The order-disorder transition of the (3x3)Sn/Ge(111) phase

Abstract

Growing attention has been drawn in the past years to the α-phase (1/3 monolayer) of Sn on Ge(111), which undergoes a transition from the low temperature (3x3) phase to the room temperature (\sqrt3 x \sqrt3)R30 one. On the basis of scanning tunnelling microscopy experiments, this transition was claimed to be the manifestation of a surface charge density wave (SCDW), i.e. a periodic redistribution of charge, possibly accompanied by a periodic lattice distortion, which determines a change of the surface symmetry. As further experiments with different techniques were being performed, increasing doubts were cast about the SCDW model. We have measured by He scattering the long range order of the 1/3 monolayer phase of Sn on the Ge(111) surface throughout the phase transition. The transition has been found of the order-disorder type with a critical temperature Tc=220 K. The expected 3-State Potts critical exponents are shown to be consistent with the observed power law dependence of the (3x3) order parameter and its correlation length close to Tc, thus excluding a charge density wave driven phase transition.

6 pages with 4 figures; updated references

References in corpus (5)

• Phase transitions in two dimensions - the case of Sn adsorbed on Ge(111) surfaces
• The mechanism for the 3 x 3 distortion of Sn/ge (111)
• Determination of the (3x3)-Sn/Ge(111) structure by photoelectron diffraction
• First Principles Calculations of Charge and Spin Density Waves of sqr3-Adsorbates on Semiconductors
• Charge-density-wave formation by Van Hove nesting in the α-phase of Sn/Ge(111)

Cited by in corpus (3)

• Universal Window for Two Dimensional Critical Exponents
• The order-disorder character of the (3x3) to (sqrt3 x sqrt3)R30° phase transition of Sn on Ge(111)
• Doping-dependent charge- and spin-density wave orderings in a monolayer of Pb adatoms on Si(111)