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Issue 39, 2018
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HfO2/HfS2 hybrid heterostructure fabricated via controllable chemical conversion of two-dimensional HfS2

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Abstract

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 Dit of 6 × 1011 cm−2 eV−1 between the HfS2 channel and the converted HfO2 dielectric, and a high on/off current ratio above 107. Our approach provides a low cost, simple, and ultraclean manufacturing technique for integrating 2D material into device applications.

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

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Publication details

The article was received on 26 Jul 2018, accepted on 24 Sep 2018 and first published on 27 Sep 2018


Article type: Paper
DOI: 10.1039/C8NR06020G
Citation: Nanoscale, 2018,10, 18758-18766
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    HfO2/HfS2 hybrid heterostructure fabricated via controllable chemical conversion of two-dimensional HfS2

    S. Lai, S. Byeon, S. K. Jang, J. Lee, B. H. Lee, J. Park, Y. Kim and S. Lee, Nanoscale, 2018, 10, 18758
    DOI: 10.1039/C8NR06020G

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