Inducing desorption of organic molecules with a scanning tunneling microscope: Theory and experiments

A scanning-tunneling microscope has been used to induce efficient local desorption of benzene from Si(100) at low currents (<100 pA), sample biases (-2.4 V) and temperatures (22 K). A theoretical model based upon first principles electronics structure calculations and quantum mechanical wave packet dynamics describes this process as occurring via transient ionization of a rr state of the adsorbed molecule. This model accounts for the unexpected efficiency and sharp threshold of the yield.