Unravelling oxygen driven α to β phase transformation in tungsten
Ananya Chattaraj, Mohammad Balal, Ashok K. Yadav, S. R. Barman, A. K. Sinha, S. N. Jha, S. Joulié, V. Serin, A. Claverie, Vijay Kumar, A. Kanjilal
Abstract
Abstract Thin films of β -W are the most interesting for manipulating magnetic moments using spin–orbit torques, and a clear understanding of α to β phase transition in W by doping impurity, especially oxygen, is needed. Here we present a combined experimental and theoretical study using grazing incidence X-ray diffraction, photoelectron spectroscopy, electron microscopy, and ab initio calculations to explore atomic structure, bonding, and oxygen content for understanding the formation of β -W. It is found that the W films on SiO 2 /Si have 13–22 at.% oxygen in A15 β structure. Ab initio calculations show higher solution energy of oxygen in β -W, and a tendency to transform locally from α to β phase with increasing oxygen concentration. X-ray absorption spectroscopy also revealed local geometry of oxygen in β -W, in agreement with the simulated one. These results offer an opportunity for a fundamental understanding of the structural transition in α -W and further development of β -W phase for device applications.