Space charge distribution of organic-molecular-beam-deposited titanylphthalocyanine films on metal electrodes

Space charge distributions of organic-molecular-beam-deposited titanylphtha locyanine (TiOPc) films on metal electrodes were investigated by measuring surface potentials at various deposited thickness of TiOPc. The island grow th of TiOPc on Au, Cr, and Al electrodes was observed by atomic force micro scopy (AFM) image. Mean thickness of TiOPc films was evaluated by combining the results of absorbance and frequency-height dependence of the AFM image . Surface potentials across TiOPc film due to the space charges at the meta l-TiOPc interface were discussed by taking into account the surface roughne ss. It was found that the surface potential-film thickness relationship of TiOPc films is similar to that of Langmuir-Blodgett films. The space charge distributions in TiOPc films on Au, Cr, and Al electrodes were determined from the thickness dependence of the surface potentials. It is shown that t he space charges are excessive electrons transferred from metals, and 90% o f them concentrate on the metal-TiOPc interface at a range of 10 nm. (C) 19 99 American Institute of Physics. [S0021-8979(99)06718-3].