Phase contrast in simultaneous topography and recognition imaging

The operation of a force microscope in Simultaneous Topography and Recognition Imaging (TREC) mode is analyzed by means of numerical simulations. Both topography and recognition signals are analyzed by using a worm-like chain force as the specific interaction between the functionalized tip probe and the sample. The special feedback mechanism in this mode is shown to couple the phase signal to the presence of molecular recognition interactions even in absence of dissipation.M.F. acknowledges the hospitality offered to her by P. Hinterdorfer’s group at the Institute of Biophysics, University of Linz, during the completion of this work. This work was supported by the Spanish MICINN through the projects CTQ2005-07993-C0202/BQU, NAN2004-09125-C07-02, FIS2006-11170-C02-02, and FIS2005-05137, the Comunidad de Madrid Project Microseres-MC and by the EU IP “Molecular Imaging” (LSHG-CT-2003-503259). M.F. acknowledges financial support from the MICINN. M.K. acknowledges an I3P scholarship. M.L. acknowledges financial support from the MICINN through the Ramón y Cajal program.Peer reviewe