Interlayer Coupling in Electronic Structures of WS2/MoS2 Vertical Heterojunctions

碩士 === 國立交通大學 === 電子物理系所 === 106 === Vertically stacked heterojunctions made of atomically thin two-dimensional (2D) layered materials such as graphene, boron nitride, and transition metal dichalcogenides (TMDs) are now attractive due to their versatility in creating functional artificial materials....

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Main Authors: Wu, Po-Hsun, 吳柏勳
Other Authors: Chang, Wen-Hao
Format: Others
Language:en_US
Published: 2018
Online Access:http://ndltd.ncl.edu.tw/handle/te4g3p
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spelling ndltd-TW-106NCTU54290452019-05-16T01:24:31Z http://ndltd.ncl.edu.tw/handle/te4g3p Interlayer Coupling in Electronic Structures of WS2/MoS2 Vertical Heterojunctions 二硫化鎢/二硫化鉬垂直異質接面之層間耦合電子特性 Wu, Po-Hsun 吳柏勳 碩士 國立交通大學 電子物理系所 106 Vertically stacked heterojunctions made of atomically thin two-dimensional (2D) layered materials such as graphene, boron nitride, and transition metal dichalcogenides (TMDs) are now attractive due to their versatility in creating functional artificial materials. Replacing the constituent materials and controlling the structure pave the way for future designing of heterojunction devices. Therefore, understanding the interlayer interactions plays a key role in artificial stacking. This dissertation is devoted to the electronic and optical properties of vertically stacked WS2/MoS2 heterojunctions grown by chemical vapor deposition. At first, the stacking configuration of heterojunctions are identified by Raman spectroscopy, second harmonic generation (SHG) and scanning transmission electron microscopy (STEM). There are five kinds of stacking configuration, each is 3R (0o), 3R’ (0o), 2H (60o), AB (60o) for commensurate stacking and Twist for incommensurate stacking. Then, the evolution of interlayer electronic coupling with stacking configurations is investigated by photoluminescence (PL) spectroscopy and density function theory (DFT). Emerging emission of interlayer exciton is due to type-II band alignment of TMD heterojunction. The emission energy of interlayer exciton is found to vary appreciably with twist angle, revealing that the strong electronic coupling at valence band Γ point of Brillouin zone. In addition, the PL excitation spectra further reveal the recombination channel form electron and hole occupied at Q and Γ points respectively, leading to momentum indirect optical transition. Owing to strong band hybridization by interlayer coupling, the interlayer exciton should be called as interfacial exciton which electron and hole wavefuction are hybridized in both WS2 and MoS2 layer. Furthermore, orientation of transition dipole moment and constituent electronic orbital for exciton are studied by momentum-resolved PL. The intralayer exciton of MoS2 monolayer is found to exhibit pure in-plane dipole radiation. However, there is up to 35% out-of-plane orientation transition dipole moment for interlayer exciton in WS2/MoS2 heterojunction showing the part of z-directional electronic orbital is composed in transition dipole. The study provides a solid foundation of understanding interlayer coupling of 2D materials heterojunctions and next-generation optical and electronic devices. Chang, Wen-Hao 張文豪 2018 學位論文 ; thesis 59 en_US
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description 碩士 === 國立交通大學 === 電子物理系所 === 106 === Vertically stacked heterojunctions made of atomically thin two-dimensional (2D) layered materials such as graphene, boron nitride, and transition metal dichalcogenides (TMDs) are now attractive due to their versatility in creating functional artificial materials. Replacing the constituent materials and controlling the structure pave the way for future designing of heterojunction devices. Therefore, understanding the interlayer interactions plays a key role in artificial stacking. This dissertation is devoted to the electronic and optical properties of vertically stacked WS2/MoS2 heterojunctions grown by chemical vapor deposition. At first, the stacking configuration of heterojunctions are identified by Raman spectroscopy, second harmonic generation (SHG) and scanning transmission electron microscopy (STEM). There are five kinds of stacking configuration, each is 3R (0o), 3R’ (0o), 2H (60o), AB (60o) for commensurate stacking and Twist for incommensurate stacking. Then, the evolution of interlayer electronic coupling with stacking configurations is investigated by photoluminescence (PL) spectroscopy and density function theory (DFT). Emerging emission of interlayer exciton is due to type-II band alignment of TMD heterojunction. The emission energy of interlayer exciton is found to vary appreciably with twist angle, revealing that the strong electronic coupling at valence band Γ point of Brillouin zone. In addition, the PL excitation spectra further reveal the recombination channel form electron and hole occupied at Q and Γ points respectively, leading to momentum indirect optical transition. Owing to strong band hybridization by interlayer coupling, the interlayer exciton should be called as interfacial exciton which electron and hole wavefuction are hybridized in both WS2 and MoS2 layer. Furthermore, orientation of transition dipole moment and constituent electronic orbital for exciton are studied by momentum-resolved PL. The intralayer exciton of MoS2 monolayer is found to exhibit pure in-plane dipole radiation. However, there is up to 35% out-of-plane orientation transition dipole moment for interlayer exciton in WS2/MoS2 heterojunction showing the part of z-directional electronic orbital is composed in transition dipole. The study provides a solid foundation of understanding interlayer coupling of 2D materials heterojunctions and next-generation optical and electronic devices.
author2 Chang, Wen-Hao
author_facet Chang, Wen-Hao
Wu, Po-Hsun
吳柏勳
author Wu, Po-Hsun
吳柏勳
spellingShingle Wu, Po-Hsun
吳柏勳
Interlayer Coupling in Electronic Structures of WS2/MoS2 Vertical Heterojunctions
author_sort Wu, Po-Hsun
title Interlayer Coupling in Electronic Structures of WS2/MoS2 Vertical Heterojunctions
title_short Interlayer Coupling in Electronic Structures of WS2/MoS2 Vertical Heterojunctions
title_full Interlayer Coupling in Electronic Structures of WS2/MoS2 Vertical Heterojunctions
title_fullStr Interlayer Coupling in Electronic Structures of WS2/MoS2 Vertical Heterojunctions
title_full_unstemmed Interlayer Coupling in Electronic Structures of WS2/MoS2 Vertical Heterojunctions
title_sort interlayer coupling in electronic structures of ws2/mos2 vertical heterojunctions
publishDate 2018
url http://ndltd.ncl.edu.tw/handle/te4g3p
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