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

TL;DR

This study investigates the relationship between dopant concentration and phase fractions in tungsten thin films, revealing weak dependence and non-uniform phase transformation behavior during annealing.

Contribution

It provides experimental evidence that dopant concentration has minimal impact on phase fraction in doped tungsten films, challenging prior assumptions.

Findings

Oxygen doped β W contains ~9% oxygen by SIMS.

Nitrogen doped β W has ~0.15% nitrogen, lower than predicted.

Phase transformation exhibits growth exponent <1, indicating non-uniform nucleation.

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.