| Summary: | 碩士 === 國立臺灣師範大學 === 物理學系 === 93 === The Co magnetic super thin films on semiconductor Ge(111) surface are grown successfully by in situ depositing with MBE. Their growth behaviors and equilibrium structures are observed by STM and LEED. In order to prevent alloy reactions of cobalt and germanium, the Ag/Ge(111)√3×√3 surface, produced by depositing 1ML Ag onto Ge(111)-c(2×8) and anneal up to 500℃, is chosen as substrate. After depositing 0.35ML cobalt and annealing to 200℃, some structured 2D cobalt islands were started to be found. Raising the annealing temperature to 300℃~500℃,the islands become larger and higher. These 2D Co islands construct two shapes, the lower Shape 1 and the higher Shape 2. The Shape 1 islands (under 2 atomic layers) have the period of (√13×√13) and each layer separates with 0.05nm. Especially, the structure of this shape is of reflection symmetry and the mirror planes are along , , and axes of the Ge(111) surface. The Shape 2 islands (over 3 atomic layers) show another period of (2×2) and return to cobalt own separation of 0.2nm. Those island sizes also depend on annealing temperatures. Besides, by nucleation theory, the total diffusion activation energy E=2.39eV. All of the phenomenon may relate to the surface free energy and interface constrains.
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