Thermal stability of W/C multilayer films

W(15 A)/C(15 A), W(50 A)/C(50 A) and W(100 A)/C(100 A) periodic multilayer films were prepared by magnetron sputtering and subsequently annealed at 980, 730 and 5000C. The changes of layered and crystal structures were studied by x-ray diffraction. The results depended largely on the thickness of W layers and their initial crystal structures of W. The kinds of transformations are classified into two types: one is the non-reacting type in the case of multilayers having the thinner W layers like W(15 A)/C(15 A), in which the crystallization of W layers prevails over the reactions between W and C layers; the other, the reacting type in the multilayers having thicker W layers like W(50 A)/C(50 A) and W(100 A)/C(100 A), in which reactions prevail over crystallization. A tentative model in which the effective reaction rate between amorphous-W and amorphous-C is much smaller than that of crystalline-W(beta phase) and amorphous-C is proposed to explain the origin of the phenomena