1986 s Nobel Prize in Physics

Transcription

1 Revised version: s Nobel Prize in Physics (Electron Microscope & STM) Huiwon Ahn Seoul National University Department of Physics & Astronomy, Korea Abstract The structure of matter or organisms has helped to elucidate the curiosity and phenomena of people. A microscope is a very good tool to magnify an object to reveal its structure, and an optical microscope that magnifies the image through light has been used for about 400 years. High-magnification and high-resolution microscopes were invented using various principles including an electron microscope that analyze information on structures by electrons. Ernst Ruska received the Nobel Prize in 1986 for inventing an electron microscope. At present, the microscope has been developed to be able to see atoms, and it is very helpful in various fields. Introduction People have always wondered what an material is made of and what structure it is. The material is made up of very small, but the human eye has no ability to see it. A microscope is a tool for magnifying objects. The person who made the beginning of the current optical microscope was a man named Jansen in At that time, he invented the use of a telescope for marine exploration. As the lens processing technique develops, it is found that the focal length (the distance between the central axis of the lens and the focal point) greatly affects the lens magnification. And They made a microscope using magnification. Optical Microscope -Magnification- An optical lens is a tool made of glass that collects or spreads light according to its shape. The convex lens that collects light greatly expands the material and is used in optical microscopes. A typical optical microscope consists of two optical Fig.1. Inside the Optical Microscope[1] (Ocular lens is Eyepiece. m is magnification of lens)

2 lenses. The magnification of the optical lens is a product of the lens magnification, and the total magnification can be expressed as follows:. is total magnification. is objectiove len s, is eyepiece,, are the respec tive focal lengths, s is distance between and ). (Fig.1) However, high magni fication alone does not allow the object to be seen clearly -Resolution- The magnitude of the distinction between objects in the magnified state is an important factor in microscopy as well as magnification, which is called resolution. resolution, d is expressed as follows : (NA : Numerical Aperture). If the resolution is bad, it looks like the image is blurred. As can be seen from the equation, the resolution depends on the wavelength. In addition, the refractive index of the wavelength differs depending on the color, so the color spreads after passing through the lens. Therefore, in the case of white light with all colors, the colors appear to spread, and this is called chromatic aberration. There are other aberrations as well. The spherical aberration is a phenomenon in which the focusing position deviates from the front and back as the parallel rays move away from the optical axis. That is, since the focus and the optical axis are different, the phase is distorted. The light passing through the center of the lens is generally focused at one point. As it gets farther from the center, it does not focus on one point, causing the phenomenon of light spreading. This is called coma aberration. The coma aberration occurs because the magnification, which is the ability to gather light well, is not the same throughout the lens.(fig.2,3) There are many other aberrations. We can now eliminate the aberration quite a bit, but we did not have this technology at the time. There are too many areas to Fig.2. Coma Aberration(Top), Spherical Aberration(Bottom) [2] Fig.3. Chromatic aberration(left) [3] Coma Aberration(Right) [2]

3 consider, and the magnification can only be up to 4000 times (microscale) due to the aberration limit. This is the limit that we can not get what we want magnification(nanoscale). Electron Microscope -Electron lens- For the first time, Hans Busch has shown that electrons can be focused in one place by magnetic force. Later, Ernst Ruska called it an electron lens, similar to the way an optical lens collects light using a tool that uses this focused phenomenon. There are two types of electron lenses, which are the core of the electron microscope. One is an electric lens using electric force, and the other is a magnetic lens using magnetic force. The method of the electric lens is as follows : (Fig.4) 1. The electric lens is set up with two minus left and right plus the electrodes up and down. 2. When a voltage is applied to the electrode, an equipotential line is formed. 3.When electrons are emitted between equipotential lines between electrodes, electrons gather in one place by electric force perpendicular to equipotential line. However, electric lenses easily absorbed electrons, so information was lost and it was not actually used because it was difficult to keep the equipotential lines. So most of the electronic lenses are magnetic lenses. The magnetic lens is cylindrical, with a magnet on the outside and a coil on the inside, with a hole that electron can through pass in the center. The magnetic lens utilized principle that lines of magnetic force, and movement of electric charge is vertical. The method of the magnetic lens is as follows : (Fig.4) 1.It makes ultra high vacuum state(10 torr) 2.The electrons are made perpendicular movement by the anode Fig.4. electric lens(top), magnetic lens (Bottom) [4]

4 3.Electrons are focused by a magnetic lens and scanned onto a specimen 4.Accepts the information of the electrons by the detector and converts them visible to sum up, The electron rotates around the optical axis by the Lorentz force and is focused on spot. Precisely, it is a spiral motion, not a rotational motion. The spiral motion cycle is as follows. T=(2π /1.76)(1/H) (Sec). H is magnetic filed strength. It can be seen that only the magnetic force, not the energy of the electrons, influences the electron spiral motion through the period equation. This means that the electrons gather in one place by doing spiral motion whatever energy they have(fig.2). Electrons bounce off the sample are into the detector. The electrons display the information about the sample in current and vibration (db) and image it based on it. -Improving- But it did not work well from the beginning. Because the energy of the electron is the amount of the information of the sample, they did not know how much to inject this energy. They was increased energy of the electrons five-fold based on the de Broglie's matter wave theory discovery which was announced at the time of electron microscope development. As a result, they were able to achieve enormous magnification same as theory. However, the sample was damaged by increasing the energy of the electron, but it was prevented by using liquid helium at an extremely low temperature. However, another problem arises. This time, the residual gas is stuck to the sample due to the cryogenic temperature, and the sample is no longer visible. This problem was solved by a technique called ultramicrotomes which slices the material to 30 to 60 nm. The thinned sample does not matter Even if the residual gas is attached, the problem is eliminated. The electron microscope invented by E.Ruska has a magnification of about 100,000 times, Microorganisms such as molecular structure and bacteria can be seen. In addition, since the information of the electron is visualized as it is, it can be seen in seen only in a plane view. -Influencethe electron microscope then develops with SEM and TEM (Fig.5). The SEM(Scanning Electron Microscope) is almost the same as the conventional electron microscope. It detects the backscattering electrons and secondary electrons from the collision between the sample and the electron and sees the sample. And TEM(Transmission

5 Fig.5. (L) Silica(SiO2) structure MA : 100,000 x. SEM (R) Bacteriaphage. TEM Negative stain [5],[6] Electron Microscope) is magnifies and observes an electron beam that has passed through a specimen using an electron beam. Finally, nanoscale, which was impossible with optical microscopes, has become possible. In addition, not 2D, It's 3D. Electron microscopy is so useful that it is still in use even though it has been invented for a long time. S T M -Principle- STM(Scanning Tunneling Microscope) was developed in 1981 by Heinrich Rohrer and Gerd Binnig, who won the Nobel Prize in 1986 with E.RUSKA. STM consists of a tip, a sample, and a voltage device. STM used the tunneling effect, Tunneling effect refers to the phenomenon that a particle stochastically passes an energy barrier higher than that of particle(fig.6). If the distance between the tip and the sample is several nanometers, the electrons that escape from the sample through the tunneling effect are formed between the tip and the sample, which is called electron cloud. When electrodes are placed on the tip and the sample, current flows through the electron cloud even though they are separated from each other. Tunneling current : ~. It can be seen that the current is correlated with the distance, which changes exponentially if it changes very finely. It is to judge the structure of the material by measuring the change using this sensitivity. STM has two modes(fig.7). One is a constant current mode, in which the current is kept constant and the structure is grasped by changing the height of the tip. Fig.6. Tunneling Effect [7] Fig.7. STM s two mode. (a) constant height of tip (b)constant current [8]

6 The other is to keep the height of the tip constant and to grasp the structure by changing the current. The latter is actually the most common method, because the former method has been damaged tip and surface by hit each other. -Signification- STM does not need a lamp or an electronic source and lens because it only operates with current. STM is the first device to measure the spatial image of a surface with atomic resolution. Let me tell you why this is important. The atoms inside the solid are surrounded by other atoms. Atoms on the surface do not interact with other atoms on the surface, atoms just above the surface, and atoms just below the surface. Therefore, the properties of the solid surface are fundamentally different from those of the interior(fig.8). Fig.8. Surface of Gold. STM [9] As an example, surface atoms attempt to have an array that differs from that of internal atoms several times in order to minimize the surface energy. Because of this, the structure of the surface becomes more complex, and it has long been impossible to elucidate its structure experimentally and theoretically. However, STM has solved the problem of identifying the surface structure by identifying up to one-millionth of the atomic size. In addition, STM has made tremendous contributions to the precision process, chemistry, biology and medicine. CONCLUSION After the electron microscope and STM, many ATMs and CEM-like microscopes were invented. The electron microscope showed a better magnification, breaking the prejudice that viewing the structure is not limited to light, and STM solved the surface structure problem that had not been solved previously. Also, other fields, especially chemistry, have had a tremendous impact on the structure of the material, and on the biology of the organism. it made possible something impossible. At present, electrons, protons, and quarks that are

7 smaller than atoms can not be seen. However, in the future, we will be able to see these small particles so that scientists will be able to broaden their sight. and i expect. Reference [1] microscope/bz-x700/study/principle/ 003/index.jsp [2] [3] nhn?volumeno=133920&memberno=34818 [4] docid= &cid=40942&categoryid= [5] ilica_polymorphs/index.html [6] ri nciple-of-negative-staining/ [7] ntum_tunnelling [8] php/kr/park-spm-modes/electricalproperti es/241-scanning-tunnelingmicroscopy-stm [9] wiki/file:atomic_resolution_au100.jp g

8 First version: s Nobel Prize in Physics (Electron Microscope & STM) Huiwon Ahn Seoul National University Department of Physics & Astronomy, Korea Abstract The structure of matter or organisms has helped to elucidate the curiosity and phenomena of people. A microscope is a very good tool to magnify an object to reveal its structure, and an optical microscope that magnifies the image through light has been used for about 400 years. High-magnification and high-resolution microscopes were invented using various principles including an electron microscope that analyze information on structures by electrons. Ernst Ruska received the Nobel Prize in 1986 for inventing an electron microscope. At present, the microscope has been developed to be able to see atoms, and it is very helpful in various fields. Introduction Optical Microscope People have always wondered what an material is made of and what structure it is. The material is made up of very small, but the human eye has no ability to see it. A microscope is a tool for magnifying objects. The person who made the beginning of the current optical microscope was made by a man named Jansen in At that time, he invented the use of a telescope for marine exploration. As the lens processing technique develops, it is found that the focal length (the distance between the central axis of the lens and the focal point) greatly affects the lens magnification. And They made a microscope using magnification. An optical lens is a tool made of glass that collects or spreads light according to its shape. The convex lens that collects light greatly expands the material and is used in optical microscopes. A typical optical microscope consists of two optical lenses. The magnification of the optical lens is a product of the lens magnification, and the total magnification can be expressed as follows. ((Fig.1) is total magnification, Fig.1. Inside the Optical Microscope[1]

9 is objectiove lens, is eyepiece,, are the respective focal lengths, s is distance between and ). However, high magnification alone does not allow the object to be seen clearly. The magnitude of the distinction between objects in the magnified state is an important factor in microscopy as well as magnification, which is called resolution. resolution, d is expressed as follows : (NA : Numerical Aperture) If the resolution is bad, it looks like the image is blurred. As can be seen from the equation, the resolution depends on the wavelength. Therefore, in the case of white light with all colors, the colors appear to spread, and this is called chromatic aberration. In addition, aberrations are also related to the focal length associated with the magnification, which inevitably leads to poor resolution if magnification is improved. As a result, the maximum magnification of an optical microscope with a clearly visible image is about 4000 times. and the optical microscope reaches its limit. Electron Microscope For the first time, z has shown that electrons can be focused in one place by magnetic force. Later, Ernst Ruska called it an electron lens, similar to the way an optical lens collects light using a tool that uses this focused phenomenon. There are two types of electron lenses, which are the core of the electron microscope. One is an electric lens using electric force, and the other is a magnetic lens using magnetic force. The method of the electric lens is as follows. 1. The electric lens is set up with two minus left and right plus the electrodes up and down. 2. When a voltage is applied to the electrode, an equipotential line is formed. 3.When electrons are emitted between equipotential lines between electrodes, electrons gather in one place by electric force perpendicular to equipotential line.however, electric lenses easily absorbed electrons, so information was lost and it was not actually used because it was difficult to keep the equipotential lines. So most of the electronic lenses are magnetic lenses. The magnetic lens is cylindrical, with a magnet on the outside and a coil on the inside, with a hole that electron can through pass in the center. The magnetic lens utilized principle that lines of magnetic force, and electric charge is vertical. The method of the magnetic lens is as follows

10 Fig.2. electron's spiral motion in magnetic lens[2] 1.It makes ultra high vacuum state(10^-10 torr) 2.The electrons are made perpendicular movement by the anode 3.Electrons are focused by a magnetic lens and scanned onto a specimen 4.Accepts the information of the electrons by the detector and converts them visible to sum up, The electron rotates around the optical axis by the Lorentz force and is focused on spot. Precisely, it is a spiral motion, not a rotational motion. The spiral motion cycle is as follows. T=(2π/1.76)(1/H) (Sec). H is magnetic filed strength. It can be seen that only the magnetic force, not the energy of the electrons, influences the electron spiral motion through the period equation. (Fig.2) But it did not work well from the beginning. Because the energy of the electron is the amount of the information of the sample, they did not know how much to inject this energy. They was increased energy of the electrons five-fold based on the de Brog's matter wave theory discovery which was announced at the time of electron microscope development. As a result, they were able to achieve enormous magnification same as theory. However, the sample was damaged by increasing the energy of the electron, but it was prevented by using liquid helium at an extremely low temperature. However, another problem arises. This time, the residual gas is stuck to the sample due to the cryogenic temperature, and the sample is no longer visible. This problem was solved by a technique called ultramicrotomes which slices the material to 30 to 60 nm. The thinned sample does not matter Even if the residual gas is attached, the problem is eliminated. The electron microscope invented by E.Ruska has a magnification of about 100,000 times, Microorganisms such as molecular structure and bacteria can be seen. In addition, since the information of the electron is visualized as it is, it can be seen in seen only in a plane view. And the electron microscope then develops Fig.3. (L)Silica(SiO2) structure MA : 100,000 x. SEM (R) Bacteriaphage. TEM Negative stain [3],[4]

11 with SEM and TEM(Fig.3). The SEM(Scanning Electron Microscope) is almost the same as the conventional electron microscope. It detects the backscattering electrons and secondary electrons from the collision between the sample and the electron and sees the sample. And TEM(Transmission Electron Microscope) is magnifies and observes an electron beam that has passed through a specimen using an electron beam. Electron microscopy is so useful that it is still in use even though it has been invented for a long time. S T M STM(Scanning Tunneling Microscope) was developed in 1981 by Heinrich Rohrer and Gerd Binnig, who won the Nobel Prize in 1986 with E.RUSKA. STM consists of a tip, a sample, and a voltage device. Stm used the tunneling effect, Tunneling effect refers to the phenomenon that a particle stochastically passes an energy barrier higher than that of particle(fig.4). If the distance between the tip and the sample is several nanometers, the electrons that escape from the sample through the tunneling effect are formed between the tip and the sample, which is called electron cloud. When electrodes are placed on the tip and the sample, current flows through the electron cloud even though they are separated from each other. Tunneling current : IT ~ I T ~ e -2kd It can be seen that the current is correlated with the distance, which changes exponentially if it changes very finely. It is to judge the structure of the material by measuring the change using this sensitivity. stm has two modes. One is a constant current mode, in which the current is kept constant and the structure is grasped by changing the height of the tip. The other is to keep the height of the tip constant and to grasp the structure by changing the current. The latter is actually the most common method, because the former method has been damaged tip and surface by hit each other. Fig.4. Tunneling Effect [5] Fig.5. STM s two mode [6 (a) constant height of tip (b)constant current

12 STM does not need a lamp or an electronic source and lens because it only operates with current. STM is the first device to measure the spatial image of a surface with atomic resolution. Let me tell you why this is important. The atoms inside the solid are surrounded by other atoms. Atoms on the surface do not interact with other atoms on the surface, atoms just above the surface, and atoms just below the surface. Therefore, the properties of the solid surface are fundamentally different from those of the interior. As an example, surface atoms attempt to have an array that differs from that of internal atoms several times in order to minimize the surface energy. Because of this, the structure of the surface becomes more complex, and it has long been impossible to elucidate its structure experimentally and theoretically. However, STM has solved the problem of identifying the surface structure by identifying up to one-millionth of the atomic size. In addition, STM has made tremendous contributions to the precision process, chemistry, biology and medicine. CONCLUSION After the electron microscope and stm, many ATMs and CEM-like microscopes were invented. The electron microscope showed a better magnification, breaking the prejudice that viewing the structure is not limited to light, and STM solved the surface structure problem that had not been solved previously. Also, other fields, especially chemistry, have had a tremendous impact on the structure of the material, and on the biology of the organism. it made possible something impossible. At present, electrons, protons, and quarks that are smaller than atoms can not be seen. However, in the future, we will be able to see these small particles so that scientists will be able to broaden their sight. and i expect. Fig.6. Surface of Gold. STM [7]

13 Reference [1] ts/microscope/bz-x700/study/principle/ 003/index.jsp [2] ocid= &cid=40942&categoryid= [3] ilica_polymorphs/index.html [4] nciple-of-negative-staining/ [5] ntum_tunnelling [6] php/kr/park-spm-modes/electricalproperties/241-scanning-tunnelingmicroscopy-stm [7] wiki/file:atomic_resolution_au100.jp g