HfO2/HfS2 hybrid heterostructure fabricated via controllable chemical conversion of two-dimensional HfS2

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While preparing uniform dielectric layers on two-dimensional (2D) materials is a key device architecture requirement to achieve next-generation 2D devices, conventional deposition or transfer approaches have been so far limited by their high cost, fabrication complexity, and especially poor dielectric/2D material interface quality. Here, we demonstrate that HfO2, a high-K dielectric, can be prepared on the top surface of 2D HfS2 through plasma oxidation, which results in a heterostructure composed of a 2D van der Waals semiconductor and its insulating native oxide. A highly uniform dielectric layer with a controlled thickness can be prepared; the possibility of unlimited layer-by-layer oxidation further differentiates our work from previous attempts on other 2D semiconducting materials, which exhibit self-limited oxidation up to only a few layers. High resolution transmission electron microscopy was used to show that the converted HfO2/HfS2 hybrid structure is of high quality with an atomically abrupt, impurity- and defect-free interface. Density functional theory calculations show that the unlimited layer-by-layer oxidation occurs because oxygen atoms can barrierlessly penetrate into the HfS2 surface and the extracted sulfur atoms are absorbed into the oxygen vacancy sites within HfO2 under O-rich conditions. A top-gated field-effect transistor fabricated with the converted HfO2/HfS2 hybrid structure was found to exhibit a low interface trap density D-it of 6 x 10(11) cm(-2) eV(-1) between the HfS2 channel and the converted HfO2 dielectric, and a high on/off current ratio above 10(7). Our approach provides a low cost, simple, and ultraclean manufacturing technique for integrating 2D material into device applications.
Publisher
ROYAL SOC CHEMISTRY
Issue Date
2018-10
Language
English
Article Type
Article
Keywords

FIELD-EFFECT TRANSISTORS; HEXAGONAL BORON-NITRIDE; ATOMIC LAYER DEPOSITION; MOS2 TRANSISTORS; OXIDATION; GRAPHENE; OXIDE; HFO2; WSE2

Citation

NANOSCALE, v.10, no.39, pp.18758 - 18766

ISSN
2040-3364
DOI
10.1039/c8nr06020g
URI
http://hdl.handle.net/10203/246712
Appears in Collection
EEW-Journal Papers(저널논문)
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