TUNNELING MECHANISMS IN ELECTROCHEMICAL STM - DISTANCE AND VOLTAGE TUNNELING SPECTROSCOPY

The tunneling mechanisms in electrochemical STM are studied by distanc e and voltage tunneling spectroscopy in different model systems. The e xperimental results indicate an indirect tunneling process via interme diate states. Significant influences of the chemical nature and crysta llographic orientation of the substrate and the structure of 2-D upd a dlayers on the effective barrier height of the tunneling process are o bserved. The intermediate states are related to dipole resonances of w ell-ordered water dipoles located in the electrochemical double layers at the tip/electrolyte and substrate/electrolyte interfaces.