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Showing papers by "S. Roth published in 1995"


Journal ArticleDOI
TL;DR: In this paper, a symmetric sandwich structure of the sequence gold/Langmuir-Blodgett film/gold was prepared by employing a novel evaporation technique.
Abstract: We prepared symmetric sandwich structures of the sequence gold/Langmuir–Blodgett film/gold by employing a novel evaporation technique. As molecular systems, we used an octasubstituted palladiumphthalocyanine and a perylene‐3,4,9,10‐tetracarboxyldiimide derivative. Electronic transport measurements show a tunneling characteristic which arises from a direct tunneling process through molecular states. The current/voltage curves are symmetric for positive and negative bias proving the identical electronic behavior of the two organic/inorganic interfaces at the top and bottom electrode.

87 citations



Journal ArticleDOI
TL;DR: In this article, high temperature dc, ac and contactless microwave conductivity results on solid-state C60 (films and crystals) from room temperature up to 850 K were presented.
Abstract: We present high temperature dc, ac and contactless microwave conductivity results on solid-state C60 (films and crystals) from room temperature up to 850 K. Heating pristine samples, which were exposed to the ambient atmosphere, under dynamic vacuum at first leads to a reduction of the electrical resistance and finally, above 700 K, to an increase in the resistance. The decrease is ascribed to oxygen desorption and the increase to the chemical reactivity of residual chemisorbed oxygen with the C60 host molecules, respectively. Samples, annealed above 800 K, display a reversible temperature dependence of the resistance. The high temperature regime of their resistance exhibits an activated behaviour with an universal activation energy of 2Ea = 1.85 ± 0.04 eV for crystals and films, which is identical to the HOMO—LUMO splitting of the C 60 -molecules.

6 citations


Journal ArticleDOI
TL;DR: In this article, a bilayer sandwich structure was fabricated by the sequential thermal evaporation of gold, copper phthalocyanine (CuPc), C60 and gold onto sapphire substrates.
Abstract: Bilayer sandwich structures were fabricated by the sequential thermal evaporation of gold, copper phthalocyanine (CuPc), C60 and gold onto sapphire substrates. When the current—voltage characteristics of a freshly made device are measured in an atmosphere of argon, fairly strong rectification is observed. When the bilayer device is exposed to ammonia vapor, the rectification slowly decreases and almost disappears. If the device is then placed under vacuum and the ammonia removed, the initial conditions slowly return. We attribute the rectification to the formation of a p—n junction. PACS numbers: 73.40.—c, 73.40.Ei, 73.61.Ph

2 citations