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

We present the fabrication of a MoS_2-xSe_x thin film from a co-sputtering process using MoS₂ and MoSe₂ commercial targets with 99.9% purity. The sputtering of the MoS₂ and MoSe₂ was carried out using a straight and low-cost magnetron radio frequency sputtering recipe to achieve a MoS_2-xSe_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-xSe_x thin film, indicated by a blue shift in the A_1g and E¹_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-xSe_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.