High-yield synthesis and liquid-exfoliation of two-dimensional belt-like hafnium disulphide

Producing environmentally stable monolayers and few-layers of hafnium disulphide (HfS2) with a high yield to reveal its unlocked electronic and optoelectronic applications is still a challenge. HfS2 is a layered two-dimensional material of group-IV transition metal dichalcogenides. For the first time, we demonstrate a simple and cost-effective method to grow layered belt-like nanocrystals of HfS2 with a notably large interlayer spacing followed by their chemical exfoliation. Various microscopic and spectroscopic techniques confirm that these as-grown crystals exfoliate into single or multiple layers in a few minutes using solvent assisted ultrasonification method in N-cyclohexyl-2-pyrrolidone. The exfoliated nanosheets of HfS2 exhibit an indirect bandgap of 1.3 eV with high stability against surface degradation. Furthermore, we demonstrate that these nanosheets hold potential for electronic applications by fabricating a field-effect transistor based on few-layered HfS2, exhibiting a field-effect mobility of 0.95 cm(2)/(V.s) with a high on/off current modulation ratio of 10,000 in ambient conditions. The method is scalable and has a potential significance for both academic and industrial purposes.