Direct observation of a local structural transition for molecular recording with scanning tunneling microscopy

We present a direct observation of a structural transition at molecular sca le in an organic p-nitrobenzonitrile (PNBN) thin film using scanning tunnel ing microscopy (STM). STM images clearly show an ordered molecular structur e of unrecorded regions in the films, while the PNBN molecular arrangements are disordered in the recorded regions. The current-voltage (I-V) measurem ents from the STM demonstrate a great increase of the conductance transitio n in the recorded regions after the voltage pulses. Those results suggest t hat the recording mechanism may be due to a crystalline structural transiti on, which is consistent with our previously proposed mechanism in another o rganic system for ultrahigh density data storage. (C) 2000 American Institu te of Physics. [S0003-6951(00)04746-X].