Berlin 2005 – wissenschaftliches Programm
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O: Oberflächenphysik
O 36: Postersitzung (Elektronische Struktur, Grenzfl
äche fest-flüssig, Halbleiteroberfl
ächen und -grenzfl
ächen, Nanostrukturen, Oberfl
ächenreaktionen, Teilchen und Cluster, Struktur und Dynamik reiner Oberfl
ächen)
O 36.43: Poster
Montag, 7. März 2005, 15:00–18:00, Poster TU F
Nanostructured Ag wetting layers on Si via e-beam lithography — •T. Block, V. Zielasek, and H. Pfnür — Institut für Festkörperphysik, Universität Hannover, Appelstrasse 2, 30167 Hannover
o We present a lithography method taking place entirely in UHV for the formation of metal nanostructures of arbitrary shape. A combined SEM-STM instrument is used to perform electron beam lithography and subsequent investigations with STM within the same vacuum system. We employ electron-beam stimulated thermal desorption of oxygen (EBSTD) from ultrathin SiO2 layers on a Si(111) surface to generate windows of clean Si in a SiO2 mask, usually in the form of narrow (≤20nm) lines. During subsequent Ag deposition two different morphologies of nanowires are formed, depending on the annealing treatment. Percolated epitaxial crystalline silver islands are observed at low temperatures and a continuous wetting layer emerges at elevated temperatures. The wetting layer forming at 790K shows the well-known (√3×√3) Ag reconstruction, which exhibits a metallic surface state band and a conductivity of about 5−10× 10−5 Ω−1, as demonstrated elsewhere [1]. Continuous layers are already formed at a coverage of 0.5 ML, indicating accumulation of Ag from the neighboring SiO2 covered areas, an effect not observed for thicker films deposited at 130K and annealed to ≈700K. The crystalline silver islands as well as the wetting layer appear in our experiment restricted to the size and shape of the prepared Si window areas.
[1] C.-S. Jiang et. al. , Phys. Rev. B 54 10389 (1996)