The molecular beam epitaxy was carried out in a high vacuum or ultra-high vacuum (1 x 10^-8 Pa) environment. The most important aspect of molecular beam epitaxy is its low deposition rate, which usually allows the film to epitaxial grow at a rate of less than 3000 nm per hour. Such a low deposition rate requires a high enough vacuum to achieve the same level of cleanliness as other deposition methods.

To meet the ultra-high vacuum described above, the MBE device （Knudsen cell）has a cooling layer, and the ultra-high vacuum environment of the growth chamber must be maintained using a liquid nitrogen circulation system. Liquid nitrogen cools the device's internal temperature to 77 Kelvin (−196 °C). The low temperature environment can further reduce the content of impurities in vacuum and provide better conditions for the deposition of thin films. Therefore, a dedicated liquid nitrogen cooling circulation system is required for the MBE equipment to provide a continuous and steady supply of -196 °C liquid nitrogen.