INITIAL PHASE-FORMATION IN NB SI MULTILAYERS DEPOSITED AT DIFFERENT TEMPERATURES/

The initial phase formation in Nb/Si multilayers deposited at 25 and 2 00 degrees C was studied by high-resolution transmission electron micr oscopy and x-ray diffraction. When Nb/Si multilayers were deposited at 25 degrees C, the multilayers with a modulation period L of 4 nm were in the amorphous state, with Nb-rich amorphous silicide layers and Si -rich amorphous silicide layers. The multilayers with a modulation per iod L of 100 nm also had an amorphous structure, consisting of intermi xed layers of amorphous Nb silicide between the amorphous Si (a-Si) an d amorphous Nb (a-Nb) layers. The initial amorphization reaction in Nb /Si multilayers is thermodynamically and kinetically favored. When the multilayers were deposited at 200 degrees C, a crystalline cubic Nb3S i phase with AuCu3 structure was formed in the multilayer samples. The interfacial energy and modified heat of formation are used to explain why the crystalline phase is formed and Nb3Si is the first phase form ed during deposition at so low a temperature. (C) 1996 American Instit ute of Physics.