Growth, structure and stability of sputter-deposited MoS2 thin films

Molybdenum disulphide (MoS ₂) thin films have received increasing interest as device-active layers in low-dimensional electronics and also as novel catalysts in electrochemical processes such as the hydrogen evolution reaction (HER) in electrochemical water splitting. For both types of applications, industrially scalable fabrication methods with good control over the MoS ₂ film properties are crucial. Here, we investigate scalable physical vapour deposition (PVD) of MoS ₂ films by magnetron sputtering. MoS ₂ films with thicknesses from ≈10 to ≈1000 nm were deposited on SiO ₂/Si and reticulated vitreous carbon (RVC) substrates. Samples deposited at room temperature (RT) and at 400 °C were compared. The deposited MoS ₂ was characterized by macro- and microscopic X-ray, electron beam and light scattering, scanning and spectroscopic methods as well as electrical device characterization. We find that room-temperature-deposited MoS ₂ films are amorphous, of smooth surface morphology and easily degraded upon moderate laser-induced annealing in ambient conditions. In contrast, films deposited at 400 °C are nano-crystalline, show a nano grained surface morphology and are comparatively stable against laser-induced degradation. Interestingly, results from electrical transport measurements indicate an unexpected metallic-like conduction character of the studied PVD MoS ₂ films, independent of deposition temperature. Possible reasons for these unusual electrical properties of our PVD MoS ₂ thin films are discussed. A potential application for such conductive nanostructured MoS ₂ films could be as catalytically active electrodes in (photo-)electrocatalysis and initial electrochemical measurements suggest directions for future work on our PVD MoS ₂ films.