Recent Advances in Properties, Synthesis and Applications of Two-Dimensional HfS2

As a member of transition metal dichalcogenides (TMDs) family, two-dimensional (2D) hafnium disulphide (HfS2) has attracted significant interest because of its excellent properties, including reasonable bandgap, ultrahigh room-temperature mobility and sheet current density, and definite chemical stability, which make 2D HfS2 a potential candidate material for future electronic and or optoelectronic devices. This review mainly focuses on the recent progress in the properties, synthesis and applications of 2D HfS2. Following a brief introduction on the structure of HfS2, we present its bandgap and electrical properties, as well as chemical stability. Up to now, analogously to what has been implemented for graphene, various synthesis techniques, such as mechanical exfoliation and chemical vapor deposition (CVD), have been developed to prepare ultrathin 2D HfS2 layers, and the advantages and limitations of each method are presented along with addition of personal insights. Meanwhile, diverse characterization methods of 2D HfS2 are listed and discussed, which are quite useful for uncovering the correlations between structures and properties. Then, we thoroughly illustrate the existing and potential applications of 2D HfS2, especially focusing on the field of field-effect transistors, photodetectors and phototransistors. Finally, current status and future prospects for this emerging material are discussed.