Regular ridge-and-valley surface structures were spontaneously formed by the homoepitaxial, growth of LiF(110) and CaF2(110). The surface structure was examined by in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM). The LiF(110) homoepitaxial surfaces exhibited regular ridge-and-valley structures composed of {100} facets and [001] macrosteps, and the ridge, spacings increased with growth temperature. The CaF2(110) surfaces also exhibited regular ridge-and-valley structures composed of {111} facets and [110] macrosteps when deposited above 400 degrees C. Annealing alone did not produce a well-developed ridge-and-valley structure. The highly mobile admolecules supplied during deposition played a central role on the morphological evolution of the surfaces. The heteroepitaxial growth of LiF and CaF2 on I I 001-faceted NaCI(110) substrates was also examined. Although the LiF(110) exhibited a regular ridge-and-valley structure, CaF2(110) formed arrays of islands at the bottom of the grooves. (c) 2005.