Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 47: Methods: Scanning probe techniques II

O 47.2: Talk

Thursday, March 26, 2009, 10:45–11:00, SCH A316

Towards a quantitative tunneling spectroscopy: Using differential barrier heights for a deconvolution of the tip and sample density of states — •Holger Pfeifer, Berndt Koslowski, Anna Tschetschetkin, and Paul Ziemann — Institut für Festkörperphysik, Universität Ulm, D-89069 Ulm, Germany

Based on the recently developed method for recovering the electronic density of states (DOS) from scanning tunneling spectroscopy (STS) data [1], we analytically calculate the differential barrier (∂_z∂_VI) for an energy-dependent DOS of either the sample or the tip. It turns out that (i) considering a peaked DOS the sign of the peak reveals whether this peak belongs to the sample or the tip, and (ii) the formula for the differential barrier can be rewritten to form an additional Volterra integral equation of the second kind for both the DOS of sample and tip, respectively. Additionally to the equations obtained earlier from the differential conductivity (∂_VI), these equations can be exploited by using the Neumann approximation to optimize iteratively the recovered DOS’ being then self-consistent with the WKB approximation and measured data (I, ∂_VI, and ∂_z∂_VI). By comparing these results with experimental data obtained on Nb(110) we analyze how far the proposed scheme enables deconvolution of the DOS’ of sample and tip.

[1] B. Koslowski, Ch. Dietrich, A. Tschetschetkin, P. Ziemann, Phys. Rev B 75, 035421 (2007)