A thermodynamic model was suggested for (3x3)-type structure formation with a charge density wave arising against the background of a (√3 x √3)R30°-type structure in a group-IV metal (Sn, Pb) sub-monolayer adsorbed with a coverage of about 1/3 at the (Ge, Si) semiconductor (111) surface. Calculations were carried out by using a self-consistent theory for static fluctuations of the order parameter amplitude. It was shown that the low-symmetry (3x3) phase could nucleate at point defects of the sub-monolayer as charge-ordered areas of finite radius. The spatial configuration of the charge density wave and its temperature dependence were calculated. The results obtained were compared with the experimental data for the Sn/Ge(111) system.

Charge Ordering Induced by Intrinsic Defects in Sn/Ge(111) Sub-Monolayers with a Coverage Close to 1/3. V.N.Menshov, V.V.Tugushev: Physics of the Solid State, 2003, 45[8], 1600-5