LOCAL BOND BREAKING VIA STM-INDUCED EXCITATIONS - THE ROLE OF TEMPERATURE

We discuss the influence of temperature on local bond breaking through multiple vibrational excitations induced by inelastic tunneling in th e STM. We focus on hydrogen desorption from the H-Si(lll) and H-Si(100 ) systems, but the results are general. The substrate temperature affe cts the desorption yield in two important ways: first, lowering the te mperature increases the H-Si vibrational energy relaxation time, resul ting in a higher effective adsorbate temperature and an increased deso rption yield. Second, lowering the substrate temperature decreases the dephasing rate of the H-Si modes (manifested by a decrease of the inf rared absorption linewidth), which then reduces the rate of incoherent (Forster) vibrational energy transfer away from the Stark-shifted K-S i mode under the tip. This increases the localization of the vibration al energy and enhances the probability for multiple vibrational excita tion and desorption. Finally, we discuss the possible implications of our findings on the mechanism of MOS device degradation by hot electro ns. (C) 1997 Elsevier Science B.V.