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We report the direct observation of induced molecular reorientation on a ferroelectric copolymer with a scanning tunneling microscope (STM). Ultrathin copolymer films of vinylidene fluoride (70%) with trifluoroethylene (30%) revealed a quasihexagonal close-packing structure with long-range polymer chain ordering. By flipping the polarity of the STM tip bias voltage, a reversal of local polarization was observed through an apparent lattice shift and was accompanied by an asymmetric ‘‘diode-like’’ character in tunneling current I(V). These results clearly demonstrated conductance switching behavior on nanoscale with local polarization reversal. © 2003 American Institute of Physics.