Substrates effects on the growth behavior of Copper tetra-tert-butyl phthalocyanine films studied by atomic force microscopy

Copper tetra-tert-butyl Phthalocyanine (CuTTBPc) was vacuum deposited onto substrates of hydrophilic glass, hydrophobic silanized-glass, and one layer CuTTBPc LB film. The effects of substrates on the growth behavior and film characteristics of CuTTBPc were studied by atomic force microscopy as well as XRD and dynamic contact angle analyzer. The results show that, in the early growth stage, the island density and coverage ratio of CuTTBPc are small on hydrophilic glass surface. This result is caused from the weak interaction of CuTTBPc molecules to the glass which leads to a small nucleation rate and rougher morphology in the early growth stage. On the contrary, the nucleation rate of CuTTBPc on the silanized-surface is high and thus a much smoother film comprises densely distributed fine-grain clusters was observed. This fact indicates the higher adhesive force of CuTTBPc molecules to the silanized-surface. On the LB film, the CuTTBPc molecules are arranged in aggregative domains which are separately distributed on the glass surface. These domains act as active sites for the nucleation and growth of the later deposition process and thus, high density clusters were found in the early growth stage. The XRD results demonstrate that the film grown on glass has higher degree of crystalline structure than the others which is resulted from the distinction of the initial growth stage. (C) 2002 Elsevier Science B.V. All rights reserved.