Temperature dependent oxygen depletion in tungsten: a quantitative analysis ofβtoαphase transition

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Thin films of beta-tungsten (β-W) are critical for spintronic and magnetic random-access memory applications.
• The thermal stability and phase transformation behavior of β-W films remain poorly understood, hindering their technological application.

Purpose of the Study:

• To systematically investigate the thermal stability and phase transformation of β-W thin films.
• To elucidate the role of oxygen content in the phase transformation of β-W films.

Main Methods:

• X-ray diffraction (XRD) for structural analysis.
• X-ray photoelectron spectroscopy (XPS) for surface composition and electronic structure.
• Secondary ion mass spectroscopy (SIMS) and thermal desorption spectroscopy (TDS) for compositional depth profiling and gas evolution.

Main Results:

• β-W films irreversibly transform to the α-W phase upon heating above 200 °C.
• Initial β-W films contain approximately 12 at.% oxygen, which decreases to a few percent after annealing up to 500 °C.
• Density functional theory (DFT) and molecular dynamics simulations confirm that the α phase is more stable at low oxygen concentrations (~10 at.%).

Conclusions:

• Oxygen desorption drives the phase transformation from β-W to α-W during thermal treatment.
• Understanding this thermal behavior is essential for optimizing β-W films in spintronic devices.
• The findings provide critical insights into the material properties for advanced memory applications.