*typical representative size, areas/dimensions may vary
||~ 1.1 eV (indirect)
||Hafnium selenide, Bis(selanylidene)hafnium
|Classification / Family
Transition metal dichalcogenides (TMDCs), 2D Semiconductor Materials, Nano-electronics, Nano-photonics, Photovoltaic, Materials science
||Synthetic - Chemical Vapour Transport (CVT)
||Dark brown crystal
Hafnium diselenide (HfSe2) is a layered 2D semiconducting material. It is part of the Group IV transition metal dichalcogenides (TMDCs). HfSe2 adopts the CdI2 structure (1T), consisting of a single-layer plane of hexagonal close-packed Hf atoms sandwiched by two-layer planes of hexagonal close-packed Se atoms. The Hf atom is octahedrally coordinated with the chalcogen atoms. The layers are stacked together by weak van der Waals (vdW) forces, and can be exfoliated into thin 2D layers.
HfSe2 has an indirect bandgap with a measured bulk value of Eg = 1.1 eV (similar to that of silicon) and a remarkably high phonon-limited mobility of about 3500 cm2/V·s at room temperature.
Hafnium diselenide is slightly n-type with an indirect band gap of ∼1.1 eV, making it a great candidate for field-effect transistors and photovoltaic applications. Au-contacted HfSe2 phototransistors give a high on/off ratio of 106 and mobilities in the range of 2.6–6.5 cm2 V−1 s−1, with a high responsivity of 252 A/W and an ultrafast response time of 7.8 ms.
Hafnium diselenide is manufactured using chemical vapour transport (CVT) crystallisation, with crystals having a purity in excess of 99.999%.
Hafnium diselenide single crystals can be used to prepare monolayer and few-layer HfSe2 by mechanical or liquid exfoliation.
Literature and Reviews
Two-dimensional semiconductor HfSe2 and MoSe2/HfSe2 van der Waals heterostructures by molecular beam epitaxy, K. E. Aretouli et al., Appl. Phys. Lett. 106, 143105 (2015); doi: 10.1063/1.4917422.
Tunable electrical properties of multilayer HfSe2 field effect transistors by oxygen plasma treatment, M. Kang et al., Nanoscale, 9, 1645 (2017); DOI: 10.1039/c6nr08467b.
3d transition metal doping-induced electronic structures and magnetism in 1T-HfSe2 monolayers, X. Zhao et al., RSC Adv., 7, 52747–52754 (2017); DOI: 10.1039/c7ra11040e.
HfSe2 Thin Films: 2D Transition Metal Dichalcogenides Grown by Molecular Beam Epitaxy, R. Yue et al., ACS Nano, 9 (1), 474–480 (2015);
Ultrafast and ultrasensitive phototransistors based on few-layered HfSe2, L Yin et al., Appl. Phys. Lett. 109, 213105 (2016); dio: 10.1063/1.4968808.