GASEOUS OXIDATION AND COMPENSATING REDUCTION OF LUTETIUM BIS-PHTHALOCYANINE AND LUTETIUM PHTHALO-NAPHTHALOCYANINE FILMS

Thin films are deposited from lutetium bisphthalocyanine (LuPc(2)) and lutetium phthalo-naphthalocyanine (LuPNc) that are intrinsic, easily oxidizable, molecular semiconductors. Oxidation of the films by NO2 or Br-2 vapours is studied by visible absorption spectroscopy on ''neutr al'' and oxidized films and by in-situ measurements of conductivity an d sorbed dopant mass uptake, Exposures of the oxidized LuPc(2) and LuP Nc films to NH3 lead to a conductivity increase or decrease depending on the oxidation degree of the films. The whole set of results is in a greement with a model that describes the existence of a conductivity m aximum in LuPc(2) and LuPNc during oxidation as the consequence of bot h a trapping process of the charge carriers and a reduction of their m obility when the concentration of oxidized phthalocyanine molecules be comes too high.