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Nanoscale Investigation of Defects and Oxidation of HfSe(2)
[Image: see text] HfSe(2) is a very good candidate for a transition metal dichalcogenide-based field-effect transistor owing to its moderate band gap of about 1 eV and its high-κ dielectric native oxide. Unfortunately, the experimentally determined charge carrier mobility is about 3 orders of magnit...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Chemical
Society
2018
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6231157/ https://www.ncbi.nlm.nih.gov/pubmed/30450151 http://dx.doi.org/10.1021/acs.jpcc.8b08713 |
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author | Yao, Qirong Zhang, Lijie Bampoulis, Pantelis Zandvliet, Harold J. W. |
author_facet | Yao, Qirong Zhang, Lijie Bampoulis, Pantelis Zandvliet, Harold J. W. |
author_sort | Yao, Qirong |
collection | PubMed |
description | [Image: see text] HfSe(2) is a very good candidate for a transition metal dichalcogenide-based field-effect transistor owing to its moderate band gap of about 1 eV and its high-κ dielectric native oxide. Unfortunately, the experimentally determined charge carrier mobility is about 3 orders of magnitude lower than the theoretically predicted value. This strong deviation calls for a detailed investigation of the physical and electronic properties of HfSe(2). Here, we have studied the structure, density, and density of states of several types of defects that are abundant on the HfSe(2) surface using scanning tunneling microscopy and spectroscopy. Compared to MoS(2) and WSe(2), HfSe(2) exhibits similar type of defects, albeit with a substantially higher density of 9 × 10(11) cm(–2). The most abundant defect is a subsurface defect, which shows up as a dim feature in scanning tunneling microscopy images. These dim dark defects have a substantially larger band gap (1.25 eV) than the pristine surface (1 eV), suggesting a substitution of the Hf atom by another atom. The high density of defects on the HfSe(2) surface leads to very low Schottky barrier heights. Conductive atomic force microscopy measurements reveal a very small dependence of the Schottky barrier height on the work function of the metals, suggesting a strong Fermi-level pinning. We attribute the observed Fermi-level pinning (pinning factor ∼0.1) to surface distortions and Se/Hf defects. In addition, we have also studied the HfSe(2) surface after the exposure to air by scanning tunneling microscopy and conductive atomic force microscopy. Partly oxidized layers with band gaps of 2 eV and Schottky barrier heights of ∼0.6 eV were readily found on the surface. Our experiments reveal that HfSe(2) is very air-sensitive, implying that capping or encapsulating of HfSe(2), in order to protect it against oxidation, is a necessity for technological applications. |
format | Online Article Text |
id | pubmed-6231157 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | American Chemical
Society |
record_format | MEDLINE/PubMed |
spelling | pubmed-62311572018-11-14 Nanoscale Investigation of Defects and Oxidation of HfSe(2) Yao, Qirong Zhang, Lijie Bampoulis, Pantelis Zandvliet, Harold J. W. J Phys Chem C Nanomater Interfaces [Image: see text] HfSe(2) is a very good candidate for a transition metal dichalcogenide-based field-effect transistor owing to its moderate band gap of about 1 eV and its high-κ dielectric native oxide. Unfortunately, the experimentally determined charge carrier mobility is about 3 orders of magnitude lower than the theoretically predicted value. This strong deviation calls for a detailed investigation of the physical and electronic properties of HfSe(2). Here, we have studied the structure, density, and density of states of several types of defects that are abundant on the HfSe(2) surface using scanning tunneling microscopy and spectroscopy. Compared to MoS(2) and WSe(2), HfSe(2) exhibits similar type of defects, albeit with a substantially higher density of 9 × 10(11) cm(–2). The most abundant defect is a subsurface defect, which shows up as a dim feature in scanning tunneling microscopy images. These dim dark defects have a substantially larger band gap (1.25 eV) than the pristine surface (1 eV), suggesting a substitution of the Hf atom by another atom. The high density of defects on the HfSe(2) surface leads to very low Schottky barrier heights. Conductive atomic force microscopy measurements reveal a very small dependence of the Schottky barrier height on the work function of the metals, suggesting a strong Fermi-level pinning. We attribute the observed Fermi-level pinning (pinning factor ∼0.1) to surface distortions and Se/Hf defects. In addition, we have also studied the HfSe(2) surface after the exposure to air by scanning tunneling microscopy and conductive atomic force microscopy. Partly oxidized layers with band gaps of 2 eV and Schottky barrier heights of ∼0.6 eV were readily found on the surface. Our experiments reveal that HfSe(2) is very air-sensitive, implying that capping or encapsulating of HfSe(2), in order to protect it against oxidation, is a necessity for technological applications. American Chemical Society 2018-10-18 2018-11-08 /pmc/articles/PMC6231157/ /pubmed/30450151 http://dx.doi.org/10.1021/acs.jpcc.8b08713 Text en Copyright © 2018 American Chemical Society This is an open access article published under a Creative Commons Non-Commercial No Derivative Works (CC-BY-NC-ND) Attribution License (http://pubs.acs.org/page/policy/authorchoice_ccbyncnd_termsofuse.html) , which permits copying and redistribution of the article, and creation of adaptations, all for non-commercial purposes. |
spellingShingle | Yao, Qirong Zhang, Lijie Bampoulis, Pantelis Zandvliet, Harold J. W. Nanoscale Investigation of Defects and Oxidation of HfSe(2) |
title | Nanoscale Investigation of Defects and Oxidation of
HfSe(2) |
title_full | Nanoscale Investigation of Defects and Oxidation of
HfSe(2) |
title_fullStr | Nanoscale Investigation of Defects and Oxidation of
HfSe(2) |
title_full_unstemmed | Nanoscale Investigation of Defects and Oxidation of
HfSe(2) |
title_short | Nanoscale Investigation of Defects and Oxidation of
HfSe(2) |
title_sort | nanoscale investigation of defects and oxidation of
hfse(2) |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6231157/ https://www.ncbi.nlm.nih.gov/pubmed/30450151 http://dx.doi.org/10.1021/acs.jpcc.8b08713 |
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