Electronic Properties of Various Two-Dimensional Materials

Research output: ThesisPhD Thesis - Research UT, graduation UTAcademic

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Abstract

Measuring the physical properties of 2D materials and correlating the spatial variation of these physical properties to the structure provides a route to better understand these materials. A very powerful tool for probing the surface structure and local electronic properties is scanning tunneling microscopy. Scanning tunneling spectroscopy allows the observation of electronic spectral properties with a resolution down to the atomic scale. In this thesis, we mainly employed scanning tunneling microscopy and scanning tunneling spectroscopy to study the structure and electronic properties of different types of 2D materials. Such fundamental research can help us to understand the 2D materials at the nano-scale, and pave the way towards the application of these materials in future electronic devices.
In this thesis, we have studied the structural and electronic properties of various 2D materials by using scanning tunneling microscopy and scanning tunneling spectroscopy techniques. Their intrinsic electronic properties are modified via varied ways, such as stacking, hydrogenation, defects and so on. The main points are as follows. In the twisted graphene with a twisted angle of 2o, we have revealed the Van Hove singularities and spatially mapped the electronic structure with the atomic resolution.
With the help of dI/dz spectroscopy, we have proved the growth behavior of silicon on TMDs at room temperature. We propose that the silicon atoms prefer to intercalate in the TMDs at the beginning of the growth due to defects in TMDs. For the first time, we have successfully synthesized germanene on a bandgap material, which paves the way towards determining the intrinsic properties of this novel 2D buckled Dirac material. The existence of charge puddles in germanene on MoS2 substrate is resulted from the charge-donating impurities in MoS2. Hydrogenation of germanene, synthesized on Ge2Pt nanocrystals, results in the opening of a bandgap of about 0.5 eV, which means hydrogenated germanene is a promising material for applications of field-effect devices. The high density of defects in HfSe2 mainly degrade its electrical performance, thus the quality of HfSe2 crystal should be carefully evaluated before it is used to make devices.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • University of Twente
Supervisors/Advisors
  • Zandvliet, H.J.W., Supervisor
Award date11 Sep 2019
Place of PublicationEnschede
Publisher
Print ISBNs978-90-365-4846-5
DOIs
Publication statusPublished - 11 Sep 2019

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Electronic properties
Scanning tunneling microscopy
Spectroscopy
Silicon
Scanning
Defects
Hydrogenation
Energy gap
Physical properties
Graphite
Surface structure
Nanocrystals
Electronic structure
Structural properties
Impurities
Atoms
Crystals
Substrates

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Yao, Qirong. / Electronic Properties of Various Two-Dimensional Materials. Enschede : University of Twente, 2019. 92 p.
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title = "Electronic Properties of Various Two-Dimensional Materials",
abstract = "Measuring the physical properties of 2D materials and correlating the spatial variation of these physical properties to the structure provides a route to better understand these materials. A very powerful tool for probing the surface structure and local electronic properties is scanning tunneling microscopy. Scanning tunneling spectroscopy allows the observation of electronic spectral properties with a resolution down to the atomic scale. In this thesis, we mainly employed scanning tunneling microscopy and scanning tunneling spectroscopy to study the structure and electronic properties of different types of 2D materials. Such fundamental research can help us to understand the 2D materials at the nano-scale, and pave the way towards the application of these materials in future electronic devices.In this thesis, we have studied the structural and electronic properties of various 2D materials by using scanning tunneling microscopy and scanning tunneling spectroscopy techniques. Their intrinsic electronic properties are modified via varied ways, such as stacking, hydrogenation, defects and so on. The main points are as follows. In the twisted graphene with a twisted angle of 2o, we have revealed the Van Hove singularities and spatially mapped the electronic structure with the atomic resolution.With the help of dI/dz spectroscopy, we have proved the growth behavior of silicon on TMDs at room temperature. We propose that the silicon atoms prefer to intercalate in the TMDs at the beginning of the growth due to defects in TMDs. For the first time, we have successfully synthesized germanene on a bandgap material, which paves the way towards determining the intrinsic properties of this novel 2D buckled Dirac material. The existence of charge puddles in germanene on MoS2 substrate is resulted from the charge-donating impurities in MoS2. Hydrogenation of germanene, synthesized on Ge2Pt nanocrystals, results in the opening of a bandgap of about 0.5 eV, which means hydrogenated germanene is a promising material for applications of field-effect devices. The high density of defects in HfSe2 mainly degrade its electrical performance, thus the quality of HfSe2 crystal should be carefully evaluated before it is used to make devices.",
author = "Qirong Yao",
year = "2019",
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day = "11",
doi = "10.3990/1.9789036548465",
language = "English",
isbn = "978-90-365-4846-5",
publisher = "University of Twente",
address = "Netherlands",
school = "University of Twente",

}

Electronic Properties of Various Two-Dimensional Materials. / Yao, Qirong.

Enschede : University of Twente, 2019. 92 p.

Research output: ThesisPhD Thesis - Research UT, graduation UTAcademic

TY - THES

T1 - Electronic Properties of Various Two-Dimensional Materials

AU - Yao, Qirong

PY - 2019/9/11

Y1 - 2019/9/11

N2 - Measuring the physical properties of 2D materials and correlating the spatial variation of these physical properties to the structure provides a route to better understand these materials. A very powerful tool for probing the surface structure and local electronic properties is scanning tunneling microscopy. Scanning tunneling spectroscopy allows the observation of electronic spectral properties with a resolution down to the atomic scale. In this thesis, we mainly employed scanning tunneling microscopy and scanning tunneling spectroscopy to study the structure and electronic properties of different types of 2D materials. Such fundamental research can help us to understand the 2D materials at the nano-scale, and pave the way towards the application of these materials in future electronic devices.In this thesis, we have studied the structural and electronic properties of various 2D materials by using scanning tunneling microscopy and scanning tunneling spectroscopy techniques. Their intrinsic electronic properties are modified via varied ways, such as stacking, hydrogenation, defects and so on. The main points are as follows. In the twisted graphene with a twisted angle of 2o, we have revealed the Van Hove singularities and spatially mapped the electronic structure with the atomic resolution.With the help of dI/dz spectroscopy, we have proved the growth behavior of silicon on TMDs at room temperature. We propose that the silicon atoms prefer to intercalate in the TMDs at the beginning of the growth due to defects in TMDs. For the first time, we have successfully synthesized germanene on a bandgap material, which paves the way towards determining the intrinsic properties of this novel 2D buckled Dirac material. The existence of charge puddles in germanene on MoS2 substrate is resulted from the charge-donating impurities in MoS2. Hydrogenation of germanene, synthesized on Ge2Pt nanocrystals, results in the opening of a bandgap of about 0.5 eV, which means hydrogenated germanene is a promising material for applications of field-effect devices. The high density of defects in HfSe2 mainly degrade its electrical performance, thus the quality of HfSe2 crystal should be carefully evaluated before it is used to make devices.

AB - Measuring the physical properties of 2D materials and correlating the spatial variation of these physical properties to the structure provides a route to better understand these materials. A very powerful tool for probing the surface structure and local electronic properties is scanning tunneling microscopy. Scanning tunneling spectroscopy allows the observation of electronic spectral properties with a resolution down to the atomic scale. In this thesis, we mainly employed scanning tunneling microscopy and scanning tunneling spectroscopy to study the structure and electronic properties of different types of 2D materials. Such fundamental research can help us to understand the 2D materials at the nano-scale, and pave the way towards the application of these materials in future electronic devices.In this thesis, we have studied the structural and electronic properties of various 2D materials by using scanning tunneling microscopy and scanning tunneling spectroscopy techniques. Their intrinsic electronic properties are modified via varied ways, such as stacking, hydrogenation, defects and so on. The main points are as follows. In the twisted graphene with a twisted angle of 2o, we have revealed the Van Hove singularities and spatially mapped the electronic structure with the atomic resolution.With the help of dI/dz spectroscopy, we have proved the growth behavior of silicon on TMDs at room temperature. We propose that the silicon atoms prefer to intercalate in the TMDs at the beginning of the growth due to defects in TMDs. For the first time, we have successfully synthesized germanene on a bandgap material, which paves the way towards determining the intrinsic properties of this novel 2D buckled Dirac material. The existence of charge puddles in germanene on MoS2 substrate is resulted from the charge-donating impurities in MoS2. Hydrogenation of germanene, synthesized on Ge2Pt nanocrystals, results in the opening of a bandgap of about 0.5 eV, which means hydrogenated germanene is a promising material for applications of field-effect devices. The high density of defects in HfSe2 mainly degrade its electrical performance, thus the quality of HfSe2 crystal should be carefully evaluated before it is used to make devices.

U2 - 10.3990/1.9789036548465

DO - 10.3990/1.9789036548465

M3 - PhD Thesis - Research UT, graduation UT

SN - 978-90-365-4846-5

PB - University of Twente

CY - Enschede

ER -