A recent paper in Journal of Physics: Condensed Matter presented a comprehensive investigation of the thermal stability and phase transformation of β-tungsten (β-W) films. The study was motivated by the growing interest in β-W for spintronic devices due to its large spin Hall effect and suitability for magnetic random-access memory applications. Despite these promising properties, the stability of β-W under thermal treatment remains a critical issue for device fabrication and reliability. To address this, the authors carried out a systematic experimental and theoretical studies using several complementary characterisation techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), and thermal desorption spectroscopy (TDS), supported by density functional theory (DFT) and ab initio molecular dynamics simulations.
A key focus of the work was the use of TDS to understand the role of oxygen in stabilising the metastable β phase and driving the phase transition to the α phase. The TDS measurements were performed in an ultrahigh vacuum (∼10-9 Torr) chamber at Hiden Analytical using a high precision triple filter quadrupole mass spectrometer, while a PID control module was used for measuring temperature up to 1000 °C with a heating ramp of 1°C/min. The evolution of desorbed atomic and molecular species was monitored by tracking specific mass-to-charge ratios corresponding to oxygen (m/z = 16), oxygen molecules (m/z = 32), tungsten-related fragments, and silicon signals originating from the substrate interface. This instrumental configuration allowed the authors to obtain detailed information on the temperature-dependent desorption processes occurring in the films.
Figure 1. TDSLab-6, Hiden Analytical.
The TDS results reveal that oxygen desorption occurs in multiple stages during heating. A low-temperature desorption feature is attributed to the removal of weakly adsorbed oxygen species from the film surface. A more pronounced desorption peak appears in the intermediate temperature range, indicating the release of oxygen incorporated within the film structure. This process is closely correlated with structural changes detected by XRD and compositional variations observed in XPS and SIMS measurements. A significant reduction in oxygen content from ~12 at.% to only a few atomic percent was evidenced with increasing temperature by heating up to ~500oC. This provided direct evidence of β-to-α phase transformation due to oxygen desorption. Moreover, atomic-scale analyses based on DFT and ab initio molecular dynamics calculations revealed the formation of energetically favourable α phase at relatively low oxygen concentrations (up to ~10 at.%), in good agreement with the experimentally observed β-to-α phase transformation by oxygen desorption. A comprehensive understanding of the thermal stability of such b-W films is therefore essential for practical device applications.
Project Summary by: Prof. Aloke Kanjilal, Department of Physics, School of Natural Sciences, Shiv Nadar Institution of Eminence Deemed to be University, Delhi-NCR, NH-91, Tehsil Dadri, Gautam, Buddha Nagar, Uttar Pradesh, PIN – 201314, India.
Paper Reference: Patajoshi, S., Rao, P. N., Tayyab, S., Rai, S. K., Betti, M. G., Mariani, C., Kumar, V. and Kanjilal, A. (2026) ‘Temperature dependent oxygen depletion in tungsten: a quantitative analysis of β to α phase transition.’ Journal of Physics: Condensed Matter. IOP Publishing, 38(8) p. 085701. DOI: 10.1088/1361-648X/ae45e3.
Hiden Product: TDSLab-6.
