Strain induced FCC to BCC structural change in sputtered molybdenum thin films

Abstract

We find direct evidence of stain driven phase transition from face centered cubic (FCC) to body centered cubic (BCC) structure in radio frequency (RF) sputtered molybdenum (Mo) thin films as a function of deposition parameters. The structural, microstructural and electrical behavior of the Mo films are greatly influenced by the sputtering parameters i.e. RF power and argon (Ar) pressure. Although Mo is reported to be stable in BCC structure, our findings reveal that at certain deposition conditions, Mo films crystallize in FCC structure with good adherence to glass substrate; high resistance and strain (~214 Ω/□, ~3.43%). On varying sputtering parameters, strain releases and Mo films crystallize in mixed phase (FCC and BCC) which turns into pure BCC phase on further optimization. The stable BCC structured films have low resistance and strain (~1.29 Ω/□, ~−0.23%). We deposited bi-layer of Mo, where the bottom layer has strong adhesion to the substrate and top layer has low resistance (~0.81 Ω/□). The Mo film that crystallized in pure BCC form showed a strain value of −0.09% (compressive).