Phase evolution during crystallization of sputter-deposited amorphous titanium–aluminium alloy thin films: Dimensional and solute effects

Abstract

Abstract Ti-Al thin films have been deposited by magnetron sputtering on oxidized Si substrates. The targets consisted of a binary Ti-48 at.% Al alloy and a quaternary Ti–48 at.% Al–2at.% Nb–2at.% Mn alloy. In the as-deposited condition, the thin film grown from the quaternary alloy was completely amorphous whereas the film grown from the binary alloy consisted of crystalline α-Ti(Al) precipitates embedded in an amorphous matrix. In order to study the microstructural evolution during crystallization of these thin films two types of annealing experiment have been performed: ex situ in a furnace under a protective Ar atmosphere and in situ on a hot stage in the transmission electron microscope. Both the binary and the quaternary films crystallized into a two-phase mixture of γ-Tial and α2-Ti3Al as a result of ex situ crystallization. A thickness dependence in the evolution of microstructure has been observed during the in situ annealing. Thus, thick regions on the binary film evolved into the two phase micr...