CAF2-SI(111) AS A MODEL IONIC-COVALENT SYSTEM - TRANSITION FROM CHEMISORPTION TO EPITAXY

The demands of chemisorption and epitaxy are quite different for elect ronically dissimilar systems. The transition between these two regimes in CaF2-Si(111) is studied with transmission-electron microscopy and photoemission. Changes in the electronic structure of the evolving gro wth surface are expressed in the composite growth mode, a Stranski-Kra stanow pathway to layer-by-layer growth, which begins with CaF2 cohere nt island formation on a Si-CaF layer. After this transition, layer-by -layer CaF2 homoepitaxy is possible even at room temperature, and the critical thickness can be extended.