Removal of the surfactant in Bi/Ge/Si(1 1 1) surfactant-mediated epitaxy

Surfactant-mediated epitaxy of 6 nm Ge on a Bi terminated Si(1 1 1) surface results in a smooth, two dimensional, defect free Ge film on Si(1 1 1) where 1 monolayer Bi covers the film surface. Heating the Ge film results in desorption of bismuth but the Ge film breaks up and deep holes form. Using ion beam sputtering we have removed the Bi surfactant from the film in situ and the remaining Ge/Si film is still two dimensional, smooth and defect free. Subsequent deposition of 5 bilayers germanium on the sputtered surface leads to growth of 3D islands as observed by scanning tunneling microscopy (STM). This behavior can be explained by residual stress in the Ge film.