Surface alloys, overlayer and incommensurate structures of Bi on Cu(111)

Temperature-dependent structure, elasticity, and entropic stability of Bi phases on Cu{111}

“…2, we conclude that the electron reflectivity is not only a sensitive measure for the density of a dense Bi overlayer phase, but that the density of the overlayer phase is approximately constant until 796 K. To reconcile the total amount of Bi that is deposited with the relative fractions of the two visible phases, and produce a coverage of the √ 3 phase of 0.276 ML at 680 K, the Bi coverage of the overlayer phase was used as a free parameter. The value that yields best agreement is a Bi coverage of the overlayer of 0.465 ± 0.003 ML [8] for the temperature interval from 600 to 796 K. This value is consistent with the coverage of the crystalline overlayer phase of 0.5 ML that was determined for a crystalline overlayer phase at room temperature using surface x-ray diffraction (SXRD) [6,12].…”

“…Any additional Bi that is deposited in excess of 1/3 ML is incorporated in an overlayer phase [6,[9][10][11]. The precise structure of the overlayer phase depends on coverage and temperature and has been described in detail elsewhere [12].…”

“…Bi was vapor deposited from a Knudsen cell. An accurate temperature measurement was achieved by comparing to previous SXRD and LEEM data sets that we have for this system and cross correlating the observed phase transitions and other phenomena [6,12].…”

“…When the data of Fig. 3 are combined with the electron reflectivity and SXRD data of the overlayer phase [6], a complete and comprehensive picture of the temperature-dependent structure of the √ 3 phase is realized.…”

“…Moreover, experiments that yield a comprehensive picture of all relevant parameters are difficult to perform with a single technique [5]. Diffraction experiments typically allow for an accurate characterization of the atomic structure, but average out the spatial diversity of the various phases that coexist [6]. High resolution forms of microscopy with a narrow field of view allow for a detailed characterization of atomic composition and kinetics, but fail to dynamically visualize the thermodynamically driven collective behavior that determines the stability of different surface phases on a larger length scale.…”