Beryllium (Be) is a chemical element with the symbol Be and atomic number 4. In MBE systems, beryllium can be used as a material in the construction of the vacuum chamber, evaporation sources, and other components. It is a good choice for these applications because it has a low atomic mass, which makes it easy to evaporate, and it has a high melting point, which makes it resistant to thermal degradation. Beryllium is also an excellent thermal and electrical conductor, which can be useful for certain applications. However, beryllium is a toxic material and precautions must be taken to avoid exposure when working with it.
The purity of the beryllium used in MBE systems is typically very high, often 99.999% or higher. This is because impurities in the beryllium can affect the performance and reliability of the MBE system. For example, impurities can alter the evaporation rate of the beryllium, leading to variations in the film thickness and composition. To achieve the highest level of purity, beryllium can be purified through a process called zone refining, in which the material is melted and recrystallized multiple times to remove impurities. The purity of the beryllium can also be verified using analytical techniques such as inductively coupled plasma mass spectrometry (ICP-MS).
