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Growth and Characte...
Growth and Characterization of ZnO Nanocrystals
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- Ericsson, Leif KE (författare)
- Karlstads universitet,Institutionen för ingenjörsvetenskap och fysik (from 2013)
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- Magnusson, Kjell O, Prof. (preses)
- Karlstads universitet,Institutionen för ingenjörsvetenskap och fysik (from 2013)
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- Johansson, Lars SO, Prof. (preses)
- Karlstads universitet,Institutionen för ingenjörsvetenskap och fysik (from 2013)
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- Zhang, Hanmin M, Dr. (preses)
- Karlstads universitet,Institutionen för ingenjörsvetenskap och fysik (from 2013)
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- Nour, Omer, Docent (opponent)
- Linköping University
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(creator_code:org_t)
- ISBN 9789170635038
- Karlstad : Karlstads universitet, 2013
- Engelska 56 s.
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Serie: Karlstad University Studies, 1403-8099 ; 2013:26
- Relaterad länk:
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https://kau.diva-por... (primary) (Raw object)
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Abstract
Ämnesord
Stäng
- The understanding of surfaces of materials is of crucial importance to all of us. Considering nanocrystals (NCs), that have a large surface to bulk ratio, the surfaces become even more important. Therefore, it is important to understand the fundamental surface properties in order to use NCs efficiently in applications. In the work reported in this thesis ZnO NCs were studied.At MAX-lab in Lund, synchrotron radiation based Spectroscopic Photoemission and Low Energy Electron Microscopy (SPELEEM) and X-ray Photoelectron Spectroscopy (XPS) were used. At Karlstad University characterization was done using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Scanning Tunnelling Microscopy (STM), Auger Electron Spectroscopy (AES), and XPS.The fundamental properties of ZnO surfaces were studied using distributions of ZnO NCs on SiO2/Si surfaces. The conditions for distribution of ZnO NCs were determined to be beneficial when using ethanol as the solvent for ultrasonically treated dispersions. Annealing at 650 °C in UHV cleaned the surfaces of the ZnO NCs enough for sharp LEEM imaging and chemical characterization while no sign of de-composition was found. A flat energy band structure for the ZnO/SiO2/Si system was proposed after 650 °C. Increasing the annealing temperature to 700 °C causes a de-composition of the ZnO that induce a downward band bending on the surfaces of ZnO NCs.Flat ZnO NCs with predominantly polar surfaces were grown using a rapid microwave assisted process. Tuning the chemistry in the growth solution the growth was restricted to only plate-shaped crystals, i.e. a very uniform growth. The surfaces of the NCs were characterized using AFM, revealing a triangular reconstruction of the ZnO(0001) surface not seen without surface treatment at ambient conditions before. Following cycles of sputtering and annealing in UHV, we observe by STM a surface reconstruction interpreted as 2x2 with 1/4 missing Zn atoms.
- BaksidestextThe understanding of the surfaces of materials is of crucial importance to all of us. Considering nanocrystals (NCs), that have a large surface to bulk ratio, the surfaces become even more important. In the work in this thesis ZnO NCs were studied.The fundamental properties of ZnO surfaces were studied using distributions of ZnO NCs on SiO2/Si surfaces. Annealing at 650 °C in UHV cleaned the surfaces of the ZnO NCs enough for sharp LEEM imaging and chemical characterization while no sign of de-composition was found. A flat energy band structure for the ZnO/SiO2/Si system was proposed after 650 °C. Increasing the annealing temperature to 700 °C causes a de-composition of the ZnO that induce a downward band bending on the surfaces of ZnO NCs.Flat ZnO NCs with predominantly polar surfaces were grown using a microwave assisted process. Tuning the chemistry in the growth solution the growth was restricted to only plate-shaped crystals, i.e. a very uniform growth. The surfaces of the NCs were characterized using AFM, revealing a triangular reconstruction of the ZnO(0001) surface not seen without surface treatment at ambient conditions before. Following cycles of sputtering and annealing in UHV, we observe by STM a surface reconstruction interpreted as 2x2 with 1/4 missing Zn atoms.
Ämnesord
- TEKNIK OCH TEKNOLOGIER -- Nanoteknik (hsv//swe)
- ENGINEERING AND TECHNOLOGY -- Nano-technology (hsv//eng)
- NATURVETENSKAP -- Fysik -- Den kondenserade materiens fysik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Condensed Matter Physics (hsv//eng)
Nyckelord
- ZnO
- Nanocrystals
- Surface physics
- XPS
- SEM
- AES
- AFM
- STM
- Physics
- Fysik
Publikations- och innehållstyp
- vet (ämneskategori)
- dok (ämneskategori)
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