PHASE-SELECTIVE FORMATION OF TITANYLPHTHALOCYANINE THIN-FILMS BY ORGANIC MOLECULAR-BEAM DEPOSITION

Organic molecular beam deposition (OMBD) was used to;selectively grow phase I and phase II titanylphthalocyanine (TiOPc) thin films deposite d on sapphire R(<1(1)over bar 02>) surfaces. The dependence of the cry stal phase and film quality on substrate temperature and deposition ra te were investigated by X-ray diffraction, UV and visible absorption s pectroscopy, and scanning electron microscopy. Crystalline films were not obtained at substrate temperatures of 25 degrees C or less. Phase II growth occurred at and above 100 degrees C, and the optimum growth condition for phase II was 150 degrees C and 0.2 nm/min. The mixture o f another phase was observed when the growth temperature was higher th an 150 OC. Phase I growth was observed only at 100 degrees C, and the optimum deposition rate for phase I was 0.05 nm/min. The crystal quali ty and surface flatness of phase I films were not as good as those of phase II, films. A large red shift in the Q-band peak was observed in absorption spectra of phase LI films. The origin of this red shift is discussed according to the molecular exciton theory. Precise control o f the substrate temperature and deposition rate possible by OMBD enabl ed phase-selective growth of TiOPc thin films. The correlation between phases and absorption spectra of TiOPc is discussed.