Weak dependence of phase fraction and dopant concentration in \{beta}, α phase mixture of W

Abstract

Dopant concentration and $\alpha$, $\beta$ phase fraction is studied in doped W thin films. Oxygen doped $\beta$ W films are found to have 9.0~$\pm$~0.9 at.\% of oxygen as measured from \ac{SIMS}. Whereas, nitrogen doped $\beta$ W films have 0.15~$\pm$~0.02 at.\% of nitrogen, much lower than the theoretically predicted value of 11 at.\%. $\beta$-W films partially phase transform to $\alpha$ by annealing at 175~${}^{\circ }$C, up to maximum time of 72 hours. Weak dependence between dopant concentration and phase fraction is observed in the annealed films. The growth exponent of the phase transformation was calculated to be $<$1 in both the films, indicating a non-uniform nucleation of the $\alpha$ phase.