  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.

Materials Science