EFFECTS OF SOLVENT ON THE MORPHOLOGY AND CRYSTALLINE-STRUCTURE OF LITHIUM PHTHALOCYANINE THIN-FILMS AND POWDERS

The effect of acetone vapours on the phase transformation x --> alpha was studied by means of electron microscopy, X-ray diffractometry, ele ctron spin resonance (ESR) and optical spectroscopy on thin films and powders of lithium phthalocyanine (PcLi). The exposure of amorphous fi lms of PcLi, deposited at a substrate temperature of 15 degrees C onto glass slides, to solvent vapours of acetone at room temperature, indu ces important changes in the morphology and crystalline structure of t he films. Exposure to acetone vapours under low pressure (200 mbar) le ads to an x-like structure with low crystallinity, uniform coverage an d no preferential ordering. Longer exposure in a saturated acetone vap our atmosphere results in an important phase transformation to the ct form which leads to crystallites up to several micrometres large lying in the plane of the substrate and forming a discontinuous coverage. I n the case of x powders treated in liquid acetone, a phase transformat ion to the alpha form of PcLi is observed. This x --> alpha phase chan ge induced by the acetone vapour treatment is interpreted in terms of crystal size effects and compared with the phase transformation observ ed in thin films deposited at various substrate temperatures in the ra nge 25-225 degrees C.