A SCANNING TUNNELING MICROSCOPE CONSTRUCTED FOR STUDIES OF LB FILMS, ORGANIC AND BIOLOGICAL MACROMOLECULES

A scanning tunneling microscope (STM) operating in ambient pressure de signed for studying organic and biological materials deposited on cond ucting substrates is described. The atomic resolution of the construct ed STM was confirmed with highly oriented pyrolytic graphite (HOPG). T he spectroscopic I/V mode was tested with HOPG and gallium arsenide, a nd it can be used for distinguishing organic materials from the conduc ting substrates. The performance of the STM apparatus was checked with gold sputtered on polished steel. The increase in the grain size of g old particles with increasing layer thickness was also confirmed. Gold , ITO, silicon and HOPG substrates were tested as substrate materials for Langmuir-Blodgett (LB) films with protein incorporated in phosphol ipid matrix in LB film, namely, bacteriorhodopsin (bR) in an added soy a phosphatidylcholine matrix (bR:soya-PC LB films). The STM imaging sh owed that HOPG substrates were most suitable for these particular LB f ilms. The constructed STM was also used in studying the structure of t he biological aldose hydrogenase enzyme. The images revealed that the enzymes formed chain structures on HOPG.