What Is a Scanning Electron Microscope?

Scanning electron microscope (SEM) is a more modern cell biology research tool invented in 1965. It mainly uses secondary electron signal imaging to observe the surface morphology of the sample, that is, the sample is scanned with a very narrow electron beam. The interaction of the sample produces various effects, among which is mainly the secondary electron emission of the sample.

Scanning electron microscope (SEM) is between

* 1873 Abbe and Helmholfz proposed the resolution and light

Scanning electron microscopes are manufactured based on the interaction of electrons with matter.

Scanning electron microscopy is, in principle, scanning a sample with a highly focused high-energy electron beam to excite various physical information. By receiving, magnifying, and displaying imaging of this information, an observation of the surface morphology of the test specimen is obtained.

Scanning electron microscope

magnification

And ordinary

Creatures: Seeds, pollen, bacteria ...

Medicine: blood cells, viruses ...

(3) Animals: large intestine, villi, cells, fibers ...

Materials ^[1] : ceramics, polymers, powders, metals, metal inclusions, epoxy resins ...

Chemical, physics, geology, metallurgy, minerals, sludge (bacilli), machinery, electrical machinery and conductive samples, such as semiconductors (IC, line width measurement, section, structural observation ...) electronic materials, etc.

Application of scanning electron microscope in microanalysis of new ceramic materials

1 Analysis of microstructure

During the preparation of ceramics, the micro-morphology, pore size, grain boundaries, and degree of agglomeration of the original material and its products will determine its final properties. Scanning electron microscope can clearly reflect and record these microscopic features, and it is an effective and convenient method for observing and analyzing the microstructure of the sample. The sample does not need to be prepared and can be directly enlarged into the sample chamber for observation. At the same time, the scanning electron microscope can realize the test. For positioning analysis of samples from low magnification to high magnification, the sample in the sample chamber can not only move in three-dimensional space, but also can be rotated in space according to the observation needs, so as to facilitate users to perform continuous and systematic observation and analysis of the area of interest. The images taken by the scanning electron microscope are real, clear, and rich in three-dimensionality, and have been widely used in the observation and research of the three-dimensional microstructure of new ceramic materials.

Because the scanning electron microscope can comprehensively analyze the sample with a variety of physical signals, and has the characteristics of direct observation of larger samples, wide magnification range, and large depth of field. When the ceramic materials are in different external conditions and chemical environments, the scanning electron microscope Microscopes also show great advantages in their microstructural analysis. The main manifestations are: (1) Research on microscopic dynamics (crack propagation) under mechanical loading; (2) Research on crystal synthesis, gasification, and polymerization under heating conditions; (3) Research on crystal growth mechanism, growth steps, defects, and dislocations; (ii) Composition Research on the non-uniformity, shell-core structure, and encapsulation structure; The study on the difference of grain phase composition in chemical environment, etc.

2 Nano-sized studies

Nanomaterials are the most basic component of nanoscience and technology. Physical, chemical, and biological methods can be used to prepare "particles" with only a few nanometers. Nanomaterials are widely used. For example, ceramic materials generally have the advantages of high hardness, wear resistance, and corrosion resistance. Nanoceramics can also increase toughness and improve brittleness to a certain extent. New ceramic nanomaterials such as nanoscale and nanoscale are equal. It is also an important application area. All the uniqueness of nanomaterials is mainly derived from its nanometer size. Therefore, its size must be known accurately first, otherwise the research and application of nanomaterials will lose its foundation. Looking at the current research status and latest achievements at home and abroad, the detection methods and characterization methods in this field can use technologies such as transmission electron microscope, scanning tunneling microscope, atomic force microscope, but the morphology of high-resolution scanning electron microscopes at the nanometer level. Observation and size detection are widely used due to their advantages of simplicity and operability. In addition, if a scanning electron microscope and a scanning tunnel microscope are combined, the ordinary scanning electron microscope can be upgraded to an ultra-high resolution scanning electron microscope.

3 Observation of ferroelectric domains

Piezoelectric ceramics have been widely used in the fields of multilayer ceramic actuators, micro-displacers, transducers, and smart materials and devices due to their large electro-mechanical function conversion rates and good performance controllability. With the development of modern technology, ferroelectric and piezoelectric ceramic materials and devices are becoming smaller, integrated, multifunctional, intelligent, high-performance and composite structures, and play an important role in the development and research of new ceramic materials effect. Ferroelectric domains (electric domains for short) are their physical foundations. The structure of domains and the law of domain changes directly determine the physical properties and application direction of ferroelectrics. Electron microscopy is the main method for observing electrical domains. It has the advantage of high resolution. It can directly observe the microstructure of electrical domains and domain walls and the dynamic in situ observation of phase transitions (electric domain wall migration).

Scanning electron microscopy is used to observe the electrical domains in advance by chemically etching the surface of the sample. Because the domains of different polarities are etched to different degrees, the use of an etchant can form uneven areas on the surface of the ferroelectric, which can be used in the microscope. Make observations. Therefore, after the surface of the sample is chemically etched in advance, the black and white contrast in the scanning electron microscope image can be used to determine the electrical domain structures of different orientations. Selecting the appropriate etchant type, concentration, etching time and temperature for different ferroelectric crystals can show good domain patterns. Fig. 3 is a 90 ° electric domain of a PLZT material observed by a scanning electron microscope. A combination of a scanning electron microscope and other equipment for a variety of analytical functions.

In actual analysis work, often after obtaining a magnified image of a morphology, it is hoped that the in-situ chemical composition or crystal structure analysis can be performed on the same instrument to provide rich data including morphology, composition, crystal structure or orientation. In order to enable a more comprehensive and objective judgment analysis. In order to meet the requirements of different analysis purposes, many accessories have been successively installed on the scanning electron microscope, which realizes a multi-purpose machine and becomes a fast, intuitive, and comprehensive analysis instrument. Extending the scope of scanning electron microscopy to a variety of microscopy or microarea analysis has fully demonstrated the various performances and broad application prospects of scanning electron microscopy.

At present, the main combined analysis functions of scanning electron microscopes are: X-ray microscopic analysis systems (ie, energy spectrometers, EDS), which are mainly used for qualitative and quantitative analysis of elements, and can analyze information such as the chemical composition of the micro area of the sample; electronics Backscattering system (ie crystallographic analysis system), mainly used for crystal and mineral research. With the development of modern technology, other combined scanning electron microscope analysis functions have also appeared one after another, such as micro hot stage and cold stage systems, which are mainly used to observe and analyze the changes in the microstructure of materials during heating and freezing; stretching Table system is mainly used to observe and analyze the microstructural changes of materials during the process of stress. The new analysis function of scanning electron microscope combined with other equipment plays an important role in the exploration and research of new materials and processes.