STRUCTURAL STUDIES OF THERMALLY EVAPORATED THIN-FILMS OF COPPER PHTHALOCYANINE

Thin films of the organic semiconductor copper phthalocyanine (CuPc) are deposited onto glass substrates maintained at room temperature, and their structures investigated using X-ray diffractometry and infrared light absorption. Films of thicknesses approximately 0.1-mu-m are preferentially oriented in the [001] direction. Further growth of thicker films has the effect of randomizing the orientation of the phthalocyanine crystallites, with structure mainly of the alpha-form. Prolonged heating at 240-degrees-C produces a structural transformation of much of the material from the alpha- to the stable beta-form, with the films preferentially oriented in the [201BAR] direction. These structural changes are confirmed by infrared optical absorption analysis.