Phthalocyanine films have been synthesized by vapor deposition on quartz substrates. Some substrates were coated with a very thin gold film for introducing electrical fie.d These films have been characterized by x-ray diffraction and scanning electron microscopy. The films have excellent chemical and optical stability. However, the surface of these films grown without electrical field shows whisk-like morphology. When films are deposited under an electrical field, a dense film with flat surface is obtained. A change of film in growth orientations and solid state phase is also observed for the film synthesized under electrical fields.
A growth mechanism is studied by investigating the morphology and structure of ZnO films under different growth conditions and orientations. ZnO films are deposited on )0001) sapphire and quartz substrates by off-axis sputtering deposition at various pressures and temperatures. All films reveal highly textured structures on glass substrates and epitaxial growth on sapphire substrates. X-ray diffraction, scanning probe microscopy, and electrical measurements are used to characterize these films. The full width at half maximum of theta rocking curves for epitaxial films is less than 0.5°. In textured films, it rises to several degrees. The morphology on the surface of textured films is of a granular round shape. The epitaxial films reveal flat surface but some hexagonal facets appear when the growth temperature is increased. At a pressure of 150 mTorr, a morphology transition form large flat grains to hexagonal facets occurs at 550°C. Also, the conductivity of films decreases with the increase of growth temperatures.
We have made room-temperature measurements of transfer of electronic energy in calf thymus DNA in which 75% of the guanine residues are methylated at position N-7. The methylated residues absorb light at much longer wavelengths than the nonmethylated residues and, as a result, constitute an irreversible energy trap. For excitation at 270 nm the efficiency of intrastrand transfer is found to be 0.31. We note that this is the first measurement of the efficiency of energy transfer along the double helix of a nucleic acid. In addition, the data have been simulated by using a stochastic model in terms of Förster's theory for dipole-dipole transfer. The adequacy of the latter is discussed. Preliminary measurements of the dependence of the fluorescence spectrum and of the fluorescence anisotropy of the alternating polynucleotide poly(dA-dT).poly(dA-dT) on the excitation wavelength and temperature are interpreted in terms of emission from molecular complexes formed between A and T residues.