Studying the Electrical Properties of Single Molecules by Break Junction Techniques

Abstract

Electrical properties of molecules at the single molecule level can be efficiently studied by break junction techniques. This article describes the most frequently used experimental methods such as scanning tunneling microscopy (STM BJ), current sensing atomic force microscopy (CS-AFM BJ), and mechanically controllable (MC BJ) break junction techniques for charge transport studies in metal-molecule-metal junctions. It explains junction formation process, methodology of data acquisition and treatment, as well as the description of charge transport mechanisms including direct tunneling, Fowler-Nordheim tunneling, thermionic emission, and hopping conduction. Finally, experimental methods beyond the conductance measurements are briefly discussed. They include current–voltage, transition voltage, and inelastic electron tunneling spectroscopies, electrochemical STM BJ method, and determination of thermoelectric and mechanical single molecule junction properties.