Segregation control for ultrathin Ge layer in Al/Ge(111) system

An impact of the vacuum anneal of Al/Ge(111) structure on the Ge segregation have been investigated to get an insight into the precise control of ultrathin Ge crystalline growth. The Al/Ge(111) structure was prepared by thermal evaporation of Al on wet-cleaned Ge(111), and subsequent vacuum anneal without air exposure was carried out to promote a Ge formation on the Al surface. The Ge formation and its chemical bonding features have been evaluated from the x-ray photoelectron spectroscopy (XPS) analysis. In addition, change in the average Ge thickness with the anneal temperatures and times was crudely estimated. We found that anneal temperature rather than the time was found to be quite important for the control of a sub-nanometer scale Ge growth.