Molecular organization and electric property of azobenzene derivative at liquid/graphite interface studied by scanning tunneling microscopy

Topography and electric property of the physisorbed monolayer of an azobenzene derivative, 4,4′-dihexyloxy-2-hydroxy-azobenzene (Azo), at the liquid/graphite interface were investigated by scanning tunneling microscopy (STM). The STM observations show that the azobenzene derivative can form an ordered row-like structure at the interface and the periodicity of the row is 3.0 nm, corresponding to the length of the molecule. Electric property of this organic tunnel junction at the liquid/graphite interface was examined by the measurement of the current–voltage (I–V) curve. The I–V curve is asymmetric for positive and negative voltages, indicating the rectifying behavior of the adlayer.