ATOMIC-SCALE DESORPTION THROUGH ELECTRONIC AND VIBRATIONAL-EXCITATIONMECHANISMS

The scanning tunneling microscope has been used to desorb hydrogen fro m hydrogen-terminated silicon (100) surfaces. As a result of control o f the dose of incident electrons, a countable number of desorption sit es can be created and the yield and cross section are thereby obtained . Two distinct desorption mechanisms are observed: (i) direct electron ic excitation of the Si-H bond by field-emitted electrons and (ii) an atomic resolution mechanism that involves multiple-vibrational excitat ion by tunneling electrons at low applied voltages. This vibrational h eating effect offers significant potential for controlling surface rea ctions involving adsorbed individual atoms and molecules.