Photoelectric field

The electricity produced by the action of light is called photoelectricity.

Based on Optoelectronics, it is a technical discipline that comprehensively uses optics, precision machinery, electronics and computer technology to solve various engineering application problems. The information carrier is expanding from electromagnetic band to optical band, so that the Optoelectronic Science and optoelectronic mechatronics technology focus on the optoelectronic information industry of optical information acquisition, transmission, processing, recording, storage, display and sensing.

The electricity produced by the action of light is called photoelectricity.

Based on Optoelectronics, it is a technical discipline that comprehensively uses optics, precision machinery, electronics and computer technology to solve various engineering application problems.

The information carrier is expanding from electromagnetic band to optical band, so that the Optoelectronic Science and optoelectronic mechatronics technology focus on the optoelectronic information industry of optical information acquisition, transmission, processing, recording, storage, display and sensing.

The main applications in photoelectric field are focused on precision detection and optical imaging. The application of light wave represented by photon computer is an attractive place of photoelectricity, but it will take a long time to achieve this goal.

The major of Optoelectronics in domestic universities are Zhejiang University, Tsinghua University, Tianjin University, Huazhong University of science and technology, Changchun University of technology, University of Electronic Science and technology, etc.

The government has invested hundreds of millions in Wuhan and is planning to build a national optoelectronic laboratory.

The scope of photoelectricity involved

the rapid development of photoelectricity industry in modern times has gradually spread, which is obvious in the fields of optical communication, laser, photoelectricity display, optics, solar photovoltaic, electronic engineering, logistics network, etc.; it has gradually integrated into a wider space.

1、 Evaporation coating

1. Definition

evaporation of a substance by heating to deposit on a solid surface, called evaporation coating.

The structure of evaporation coating equipment is shown in Figure 1.

Lanxi. COM / page / 552. HTML "> metal, < A The compound is placed in the crucible or hung on the hot wire as the evaporation source, and the workpiece to be plated, such as metal, ceramics, plastics and other substrates are placed in front of the crucible. After the system is pumped to a high vacuum, the crucible is heated to evaporate the substance in it. The atoms or molecules of evaporated matter are deposited on the substrate surface by condensation.

The film thickness can be from hundreds of Angstroms to several microns. The thickness of the film depends on the evaporation rate and time of the evaporation source (or the charge), and is related to the distance between the source and the substrate. For large area coating, rotating substrate or multiple evaporation sources are often used to ensure the uniformity of film thickness. The distance from the vapor source to the substrate should be less than the average free path of the vapor molecule in the residual gas, so as to avoid the chemical effect caused by the collision between the vapor molecule and the residual gas molecule. The average kinetic energy of vapor molecules is about 0.1-0.2 ev.

3. Type

there are three types of evaporation sources:

① resistance plus heat source: the evaporated material which is made of refractory metals such as tungsten and tantalum into boat foil or silk shape and heated above it or placed in crucible by current. Resistance heating source is mainly used for evaporation of CD, Pb, Ag, Al, Cu, Cr, Au, Ni and other materials.

② High frequency induction heating source: use high frequency induction current to heat crucible and evaporated substance.

③ Electron beam plus heat source: bombard the material with electron beam to make it evaporate. It is suitable for materials with high evaporation temperature (not lower than 2000 ℃).

4. Features: it can deposit films of metals, semiconductors, insulators, alloys with different composition ratios, compounds and some basic polymers on the surfaces of metals, semiconductors, insulators and even plastics, paper and fabrics. Its application range is incomparable with that of other methods. The films can be deposited at different deposition rate, substrate temperature and incidence angle of vapor molecules, so the films with different microstructure and crystal morphology (single crystal, polycrystalline or amorphous, etc.) can be obtained. The purity of the films is very high. It is easy to detect and control the thickness and composition of the films online. The thickness control accuracy can reach the order of single molecular layer.

Definition: when bombarding the solid surface with high energy particles, the particles on the solid surface can obtain energy and escape from the surface and deposit on the substrate. The commonly used two pole sputtering equipment is shown in figure [diagram of two pole sputtering].

19166. PNG "ALT =" 615. PNG " _SRC = "http://m.hrbsbh.com/data/image/20200309/1583745358319166. PNG" >. The substrate is placed on the anode facing the target and a few centimeters away from the target. The system is pumped to a high vacuum and charged with 10-1 PA of gas (usually argon). A voltage of several thousand volts is applied between the cathode and anode, and a glow discharge is generated between the two poles. The positive ions produced by the discharge fly to the cathode under the action of electric field and collide with the atoms on the target surface. The target atoms escaping from the target surface by collision are called sputtering atoms, and their energy ranges from 1 to dozens of electron volts. Sputtered atoms are deposited on the substrate.

3. Classification

① reactive sputtering method: the reactive gas (O, N, HS, CH, etc.) is added into Ar gas, and the reactive gas and its ions react with the target atom or sputtering atom to generate compounds (such as oxides, nitrides, etc.) and deposit on the substrate, which is suitable for sputtering compound films.

② High frequency sputtering. The base plate is installed on the grounded electrode and the insulation target is installed on the opposite electrode. One end of the high frequency power supply is grounded, and the other end is connected to the electrode equipped with the insulating target through the matching network and the DC isolating capacitor. After connecting the high frequency power supply, the high frequency voltage changes the polarity continuously. The electrons and positive ions in the plasma are deposited on the insulating target at the positive and negative half cycles of the voltage respectively. Because the electron mobility is higher than that of the positive ions, the surface of the insulating target is negatively charged. When the dynamic equilibrium is reached, the target is at a negative bias potential, which makes the sputtering of the positive ions on the target continue. It is suitable for sputtering insulating films.

4. Features: the sputtering coating is not limited by the melting point of the film material, and the refractory materials such as W, Ta, C, Mo, WC and tic can be sputtered. Splash plating has the advantages of strong adhesion between electroplated layer and substrate, compact and uniform electroplated layer, etc. The sputtered particles are not affected by gravity. The target and substrate can be arranged freely. The initial nucleation density of the film is high. It can produce extremely thin continuous films below 10nm. The target has a long life and can be produced automatically for a long time. The target material can be made into various shapes. With the special design of the machine, better control and more efficient production can be achieved. High voltage electric field is used as the plasma coating material. Almost all high melting point metals, alloys and metal oxides, such as chromium, molybdenum, tungsten, titanium, silver and gold, are used. However, the processing cost is relatively high SRC = "http://m.hrbsbh.com/data/image/20200309/1583745427896050.png" title = "1583745427896050. PNG" ALT = "616. PNG" ～ SRC = "http://m.hrbsbh.com/data/image/20200309/1583745427896050. PNG" >

1. It is defined that the molecules of evaporated matter are ionized by electron collision and deposited on the solid surface with ions, which is called ion plating.

Ion plating is a combination of vacuum evaporation and cathode sputtering.

An ion plating system is shown in Figure 4 [schematic diagram of ion plating system]

2. Principle

the evaporation source is connected with the anode, and the workpiece is connected with the cathode. When three to 5000 V high-voltage direct current is applied, a glow discharge is generated between the evaporation source and the workpiece. Because the vacuum hood is filled with inert argon, part of the argon is ionized under the action of discharge electric field, thus forming a plasma dark area around the cathode workpiece. The positive charged argon ions are attracted by the negative high pressure of the cathode, which bombard the surface of the workpiece violently, causing the particles and dirt on the surface of the workpiece to be splashed out, so that the surface of the workpiece to be plated can be fully cleaned by ion bombardment. Then, turn on the AC power source of the evaporation source, the particles of the evaporation material melt and evaporate, enter the glow discharge area and are ionized. Under the attraction of the cathode, the positively charged evaporated material ions rush to the workpiece together with the argon ions. When the amount of evaporated material ions thrown on the workpiece surface exceeds the number of splashed ions, a layer of coating firmly adhered to the workpiece surface will gradually accumulate.

3. Classification: (1) magnetron sputtering ion plating; (2) reactive ion plating; (3) hollow cathode discharge ion plating; (4) multi arc ion plating.

4. Characteristics

the coating has good adhesion. The tensile test on the sample after ion plating shows that when the coating is pulled to the point of fracture, it still extends with the base metal in a plastic way, without peeling or peeling; the plating ability is strong, so this method is very suitable for the inner holes, grooves, narrow seams and other parts that are difficult to be plated by other methods; the coating quality is good, and the coating is ion plated The coating has compact structure, no pinhole, no bubble and uniform thickness, and the cleaning process is simplified.

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