Aluminum alloy ultrahigh vacuum system for molecular beam epitaxy

Abstract

As a research project for aluminum alloy molecular beam epitaxy systems, a large aluminum alloy chamber with a special surface finish was constructed. Its outgassing rate and ultimate pressure were measured. The special surface finish was analyzed using Auger electron spectroscopy. The oxide layer on the aluminum alloy was about 40 A thick. The outgassing rate before baking was measured as 10−11 Torr l/s cm2, and the rate after baking (150 °C, 24 h) was 3×10−13 Torr l/s cm2. This value is approximately one to two orders of magnitude lower than that of a stainless‐steel chamber, such as SUS 304. The ultimate pressure was 7×10−11 Torr when pumped with a turbomolecular pump and an ion pump. With addition of the newly developed titanium sublimation pump, the ultimate pressure was 6×10−12 Torr (6.5×10−12 mbar). This ultimate pressure is very low for a large aluminum alloy vacuum chamber. Ceramic coating of SiO2 using a spark discharge in a silicate solution on aluminum alloy was not corroded by gallium. This c...