Transmission Electron Microscope (TEM) is a microscope that transmits an accelerated and concentrated electron beam onto a very thin sample. The electrons collide with atoms in the sample and change direction, thereby producing solid angle scattering. The scattering angle is related to the density and thickness of the sample → it can form images with varying brightness and darkness. The image is magnified and focused and displayed on the microscope of the imaging device (such as fluorescent screen, film and photosensitive coupling components, etc.).

① The amount of sample used is small, not only the morphology, particle size, and distribution of the sample can be obtained, but also the elemental composition and phase structure information of a specific area can be obtained

② It is more suitable for morphology analysis of nanopowder samples, but the particle size should be less than 300 nm, otherwise the electron beam cannot penetrate

③For analysis of bulk samples, transmission electron microscopy generally requires thinning of the sample.

① TEM is an electronic optical instrument that uses electrons with extremely short wavelengths as the illumination source and uses an electromagnetic lens to focus the electrons passing through the sample to form an image.

② TEM can directly observe the internal structure of the material at the atomic scale, and can also conduct electron diffraction analysis of the crystal structure of the material to obtain the physical phase and crystal structure information of the material.

③TEM can be configured with X-ray energy spectroscopy (EDS), electron energy loss spectroscopy (EELS) and other accessories for measuring micro-area components.

The biggest features of TEM: electron microscopy and electron diffraction pattern

Structure: lighting system, imaging system, observation and recording system

Imaging principle:

① The sample should be thin enough, the size of the powder sample should be less than 0.2 microns, and the thickness of the film sample should be less than 0.1 microns.

② Can remain stable in high vacuum

③Do not contain moisture or other volatile substances. Samples containing moisture or other volatile substances should be dried and removed first.

④ Avoid magnetic particles, or demagnetize the magnetic sample in advance to avoid the electron beam being affected by the magnetic field during observation

Scanning Electron Microscope (SEM) is an electron microscope that uses a focused electron beam to scan the surface of a sample to produce an image of the sample surface. It is mainly used to observe the surface morphology of objects. It can directly observe the structure of the sample surface, and can also observe the sample from various angles. The sample preparation process is simple.

Vacuum systems, electron beam systems, and imaging systems

The electron beam emitted by the electron gun is concentrated by the magnetic lens system under the action of accelerating voltage to form an electron beam with a diameter of 5 nm, which is focused on the sample surface. Under the action of the deflection coil between the second condenser lens and the objective lens, the electron beam scans the sample in a raster shape, and the electrons interact with the sample to generate signal electrons. These signal electrons are collected by the detector and converted into electrical signals, which are then processed to form a surface image of the sample.

Scanning electron microscopes use scanning electron beams as illumination sources to convey the characteristics of the material structure through various information generated by the interaction between incident electrons and matter. The interaction between incident electrons and matter is the physical basis for scanning electron microscope imaging and applications.

scattering phenomenon

backscattered electrons

secondary electrons

Absorb electrons

transmitted electrons

Characteristic X-rays

Auger electron

cathodofluorescence

electron beam induced electrical effect

Conductive material: Specify the size requirements and paste it on the copper or aluminum sample holder with conductive glue

Samples with poor conductivity or insulation: (due to charge accumulation under the action of the electron beam, which affects the shape of the incident electron beam spot and the movement trajectory of the secondary electrons emitted by the sample, resulting in a decrease in image quality) spraying is required after pasting onto the sample holder. Conductive layer plating treatment

Energy dispersive spectroscopy (EDS) is a type of micro-beam analysis that determines the type and content of elements in the sample by measuring the X-ray energy generated by the interaction between the electron beam and the sample.

Microbeam analysis is a technique for analyzing tiny samples or areas that involves the use of high-energy beams (such as electrons, ions, or photons) to obtain information about the chemical composition, structure, and physical properties of the sample

High spatial resolution: capable of analyzing very small areas, down to the nanometer or even atomic level

Elemental analysis: Determining the presence and concentration of various elements in a sample

Structural analysis: study the crystal structure, micromorphology, etc. of the sample

Surface analysis: analyzing the composition and properties of the sample surface

The energy spectrum shows energy on the abscissa and intensity or counts on the ordinate.

It shows the distribution of photons or electrons at different energies, which can reflect the characteristic energy peaks of elements in the sample.

EDS data can also include quantitative analysis results (content percentage of elements, etc.), as well as element distribution maps (line scans and surface scans)

Standard sample method

Standardless method

internal fluorescence peak

He Feng

escape peak

Point analysis:

Line analysis:

face analysis;

X-Ray Diffraction (XRD) is the main method for studying the physical phase and crystal structure of substances.

When a substance (crystalline or non-crystalline) is subjected to diffraction analysis, the substance is irradiated by Substances produce unique diffraction patterns

No damage to the sample, no pollution, fast, high measurement accuracy, and can obtain a large amount of information about the integrity of the crystal

When a beam of monochromatic X-rays is incident on a crystal, since the crystal is composed of regularly arranged unit cells of atoms, and the distance between these regularly arranged atoms is of the same order of magnitude as the wavelength of the incident X-rays, the X-rays scattered by different atoms Interference produces strong X-ray diffraction in certain special directions. The orientation and intensity of the diffraction lines in space are closely related to the crystal structure.

The distribution pattern of diffraction lines is determined by the size, shape and orientation of the unit cell.

The intensity of the diffraction lines depends on the species of atoms and their positions in the unit cell

Physical phase analysis:

Determination of crystallinity:

Precise measurement of lattice parameters:

Characterization of nanomaterial particle size:

Determination of crystal orientation and texture