Regensburg 1998 – wissenschaftliches Programm
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O: Oberflächenphysik
O 8: Epitaxie und Wachstum (I)
O 8.4: Vortrag
Montag, 23. März 1998, 17:00–17:15, H36
Growth and Chemical Imaging of CaF2 on Vicinal Si(111)7x7 — •J. Viernow1, J.L. Lin2, D.Y. Petrovykh2, F.K. Men3, J. Wollsch"ager1, M. Henzler1, and F.J. Himpsel2 — 1Institut f"ur Festk"orperphysik, Universit"at Hannover, Appelstr. 2, D-30167 Hannover — 2Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, WI 53706-1390, USA — 3Department of Physics, National Chung Cheng University, Taiwan, R.O.C.
The growth modes of CaF2 on stepped Si(111)7x7 are determined by scanning tunneling microscopy and spectroscopy. CaF2 avoids the upper edge of the Si(111) steps and attaches itself to the lower step edges. The thermal conversion from the F- to the Ca-terminated interface is suppressed on terraces narrower than 15 nm. Desorption occurs before conversion in this case. A change from step flow growth to island nucleation is seen with increasing supersaturation. Chemical sensitivity to CaF2 is achieved in STM via current images at an anti-resonance, i.e., at a bias voltage where electrons from the tip tunnel into the band gap of CaF2.