Evaporation Materials

Evaporation materials are mainly used in the field of coatings, especially vacuum evaporating coating technology. Compared with the traditional coating technology, vacuum evaporation coating technology has the advantages of simple principle, easy equipment, less occupation of land, low cost and no pollution. In vacuum evaporation coating technology, the evaporation materials are heated in a vacuum environment. When it reaches a certain temperature, the evaporation materials will turn into a state of molecules or atoms. Because the environment is vacuum, the evaporation of materials (metal or non-metal) in this environment is much easier than normal pressure. In general, evaporation takes place rapidly in vacuum as long as the saturated vapor pressure is greater than 1.33 Pa by heating. Evaporation materials play important roles in vacuum evaporating coating technology, and it is necessary to fully understand their properties and select them appropriately.

Figure 1. A picture of vacuum evaporation coating technology device.

Applications:

• Solar cell field: The performance of solar cells can be greatly improved by coating evaporative materials on solar cell components through vacuum evaporation coating technology. For example, Au can be deposited on the surface of n-Si electrode to form a permeable layer between Au and Si surface, which can reduce photo-corrosion. By coating several nanometer thick metal layers, such as Pt, Ni, Au, Cu, and the others, on the surface of N-type and P-type epitaxial silicon electrodes, the optical stability can be further improved and solar cells with superior photoelectric properties can be obtained.

Figure 2. An example of evaporation materials used in solar cell.

• Microwave semiconductor devices field: Microwave semiconductor devices have been widely used in microwave communication systems, telemetry systems, radar, navigation, biomedicine, electronic countermeasures, artificial satellites, spacecraft, etc. Microwave semiconductor devices have the advantages of small size, light weight and low power consumption, including microwave transistors and microwave diodes. Coating suitable evaporation materials on the chip surface can greatly improve the properties of microwave semiconductor devices.
• LED lighting field: Evaporation materials are widely used in LED lighting field. As a new type of light source in the 21st century, LED has the advantages of low energy consumption, high efficiency, long life, unbreakable, low cost and the others. It has been widely used in traffic signal lights, laptop backlight, large LED displays, landscape lights, street lamps, automobile indicators, etc. GaP / GaAsP, GaAs, GaN and other semiconductor chips are used in LED lighting. According to the types of semiconductor chips, evaporation materials will be selected for coating. The commonly used systems are Au / GaP, Au / AuBe / GaP, AuGeNi / GaAsP and the others.

Classification:

According to the composition, evaporation materials can be divided into the following categories:

• Metals and pure elements evaporation materials: Metals and pure elements evaporation materials include many materials such as aluminum, antimony, bismuth, chromium, gold, indium, iron, lead, magnesium, manganese and the others. Among them, aluminum is often used for coating. However, due to the chemical properties of aluminum is active and the fluidity is very good after melting, it will corrode many metals or compounds at high temperature.
• Oxides sulfides evaporation materials: Oxides sulfides evaporation materials mainly involve aluminum oxide, magnesium oxide, neodymium oxide, silicon dioxide tantalum oxide, titanium oxide, titanium oxide and the others.
• Borides selenides evaporation materials: This type of materials generally refer to molybdenum selenide, niobium selenide, tantalum selenide, tungsten selenide, zinc selenide and the others.
• The others: In addition to the materials mentioned above, the evaporation materials also include fluorides, nitrides and the others. The representatives are aluminum fluoride, calcium fluoride, boron nitride, vanadium nitride and the others.

Reference:

1. Elseman A M. Organometal Halide Perovskites Thin Film and Their Impact on the Efficiency of Perovskite Solar Cells[M]. Coatings and Thin-Film Technologies. 2018.