title: Novel electrical properties of nanoscale thin films of a semiconducting polymer: quantitative current-sensing AFM analysis.
abstract: Thin films (20-150 nm thickness) of poly(o-anthranilic acid) with various doping levels were prepared on silicon substrates with deposited indium tin oxide, and their topography and current-voltage (I-V) characteristics were quantitatively investigated using current-sensing atomic force microscopy with a platinum-coated tip. The films were found to have a surface morphology like that of orange peel, with a periodic modulation and a surface roughness. The films exhibited nonuniform current flows and I-V characteristics that depended on the doping level as well as on the film thickness. Films with a high doping level were found to exhibit Zener diode switching behavior, whereas the films with a very low doping level (or that were dedoped) exhibited no current flow at all, and so are insulators. Interestingly, self-doped films (which are at an intermediate doping level) were found to have a novel electrical bistability, i.e., a switching characteristic like that of Schottky diodes, and increasingly insulating characteristics as the film thickness was increased. The films with thickness < or =62 nm, which exhibited this novel and stable electrical bistability, can potentially be used in the fabrication of high-density, stable, high-performance digital nonvolatile memory devices based only on transistors. The measured current images and I-V characteristics indicate that the electrical switching and bistability of the films are governed by local filament formation and charge traps.
authors.affiliation: Department of Chemistry, Center for Integrated Molecular Systems, Pohang University of Science and Technology (Postech), Pohang 790-784, Republic of Korea.
authors.forename: Jiyoun
authors.initials: J
authors.lastname: Kim
authors.forename: Shinhyo
authors.initials: S
authors.lastname: Cho
authors.forename: Seungchel
authors.initials: S
authors.lastname: Choi
authors.forename: Sungsik
authors.initials: S
authors.lastname: Baek
authors.forename: Dongjin
authors.initials: D
authors.lastname: Lee
authors.forename: Ohyun
authors.initials: O
authors.lastname: Kim
authors.forename: Su-Moon
authors.initials: SM
authors.lastname: Park
authors.forename: Moonhor
authors.initials: M
authors.lastname: Ree