Structure and phase formation in Cu–Mn alloy thin films deposited at room temperature

Abstract

Transmission electron microscopy characterization of Cu–Mn alloy thin films deposited by DC magnetron sputtering is applied to reveal the formation of phases throughout the composition range. Pure Cu and Mn films exhibit face-centred cubic (fcc) Cu and α-Mn phases, respectively. At room temperature the low Mn content films have fcc structure (γ-phase). Mn can substitute Cu in the fcc Cu lattice up to ∼35at.% Mn. The lattice parameter of fcc Cu–Mn alloy films follows a linear relationship of a0=aCu+0.322c (in Å), where aCu=3.615Å is the lattice parameter of Cu and c is the Mn atomic concentration. At high Mn content, above 50at.% Mn, a homogeneous one-phase structure is observed, possessing the short-range order of α-Mn. The incorporation of Cu into Mn suggests that this structure changes from crystalline α-Mn to disordered structure as the Cu content increases. A narrow two-phase region exists between 35 and 45at.% Mn. A grain size minimum of 2–3nm was observed in the 35–65at.% Mn region.