Ni phthalocyanine (NiPc) and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) were deposited alternately on glass substrates under a pressure of 2 x 10(-4) Pa. When PTCDA was deposited first followed by NiPc, both materials were considered to diffuse mutually; this was deduced from X-ray diffraction analyses and optical absorption spectra. On the contrary, when NiPc was deposited first and followed by PTCDA, the mixing of the two substances was not apparent.