Thermal Evaporation — What Is It and How Do You Use It?

Thermal Evaporation — What Is It and How Do You Use It?

Thermal evaporation is used in the production of thin-film devices like OLED screens, solar cells, and thin-film transistors. There are thousands of applications for vacuum coating technologies, and it will continue to play a role both in manufacturing existing and new products.

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Thermal Evaporation — What Is It and How Do You Use it?

Thermal evaporation is a physical vapor deposition technique (PVD) used to deposit a thin layer of metallic film (like aluminum, silver, nickel, chrome, magnesium, etc.) on the surface of an object.

Like many inventions, it’s difficult to establish exactly where thermal evaporation originated. The Society of Vacuum Coaters credits W.R. Grove as the first person to study what would become known as sputtering. In 1852, Grove held the tip of a wire close to a highly-polished silver surface and noticed a deposit on the silver surface. Thomas Edison filed the first patent for thermal evaporation in 1884, but the technique would not become known by that name until Powell, Oxley, and Blocher wrote the book Vapour Deposition 1966.

The thermal evaporation industry is only about 80 years old. Manufacturers used the technique in the 1930s, but it wasn’t until the invention of semiconductor technology, and the rising demand for computer hard disks in the 1970s, that thermal evaporation became widespread.

The process for thermal evaporation involves placing a source material (target) and an object (substrate) in a high-vacuum environment. The target metal sits in an evaporated called a ‘boat’. The manufacturer heats the boat using electrical energy to the point that the metal evaporates, and the molecules travel to the surface of the substrate. There, the vaporized molecules condense back into a solid state, forming a thin-film coating. This is known as deposition. Technologies like Angstrom’s sputtering system can control the deposition rate using a quartz rate sensor, temperature, or optical monitoring.