Para-sexiphenyl (p-6P) ultrathin film was utilized as the modified layer to grow copper phthalocyanine (CuPc) thin film. The order of the CuPc thin-film morphology exhibits an obvious dependence on p-6P thickness. A conversion of p-6P growth mode from layer-by-layer to island growth was observed. The highest mobility of CuPc transistor based on p-6P modified layer has been obtained by 0.18 cm(2)/V s with the p-6P thickness of 2.4 molecule layer. Therefore, the thickness of modified layer plays a crucial role in thin film growth of organic semiconductor that results in a remarkable influence on the electric characteristics of devices. (C) 2013 Elsevier Ltd. All rights reserved.