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The close-packed two-dimensional structures of Pb on Ge(ill) and Si(111) have been studied with scanning tunneling microscopy (STM), re6ection high-energy electron diKraction, and lowenergy electron diffraction. Several closely-related commensurate and incommensurate phases were observed. For both adsorbate systems schematic phase diagrams are derived and compared to the predictions of the domain-wall theory for commensurate-incommensurate phase transitions. A complex structural model is presented, which describes the various incommensurate phases and is in good agreement with the STM data.

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Abstract. 2014 We present the first results of a combined scanning tunneling microscopy (STM) and surface X-ray diffraction (SXRD) study of Ag monolayer deposited on Cu(111). The STM images of Ag monolayer show a periodic frame of triangles, 4 or 5 atomic row wide with 1 or 3 atoms protruding in the centre respectively. Away from the triangles, the corrugation of the atomic rows is about 0.05 Å while the depth of the triangles is about 0.5 Å. SXRD shows an "average" Ag surface unit cell (9.43 x 9.43) times the Cu(111) surface unit cell without rotation in good agreement with STM observations.

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