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O: Oberflächenphysik
O 9: Rastersondentechniken I
O 9.10: Talk
Monday, March 8, 2004, 18:00–18:15, H36
Observation of the complete graphite unit cell with a low-temperature atomic force microscope — •Stefan Hembacher1, Franz J. Giessibl1, Jochen Mannhart1, and Calvin F. Quate2 — 1Universität Augsburg, Lehrstuhl für Experimentalphysik VI, Zentrum für Elektronische Korrelationen und Magnetismus — 2Ginzton Laboratory, Stanford University, Stanford CA 94305
A new helium-temperature scanning tunneling/dynamic force microscope
employing the qPlus sensor is introduced. First measurements on HOPG
(highly oriented pyrolytic graphite), where the benefits of combined
STM/AFM measurements at helium temperature are clearly evident, are
presented. At low temperatures, thermal drift is only of the order of 25
pm/h enabling slow scanning in constant height mode. Because
the noise in Δ f measurements scales as B3/2, tiny forces can
be measured with good S/N ratio.
Graphite has a hexagonal structure with two atoms in the surface unit cell.
While the α-atoms have a neighbor directly underneath, the
β-atoms have no direct neighbor in the
layer below the surface layer. In scanning tunneling microscopy
experiments, only the β-atoms are visible. In AFM, with repulsive
forces, both α- and β-atoms should appear.
Simultaneously recorded frequency shift and tunneling current images in
constant height mode show the α- and the β-atoms in the
frequency shift channel, while in the current channel only the
β-atoms are observed.