The crystalline morphology of PCL (poly(ε-caprolactone)) thin film was investigated by AFM (atomic force microscopy)．1％ PCL/chloroform solution was spun-cast on different substrates to get thin films．The thickness of the films is about 100 nm．The thin films were annealed at 120℃ for 48 h

then crystallized at 55℃ for 72 h AFM observation showed that two kinds of crystal morphology formed in PCL thin films on polished quartz substrate

i．e．typical spherulite and unusual pinetree branch-like crystal morphologies．It is considered that the diffusion-control crystallizing process results in the formation of the unusual pinetree branch-like crystal morphology while the PCL film is thin enough. It might be the main reason that the interaction between the substrate and the PCL molecules confines the chain diffusion．When the PCL solution was cast on a quartz substrate with designed aluminum grooves of 10 μm wide

it was observed that the crystallites in the PCL thin film exhibited a regular oriented alinement．The orientation along the groove is preponderant．It implies that the crystal first formed from the edges of the aluminum groove and then grew along the groove．When strong electrostatic field is applied to the groove

the PCL crystallization in the thin film exhibited a different morphology

i．e．the crystal arrangement tends to be parallel to the electrostatic field．