  $\beta$-Tungsten ($\beta$-W), a A15 cubic phase of Tungsten exhibits giant
spin hall angle as compared to its bcc-phase $\alpha$-Tungsten ($\alpha$-W),
making high quality $\beta$-W film desirable for spin-based application. We
report on the substrate bias driven on-demand growth of $\beta$-W film on
SiO$_2$ coated silicon (SiO$_2$/Si) using DC sputtering. GIXRD plots and SEM
images are used to show a systematic change on the structure and grain size of
the deposited films with the application of substrate bias. It is observed that
zero bias film are amorphous in nature and changes phase from $\alpha$ to
$\beta$ or mixed ($\alpha$ + $\beta$) depending upon the sign and magnitude of
the substrate bias. We performed One-Dimensional Power spectrum density of the
AFM images which revealed that the pure $\beta$-W film grown at a positive bias
of +50V has the minimum roughness as compared to films grown at different
substrate bias. We further confirm the metallic surface homogeneity using the
room temperature STM. Our results shows that the substrate bias which controls
the energy of the deposited atom, is a crucial parameter for an on demand
growth of $\beta$-W, an important material for spintronic applications.
