Phase tailoring of Ta films via buffer layer-thicknesses controlling

Hard β-Ta phase is generally produced during Ta film deposition. While in some cases, soft α-Ta phase is preferred to ensure deformation capability. In this work, templated growth strategy by introducing Cr buffer layer is proposed to tailor the phase composition in Ta films. A broad spectrum of β-Ta/α-Ta ratio from 90% to 0% can be continuously and precisely achieved when the buffer layer thickness is correspondingly controlled from 0 to ∼90 nm. Hardness of the Ta films is well proportional to the β-Ta/α-Ta ratio. The underlying mechanism of phase tailoring is rationalized by demonstrating the thickness-dependent crystallization of buffer layer.