Solid phase epitaxial growth anisotropy of vacuum-deposited amorphous silicon

The crystallization of amorphous silicon deposited in ultra-high vacuum onto silicon crystalline substrates with different orientations is studied by low energy electron diffraction. Layer-by-layer epitaxial regrowth with an activation energy of (3.0+-0.2) eV is found to occur for all substrate orientations studied. The regrowth rate is strongly dependent on the orientation of the underlying silicon crystal: the regrowth rate in <100> direction is the fastest and is 2 and 20 times that in the <110> and <111> ones, respectively. A comparison is made of these results with those obtained by other investigators for ion-implanted Si and Ge. The proposed model explains the regrowth rate anisotropy by the difference in formation probabilities of atomic configurations typical for different crystal planes. The evolution of surface structure during crystallization is investigated. (author)