Phases and Phase Diagrams of Xenon Adsorbed on Epitaxial NaCl(100) Films and on Ge(100)
Thin films of NaCl were grown as epitaxial films on Ge(100). Analyzing LEED profiles we are able to show quantitatively that the NaCl films accommodate monoatomic steps of the Ge substrate by elastic strain which is distributed over many lattice constants, forming an elastic “carpet”. Ordered phases and phase diagrams of Xe adsorbed on NaCl(100) and on Ge(100) were investigated in quasi-equilibrium with room temperature gas using high resolution LEED (SPA-LEED). First order phase transitions for Xe/NaCl are observed between a disordered lattice gas and a distorted hexagonal phase and between this phase and the hexagonal multi-layer bulk phase. The distorted hexagonal phase is commensurate with the substrate in only one direction. The hexagonal phase only forms small crystals (average grain size 80 Å), but is still oriented along  with one of its axes. On Ge(100) no additional superstructure spots are induced by Xe before the bulk phase grows, but characteristic jumps in intensity of integral order as well as of half order beams are observed as a function of temperature and pressure.
KeywordsLEED Pattern Substrate Spot Monoatomic Step Spot Profile Thermal Programme Desorption
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