*typical representative size, areas/dimensions may vary
||~ 2.0 eV (indirect); ~ 1.2 eV (direct)
|Classification / Family
Transition metal dichalcogenides (TMDCs), 2D Semiconductor materials, Nano-electronics, Nano-photonics, Photovoltaic, Materials science
||Synthetic - Chemical Vapour Transport (CVT)
Hafnium disulfide (HfS2) is another layered 2D semiconducting material that is part of the Group IV transition metal dichalcogenides (TMDCs). HfS2 adopts the CdI2 structure (1T structure) with a single-layer plane of hexagonal close-packed Hf atoms sandwiched by two-layer planes of hexagonal close-packed S atoms. The layers are stacked together by weak van der Waals (vdW) interactions, and can be exfoliated into thin 2D layers.
Hafnium disulfide is a semiconductor with an indirect band gap of ~ 2.0 eV. Single layers of HfS2 are predicted to have a direct band gap of ~1.2 eV.
Hafnium disulfide based field-effect transistors (FETs) can have sheet current densities of up to 650 μA μm−1 (about 85 times higher than that of MoS2), making HfS2 an attractive candidate for applications in logic and optoelectronic devices. Exfoliated few-layer HfS2 has also been built into ultra-sensitive photo-transistors and high-performance FETs.
Hafnium disulfide is manufactured using chemical vapour transport (CVT) crystallisation, with crystals having a purity in excess of 99.999%.
Hafnium disulfide single crystals can be used to prepare monolayer and few-layer HfS2 by mechanical or liquid exfoliation.
Literature and Reviews
Selective Direct Growth of Atomic Layered HfS2 on Hexagonal Boron Nitride for High Performance Photodetectors, D. Wang et al., Chem. Mater.,30, 3819−3826 (2018); DOI: 10.1021/acs.chemmater.8b01091.
Impact of Metal Contacts on the Performance of Multilayer HfS2 Field-Effect Transistors, X. Nie et al., ACS Appl. Mater. Interfaces, 9, 26996−27003 (2017); DOI: 10.1021/acsami.7b06160.
2D-HfS2 as an efficient photocatalyst for water splitting, D. Singh et al., Catal. Sci. Technol., 6, 6605–6614 (2016); DOI: 10.1039/c6cy01172a.
Efficient charge separation and visible-light response in bilayer HfS2-based van der Waals heterostructures, B. Wang et al., RSC Adv., 8, 18889 (2018); DOI: 10.1039/c8ra03047b.
Van der Waals Epitaxial Growth of Atomic Layered HfS2 Crystals for Ultrasensitive Near-Infrared Phototransistors, L. Fu et al., Adv. Mater., 29, 1700439 (2017); DOI: 10.1002/adma.201700439.
Valence and conduction band states of HfS2: From bulk to a single layer, C. Kreis et al., Phys. Rev. B, 68, 235331 ~2003!; DOI: 10.1103/PhysRevB.68.235331.