Regensburg 2019 – wissenschaftliches Programm
O 95.6: Vortrag
Freitag, 5. April 2019, 11:45–12:00, H14
Temperature-dependent order-disorder transition in the Si(553)-Au nanowire system — •Bernd Hafke1, Tobias Witte1, Christian Brand1, Simone Sanna2, Christian Braun3, Wolf Gero Schmidt3, and Michael Horn-von Hoegen1 — 1Universität Duisburg-Essen, Lotharstr. 1, 47057 Duisburg — 2Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen — 3Universität Paderborn, Pohlweg 55, 33098 Paderborn
Deposition of 0.5 ML Au on Si(553) at 650 ∘C results in the formation of Au double-strand metallic chains with a twofold periodicity along the terraces of the vicinal Si surface. The step edge atoms of the Si terraces are characterized by a threefold periodicity, due to the presence of unoccupied dangling bonds [1,2]. The long-range interaction of the twofold and threefold periodicity is investigated by spot-profile analysis in LEED as function of temperature between 60 K and 190 K. The correlation length of Si step edge atoms along and perpendicular to the steps abruptly decreases upon heating above a temperature of T≈100 K, respectively. These findings are explained within a scenario of an order-disorder transition, where the thermal creation of solitons destroy the long-range ordering. Additionally, time-resolved ultra-fast RHEED experiments show the streak-like intensity, indicative for the twofold periodicity of the Au atoms, to decrease upon intense fs-optical excitation. This indicates transient weakening of the dimerization within the Au double-strand.
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