Electronic microscope - Reboring for monitoring and photographing repeatedly (up to 10 6 times) an enlarged image of an object, in K-ROM instead of light rays used, accelerated to large energies (30-1000 keV or more) under conditions of deep. Phys. Basics of corpuscular radiation optics. The devices were laid in 1827, 1834-35 (almost a hundred years before the appearance of E. m.) U. P. Hamilton (WR Gamil-Ton), which established the existence of analogy between the passage of light rays in optically inhomogeneous media and trajectories of particles in power fields . The feasibility of creating E. m. She became apparent after nomination in 1924 hypotheses about de Broglyl waves, and tehn. The prerequisites were created by X. Bush (H. BUSCH), which in 1926 investigated the focusing properties of axisymmetric fields and developed Magn. Electronic lens. In 1928 M. Knoll (M. Knoll) and E. Ruska (E. Ruska) began to create the first Magn. Translucent E. m. (PEM) and three years later, they obtained an image of an object formed by electron beams. In subsequent years, the first raster e. m. (Rem), operating on the scanning principle, i.e., sequential on the point to the point of movement of a thin electron beam (probe) on the object. To gray. 1960s. Ram reached high tech. Perfections, and since that time there began their widespread use in scientific. Research. PEM have the highest leaving abilitysurpassing this parameter light microscopes in several thousand times. PR EI L R A S R E W E H I, characterizing the ability of the device to display separately two as close as possiblely arranged parts of the object, in the PEM is 0.15-0.3 Hm, i.e. reaches a level that allows you to observe atomic and the molecular structure of the objects under study. Such high permissions are achieved due to the extremely low wavelength of the electron wave. E. lenses. Possess aberrations, effective methods of correction to-rykh not found in contrast to the light microscope (see Electronic and ion optics). Therefore in PEM Magn. electronic lenses (EL), in re-aberration, the magnitude of the magnitude is less, completely supplanted electrostatic. Optimal diaphragmation (see Diaphragm In the event and and about nn about th and and about n about p t and to e), it is possible to reduce spheric. Lens aberration affecting
on the resolution of E. m. Instruction PEM can be divided into three groups: E. m. High resolution, simplified PEM and unique ultrahols and carpet e. m.
High Resolution PEM (0.15-0.3 nm) - universal multipurpose devices. Used to observe the image of objects in a light and dark field, studying their structure of electro-nogs. method (see Electronography), local quantities. With the help of the energy spectrometer. Losses of electrons and X-ray crystal. and semiconductor and receiving spectroscopic. Images of objects using a filter, selecting electrons with energies outside the specified energy. window. The energy loss of electrons skipped by the filter and forming an image is caused by the presence in the object of some one whim. element. Therefore, the contrast of the plots, in which this element is present, increases. Moving the window by energy. The spectrum is obtained solutions. Elements contained in the object. The filter is also used as a monochromator to increase the resolution of E. M. In the study of the objects of high thickness, increasing the scatter of electrons by energies and (as a result) chromatic aberration.
With the help add. Devices and consoles studied in PEM object can be tilted in different planes to large corners to optch. Axis, heated, cool, deform. Accelerating electrons Voltage in high-resolution E. m. Is 100-400 kV, it is adjustable stepwise and differs high stability: for 1 - 3 minutes, it is not allowed to change its value more than (1-2) · 10 -6 from the source value. The thickness of the object is depends on the accelerating voltage, which can be "enlighten by" an electron beam. In 100 kilovolt, E. m. Learn objects with a thickness of 1 to several. tens nm.
Schematically, the PEM of the described type is shown in Fig. 1. In its electronic optical. The system (column) using a vacuum system is a deep vacuum (pressure up to ~ 10 -5 pa). Electron Optic Scheme. PEM systems are presented in Fig. 2. The bunch of electrons, the source of the to-rye serves as a thermocheate, is formed in e-gun and the high-voltage accelerator and then twice focuses the first and second condensors creating an electronic "spot" of small sizes on the object (when adjusting the diameter of the spot can vary from 1 to 20 microns). After passing through the object, the part of the electrons is dissipated and delayed by aperture diaphragm. The unprotected electrons pass through the hole of the diaphragm and focus with the lens in the intermediate electron lens plane. Here is the first enlarged image. Subsequent lenses create a second, third, etc. images. The latest - projection - lens forms an image on a catodoluminescent screen, which glows under the influence of electrons. The degree and nature of the scattering of electrons of the components at various points of the object, since the thickness, structure and chemical. The composition of the object varies from point to point. Accordingly, the number of electrons passed through an aperture diaphragm, and consequently, the current density in the image. The amplitude contrast occurs, the to-ry is converted into the light contrast on the screen. In the case of thin objects prevails phase contrastcaused by a change in phases scattered in the object and interfering in the image plane. Under the screen E. m. There is a store with photoflaxes, when photographing, the screen is cleaned and the electrons affect the photoemulsion layer. The image is focused by an objective lens using a smooth current adjustment that changes its magn. field. Currents of other electronic lenses are regulated by an increase in E. m., It is equal to the product of increasing all lenses. With large zooms, the brightness of the screen glow becomes insufficient and the image is observed using the brightness amplifier. To analyze the image, an analog-to-digital conversion is manufactured in it and processing on a computer. The image enhanced and processed according to the specified program is displayed on the computer screen and, if necessary, is entered into the storage device.
Fig. 1. Electronic translucent type microscope (PEM): 1
-Electronic gun with accelerator; 2-Condeweighing lenses; 3
-Please lens; 4
- projection lenses; 5
- Light microscope, additionally increasedthe image observed on the screen; b.-Thebus with viewing windows through which you can observegive an image; 7
- high-headed cable; 8
- vacuum system; 9
- Remote Control; 10
-stand; 11
- high-voltage feeder; 12
- power supply lenses.
Fig. 2. Electronic optical scheme PEM: 1
-cathode; 2 - focusing cylinder; 3
-accelerator; 4
-Pr.(short-phocus) condenser creating reduced image of an electron source; 5
- second (long-focus) condenser, which transfer a reduced source image electrons on the object; 6
-an object; 7
-APfragma lens; 8
- lens; 9
, 10, 11
-system projection lenses; 12
-Catrominescent screen.
Simplified PEM. Designed for scientific. Research, in which it does not require high resolution. They are also used to finish. view objects, routine work and for academic purposes. These devices are simple in design (one condenser, 2-3 electronic lenses to increase the image of the object), have a smaller (60-100 kV) accelerating voltage and lower stability of high voltage and lenses currents. Their resolution of 0.5-0.7 nm.
Ultrah high-voltage E. M. . (SVEM) - devices with accelerating voltage from 1 to 3.5 Mb - are large-sized structures with a height of 5 to 15 m. For them, the specials are equipped. Premises or build individual buildings, which are an integral part of the SVEM complex. The first SVEM was intended to study objects of large (1 -10 μm) thickness, the properties of a massive solid body are preserved. Due to the strong influence of chromatić. Aberration Resolving the ability of such E. M. Reduced. However, compared to 100 kilovolt e. m. Resolution of the image of thick objects in SVEM is 10-20 times higher. Since electrons energy in SVEM is larger, then the length of their waves is less than in the High Resolution PEM. Therefore, after solving complex tech. There are no problems on this (this is not one decades) and the implementation of high vibration resistance, reliable vibration insulation and sufficient mechanical. and electric. Stability on SVEM was achieved the highest (0.13-0.17 nm) for translucent E. M. Resolution, which allowed photographing images of atomic structures. However, Spherich. Aberration and defocusing of the lens distort images obtained with the limit resolution and interfere with obtaining reliable information. This informational barrier is overcome using focal series of images, which are obtained at RM. Defocusing lens. In parallel, for the same defocuses, modeling the studied atomic structure on the computer is carried out. Comparison of focal series with lots of model images helps to decipher the micrographs of atomic structures made on a silver resolution. In fig. 3 shows the SVEM scheme placed in specials. Building. OSN. The assemblies of the device are combined into a single complex using the platform, K-paradium is suspended to the ceiling on four chains and depreciation springs. From above on the platform there are two tanks filled with an electrical insulating gas under pressure of 3-5 atm. One of them is placed a high-voltage generator, in another electrostatich. Electron accelerator with electronic cannon. Both tanks are connected by a nozzle, through a digital high voltage from the generator is transmitted to the accelerator. Bottom to Baku with an accelerator adjoins electronically optical. The column located at the bottom of the building, protected by the overlapping from the X-ray. Radiation arising in an accelerator. All listed nodes form a hard design with the properties of Piz. Pendulum with a large (up to 7 seconds) the period of his own. Fit for liquid dampers. The pendulum suspension system provides effective SVEM insulation from external. vibrations. The device is controlled from the remote contained near the column. The device of lenses, columns, etc. The instrument nodes like the appropriate PEM devices and differs from them large dimensions and weight.
Fig. 3. Ultrahhhhhhhhhhnyh electronic microscope (SVEM): 1-vibration-insulating platform; 2-chains, on which platform hangs; 3 - amortization springs; 4-tanks in which the generator are yousoft voltage and electron accelerator with electrona mellow; 5-electron-optical column; 6.- overlap separating the building of SVEM to the upper and nizhny Hall and Protecting Personnel lower hall, from X-ray radiation; 7 - Remote microscope control.
Raster E. M.. (RAM) with a thermionic gun - the most common type of appliances in electron microscopy. They use tungsten and hexaber-reed lanthanum thermocamation. The resolution of the RAM depends on the electron brightness of the gun and in the instruments of the class under consideration is 5-10 nm. The accelerating voltage is adjusted from 1 to 30-50 kV. The RAM device is shown in Fig. 4. With two or three electronic lenses on the sample surface, a narrow electronic probe focuses. Magn. Deviation coils deploy the probe along the specified area on the object. In the interaction of the electrons of the probe with the object there are several types of radiation (Fig. 5): secondary and reflected electrons; Auger electrons; X-ray brake radiation and characteristic radiation (see Characteristic spectrum); Light radiation, etc. Any of emissions, the currents of the electrons that have passed through the object (if it is thin) and absorbed in the object, as well as the voltage induced on the object can be recorded by the corresponding detectors converting these radiation, currents and voltages in the electric. The signals, which, after the amplification, are fed to the electron beam tube (CRT) and modulate its bundle. The emission of the ELT beam is made synchronously with the spreading of the electronic probe in Rem, and an enlarged image of the object is observed on the ELT screen. An increase is equal to the ratio of the frame size on the CRT screen to the corresponding size on the scanned surface of the object. Photograph the image directly from the CRT screen. OSN. The advantage of RAM is the high informativeness of the device, due to the ability to observe images using the SIGNAL signals. detectors. With the help of RAM, you can explore the microrelief, the distribution of chemical. composition on the object, p-N.-Trans, produce RENTG. Spectral analysis and other RAM are widely used in tehnol. processes (control in electron-litog rafić. Technologies, checking and identification of defects in chips, Metrology of microcradisisi, etc.).
Fig. 4. Raster electron microscope scheme (RAM): 1
-Helator electo gun; 2
-V.-formthermocatus; 3
-focusing electrode; 4
- anode; 5
- condense lenses; 6
-diaphragm; 7
- bunk deflecting system; 8
-lens; 9
-Earturial diaphragm of the lens; 10
-an object; 11
-dector secondary electrons; 12
-crystalchimney spectrometer; 13
-proportional counter; 14
- pre-amplifier; 15
- gain strengthening; 16, 17
Apparatus for registration x-ray radiation; 18
- strengthening unit; 19
- block adjustment unit; 20, 21
- Blocks Gor.umbrella and vertical expandment; 22, 23
-Eckthrink-ray tubes.
Fig. 5. Registration scheme for object information, obtained in REM; 1-primary electron beam; 2-detector of secondary electrons; 3-detector RENTgenovsky radiation; 4-detector of reflected electrorons; 5-detector AUG-electrons; 6-detectoremitted radiation; 7 - Detector of the past electronew; 8 - scheme for registering current electron object; 9-scheme for current registration absorbed in the electron object; 10-scheme for rehardware induced at an electric facility potential.
The high resolution RAM ability is implemented when the image is generated using secondary electrons. It is in the inverse dependence on the diameter of the zone, from which these electrons are emissive. The size of the zone depends on the diameter of the probe, the properties of the object, the electron velocity of the primary beam, etc. With a large depth of penetration of primary electrons, secondary processes developing in all directions increase the diameter of the zone and the resolution falls. The detector of secondary electrons consists of photoelectronic multiplier (FEU) and electron-photon transducer, land. An element is a scintillator-lator. The number of scintillator outbreaks is proportional to the number of secondary electrons, knocked out at this point of the object. After amplifying to the FEU and in the video amplifier, the signal modulates the bunch of the ELT. The magnitude of the signal depends on the topography of the sample, the presence of local electric. and Magn. Micropoles, coefficient values. Secondary electronic emissions, which, in turn, depends on the chemical. The composition of the sample at this point.
Reflected electrons are captured by a semiconductor detector with P - N-There. The contrast of the image is due to the dependence of the COEF. reflections from the angle of incidence of the primary beam at this point of the object and from the at. Numbers substance. The resolution of the image obtained in the "reflected electrons" is lower than that obtained using secondary electrons (sometimes an order of magnitude). Due to the rectinity of electron flight information about PL. Lands of the object, from the to-ry direct path to the detector there, is lost (shadows occur). To eliminate the loss of information, as well as to form an image of the sample relief, it does not affect its elemental composition and, on the contrary, to form a pattern of the distribution of chemical. The elements in the object, the relief does not affect its relief, the detector system consisting of several is applied in REM. The detectors placed around the object, the signals of the to-rye are subtracted one of the other or summed, and the resulting signal after the amplification is supplied to the CRT modulator.
RENTH. Characteristics. Radiation is recorded by Cry-Stallee. (Wavestone) or semiconductor (energy-dispersed) spectrometers, which are mutually complementing each other. In the first case of RENTG. radiation after the reflection of the spectrometer crystal falls into the gas proportional counter, and in the second - RENTG. Quanta excite signals in semiconductor cooled (to reduce noise) silicon detector doped with lithium, or from Germany. After amplification, the spectrometer signals can be filed to the CRT modulator and a picture of the distribution of one or another chemical appears on its screen. Element on the surface of the object.
On RM, equipped with a RENTG. Spectrometers produce local quantities. Analysis: The number of pulses excited by the RENTG is recorded. Quantas from the site, the electronic probe was stopped on the rum. Crystalleg. The spectrometer with the help of a set of analyzer crystals with Split. interplanar distances (see Bragg-Wulf Condition) Discriminates a high spectrum. resolution of characteristics. Spectrum on wavelengths, overlapping the range of elements from BE to U. Semiconductor spectrometer discriminates RENTG. Quanta by their energies and registers all elements from into (or c) to U. Its spectral resolution is lower than that of crystalline. spectrometer, but above sensitivity. There are also other benefits: fast issuance of information, simple design, high performance characteristics.
Raster Age-E. M.. (ROEM) -Ribor, in which, when scanning an electron probe, Auger electrons are detected from the depth of the object not more than 0.1-2 nm. Under such a depth of the exit zone, the AUG-electrons does not increase (in contrast to the electron of the secondary emission) and the device resolution depends only on the diameter of the probe. The device works with ultrahigh vacuum (10 -7 -10 -8 pa). Its accelerating voltage is OK. 10 square meters In fig. 6 is represented by the ROEM device. The electron cannon consists of a hexaboride-lanthanum or tungsten thermocathimmer operating in Schottki mode, and three-electrode electrostatic. lenses. The electronic probe focuses on this lens and magn. The lens in the focal plane of the to-it is an object. Collection of Age-electrons is made using cylindrich. The mirror analyzer of the energy, the internal electrode of which covers the lens housing, and the external adjoins the object. With the help of an analyzer discriminating AUG-electrons by energies, the distribution of chemical is investigated. Elements in the surface layer of an object with submicron resolution. To study the deep layers, the device is equipped with an ion gun, with the help of a to-point, the upper layers of the object by the method of ion-radiation etching are removed.
Fig. b. Scheme of raster AUG-electron microscope (ROOM): 1 - ion pump; 2-cathode; 3 - three-enecotted electrostatic lens; 4-multichannel detector; 5-aperture diaphragm of the lens; 6-bunk deflecting system for expanding the electronic probe; 7-lens; 8- outer electrode cylindrical mirror analyzer; 9-object.
Ram with auto-emission gun Have a high resolution (up to 2-3 nm). A cathode in the shape of the island is used in the auto-emission cannon, the top of the to-it occurs a strong Elekgrich. The field feeding electrons from the cathode ( auto-electronic emission). The electronic brightness of the gun with an auto-emission cathode of 10 3 -10 4 times higher than the brightness of the gun with a thermocheate. Accordingly, the current of the electronic probe increases. Therefore, in RAM with an auto-emission gun, along with a slow fast spread, and the diameter of the probe is reduced to increase the resolution. However, the auto-emission cathode is resistant only with ultra-high vacuum (10 -7 -10 -9 PA), which complicates the design and operation of such RAM.
Translucent raster e. m. (PrSEM) have an equally high resolution, as well as PEM. In these devices, auto-emission guns operating under ultra-high vacuum (up to 10 -8 PA), providing sufficient current in a small diameter probe (0.2-0.3 nm). The diameter of the probe is reduced by two magnes. Lenses (Fig. 7). Below objects are the detectors - the central and ring. The first erased electrons fall on the first, and after converting and enhancing the corresponding signals on the CRT screen, a light sparkle image appears. On the ring detector, scattered electrons are assembled, creating a dark-pool image. In Progra, it is possible to explore thicker objects than in the PEM, since the increase in the number of non-abnormal electrons with thickness does not affect the resolution (after the object, the electronic optics is missing for forming). With the help of an energy analyzer, electrons that have passed through the object are divided into elastically and inelastic scattered beams. Each bundle falls on its detector, and the corresponding images containing additional are observed on the ELT. Information about the elemental composition of the object. The high resolution in Program is achieved with slow deputies, since in the probe with a diameter of only 0.2-0.3 Nm, the current is small. Prem is equipped with all device for analytical devices used in electron microscopy. Research of objects, and in particular energy spectrometers. Electron loss, RENTG. Spectrometers, complex systems for detecting past, back scattered and secondary electrons that allocate electron groups scattered on Ring. Corners having a Split. Energy, etc. The devices are equipped with a computer for comprehensive processing of incoming information.
Fig. 7. Schematic diagram of translucent rasteran electronic microscope (PREM): 1-auto issuesyon cathode; 2 intermediate anode; 3- anode; four- the diaphragm "illuminator"; 5 magnetic lens; 6-twomax rejection system for expanding electronprobe; 7 magnetic lens; 8 - Aperture lens diaphragm; 9 - object; 10 - deflecting system; 11 - Ring detector of scattered electrons; 12-detector of non-Russian electrons (removed when the operation of the magnetic spectrometer); 13 - Magnetic spectrometer; 14-deflecting system for selecting electrons with different energy loss; 15 - gap spectrometer; 16-detector spectrometer; Vuel Secondaryelectrons; hV-Rentgen radiation.
Emisy E. M.. Create an image of an electrical object, which emists the object itself when heated, bombarding the primary bunch of electrons, under the action of email. Radiation and under the superimposition of a strong electric. Fields feeding electrons from the object. These devices usually have a narrow target purpose (see Electronic projector).
Mirror E. M.. Serve ch. arr. For visualization of electricity. "potential reliefs" and Magn. Micropoles on the surface of the object. OSN. Electron Optic. An element of the device is electronic mirror While one of the electrodes serves the object itself, the to-ry is under little deny. Potential relative to the gun cathode. The electron beam is sent to the electron mirror and is reflected in the field in close proximity to the surface of the object. The mirror forms the image "in the reflected bundles" on the screen: micropolis near the surface of the object redistribute electrons of reflected beams, creating a contrast in the image, visa-lysis these micropolis.
Prospects for the development of E. M. Improving E. m. In order to increase the amount of information received, which carried out for many years will continue in the future, and improve the parameters of the instruments, and above all the increase in the resolution will remain the main task. Work on the creation of electron-optic. Systems with small aberrations have not yet led to a real increase in resolution E. m. This refers to non-axisymmetric systems for correction of aberration, cryogenic optics, to lenses with corrective spaces. In the recruitment area and other searches and research in these directions are conducted. Search works continue to create electronic good-features. systems, including and with the correction of the frequency-contrast characteristics of the lenses. Miniaturization of electrostatic. Lens and systems using micro-and-notechnology achievements will also contribute to solving the problem of creating electronic optics with small aberrations.
LIT: Practical raster electron microscopy, ed. D. Gouldstain, X. Yakovitsa, Per. from English, M., 1978; Spence D., Experimental Electronic Microscopy of High Resolution, Per. from English, M., 1986; Stoyanov P. A., Electronic Microscope SVEM-1, "Izvestia of the USSR Academy of Sciences, Ser. Piz.", 1988, vol. 52, No. 7, p. 1429; HOKS P., Casper E., Basics of electronic optics, lane. from English, t. 1-2, M., 1993; Ochsner H., Scanning Auger Microscopy, Le Vide, Les Couches Minces, 1994, t. 50, № 271, p. 141; McMul-Lan D., Scanning Electron Microscopy 1928-1965, "Scanning", 1995, t. 17, No. 3, c. 175. P. A. Stanov.
We are starting to publish a blog entrepreneur, a specialist in the field of information technology and a part-time-like-amateur designer Alexei Bragin, which tells about the unusual experience - now the year as the author of the blog is engaged in the restoration of complex scientific equipment - a scanning electron microscope - practically at home. Read about what engineering and technical and scientific tasks I had to face Alexey and how he coped with them.
I called me somehow a friend and says: I found an interesting thing, you need to bring to you, however, weighs half-bottom. So in my garage there was a column from the scanning electron microscope JEOL JSM-50A. It has long been written off from some kind of research and taken into scrap metal. The electronics lost, but the electron-optical column, together with the vacuum part, managed to save.
Once the main part of the equipment has been preserved, the question arose: is it possible to save the microscope completely, that is, to restore and bring it into a working condition? And right in the garage, with your own hands, with the help of only basic engineering and technical knowledge and remedies? True, before I have never dealt with such scientific equipment, not to mention, to be able to use them, and did not imagine how it works. But it is interesting because it is not easy to launch an old piece of iron in a working condition - it is interesting to deal with everything yourself and check if it is possible using a scientific method, to master completely new areas. So I began to restore an electron microscope in the garage.
In this blog I will tell you about what I have already managed to do and what else will have. Along the way, I will introduce you to the principles of the functioning of electronic microscopes and their main nodes, as well as tell about the set of technical obstacles that had to overcome in the course of work. So, proceed.
To restore the microscope, at least to the state, "draw an electronic beam in a luminescent screen", it was necessary:
Let's start in order. Today I will tell about the principles of the operation of electron microscopes. They are two types:
Translucent electronic microscope
PEM is very similar to the usual optical microscope, only the studied sample is irradiated not with light (photons), and electrons. The wavelength of the electron beam is much smaller than the photon, so you can get a much greater permit.
The focusing of the electron beam and the management of them is carried out with the help of electromagnetic or electrostatic lenses. They even have the same distortions (chromatic aberrations) as optical lenses, although the nature of physical interaction here is completely different. It, by the way, adds new distortions (caused by the spinning of electrons in the lens along the axis of the electron beam, which does not occur with photons in the optical microscope).
Pam has shortcomings: the samples under study should be very thin, thinner 1 micron, which is not always convenient, especially when working at home. For example, to look at your hair on the lumen, it must be cut along at least 50 layers. This is due to the fact that the penetrating ability of the electron beam is much worse than photon. In addition, PEM, with rare exceptions, quite cumbersome. This apparatus, shown below, seems to be not so big (although it is above human growth and has a solid cast-iron bed), but the power supply is still attached to it with a large closet size - there is almost a whole room.
But the permission from PEM is the highest. With it (if you try hard to try), you can see individual atoms of the substance.
University of Calgary.
Such permission is particularly useful for identifying a viral disease causative agent. The entire XX century viral analytics was built on the basis of the PEM, and only with the advent of cheaper methods for the diagnosis of popular viruses (for example, a polymerase chain reaction, or PCR), the routine use of the PEM for this purpose ceased.
For example, what does the H1N1 flu look like "on the lumen":
University of Calgary.
Scanning electronic microscope
SEM is used mainly to study the surface of samples with very high resolution (an increase in a million short, against 2 thousand in optical microscopes). And this is much more useful in the household :)
For example, it looks like a separate bristle of a new toothbrush:
The same should occur in the electron-optical column of the microscope, only here the sample is irradiated, and not the phosphor of the screen, and the image is formed on the basis of information from sensors fixing the secondary electrons, elastic-reflected electrons and so on. About the electron microscope is this type and will be discussed in this blog.
And the Kinescope TV, and the electron-optical column of the microscope only under vacuum. But I will tell about this in detail in the next issue.
(To be continued)
To study nano-versions of optical microscope resolution ( even using ultra-violet) It is clearly not enough. In this regard, in the 1930s. An idea has arisen to use instead of the electrons, the wavelength of which, as we know from quantum physics, is hundreds of times less than that of photons.
As is known, the basis of our view is the formation of an image of an object on the retina of the eye with light waves reflected from this object. If, before you get into the eye, the light passes through the optical system. microscope, we see an enlarged image. In this case, the light rays skillfully control the lenses that constitute the lens and the ocular of the device.
But how can I get an image of an object, and with a much higher resolution, using not light emission, and the electron flow? In other words, how can the vision of objects on the basis of use not waves, and particles?
The answer is very simple. It is known that the trajectory and velocity of electrons significantly affect the external electromagnetic fields, with which it is possible to effectively control the movement of electrons.
The science of the movement of electrons in electromagnetic fields and the calculation of devices forming the necessary fields is called electo-electo.
The electronic image is formed by electrical and magnetic fields as well as light-optical lenses. Therefore, in the electron microscope of the device, the focus sink and dispersion of the electron beam is called " electronic lenses”.
Electronic lens. The coils of the coils for which the current passes, focus the bunch of electrons just like a glass lens focus the light beam
The magnetic field of the coil acts as collecting or scattering lens. To concentrate the magnetic field, the coil is closed with a magnetic " armor»From a special ni-cell-cobalt alloy, leaving only a narrow gap in the inside. The magnetic field created in this way can be 10-100 thousand times stronger than the magnetic field of the Earth!
Unfortunately, our eyes cannot directly perceive electronic beams. Therefore, they are used for " drawing"Images in luminescent screens (which are glowing when electrons hit). By the way, the same principle underlies the work of monitors and oscil-lips.
There are a large number of different types of electronic microscopes, among which the raster electronic microscope (RAM) is most popular. We will get it a simplified scheme if you place the object being studied inside the electron-beam tube of an ordinary TV between the screen and the source of electrons.
In such microscope A thin electron beam (a beam diameter is about 10 nm) cuts (as if scanning) the sample along the horizontal line, the point per point, and synchronously transmits the signal to the kinescope. The whole process is similar to the operation of the TV in the scanning process. The source of electrons serves a metal (usually tungsten), from which, when heated, electrons are emitted as a result of thermoelectronic emission.
Scheme of a raster electron microscope
Thermoelectronic emission - Electron output from the surface of the conductors. The number of electron released is not enough at T \u003d 300K and exponentially grows with an increase in temperature.
When the electron passes through the sample, one of them is dissipated due to collisions with the nuclei of the sample atoms, the other conversion of collisions with electrons of atoms, and the third pass through it. In some cases, secondary electrons are emitted, X-ray radiation is induced, etc. All these processes are recorded by special detectors And in the converted form, displayed on the screen, creating an enlarged image of the object being studied.
An increase in this case is understood as the ratio of the size of the image on the screen to the size of the area rugged on the sample. Due to the fact that the electron wavelength is less than a photon, in modern RAM, this increase can reach 10 million15, corresponding to permission to nanometer units, which allows visualizing individual atoms.
Chief flaw electron microscopy - The need to work in complete vacuum, because the presence of some kind of gas inside the microscope chamber can lead to the ionization of its atoms and significantly distort the results. In addition, electrons have a devastating impact on biological objects, which makes them not applicable for research in many areas of biotechnology.
History of creation electronic microscope - A wonderful example of an achievement based on an interdisciplinary approach when independently developing areas of science and technology, united, created a new powerful tool of scientific research.
The vertex of classical physics was the theory of an electromagnetic field, which explained the spread of light, electricity and magnetism as the spread of electromagnetic waves. Wave optics explained the diffraction phenomenon, the image forming mechanism and the game factors determining the resolution in the light microscope. Successes quantum Physics We are obliged to open an electron with its specific corpuscularity properties. These individuals and, it would seem, independent development paths led to the creation of electronic optics, one of the most important inventions of which an electron microscope became one of the inventions.
But on this, scientists did not calm down. The electron wavelength accelerated by an electric field is several nanometers. It is not bad if we want to see a molecule or even an atomic grille. But how to look inside the atom? What is the chemical connection? What does the process of a separate chemical reaction look like? For this, today in different countries, scientists are developing neutron microscopes.
Neutrons are usually included in the atomic nuclei along with protons and have almost 2000 times a large mass than an electron. Those who have not forgotten the formula de Broglie from Quantum chapter will immediately contemplate that the length of the wave at the neutron is less than the same time less, that is, makes up the thousandths of the nanometer! This is the atom and will represent researchers not as a vague spot, but in all its glory.
Neutron microscope It has many advantages - in particular, neutrons well reflect hydrogen atoms and easily penetrate into thick layers of samples. However, it is very difficult to build it: neutrons do not have an electric charge, so they calmly ignore the magnetic and electric fields and storing themselves to slip away from the sensors. In addition, it is not so easy to drive out large non-robust neutrons from atoms. Therefore, today the first prototypes of the neutron microscope are still far from excellence.
ELECTRON MICROSCOPE
The device that allows you to get a highly enlarged image of objects using electrons for their illumination. The electron microscope (EM) makes it possible to see the details, too small so that they can solve the light (optical) microscope. EM is one of the most important devices for fundamental scientific research of the structure of the substance, especially in such areas of science as biology and solid physics. There are three main types of EM. In the 1930s, a conventional transmission electron microscope (OPEM) was invented, in the 1950s - raster (scan) electron microscope (RAM), and in the 1980s - raster tunnel microscope (RTM). These three types of microscopes complement each other in studies of structures and materials of different types.
Normal translucent electron microscope
OPEM is largely similar to the light microscope, see the microscope, but only for the lighting of the samples is not used in it, but an electron beam. It has an electronic spotlight (see below), a series of condense lenses, an objective lens and a projection system that corresponds to the eyepiece, but proacts the actual image to the fluorescent screen or a photographic plate. The source of electrons is usually served by a heated cathode from tungsten or Lanthan hexaboride. The cathode is electrically isolated from the rest of the instrument, and electrons are accelerated by a strong electric field. To create such a field, the cathode is maintained under the potential of order -100,000 in relatively other electrodes focusing electrons into a narrow beam. This part of the device is called an electronic spotlight (see Electronic Gun). Since the electrons are strongly dissipated by the substance, in the microscope column where the electrons move, there should be a vacuum. Here is maintained pressure not exceeding one billionth atmospheric.
Electronic optics. The electronic image is formed by electrical and magnetic fields as well as light-optical lenses. The principle of operation of the magnetic lens is illustrated by the scheme (Fig. 1). The magnetic field created by the coils coils, which passes the current, acts as a collecting lens, whose focal length can be changed by changing the current. Since the optical force of such a lens, i.e. The ability to focus electrons depends on the magnetic field strength near the axis, it is advisable to consecrate the magnetic field in the lowest possible volume to increase it. Almost this is achieved by the fact that the coil is almost completely covered with magnetic "armor" from a special nickel-cobalt alloy, leaving only a narrow gap in its inner part. The magnetic field created in this way can be 10-100 thousand times stronger than the magnetic field of the Earth on the earth's surface.
OPEM scheme is presented in Fig. 2. A series of condense lenses (only last) focuses the electronic beam on the sample. Usually the first of them creates an unbaptated image of an electron source, and the latter controls the size of the illuminated area on the sample. The diaphragm of the last condenser lens is determined by the beam width in the plane of the object. The sample is placed in a magnetic field of an objective lens with a large optical power - the most important lenses of OPEM, which determines the limit possible resolution of the device. The aberration of the objective lens is limited to its diaphragm as well as this happens in the camera or light microscope. An objective lens give an enlarged image of an object (usually with an increase in order 100); An additional increase made by intermediate and projection lenses lies within the limits of a slightly less than 10 to several more than 1000. Thus, an increase that can be obtained in modern OPM is from less than 1000 to electronic microscope1,000,000. (with an increase in a million times Grapefruit grows to the size of the Earth.) The object under study is usually placed on a very fine grid invested in a special holder. The holder can be mechanically or electrically moving up and down and left.
Picture. The contrast in OPEM is due to the scattering of electrons when the electron beam passes through the sample. If the sample is quite thin, then the share of scattered electrons is small. When electron passes through the sample, one of them is dissipated due to collisions with nuclei of the sample atoms, others - due to collisions with atom electrons, and the third pass, not undergoing scattering. The degree of scattering in any region of the sample depends on the thickness of the sample in this area, its density and the middle atomic mass (proton number) at this point. Electrons emerging from a diaphragm with an angular deviation exceeding a certain limit can no longer return to the beam, which is bearing an image, and therefore strongly dissipating areas of high density, increased thickness, the location of heavy atoms look in the image as dark areas on a light background. This image is called Svetopolna, since it is the lighter object on it. But it can be done so that the electrical deflecting system passes into the lens diaphragm only those or other of scattered electrons. Then the sample looks light on a dark field. Weakly scattering facility is often more convenient to consider in a dark field mode. The final enlarged electronic image is converted to visible by means of a fluorescent screen, which glows under the action of electronic bombardment. This image, usually weakly contrast, as a rule, is considered through a binocular light microscope. With the same brightness, such a microscope with an increase of 10 can create an image on the retina, 10 times larger than when observed with a naked eye. Sometimes to increase the brightness of a weak image, a phosphor screen with an electron optical converter is used. In this case, the final image can be displayed on a regular television screen, which allows you to write it on the video gentle. Video recording is used to register images varying in time, for example, due to the flow of a chemical reaction. Most often, the final image is recorded on a film or photoplastic. Photoflastic usually allows you to get a clearer image than the simple eye observed or recorded on the video tape, since the photographic materials, generally speaking, more efficiently register electrons. In addition, on a unit of photocillion square can be registered 100 times more signals than on the unit of the video tape. Due to this, an image registered on the film can be additionally increased by about 10 times without loss of clarity.
Resolution. Electronic beams have properties similar to the properties of light beams. In particular, each electron is characterized by a certain wavelength. The resolution of the EM is determined by the efficient wavelength of electrons. The wavelength depends on the electron velocity, and therefore, from accelerating voltage; The greater the accelerating tension, the greater the speed of the electrons and the less the wavelength, and therefore above the resolution. Such a significant advantage of the EM in the resolution is due to the fact that the length of the electron wave is much smaller than the wavelength of the light. But since the electronic lenses are not so well focused as optical (the numerical aperture of a good electron lens is only 0.09, whereas for a good optical lens this value reaches 0.95), the resolution of EM is 50-100 electron wavelengths. Even with such weak lenses in the electron microscope, you can get the limit of OK. 0.17 nm, which allows distinguishing individual atoms in crystals. To achieve the resolution of such a procedure, a very thorough adjustment of the device is needed; In particular, high-stable power supplies are required, and the device itself (which can be height approx. 2.5 m and have a mass of several tons) and its additional equipment requires installation that excludes vibration.
Raster electronic microscope
Ram, who became the most important device for scientific research, serves as a good addition to OPEM. The RAM uses electronic lenses for focusing the electron beam in a stain of very small sizes. It is possible to adjust the RAM so that the stain diameter in it does not exceed 0.2 nm, but, as a rule, it constitutes units or tens of nanometers. This stain continuously cuts some section of the sample in the same way as a beam by a television tube screen. The electrical signal that occurs when the beam electrically bombardment is used to form an image on the screen of a television kineskop or an electron-beam tube (CRT), the sweep of which is synchronized with the electron beam deviation system (Fig. 3). An increase in this case is understood as the ratio of the size of the image on the screen to the size of the area rugged on the sample. This increase ranges from 10 to 10 million.
The interaction of the electrons of a focused beam with the sample atoms can lead not only to their scattering, which is used to obtain an image in OPEM, but also to the excitation of X-ray radiation, emitting visible light and the emission of secondary electrons. In addition, since there are only focusing lenses in the RAM, it allows you to explore "thick" samples.
Reflective Rem. Reflective RAM is designed to study massive samples. Since the contrast arising from registration reflected, i.e. Refused, and secondary electrons are connected mainly with an angle of incidence of electrons per sample, the surface structure is detected on the image. (The intensity of reverse scattering and the depth on which it occurs, depend on the electron energy of the incident beam. The emission of secondary electrons is determined mainly by the composition and sample electrical conductivity.) Both of these signals carry information about the common characteristics of the sample. Due to the small convergence of the electron beam, you can conduct observations with a much greater depth of field than when working with a light microscope, and get the excellent volumetric micrographs of surfaces with a very developed relief. By registering X-ray radiation emitted by the sample, in addition to the relief data to obtain information on the chemical composition of the sample in the surface layer of the electronic microscope, 2001 mm. The composition of the material on the surface can be judged by the measured energy, with which those or other electrons are issued. All difficulties of working with RAM are mainly due to its registration and electronic visualization systems. In the device with a complete complex of detectors, along with all RAM functions, the operating mode of the electron-probe micro analyzer is envisaged.
Raster translucent electron microscope. Raster translucent electron microscope (RPEM) is a special kind of RAM. It is designed for thin samples, the same as those studied in OPEM. The RPEM scheme differs from the diagram in Fig. 3 Only the fact that it has no detectors located above the sample. Since the image is formed by a running beam (and not a bundle that illuminates the entire section of the sample section), a highly intensive source of electrons is required so that the image can be registered during an acceptable time. High-resolution RPEM uses high-brightness autoelectronic emitters. In such a source of electrons, a very strong electric field is created (approx. V / cm) near the surface of a pointed etching of a tungsten wire of a very small diameter. This field literally pulls billions of electrons from the wire without any heating. The brightness of such a source is almost 10,000 times greater than a source with a heated tungsten wire (see above), and the electrons emitted by them can be focused into a bundle with a diameter of less than 1 nm. There were even beams, the diameter of which is close to 0.2 nm. Auto-electron sources can only work under ultra-high vacuum (at pressures below PA), in which there are completely contaminants, as a pair of hydrocarbons and water, and it becomes possible to obtain high-resolution images. Thanks to such supercure conditions, it is possible to explore processes and phenomena, inaccessible EM with conventional vacuum systems. Research in RPEM is carried out on ultra-thin samples. Electrons pass through such samples almost without scattering. Electrons scattered on the corners of more than a few degrees without deceleration are recorded, falling onto a ring electrode located under the sample (Fig. 3). The signal removed from this electrode strongly depends on the atomic number of atoms in the area through which electrons pass are, more severe atoms dispel more electrons in the direction of the detector than the lungs. If the electronic bundle is focused on a point with a diameter of less than 0.5 nm, then the image of individual atoms can be obtained. It is really possible to distinguish between the image obtained in RPEM, individual atoms with atomic weight of iron (ie, 26 or more). Electrons, not undergoing scatters in the sample, as well as electrons, slowed down as a result of interaction with the sample, pass into the hole of the ring detector. The energy analyzer located under this detector allows you to separate the first from the second. Measuring energy lost by electrons when scattered, you can get important information about the sample. The loss of energy associated with the excitation of X-ray radiation or knocking out secondary electrons from the sample, make it possible to judge the chemical properties of the substance in the area through which the electron beam passes.
Raster tunnel microscope
In the EM, discussed above, magnetic lenses are used to focus electrons. This section is dedicated to EM without lenses. But, before switching to a raster tunnel microscope (RTM), it will be useful to briefly stop at two old versions of the messenger microscope, which forms a projected shadow image.
Auto-electron and auto-war projectors. The auto-electron source used in RPEM has been used in shadow projectors since the beginning of the 1950s. In the auto-electronic projector, the electrons emitted by the autoelectronic emission by the edges of very small diameters are accelerated in the direction of the luminescent screen, located at a distance of several centimeters from the tip. As a result, an projected image of the surface of the isge and on this surface of the particles occurs on the screen with an increase equal to the radius of the screen to the island radius (order). Higher resolution is achieved in the auto-alert projector, in which the projection of the image is carried out by the helium ions (or some other elements), the effective wavelength of which is less than that of electrons. This allows you to obtain images showing the true arrangement of atoms in the crystal lattice of the island material. Therefore, autoion projectors are used, in particular, to study the crystal structure and its defects in materials from which such an isge can be made.
Raster tunnel microscope (RTM). In this microscope, the metal edge of the small diameter is also used, which is the source of electrons. In the gap between the edge and the surface of the sample, an electric field is created. The number of electrons drawn by the island field per unit of time (tunneling current) depends on the distance between the edges and the surface of the sample (in practice it is a distance of less than 1 nm). When moving the island along the surface of the current is modulated. This allows you to get an image associated with the relief of the sample surface. If the edge ends with a single atom, then you can form an image of the surface by passing an atom atom. The RTM can only work under the condition that the distance from the tip to the surface is constantly, and the point can be moved up to atomic sizes. Vibrations are suppressed due to the rigid design and small microscope sizes (no more fist), as well as the use of multilayer rubber shock absorbers. High accuracy provides piezoelectric materials that are lengthened and reduced under the action of an external electric field. Feeding a voltage of about 10-5 V, you can change the dimensions of such materials by 0.1 nm and less. This makes it possible to adopt the edge on the element from the piezoelectric material, move it in three mutually perpendicular directions with an accuracy of the order of atomic sizes.
Equipment electron microscopy
There is hardly any sector of research in the field of biology and materials science, where there was no transmission electron microscopy (PEM); This is ensured by the success of the preparation of samples. All techniques used in electron microscopy are aimed at obtaining an extremely thin sample and ensuring maximum contrast between it and the substrate, which is necessary for it as a support. The main technique is designed for samples with a thickness of 2-200 nm, supported by subtle plastic or carbon films, which are put on the grid with the size of the cell OK. 0.05 mm. (A suitable sample, no matter how it is obtained by it is processed so as to increase the intensity of the scattering of electrons on the object under study.) If the contrast is large enough, the eye of the observer can distinguish the parts at a distance of 0.1-0.2 mm without voltage Friend from each other. Therefore, in order for the image created by an electron microscope, the parts separated on the sample distance in 1 nm, it is necessary to have a complete increase in order of 100-200 thousand. The best of microscopes can create an image of a sample on the photoplastic with such an increase, but at the same time A too small portion is depicted. Usually make micrographs with a smaller increase, and then increase it with photographic. Photoflastic permits at a length of 10 cm approx. 10 000 lines. If each line corresponds to a sample of a certain structure with a length of 0.5 nm, then to register such a structure, an increase of at least 20,000 is needed, whereas with the help of RAM and RPEM, in which the image is registered with an electronic system and deployed on a television screen can only be allowed OK. 1000 lines. Thus, when using a television monitor, the minimum needed increase is about 10 times more than when photographer.
Biological preparations. Electron microscopy is widely used in biological and medical research. Developed methods of fixation, fill and obtain thin tissue sections for research in OPEM and RPEM and fixation techniques for the study of volume samples in RAM. These techniques make it possible to investigate the organization of cells at the macromolecular level. Electron microscopy revealed cell components and parts of the structure of membranes, mitochondria, endoplasmic network, ribosomes and many other organelles included in the cell. The sample is first fixed with glutaraldehyde or other fixing substances, and then dehydrated and poured plastic. Methods of cryogenication (fixation with very low - cryogenic temperatures) allow you to preserve the structure and composition without the use of chemical fixing substances. In addition, cryogenic methods allow you to obtain images of frozen biological samples without dehydration. Using ultramicrothomes with blades of polished diamond or slice glass, you can make sections of tissues with a thickness of 30-40 nm. Mounted histological preparations can be painted with heavy metal compounds (lead, osmium, gold, tungsten, uranium) to enhance the contrast of individual components or structures.
Biological studies were distributed to microorganisms, especially for viruses that are not allowed by light microscopes. The PEM allowed to identify, for example, the structures of bacteriophages and the location of the subunits in the protein shells of viruses. In addition, the methods of positive and negative staining managed to identify the structure with subunits in a number of other important biological microstructures. Methods for enhancing the contrast of nucleic acids made it possible to observe one- and double-down DNA. These long linear molecules are molded in a layer of main protein and apply on a thin film. Then a very thin layer of heavy metal is applied to the sample with vacuum spraying. This heavy metal layer "shall" sample, thanks to which the latter when observed in OPEM or RPEM looks like a metal lit from the other side with which the metal has spoken. If you rotate the sample during spraying, the metal accumulates around the particles from all sides evenly (as a snowball).
Nebiological materials. The PEM applies to the studies of materials to study thin crystals and boundaries between different materials. In order to obtain an image of a partition boundary with a large resolution, the sample is poured with plastic, make a sample slice, perpendicular boundary, and then sink it so that the border is visible on a pointed edge. The crystal lattice scatters electrons strongly in certain directions, giving a diffraction picture. The image of the crystalline sample is largely determined by this picture; Contrast strongly depends on the orientation, thickness and perfection of the crystal lattice. Changes in contrast in the image allow you to study the crystal lattice and its imperfections on the scale of atomic sizes. The information obtained in this case complements the one that the radiographic analysis of bulk samples gives, since the EM makes it possible to directly see in all parts of the dislocation, the packaging defects and the grain boundaries. In addition, the EM can remove the electronograms and observe the patterns of diffraction from the selected sections of the sample. If the lens diaphragm is adjusted so that only one diffracted and non-painted central beams passed through it, then the image of a certain crystal plane system can be obtained, which gives this diffracted beam. Modern devices allow you to resolve the periods of the lattice of 0.1 nm. It is also possible to explore the crystals using a dark-axis image method at which the central beam is overlap, so that the image is formed by one or more diffracted beams. All these methods gave important information about the structure of very many materials and significantly clarified the physics of crystals and their properties. For example, the analysis of the PEM images of the crystal lattice of thin small-sized quasicrystals in combination with the analysis of their electron diffuses allowed in 1985 to open materials with the symmetry of the fifth order.
High voltage microscopy. Currently, the industry produces high-voltage options for OPEM and RPEM with accelerating voltage from 300 to 400 square meters. Such microscopes have a higher penetrating capacity than low-voltage devices, and almost no microscopes in this regard with a voltage of 1 million volts, which were built in the past. Modern high-voltage microscopes are compact enough and can be installed in a conventional laboratory room. Their enhanced penetrating ability turns out to be very valuable in the study of defects in thicker crystals, especially those of which it is impossible to make fine samples. In biology, their high penetrating ability makes it possible to explore whole cells without cutting them. In addition, with the help of such microscopes, you can get three-dimensional images of thick objects.
Low-voltage microscopy. There are also RAM with accelerating voltage constituting only a few hundred volts. Even with such low voltages, the wavelength of electrons is less than 0.1 nm, so that the spatial resolution is limited to the aberrations of magnetic lenses. However, since electrons with such low energy penetrate a shallow surface under the surface of the sample, almost all electrons involved in the formation of the image come from the region located very close to the surface, thereby increasing the resolution of the surface relief. With low-voltage RAM, images on solid surfaces of objects of less than 1 nm were obtained.
Radiation damage. Since electrons are ionizing radiation, the sample in the EM is constantly exposed to its effect. (As a result of this impact, secondary electrons used in RAM occur. Therefore, the samples are always subjected to radiation damage. A typical radiation dose absorbed by a thin model during the registration of micrographs in OPEM, roughly corresponds to the energy that would be sufficient for the complete evaporation of cold water from the pond with a depth of 4 m with an area of \u200b\u200b1 hectare surface. To reduce radiation damage to the sample, it is necessary to use various methods of its preparation: staining, fill, freezing. In addition, it is possible to register an image with electron doses, 100-1000 times smaller than the standard methodology, and then improve its computer processing methods.
HISTORICAL REFERENCE
The history of the creation of an electron microscope is a wonderful example of how independently developing areas of science and technology can, exchanging the information received and combining efforts, create a new powerful tool of scientific research. The vertex of classical physics was the theory of an electromagnetic field, which explained the propagation of light, the occurrence of electrical and magnetic fields, the movement of charged particles in these fields as the propagation of electromagnetic waves. Wave optics made clear phenomenon of diffraction, the image forming mechanism and the game factors determining the resolution in the light microscope. We are obliged to open an electron with its specific properties to successes in the field of theoretical and experimental physics. These individuals and, it would seem, independent development paths led to the creation of electronic optics, one of the most important applications of which was the invention of the EM in the 1930s. A direct hint on this possibility can be considered a hypothesis of an electron wave nature, nominated in 1924 Louis de Brogle and experimentally confirmed in 1927 K. Davisson and L. Jermer in the USA and J.Tomson in England. Thus, an analogy was prompted to build an AM according to the laws of wave optics. H.Bush found that using electrical and magnetic fields you can form electronic images. In the first two decades of the 20th century. Required technical prerequisites were created. Industrial laboratories worked on an electron-beam oscilloscope gave vacuum technique, high voltage and current sources, good electronic emitters. In 1931 R. Rudenberg filed a patent application for a transmission electron microscope, and in 1932 M. Knoll and E.Ruska built the first such microscope, applying magnetic lenses to focus electrons. This device was the predecessor of modern OPEM. (Ruska was rewarded for his works by the fact that he became a laureate of the Nobel Prize in Physics for 1986.) In 1938, RUSS and B.Fon Borris built a prototype of industrial Opos for the company "Siemens-Chalkk" in Germany; This device eventually made it possible to achieve a resolution of 100 nm. A few years later, A.Prebus and J. Chiller built the first Opos of High Resolution at the University of Toronta (Canada). Wide opportunities OPEM almost immediately became obvious. Its industrial production was started simultaneously by Siemens-Chalkk in Germany and RCA in the United States. In the late 1940s, such devices began to produce other companies. RAM in its current form was invented in 1952 charlze. True, the preliminary options for such a device were built by Knolm in Germany in the 1930s and Zvelakin with employees in the RCA Corporation in the 1940s, but only the device was able to serve as a basis for a number of technical improvements that ended in the production of industrial variant RAM in the middle 1960s. The circle of consumers is of such a pretty simple in circulation of the device with a volumetric image and an electronic output signal expanded with the speed of the explosion. Currently there is a good tens of industrial manufacturers RAM "OV on three continents and tens of thousands of such devices used in the laboratories of the whole world. In the 1960s, ultra-high-voltage microscopes were developed for studying thicker samples. The leader of this development site was G. Tyupui in France where in 1970 a device with accelerating voltage was put into effect equal to 3.5 million volts. The RTM was invented by the city of Binnig and Rorger in 1979 in Zurich. This very simple device device provides atomic resolution of surfaces. For its work For the creation of the RTM Binnig and Roar (at the same time with Ruska), the Nobel Prize in Physics was obtained.
see also
Technological archeology)
Some electronic microscopes are restored, other firmware of spacecraft, the third - are engaged in reverse engineering circuitry with microscope under the microscope. I suspect that the occupation is terribly fascinating.
And, by the way, I remembered the wonderful post about the industrial archeology.
Spoiler
Corporate memory is two species: people and documentation. People remember how things work, and know why. Sometimes they write this information somewhere and store their records somewhere. This is called "Documentation". Corporate amnesia acts in the same way: people go, and documentation disappears, rotates or simply forgetting.
I spent several decades working in a large petrochemical company. In the early 1980s, we designed and built a plant that alters some hydrocarbons to other hydrocarbons. Over the next 30 years, corporate memory has weakened about this factory. Yes, the plant still works and brings money from a firm; Maintenance is produced, and high-freed experts know that they need to be twisted and where to kick that the plant continues to work.
But the company absolutely forgotten how this plant works.
This happened due to the fault of several factors:
The decline in the petrochemical industry in the 1980s and 1990s made us stop accepting new people. In the late 1990s, the guys under the age of 35 or over 55 worked in our group, with very rare exceptions.
We slowly moved to design using computer systems.
Due to corporate reorganizations, we had to physically move to all office from place to place.
Corporate merger a few years later completely dissolved our company in a larger, causing the global restructuring of the departments and shuffling.
Industrial archeology
In the early 2000s, I and several of my colleagues retired.
In the late 2000s, the company remembered the factory and thought that it would be nice to do something with him. Say, increase production. For example, you can find a bottleneck in the production process and improve it, - the technology did not stand these 30 years in place, and maybe attach another workshop.
And then the company from all Mahi is imprinted in a brick wall. How was this plant built? Why was it built exactly so, and not otherwise? How exactly does he work? What is needed Chan A, why the workshop b and in the pipeline are connected, why the pipeline has a diameter of r, and not d?
Corporate amnesia in action. Giant machines built by aliens with their alien technology, chaviquet, as head, giving out the pile of polymers on-mountain. The company is about imperative, how to serve these cars, but it does not have the idea that the amazing magic is going on inside, and no one has the slightest idea of \u200b\u200bhow they were created. In general, the people are not even sure that it is necessary to look for, and does not know which party to unravel this tangle.
The guys are found, which during the construction of this plant already worked in the firm. Now they occupy high positions and sit in separate, air-conditioned cabinets. They are given a task to find the documentation for the factory. This is no longer corporate memory, it looks more like an industrial archaeology. No one knows what documentation on this plant exists whether it exists at all, and if so, in what form it is stored, in what formats that it includes in itself and where it lies physically. The plant was designed by the project team, which is no longer, in the company, which has since been absorbed in the office, which was closed using the methods of a pre-computer era that no longer apply.
The guys remember childhood with a mandatory smoke in the mud, rush the sleeves of expensive jackets and are accepted for work.