ENHANCEMENT IN CHEMICAL INTERACTION AT CONDUCTING POLYMERS N-SI INTERFACES BY THEIR ELECTROREDUCTION/

Studies of chemical and electronic interaction at organic/inorganic in terfaces are described; Electrochemical deposition of conducting polym ers [poly(3-methylthiophene), polythiophene, poly(3-methylpyrrole), po lypyrrole, poly(3-methylthiophene-co-pyrrole)] on an n-Si wafer does n ot give rise to high-quality p-n heterojunctions, but it is found that their junction properties are greatly improved by their electrochemic al reduction (cathodic treatment). For example, the cathodic treatment of an as-grown poly(3-methylthiophene)/n-Si junction cell with rectif ying ratio, gamma, of 1.4 x 10(1) and diode factor, n, of 2.6 gives a high quality junction with gamma = 1.7 x 10(4) and n = 1.2. The treatm ent involves not only the development of polymer films but the improve ment in junction interface, since the treatment can contribute to the improvement only when conducted in the presence of polymer films. In o rder to understand this modification at the interface, the effects of cathodic treatment conditions (treatment potential and time) and the p resence of an interfacial oxide. layer on the junction properties are investigated. As a result, it is revealed that the improvement is expl ained by a junction formation model described as the evolution of cova lent bond formation at the interface; Further electrochemical studies reveal that such bondings are disrupted by hydrolysis and/or oxidation , and the bond disruption model is used to describe the degradation of the junctions in the air.