Study on energy level bending at heterojunction of solution-processed phthalocyanine thin film and n-Si by Kelvin probe force microscopy

Surface potential of a solution-processed thin film of an organic semiconductor, 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH(2)), on n-type silicon (n-Si) substrate has been studied by using Kelvin probe force microscopy, and discussed the interface properties of organic/inorganic semiconductors. The molecular step and terrace structure was observed on the surface of solution-processed C6PcH(2) thin film as a feature of the crystallites composed of C6PcH(2) columns lying on the substrate. The surface potential changed depending on the distance from the interface, and exceeded 0.4 eV, which indicated the difference of Fermi levels between C6PcH(2) and n-Si. The linear and non-linear relationships between the surface potential and the distance from the interface were discussed by taking the vacuum level shift and impurity carriers into consideration.