Please use this identifier to cite or link to this item: https://scholarbank.nus.edu.sg/handle/10635/137281
DC FieldValue
dc.titleATOMIC SCALE STUDY OF TWO-DIMENSIONAL MATERIALS BY SCANNING TUNNELING MICROSCOPY AND FIRST-PRINCIPLES CALCULATIONS
dc.contributor.authorZHENG YUJIE
dc.date.accessioned2017-11-06T18:00:34Z
dc.date.available2017-11-06T18:00:34Z
dc.date.issued2017-08-14
dc.identifier.citationZHENG YUJIE (2017-08-14). ATOMIC SCALE STUDY OF TWO-DIMENSIONAL MATERIALS BY SCANNING TUNNELING MICROSCOPY AND FIRST-PRINCIPLES CALCULATIONS. ScholarBank@NUS Repository.
dc.identifier.urihttp://scholarbank.nus.edu.sg/handle/10635/137281
dc.description.abstractIn this thesis, the atomic structure and electronic properties of 2D-materials were investigated by first-principles calculations in combination with LT-STM/S. We first present an investigation of the native point defects in SL-WSe2. DFT calculations show that Se adatoms and vacancies are the two most stable defects, but none of the native defects were observed as the dominant point defects in STM measurements. Combining STM/S and DFT calculations, we found that the observed point defects are oxygen contaminants formed by oxygen dissociative adsorption at the Se vacancies. Next, we studied perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) monolayers adsorbed on SL-WSe2, bare graphite and Au(111) surfaces, revealing a strong dependence of the PTCDA HOMO-LUMO gap on electronic screening effects from the substrate. The SL-WSe2 interlayer provides substantial – but not complete – screening at the organic/inorganic interface. Lastly, the PTCDA monolayer adsorbed on few layer h-BN were also measured by STM/S and the measured band gap (3.8 eV) is smaller than the theoretical predicated value for isolated PTCDA molecule (5.0 eV) and layer (4.1 eV). The results show that screening by few layer hBN can substantially reduce the HOMO-LUMO gap of adsorbed molecules.
dc.language.isoen
dc.subject2D-materials, scanning tunneling microscopy/spectroscopy, first-principles calculations, atomic structure, electronic properties
dc.typeThesis
dc.contributor.departmentPHYSICS
dc.contributor.supervisorWEE THYE SHEN, ANDREW
dc.contributor.supervisorQUEK SU YING
dc.description.degreePh.D
dc.description.degreeconferredDOCTOR OF PHILOSOPHY
Appears in Collections:Ph.D Theses (Open)

Show simple item record
Files in This Item:
File Description SizeFormatAccess SettingsVersion 
ZhengYJ.pdf6.4 MBAdobe PDF

OPEN

NoneView/Download

Page view(s)

114
checked on Feb 14, 2020

Google ScholarTM

Check


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.