Applications of Scanning Tunneling Microscopy to Electrochemistry

Abstract : Our efforts through the last contract period have involved the fundamental study of the STM imaging process, the investigation of the use of partially insulated STM tips as ultramicroelectrodes, and applications of STM for the generation of lithographic features. STM investigations of conducting polymers dispersed on graphite surfaces and doped with I2 revealed that, although the conducting backbone of the polymer could be imaged under a range of tunneling conditions, the non-conducting side groups of the polymer were not imaged. These images represent the first atomic resolution images of polymers, and studies of this studies of this type, involving the simultaneous imaging of nominally conducting and non-conducting groups, should prove essential in developing a theoretical understanding of the contrast mechanisms which dominate the imaging of individual adsorbed molecules with STM. Studies of ultramicroelectrodes, fabricated initially as partially insulated STM tips for use in solutions containing significant concentrations of electroactive species, have revealed the possibility of fabricating electrodes as small as one nanometer in diameter.