Ni/Cu(100) films were prepared by thermal deposition at room temperature (RT) and 170 K low temperature (LT) separately to study the influence of substrate temperature on the spin reorientation. The critical thickness of the LT grown films is observed to be about 1 ML smaller than that of the RT films. Though both types of films show similar tetragonal distortion and chemical composition, their morphology differs dramatically: the island density of the LT films is significantly higher than that of the RT films. We use this to interpret the different magnetic behavior between the RT and LT films.