Measuring energies with an Atomic Force Microscope

¹ Institut für Chemie und Biochemie, Physikalische und Theoretische Chemie Freie Universität Berlin - D-14195 Berlin, Germany
² Center of Bioelectronics & Nanobioscience and Departament de Química-Física Universitat de Barcelona - Martí i Franquès 1, E-08028 Barcelona, Spain
³ Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) Campus UAB, E-08193 Bellaterra, Spain

Received: 29 December 2005
Accepted: 13 February 2006

Abstract

The elastic and plastic response of ordered inorganic, organic and biological materials involving nanometer-scale volumes in the nano- and low micronewton force range can be characterized by means of an Atomic Force Microscope (AFM) using ultrasharp cantilever tips with radius R typically below . Because the plastic onset can be easily identified, the maximal accumulated elastic energy can be directly determined from the force curves (force F vs. penetration δ curves), thus giving a realistic estimate of the characteristic energies of the materials. We illustrate the ability of AFMs to determine such energies with the case example of the molecular organic metal TTF-TCNQ (TTF = tetrathiafulvalene, TCNQ = tetracyanoquinodimethane), where the enthalpy of sublimation is obtained.