The effect of P content and seed layer on the crystallization process was studied in electroless Ni-P films containing 6-20 atom % P. Secondary ion mass spectroscopy (SIMS) data indicate that Ni-P films on both Co and Cu seed layers have uniform P distribution throughout the thickness of the film. Films with 20 atom % P are amorphous as deposited, and face-centered cubic Ni and tetragonal Ni3P crystallize at similar to 350 degrees C. Films containing 6-12 atom % P have Ni present as deposited, and Ni3P crystallizes at temperatures ranging from 350-410 degrees C. An atomic level model is proposed to explain the crystallization behavior. (c) 2005 The Electrochemical Society.