Interfacial reactions of electroless nickel thin films on blank silicon annealed at 300-900 degrees C have been studied by both cross-sectional and planview TEM as well as by sheet resistance measurement. Samples were prepared by depositing Ni on (0 0 1)Si substrate by electroless plating deposition followed by annealing to form a silicide. An amorphous interlayer was found in interface between electroless nickel thin films and silicon. The amorphous interlayer blocks the reaction between Ni and Si and change the silicide formation sequence. The epitaxial NiSi2 was found on electroless plating nickel thin films on silicon at the temperature as low as 300 and 400 degrees C. The presence of phosphorus in the electroless Ni films and/or amorphous interlayer between electroless Ni films and Si were found to promote the formation of the epitaxial NiSi2 at low temperature. The dominant phase was NiSi in samples annealed at 500-700 degrees C. The results have shown that NiSi film formed by electroless plating process has the same resistance property as the NiSi film formed by vacuum plating process. The electroless plating technique can provide a cheap and easy process for forming nickel silicide, and has potentiality of application for the electronic device industries. (c) 2004 Elsevier B.V. All rights reserved.