Closed cycle chiller as a low cost alternative to liquid nitrogen in molecular beam epitaxy

The high cost of cooling the cryoshroud in a molecular beam epitaxy system has been greatly reduced by replacing liquid nitrogen (LN2) as a coolant with a silicone polymer heat transfer fluid cooled to as low as −80 °C by a closed cycle chiller. Gallium arsenide epitaxial layers have been grown with two different cooling configurations of the shroud: conventional LN2 cooling and cooling to −70 °C with the chiller. The partial pressure of water …