Molecular beam epitaxy (MBE) is one of several methods of depositing single crystals. It is viewed as a key technology due to the unique structures and exact dimensional control that can be achieved. MBE systems offer an ultra-pure environment for precision fabrication of thin film structures for semiconductor, opto-electronic, photovoltaic, and magnetic applications. Devices are equipped with hardware and software capabilities to monitor, display, and control critical growth parameters. Systems are usually designed around a modular configuration consisting of several functional units.