situ apparatuses for EBSD observation. Some technical points for combining EBSD and higher temperature heating stage which can go more than 1173K are explained. Appropriate cares for building heating stage could make it possible to observe Ti α-β transformation at 1193K without any problems. Practical points for designing tensile stages are explained. Heating-tensile observation is also possible, but observation of tensile specimen under heated condition becomes far more difficult for EBSD due to specimen drift. EBSD observation using specimen bending test is easier, because of that the deformation point is fixed. But it needs to be careful to analyze the data. Deformation mechanism is more complicated by combining tensile part and compressed part. It is shown that the Kernel Average Misorientation values by EBSD analysis were increased proportionally along with the amount of deformation with specimen bending test.
Molecular linear motors in living cells, such as myosin and kinesin, play key roles to maintain life in various events, i.e., transportation of organelles, cell migration, cell division and so on. The mechanism illustrating how these motors work as a ‘molecular machine’ has been studied through biophysical approaches and well established especially at the single molecular level. The other stream to study molecular motors is to examine proteins that show continuous directed motion, such as rotation of a subunit; F1-ATPase is an extreme as the world’s smallest rotary motor with the size of 10 nm. Our approach was not only the visualization of rotational motion of the shaft, but also the simultaneous detection of a chemical reaction that drives the rotation. Techniques of our optical microscopes to detect nanometer-scale motions and their applications to molecular motors are described.
Outline of electropolishing as a method for preparation of TEM specimens is presented. After typical traditional methods are described、a novel method in which only a very small amount of electropolyte is used is introduced.
In scientific presentations and publications, "color" has become a significant vehicle for information and presentation effect. However, color perception varies greatly among individuals; in particular, red-green color blindness are found in 4-9% of males in various populations, a frequency comparable to that of the AB blood type. Thus inappropriate color choices can cause unexpected difficulty in understanding color figures. We are examining that color and color combinations are perceived by various color vision types, to develop a method for presenting color information that can convey maximal information to most color vision types including color blindness. Here I show how to make figures of multiple fluorescent staining that are friendly to colorblind people.
Claudins are integral membran proteins at tight junctions and consist of at least 24 members. Because claudins show a tissue-specific distribution, the tissue-specific morphological features and physiological properties of tight junctions may be determined by the combination and mixing ratio of claudin species in the tissue. Here, we introduce our recent results and task for the future obtained from the analyses of claudin-claudin interactions and structure and function of tight junctions.
We have developed a spherical aberration correction system with three dodeca-poles. This system corrects a six-fold astigmatism, which generally limits a uniform phase area for image forming and probe forming system in an electron microscope with the conventional two-hexapole corrector. Experimental results showed compensation of a six-fold astigmatism as well as spherical aberration. We experimentally demonstrated high-resolution images with this corrector in a transmission electron microscope and a scanning transmission electron microscope at 30-kV and 60-kV acceleration.
The stereoscopic visualization has been a matter of interest for researchers using the scanning electron microscope (SEM). For this purpose, two images of the same area with a small tilt angle difference are usually collected by sample tilting. However, we recently developed an novel SEM, which can obtain real-time stereo-images by using a beam-tilting method. In our real-time 3D SEM, each line is recorded twice with rocking beam angles during scanning, resulting in the simultaneous collection of two images with different tilt angles. To obtain high-resolution images, the off-axis aberration formed by off-axis beam deflection is corrected by inserting an additional lens. The obtained stereo images are displayed on a 3D liquid crystal display, which is also designed for representation of stereo images without using any special glasses. Thus, we could obtain stereo SEM images of various biological tissue samples in real-time at different magnifications even by naked eyes. We then installed compact manipulators in our SEM, and dissected tissue blocks during SEM operation. Because the spatial distance between the sample and needle could be recognized accurately and stereoscopically in our SEM, we could dissect samples more easily than before.