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

Abstract

Material synthesis and characterizationABSTRACT Producing monolayers and few-layers in high yield with environment-stability is still a challenge in hafnium disulphide (HfS 2 ), which is a layered two-dimensional material of group-IV transition metal dichalcogenides, to reveal its unlocked electronic and optoelectronic applications. For the first time, to the best of our knowledge, we demonstrate a simple and cost-effective method to grow layered belt-like nano-crystals of HfS 2 with surprisingly large interlayer spacing followed by its chemical exfoliation. Various microscopic and spectroscopic techniques reveal these as-grown crystals exfoliate into single or few layers in some minutes using solvent assisted ultrasonification method in N-Cyclohexyl-2-pyrrolidone. The exfoliated nanosheets of HfS 2 exhibit an indirect bandgap of 1.3 eV with high stability against ambient degradation. Further, we demonstrate that these nanosheets holds potential for electronic applications by fabricating field-effect transistors based on few layered HfS 2 exhibiting field-effect mobility of 0.95 cm 2 /V-s with a high current modulation ratio (Ion/Ioff) of 10 4 in ambient. The method is scalable and has potential significance for both academy and industry. KEYWORDS Two-dimensional materials, hafnium-disulphide, nano-crystals, liquid-phase exfoliation, environment-stability, field-effect transistor ELECTRONIC SUPPLEMENTARY MATERIAL High yield synthesis and dimensional belt like hafnium disulphide Material synthesis and characterization 1 Atomic force microscopic image of micromechanically cleaved HfSThe as-prepared crystals of HfS2 were micromechanically cleaved using scotch pasted onto cleaned silicon substrate. The adhesive of the tape on substrate were then removed using ultrasonication in acetone and propanol followed by baking the substrate at 120 o C for 2 hours in vacuum (10 the sample was taken in tapping mode. The thickness of the flake was found to be 300 nm. Figure S1AFM image of HfS2 flake on silicon wafer. The graph in the inset represents the ELECTRONIC SUPPLEMENTARY MATERIAL High yield synthesis and liquid exfoliation of two dimensional belt like hafnium disulphide

2D Group IVB Transition Metal Dichalcogenides

“…Some computational and experimental results have demonstrated that NMP, IPA, and N ‐cyclohexyl‐2‐pyrrolidone (CHP) can form solvation shells on the surface of the nanosheets to inhibit surface degradation due to water and oxygen . Srivastava and co‐workers employed CHP, which belongs in the group of amide solvents, as the solvent to exfoliate HfS 2 under ambient conditions. These results revealed that exfoliation in CHP can prepare few‐layer and monolayer HfS 2 belts with a high yield, while the degradation of the obtained sheets is effectively prevented.…”

Controllable, eco-friendly, synthesis of highly crystalline 2D-MoS 2 and clarification of the role of growth-induced strain

“…In order to successfully extend the usage of these materials from laboratory to real-life applications, large scale and cost-effective production methods are required. During the past years, several bottom-up [14,[19][20][21][22][23][24][25][26][27][28] and top-down [29][30][31][32][33][34][35] strategies for the fabrication of atomically thin films have been developed. As has already been proven in the case of graphene, chemical vapour deposition (CVD) method is compatible with industry providing large area high quality material suitable for optoelectronic applications [36].…”

Preparation and Crystal Growth of Transition Metal Dichalcogenides

“…Zr x Hf 1-x S 2 : (a) [55] On (a): In addition to substitutions in anion sub-lattices, doping or substitutions on the cation positions are also investigated. [55] HfS 2 : (a) [14][15][16]18,30,56,57] On (a): HfS 2 can be obtained in crystalline form by chemical transport with the halogens Cl 2 , Br 2 , and I 2 as well as ICl 3 in a temperature gradient around 1000°C. Thin, extrafoliated crystals were investigated for their electrical properties.…”

“…Thin, extrafoliated crystals were investigated for their electrical properties. [57] HfSe 2 : (a) [14,16,30,58] On (a): HfSe 2 can also be prepared in crystalline form by chemical transport. Iodine is described as a transport additive.…”