Abstract Scanning photoelectron spectromicroscopy (SPESM) has been used to study nickel metal induced lateral crystallization (Ni-MILC) of amorphous silicon (a-Si) thin films, produced by in situ annealing of vacuum deposited Ni patterned films on a-Si. The spatial variations in the chemical composition of the Ni-MILC of a-Si were directly imaged. High-resolution photoemission spectra of both Si 2p and Ni 3p core levels and valence band were used to evaluate morphological changes and chemical interactions. Our direct spectromicroscopic characterization clearly shows that the Ni-MILC process in UHV leads to the lower crystallization temperature and a faster crystallization speed of a-Si, and a poly-Si film with high-crystallinity can be obtained. A unified mechanism for the enhanced growth rate of the high-crystallinity poly-Si film produced by Ni-MILC in UHV is proposed.