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Scanning transmission electron microscopy

scanning electron microscope

Semiconductor analysis, processing and repair

Ion Beam Etching

Focused ion beam lithography

Transmission scanning electron microscopy
Scanning electron microscopy
Semiconductor analysis, milling and repair
Ion beam etching
Focused ion-beam lithography

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Electron Microscope Technology definitions
Chinese name: English name electron microscopy: electron microscope Other names: electron microscopy Definition 1: According to the principles of electron optics imaging the sample with an electron beam microscope Applied science: Mechanical Engineering (a subject); optical instruments (two subjects); electronic optical instruments - electron microscope (three subjects) Definition 2: one with an electron beam as the light source, the display is divided into a microscope specimen ultrastructural transmission electron microscopy and scanning electron microscopy Applied science: Cell biology (a subject. ); cell biology techniques (two subjects) The above content by the national science and technology noun released examined and approved.

Scanning electron microscopy TEM electron microscopy are commonly used (transmissionelectronmicroscope, TEM) and scanning electron microscopy (scanningelectronmicroscope, SEM). Compared with the light microscope electron microscope with an electron beam instead of visible light, instead of using the electromagnetic lens using an optical lens and the phosphor screen to the naked eye invisible electron beam imaging. Compared with the light microscope electron microscope with an electron beam instead of visible light, electromagnetic lens instead of the optical lens and the screen will be invisible using an electron beam imaging.

Electron microscope
Electron microscopy, electron microscopy referred to, based on the principles of electron optics, a lens with an electron beam and the electron beam and the optical lens in place, so that the fine structure of the material at very high magnification imaging instrument. By the electron microscope column, a vacuum apparatus and a power supply composed of three parts counter. The main tube has an electron source, the electron lens, the sample holder, the phosphor screen and the detector and other components, these components are usually assembled into a column from top to bottom. electron lens for focusing the electron is an electron microscope mirror cylinder is the most important part. generally used are magnetic lens, sometimes there are using an electrostatic lens. It uses a symmetric space-electric or magnetic tube axis of the electron trajectories to the axis formed by bending focus, its role and the optical microscope optics lens (convex lens) of the beam focusing effect is the same, so called electron lens focus of the optical lens is fixed, while the focus of the electron lens can be adjusted, and therefore, unlike electron microscope as an optical microscope has a lens system can be moved Modern electron microscopes are mostly used electromagnetic lens, strong magnetic field coil by a very stable DC excitation current generated by the pole piece band makes electronic focusing electron microscope electron source is a release of free electrons cathode, a gate, a ring of accelerated electrons anode formed voltage difference between the cathode and anode must be very high, generally between 3 million volts to several thousand volts. It can transmit and form a uniform speed electron beam, so the stability of the accelerating voltage requirements are not low in parts per million. Sample sample holder can be stably placed on a sample holder. In addition there are often used to change the sample (such as moving, rotating, heating, cooling, elongated, etc.) of the device. detector for collecting electrons signal or secondary signal vacuum means for vacuum inside the microscope guarantee, so electrons will not be absorbed in its path or biased by the mechanical vacuum pump, diffusion pump and vacuum valves, etc., and through the exhaust pipe and tube coupled to power supply cabinet by a high-voltage generator, the excitation current steady flow and a variety of regulation and control unit.

Electron microscopy can be divided according to the structure and use of transmission electron microscopy, scanning electron microscopy, electron microscopy and reflection electron microscopy emission transmission electron microscope to observe those commonly used in the fine structure of matter with an ordinary microscope can not be resolved; Scan electron microscope is mainly used solid surface morphology can also be combined with X-ray diffraction or electron spectrometer, an electronic microprobe analysis for material composition; emission electron microscope is used to emit electrons from the surface Research.
Transmission electron microscopy (TEMTransmission Electron Microscopy, also known as projection-type electron microscope) after the penetration of the sample by the electron beam, and then the electron lens forming an enlarged named. It is similar to the optical path of the optical microscope, a sample can be directly projected By Thus one can obtain electron diffraction image. Using this crystal structure can be analyzed as a sample. In this electron microscope, the contrast of the image detail is changed by the sample atoms objective lens system direct amplification one can focus the objective lens of the image. scattering of the electron beam is formed. As electronic needs through the sample, so the sample must be very thin. atomic composition of the sample atoms, the acceleration voltage of the electrons and the desired resolution obtained determine the thickness of the sample thickness of the sample can be from a few ranging from nanometers to several microns. The higher atomic weight, the lower the voltage, the sample must be thinner. Samples thinner or less dense portion, less scattering of the electron beam, so there is more electron optical column through the objective lens, participation image, in the image look bright. On the other hand, the sample portion thicker or more dense, it appears dark in the image. If the sample is too thick or too dense, the contrast of the image will deteriorate, or even due to absorption of electrons the energy beam is damaged or destroyed. Top transmission electron microscope tube is an electron gun, electrons emitted from the hot cathode tungsten, through the first, second two condenser electron beam focusing electron beam through the sample by the objective lens mirror image on the intermediate, then the intermediate mirror and a projection lens through progressively larger, the image on the screen or photographic plates. intermediate mirror mainly through the regulation of the excitation current, the magnification can be continuously varied from several tens of times to hundreds of thousands times; change the focal length of the mirror in the middle, can be obtained as electron microscopy and electron diffraction image on a small portion of the same sample in order to study samples thicker metal chips, French Duluo Si Electron Optics Laboratory developed the acceleration voltage of 3,500. EHV kV electron microscope energy filtering transmission electron microscope (Energy Filtered Transmission Electron Microscopy, EFTEM) of people in the sample when the measurement electronics by speed changes. It can be speculated that the chemical composition of the sample, such as chemical elements distribution within the sample.

Scanning electron microscopy (SEM Scanning electron microscope) of the electron beam does not pass through the sample, only try to focus the electron beams in a small area of ​​the sample, then the sample is scanned line by line. Incident electron is excited sample surface leads to a secondary electron The microscope observation of each of these points is scattered electrons out, placed next to the scintillation crystal sample receiving these secondary electrons, amplified by the electron beam intensity modulation tube, thereby changing the brightness on the CRT screen. CRT deflection coil and the electron beam on the sample surface to maintain synchronous scanning, such CRT screen on topography image shows the sample surface, which is similar to the television industry works phase. Since this is not necessary transmission electron microscope samples, so the electrons accelerated do not have a very high voltage scanning electron microscope resolution is mainly determined diameter on the sample surface of the electron beam. magnification is on the CRT scan amplitude ratio of scan amplitude of the sample can be continuously varied from a few to hundreds of thousands of times . times do not need to thin sample scanning electron microscope; has a strong three-dimensional image; able to use electron beam interaction with the material produced by secondary electrons, electron and X-ray absorption analysis and other information material composition scanning electron. microscope with an electron gun and a condenser lens of a transmission electron microscope is substantially the same, but in order to make the electron beams finer, in the condenser lens and the microscope added astigmatism elimination device, the objective lens is also equipped with two mutually perpendicular inner scan coils. objective The following sample room equipped can move, rotate and tilt the sample stage.

Field emission scanning electron microscope (FESEM) is a relatively simple scanning electron microscope, it was observed on the sample field emission due to strong electric field caused by the electron comes out. If the observed sample is through a scanning electron then, NA me this kind of microscope is called the scanning transmission electron microscope (Scanning Transmission Electron Microscopy, STEM).

Transmission electron microscope to observe those commonly used in the fine structure of matter with an ordinary microscope can not be resolved; scanning electron microscope is mainly used solid surface morphology can also be combined with X-ray diffraction or electron spectrometer, an electronic microprobe analysis for material composition; emission electron microscopy to study electron emission from the surface.

1926 Hans Bush developed the first magnetic electron lens. 1931 卢斯卡 and Max Ernst Knorr developed the first transmission electron microscope to show that when the microscope is not used in perspective sample, but a metal grid. 1986 卢斯卡 do this to get Nobel Prize in Physics in 1938 at Siemens AG, he developed the first commercial electron microscope. 1934 osmium tetroxide has been proposed to strengthen the image contrast. 1937 The first launch of a scanning transmission electron microscope electron microscope
Started to develop an electron microscope main purpose is to show in an optical microscope can not distinguish pathogens such as viruses. Materials science surge of interest in electron microscopy after 1949 can be projected foil appears. 1960 accelerating voltage transmission electron microscope increasing to look into getting a thick substance. This period reached an electron microscope able to distinguish between atoms. 1980 people can use a scanning electron microscope wet samples. In the 1990s, computers increasingly used to analyze electronic microscope image, while the use of computers can also control more complex lens system, while operating more simple electron microscope.

1. TEM techniques: TEM electron beam is focused through the sample after amplification and was later produced as projected onto photographic film or on a screen resolution of TEM observation 0.1 ~ 0.2nm, magnification. Since the electron scattering or easily absorbed by the object, so low penetrating power, necessary to prepare ultrathin sections thinner (usually 50 ~ 100nm). The preparation procedure is similar to the tens of thousands to several tens of times. with paraffin, but requires very strict. To drawn in a few minutes after the death of the body fishing, tissue blocks to small (less than 1 mm3), commonly used glutaraldehyde and hungry acid resin embedding dual fixed, (ultramicrotome) cut with a special ultra-thin slicer When into thin slices, then by uranyl acetate and lead citrate electronic staining electron beam is projected onto the sample, with the organization may constitute components of different densities corresponding electron emission occurs, such as electron beam onto a massive structure , electrons are scattered more, so small and projected onto an electronic image on the phosphor screen was dark, electronic photos on the black, said electron density (electrondense). On the contrary, it is called the electron density is low (electronlucent).
2. Scanning electron microscopy SEM secondary electron is very fine electron beam to scan the sample surface, the resulting collection with a special detector to form an electrical signal delivered to the kinescope, display of objects on the screen. (Cells, tissues) the surface of the three-dimensional conformation can be produced into a photograph. SEM sample was fixed with glutaraldehyde and hungry acid, after dehydration and critical point drying, and then to the sample surface spraying thin gold film, in order to increase the number of electrons in the second wave. Scanning electron microscope to observe the surface structure of larger organizations, because of its depth of field long, 1mm can be clear about the uneven surface of the image, so put a sample rich three-dimensional image.

Using transmission electron microscopy of biological samples before the samples must be pre-treated with the needs of scientists using different research requirements fixing a different approach: in order to try to save the sample as the sample using glutaraldehyde to harden and use osmium tetroxide to stain fat Cold Fixed: samples frozen in liquid ethane, so that the water does not crystallize, and the virus is formed under the electron microscope, the amorphous ice stored samples such damage is relatively small, but the image contrast is very low dry off. : the use of ethanol and acetone to replace the pad into the water: can be split into the mat after the sample is split: the sample using a diamond blade sliced ​​staining: heavy atoms such as lead or uranium atom is higher than the light scattering ability of electrons, thus It can be used to increase the contrast. using transmission electron microscopy before metal samples are to be cut very thin slices (about 0.1 mm), and then continue to make use of electrolytic polished metal thinning, and finally in the sample tend to form a hole in the center, electronic can pass through there very thin metal near the hole. You can not use a metal or non-conductive or poor conductive properties of the material, such as electrolytic polishing method using an ion strike after the general was first worn thin by mechanical means such as silicon continues processing. To prevent non-conductive samples in a scanning electron microscope to accumulate static their surfaces must be covered with a conductive layer to be observed in an electron microscope the sample in a vacuum, and therefore unable to observe living samples. may be generated during sample processing samples that do not have The structure, which exacerbates the difficulty of image analysis thereafter. Since the transmission electron microscope observation of only very thin samples, and conventional optical microscopy is possible with the material surface structure different from the internal structure of the material. Additionally the electron beams may be heated by collisions and destruction of the sample. The latest technology now can be observed in an electron microscope the wet sample and the sample not coated with a conductive layer (ESEM, Environmental Scanning Electron Microscopes, ESEM). If the sample compared to the situation in advance, then it can be substantially clear no damage was observed. Further electron microscope to purchase and maintain prices relatively high.

Performance Comparison
Electron microscopy is an important indicator of the ability to distinguish electron microscope resolving power of the electron microscope to minimum spacing adjacent points can distinguish it expressed it through the electron beam incident cone angle and wavelength of the sample related. Visible a wavelength of about 300 to 700 nm, and the wavelength of the electron beam acceleration voltage. based on the principle of wave-particle duality, high-speed electrons wavelength shorter than the wavelength of visible light, and the resolution of the microscope used wavelength limited thereto, Therefore, the resolution of an electron microscope (about 0.2 nm) is much higher than the resolution of an optical microscope (about 200 nm). When the accelerating voltage is 50 to 100 kV, the electron beam wavelength of about 0.0053 ~ 0.0037 nm. Due to the electron beam much smaller than the wavelength of visible light wavelengths, so even if the electron beam cone angle of only 1% of the optical microscope, electron microscope resolving power is still far superior to an optical microscope optical microscope maximum magnification of about 2000 times, and modern electronic maximum magnification of the microscope more than 300 times, so you can directly observe through an electron microscope to certain heavy metals in atomic and crystal lattice atoms arranged in neat rows. Although electron microscope resolving power far better than optical microscopy, electron microscopy but because need to work under vacuum conditions, it is difficult to observe living organisms, and irradiated with an electron beam can also cause biological sample is subjected to radiation damage. Other issues, such as the brightness of the electron gun and the electron lens to improve the quality of other issues are also to be further studied.

Image sensor: 1.3 million pixels, color CMOS, Effective Pixels 1280 (H) * 1024 (V) resolution: 650 lines or more image refresh rate: 15 frames / sec SNR:) 60dB Video Interface: standard VGA interface VGA output support : 1024X768 60Hz (default), 1024X768 75Hz Lens Mount: CS control function: Brightness, contrast, color saturation, sharpness, Cb offset, Cr offset crosshairs superimposed, vertical mirror, horizontal mirror, negative power supply: Allow 10% deviation 5V DC Working current: 400mA Power: 2W Volume: 48 * 60 * 100 (mm) Total magnification: 7-150 times Lens: 0.7-4.5 continuous zoom eyepiece: 0.5X lifting range: 270mm hand wheel adjustment focus range: 65mm center distance: 140mm column diameter: 25mm lens mount diameter: 50mm total height of the bracket: 355mm Base Dimensions: 390X270X28 Weight:. 6KG 8-inch industrial LCD monitor magnification of the microscope as needed can be 600 times the maximum observed area can be reach more than 30mm, easy to use features optional items:. XY mobile platform, LED ring light, 1X, 0.3 times 0.5 times the eyepiece, 2x objective lens, the base has a variety of options, it can be equipped with a variety of cameras.