ORGANIC SUPERLATTICE FILM BY ALTERNATE DEPOSITION OF SINGLE MOLECULARLAYERS

A 5,10,15,20-tetraphenylporphyrin (H2TPP; C44H30N4) film with an extra -flat surface was prepared on a Si(100) wafer substrate cooled down be low 233 K. The organic molecular-beam deposition technique was used fo r fabrication of the film under ultra-high vacuum between 4 x 10(-7) a nd 4 x 10(-8) Pa. The r.m.s. roughness determined by atomic-force micr oscope measurement was 0.22 nm, which is comparable to that of the Si substrate surface. Superlattice films of H2TPP/ZnTPP (5,10,15,20-tetra phenylporphyrinato zinc; C44H28N4Zn) were grown on Si and glass substr ates in the same manner. Their periods between 12.1 and 2.37 nm were m easured by small-angle X-ray scattering and confirmed by secondary-ion mass spectrometry depth profiling. The Fourier transform infrared spe ctroscopy measurement of the superlattice film with the minimum period of 2.37 nm indicated that the quasi-planar molecules of H2TPP and ZnT PP inclined at an angle of 75-degrees with respect to the substrate su rface. This suggests that an alternating molecular layer deposition of a single molecular layer was attained in the organic film for the fir st time.