Scanning tunneling microscopy

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Up to now scanning tunneling microscopy (STM) was essentially used by physicists to investigate structures of metals, semiconductors and physically interesting surface processes.

The aim of our STM-works is the study of single large molecules of importance in chemistry and biology and their association on well defined surfaces like highly oriented pyrolytic graphite (HOPG).

We focus on the association of different porphyrins especially of bacteriochlorophyll, and of carotinoides.

Study of porphyrins Size: 345K compressed

These systems play an important role in primary photophysical processes within light harvesting antenna systems and photosynthetic reaction centers as well as in advanced materials considered for opto-electronic devices.

The reduced mobility of the single molecules on the surface due to extensive hydrogen bond association allows a precise study of aggregate structure and their change by different conditions of surface preparation (different solvents, variation of dilution, different methods of surface coverage).

The main goal of our investigations is the study of the interaction of tunable UV/VIS (laser) light with the associates to obtain vibronic spectra of single molecules on the surface and more insight into morphological changes of the aggregate structures induced by light absorption. For these studies we use an STM with an extremely low spatial drift (<30 Å/h).

Study of graphite Size: 679K compressed