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The order-disorder character of the (3x3) to (sqrt3 x sqrt3)R30° phase transition of Sn on Ge(111) | | L. Petaccia
; L. Floreano
; A. Goldoni
; D. Cvetko
; A. Morgante
; L. Grill
; A. Verdini
; G. Comelli
; G. Paolucci
; S. Modesti
; | | Date: |
16 Mar 2001 | | Journal: | Phys. Rev. B 64, (2001) 193410 | | Subject: | Materials Science | cond-mat.mtrl-sci | | Affiliation: | 1,2), A. Morgante , L. Grill , A. Verdini , G. Comelli , G. Paolucci and S. Modesti ( Lab. TASC-INFM, Trieste, Italy Sincrotrone Trieste, Trieste, Italy | | Abstract: | Growing attention has been drawn in the past years to the alpha-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. Recent He diffraction studies of the (3x3) long range order have shown the transition to be of the order-disorder type with a critical temperature Tc=220 K and belonging to the 3-state Potts’ universality class. These findings clearly exclude an SCDW driven mechanism at 220 K, but they cannot exclude the occurence of a displacive transition at higher temperature. Here we present photoelectron diffraction data taken at 300 K and photoemission data taken up to 500 K (which is the maximum temperature where the (sqrt3 x sqrt3)R30° is stable) . From our analysis it is shown that the atomic structure of the Sn overlayer does not change throughout the transition up to 500 K. As a consequence the displacive hypothesis must be discarded in favour of a genuine order-disorder model. | | Source: | arXiv, cond-mat/0103358 | | Services: | Forum | Review | PDF | Favorites | |
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