ABSTRACTPcZn as a well known organic semiconductor received new examination of its growth mode in thin films and reactions to oxygen exposure. PcZn thin films were grown on glass and polyimide substrates by physical vapor deposition. Ag electrodes had been deposited by a sputter process to allow electrical contact to the films. Conductivity measurements were performed in-situ during the growth of films under high vacuum conditions. Characteristic current peaks were observed and explained by a Stranski-Krastanov growth mode. Current voltage characteristics revealing space charge limitation could be obtained beginning in the monolayer range. For pristine films n-type conduction was observed. Following deposition an increase of the conductivity was measured, caused by changes of the film structure. Ripening under high vacuum conditions could be separately discussed from doping effects caused by oxygen exposure which led to the well- known p-type characteristics of PcZn.