Ambient bistable single dipole switching in a molecular monolayer.

: We report a molecular dipole that self-assembles into highly ordered patterns at the liquid-solid interface and that can be switched at room temperature between a bright and a dark state at the single molecule level.  Using a scanning tunnelling microscope (STM) under suitable bias conditions, we can write binary information at a density of up to 41 Tb/cm 2 (256 Tb/in 2 ).  The written information is stable during reading at room temperature, but can also be erased at will instantly by proper choice of tunnelling conditions. DFT calculations indicate that the contrast and switching mechanism originate from the stacking sequence of the molecular dipole, which is reoriented by the electric field between tip and substrate.