Solid Phase Epitaxy Of Ge Films On Caf_2/si(111)

摘要

At room temperature deposited Ge films (thickness < 3 nm) homogeneously wet CaF_2/Si(111). The films are crystalline but exhibit granular structure. The grain size decreases with increasing film thickness. The quality of the homogeneous films is improved by annealing up to 200 ℃. Ge films break up into islands if higher annealing temperatures are used as demonstrated combining spot profile analysis low energy electron diffraction (SPA-LEED) with auger electron spectroscopy (AES). Annealing up to 600 ℃ reduces the lateral size of the Ge islands while the surface fraction covered by Ge islands is constant. The CaF_2 film is decomposed if higher annealing temperatures are used. This effect is probably due to the formation of GeF_x complexes which desorb at these temperatures.