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

A technical discipline based on optoelectronics, which comprehensively uses optics, precision machinery, electronics and computer technology to solve various engineering application problems. The information carrier is expanding from electromagnetic wave band to optical wave band, so that the optoelectronic science and optoelectromechanical integration technology are concentrated in 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.

A technical discipline based on optoelectronics, which comprehensively uses optics, precision machinery, electronics and computer technology to solve various engineering application problems.

The information carrier is expanding from electromagnetic wave band to optical wave band, so that the optoelectronic science and optoelectromechanical integration technology are concentrated in the optoelectronic information industry of optical information acquisition, transmission, processing, recording, storage, display and sensing.

The main applications in the photoelectric field focus on precision detection and optical imaging. The application of light wave represented by photonic computer is an attractive place for photoelectricity, but it will take time to achieve this goal.

Zhejiang University, Tsinghua University, Tianjin University, Huazhong University of Science and Technology, Changchun University of Science and 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.

Scope of photoelectricity

The photoelectric industry has also expanded rapidly in modern development, and has developed significantly in optical communication, laser, photoelectric display, optics, solar photovoltaic, electronic engineering, logistics network and other fields; Gradually integrate into wider space.

1、 Evaporation plating

1. Definitions

Evaporation coating refers to the deposition of a substance on the solid surface by heating.

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

2. Principle

Evaporated substances such as metals and compounds are placed in the crucible or hung on the hot wire as the evaporation source, and workpieces to be plated, such as metal, ceramics, plastics and other substrates are placed in front of the crucible. After the system is pumped to high vacuum, heat the crucible to evaporate the substances in it. The atoms or molecules of the evaporated substance are deposited on the substrate surface by condensation.

The film thickness can range from hundreds of angstroms to several microns. The film thickness is determined by the evaporation rate and time of the evaporation source (or by the charge amount), 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 evaporation source to the substrate should be less than the average free path of the vapor molecules in the residual gas, so as to avoid the chemical reaction caused by the collision between the vapor molecules and the residual gas molecules. The average kinetic energy of vapor molecules is about 0.1~0.2 electron volts.

3. Type

There are three types of evaporation sources:

① Resistance heating source: boat foil or wire shaped refractory metals such as tungsten and tantalum are used to heat the vaporized substances above it or placed in the crucible with current. Resistance heating source is mainly used for evaporation of materials such as Cd, Pb, Ag, Al, Cu, Cr, Au, Ni, etc.

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

③ Electron beam heating source: bombard the material with electron beam to make it evaporate. Suitable for materials with high evaporation temperature (no less 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 to other methods. The films can be evaporated at different deposition rates, different substrate temperatures and different incident angles of vapor molecules, thus obtaining films with different microstructures and crystal forms (single crystal, polycrystalline or amorphous, etc.); The purity of the film is very high; It is easy to detect and control the film thickness and composition online; The thickness control accuracy can reach the monolayer level.

Two sputter plating

1. Definitions

When high-energy particles bombard the solid surface, the particles on the solid surface can obtain energy and escape from the surface to deposit on the substrate. The commonly used bipolar sputtering equipment is shown in Figure [Schematic Diagram of Bipolar Sputtering].

2. Principle

The material to be deposited is usually made into a plate target and fixed on the cathode. The substrate is placed on the anode facing the target, a few centimeters away from the target. After the system is pumped to high vacuum, it is filled with 10~1 Pa gas (usually argon), and a voltage of several thousand volts is applied between the cathode and anode to generate glow discharge between the two poles. The positive ions generated by the discharge fly to the cathode under the action of the electric field and collide with the atoms on the target surface. The target atoms that escape from the target surface after collision are called sputtering atoms, and their energy ranges from 1 to dozens of electron volts. Sputtered atoms deposit films on the substrate surface.

3. Classification

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

② High frequency sputtering method. The substrate is installed on the grounding 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 with insulating target through matching network and DC isolation capacitor. After the high-frequency power supply is turned on, the high-frequency voltage continuously changes its polarity. 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. As the electron mobility is higher than that of positive ions, the insulating target surface is negatively charged. When the dynamic balance is reached, the target is at a negative bias potential, so that the positive ions continue to sputter the target. It is suitable for sputtering insulating films.

4. Features:

The sputtered coating is not limited by the melting point of the film material. It can sputter W, Ta, C, Mo, WC, TiC and other refractory substances. Sputtering has the advantages of strong adhesion between the electrodeposit and the substrate, compact and uniform electrodeposit. The sputtered particles are hardly affected by gravity. The positions of the target and the substrate can be arranged freely. At the initial stage of film formation, the nucleation density is high. The extremely thin continuous film below 10nm can be produced. 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, it can be better controlled and more efficient in production. Sputtering uses high voltage electric field as plasma coating material. Almost all high melting point metals, alloys and metal oxides, such as chromium, molybdenum, tungsten, titanium, silver, gold, etc., are used. However, the processing cost is relatively high

Triion plating

1. Definitions

The molecules of vaporized substances are ionized by electron collision and deposited on the solid surface as 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 to the anode, and the workpiece is connected to the cathode. When a high-voltage direct current of three to five thousand volts is applied, a glow discharge is generated between the evaporation source and the workpiece. As the vacuum hood is filled with inert argon, part of the argon is ionized under the action of the discharge electric field, thus forming a plasma dark area around the cathode workpiece. The positively charged argon ion is attracted by the cathode negative high voltage and bombards the surface of the workpiece violently, causing particles and dirt on the surface of the workpiece to be splashed and thrown out, so that the surface of the workpiece to be plated can be fully cleaned by ion bombardment. Then, connect the AC power supply of evaporation source, and the evaporated material particles melt and evaporate, enter the glow discharge area and are ionized. The positively charged evaporated material ions, attracted by the cathode, rush to the workpiece together with argon ions. When the evaporated material ions cast on the workpiece surface exceed the number of ions lost, they gradually accumulate to form a layer of coating firmly adhered to the workpiece surface.

3. Classification

① Magnetron sputtering ion plating

② Reactive ion plating

③ Hollow cathode discharge ion plating

④ Multi arc ion plating.

4. Features

The adhesion of the coating is good. The tensile test of the sample after ion plating shows that the coating still extends with the base metal plastically until it is about to break, without peeling or peeling; Because of the strong ability of winding plating, this method is very suitable for the inner holes, grooves and narrow slots on plated parts, and other parts that are difficult to be plated by other methods; The coating quality is good, and the coating structure of ion plating is dense, without pinholes, bubbles and uniform thickness; The cleaning process is simplified.

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