The growth mechanism and intriguing optical and electronic properties of few-layered HfS 2 .

Due to electronic properties superior to group VIB (Mo and W) transition metal dichalcogenides (TMDs), group IVB (Hf and Zr) TMDs have become intriguing materials in next-generation nanoelectronics. Therefore, the growth of few-layered hafnium disulfide (HfS 2 ) on c -plane sapphire as well as on a SiO 2 /Si substrate has been demonstrated using chemical vapour deposition (CVD). The structural properties of HfS 2 were investigated by recording X-ray diffraction patterns and Raman spectra. The XRD results reveal that the layers are well oriented along the (0001) direction and exhibit the high crystalline quality of HfS 2 . The Raman spectra confirm the in-plane and out-plane vibration of Hf and S atoms. Moreover, the HfS 2 layers exhibit strong absorption in the UV to visible region. The HfS 2 layer-based photodetector shows a photoresponsivity of ∼1.6, ∼0.38, and ∼0.21 μA W -1 corresponding to 9, 38, and 68 mW cm -2 , respectively under green light illumination and is attributed to the generation of a large number of electron-hole pairs in the active region of the device. Besides, it also exhibits the highly crystalline structure of HfS 2 at high deposition temperature. The PL spectrum shows a single peak at ∼1.8 eV and is consistent with the pristine indirect bandgap of HfS 2 (∼2 eV). Furthermore, a few layered HfS 2 back gate field-effect transistor (FET) is fabricated based on directly grown HfS 2 on SiO 2 /Si, and the device exhibits p-type behaviour. Thus, the controllable and easy growth method opens the latest pathway to synthesize few layered HfS 2 on different substrates for various electronic and optoelectronic devices.