Hafnium disulfide dichalcogenide material: A review of structural insights, functional properties, applications and future directions

Transition metal dichalcogenide (TMDC) materials are a type of compound known for their intrinsic and versatile properties. They are a fascinating family of two-dimensional (2D) materials with the general formula MX2, where M represents a transition metal (e.g., Mo, Hf, Ti, W, Zr) and X denotes a chalcogen (e.g., O, S, Se, Te). They usually exist in polymorphic forms such as 1T and 2H structures with remarkable electronic, optical, and mechanical properties, including a tunable band gap, high carrier mobility, strong spin-orbit coupling, and prominent excitonic effects. Among the various TMDCs reported with a range of metals, this review focuses specifically on Hafnium sulfide (HfS2) TMDCs since it stands out owing to its excellent intrinsic properties. In this review, an overview of the synthesis of HfS2 using different substrates is discussed by diverse fabrication techniques and defect engineering. Particularly, this review rationalized the electronic properties of HfS2, including its band gap, adsorption, and catalytic behaviors. Also, the review delves into the optical, magnetic, mechanical, thermal, and dielectric properties, and the potential applications of HfS2 and its alloys are discussed in detail to understand the insight of these TMDCs to explore their importance in all other possible ways.