Impurity-induced changes of overlayer symmetry and of phase transitions
Institut für Festkörperphysik, Universität Hannover
Appelstr. 2, D-30167, Hannover, Germany
2 Institute of Physics NANU - Kiev, Ukraine and Department of Physics, Texas A& M University - College Station, TX 77843-4242, USA
Accepted: 6 July 2001
We show in a Low Energy Electron Diffraction (LEED) experiment that small concentrations of oxygen atoms (2 to 12% of a monolayer) added to half a monolayer of Sr on Mo(112), ordered in a structure, do not destroy order, but introduce new correlations with different translational symmetry. Thus incommensurate structures with domain walls are formed and the is finally transformed into a structure. Temperature-driven transitions at constant average densities from incommensurate to short-range order and finally to long-range order at high temperature can be described by simultaneous melting and domain wall evaporation.
PACS: 68.55.Ln – Defects and impurities: doping, implantation, distribution, concentration etc / 68.35.Md – Surface thermodynamics, surfaces energies / 68.35.Rh – Phase transitions and critical phenomena
© EDP Sciences, 2001