The compressive stress transition in Al, V, Zr, Nb and W metal films sputtered at low working pressures☆

Transformation of sputter deposited A‐15 crystal structure tungsten thin films by rapid thermal annealing and in situ heat treatments in a transmission electron microscope was investigated. Phase transformation of A‐15 W into body‐centered‐cubic (bcc) W did not occur at a specific annealing condition but over a range of annealing times and temperatures. However, complete A‐15 to bcc W transformation occurred in all samples rapid thermal annealed at 650 °C for 1 min. Variations in the transformation time and temperature for each sample were attributed to differences in the oxygen concentration in the films. The higher the oxygen concentration in the film, the higher the temperature or longer the time required to transform A‐15 W into bcc W. No measurable difference in the oxygen concentration before and after transformation was found and the O and W atom’s binding energies were the same in both the A‐15 and bcc crystal structure. The resistivity of A‐15 crystal structure films decreased significantly after transformation into the body‐centered‐cubic phase, on the order of 80%. The decrease in resistivity as a result of the transformation was attributed to the elimination of the A‐15 defect structure and an increase in particle size by coalescence during transformation, from ∼5 nm in diameter in the as‐deposited A‐15 crystal structure to ∼25–40 nm in diameter after transformation into bcc W.

Phase transformation of sputter deposited tungsten thin films with A-15 structure

Spin-to-charge current interconversions are widely exploited for the generation and detection of pure spin currents and are key ingredients for future spintronic devices including spin-orbit torques and spin-orbit logic circuits. In the case of the spin Hall effect, different mechanisms contribute to the phenomenon and determining the leading contribution is peremptory for achieving the largest conversion efficiencies. Here, we experimentally demonstrate the dominance of the intrinsic mechanism of the spin Hall effect in highly resistive Ta. We obtain an intrinsic spin Hall conductivity for \ensuremath{\beta}-Ta of $\ensuremath{-}820\ifmmode\pm\else\textpm\fi{}120(\ensuremath{\hbar}/e)\phantom{\rule{0.16em}{0ex}}{\mathrm{\ensuremath{\Omega}}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$ from spin absorption experiments in a large set of lateral spin valve devices. The predominance of the intrinsic mechanism in Ta allows us to linearly enhance the spin Hall angle by tuning the resistivity of Ta, reaching up to \ensuremath{-}35 \ifmmode\pm\else\textpm\fi{} 3%, the largest reported value for a pure metal.

Unveiling the mechanisms of the spin Hall effect in Ta

Tungsten chemical vapor deposition using tungsten hexacarbonyl: microstructure of as-deposited and annealed films

ArF excimer laser radiation has been used to deposit W films on silicon and on SiO2 by initiating the gas phase reaction of WF6 with H2 Deposition rates >100 nm/min and film resistivities as low as two times the bulk value have been obtained at deposition temperatures of 440 °C The properties of the laser‐deposited films are compared with those of fims obtained using conventional thermal deposition techniques Film resistivity correlates with the microstructure which in turn depends on the deposition temperature; above 350 °C the low‐resistivity α‐W phase dominates

W.A. Reed

Papers

Temperature coefficient of resistance of beta-tantalum films and mixtures with b.c.c.-tantalum

Resistivity behavior and phase transformations in β-W thin films

Structural and electrical properties of sputtered tungsten films