One-step sputtering of MoSSe metastable phase as thin film and predicted thermodynamic stability by computational methods.

We present the fabrication of a MoS _2-x Se _x thin film from a co-sputtering process using MoS ₂ and MoSe ₂ commercial targets with 99.9% purity. The sputtering of the MoS ₂ and MoSe ₂ was carried out using a straight and low-cost magnetron radio frequency sputtering recipe to achieve a MoS _2-x Se _x phase with x = 1 and sharp interface formation as confirmed by Raman spectroscopy, time-of-flight secondary ion mass spectroscopy, and cross-sectional scanning electron microscopy. The sulfur and selenium atoms prefer to distribute randomly at the octahedral geometry of molybdenum inside the MoS _2-x Se _x thin film, indicated by a blue shift in the A _1g and E ¹ _g vibrational modes at 355 cm ^-1 and 255 cm ^-1 , respectively. This work is complemented by computing the thermodynamic stability of a MoS _2-x Se _x phase whereby density functional theory up to a maximum selenium concentration of 33.33 at.% in both a Janus-like and random distribution. Although the Janus-like and the random structures are in the same metastable state, the Janus-like structure is hindered by an energy barrier below selenium concentrations of 8 at.%. This research highlights the potential of transition metal dichalcogenides in mixed phases and the need for further exploration employing low-energy, large-scale methods to improve the materials' fabrication and target latent applications of such structures.
(© 2024. The Author(s).)