HETEROEPITAXY OF KCL ON KBR SUBSTRATE

The heteroepitaxy of KCl on a KBr(001) substrate, with a lattice misma tch of -4.7%, was studied, and the relaxation mechanism of the lateral lattice constant was clarified. The stable atomic configurations were calculated by minimizing the total interaction energy between the ion s. At submonolayer coverages, two-dimensional island configurations ar e more stable than three-dimensional structures, indicating a layer gr owth mode. At integer monolayer thicknesses, both the strained layer s tructure with the lateral lattice constant of KBr and the pseudomorphi c commensurate layer structure with KBr(001) were investigated. The st rained layer structure is more stable than the pseudomorphic structure below the critical thickness of three monolayers. The commensurate la yer separates into two regions: a strained layer region and a dislocat ion region with one extra cation and anion row relative to the KBr sub strate. The width of the dislocation region increases as the layer thi ckness increases, corresponding to the observed gradual relaxation of the lateral lattice constant above the critical thickness.