Full text
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| Author(s): |
Yves Maia Auad
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Física Gleb Wataghin |
| Defense date: | 2019-08-15 |
| Examining board members: |
Luiz Fernando Zagonel;
Daniel Mário Ugarte;
Fernando Loureiro Stavale Junior
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| Advisor: | Luiz Fernando Zagonel |
| Abstract | |
The development of this work was conveniently divided in three parts. The first opened the subject of Scanning Tunneling Microscope, in which standard measurements on Silicon (111) 7x7 reconstruction were performed and discussed. Dimer-Adatom-Stacking Fault model was used to compare our measurements, which included the expected local density of states and the distance between atoms. We have observed atomically resolved images and Scanning Tunneling Spectroscopy (STS) spectra consistent with a combination of signals from adatoms and rest atoms. The former was used to determine tip spatial resolution and the later to characterize the tip density of states (DOS). In the second part of this work, we have developed an optical collection system for the same STM used in the first part. This project was axed on instrumentation and the goal was to develop a robust alignment system, with a precision of approximately 50 nm, in order to use a high collective mirror to detect photon emission from the tunnel junction. The pre-alignment of the system was done visually using the concept of infinite magnification and the fine alignment was done using the actual light signal. We were able to collect light emitted from the junction by tip induced surface plasmon in which we saw peaks at approximately ~!LSP = 1.75 eV and quality factors of Q = 4:25. The quantum yield, defined as the ratio of emitted photons per unit of tunneling electrons, was determined to be around 10????7-10????8 photons/electrons, depending on the tunneling and detection conditions. In the third part of this work, we used a Scanning Transmission Electron Microscope (STEM) to also study surface plasmon modes with nanometric spatial resolution. We have performed mostly Stimulated Electron Energy Gain Spectroscopy (sEEGS), in which our work was focused on improving the system power density changing from guided space light coupling to a free space coupling. Inverted structures and silver nanocubes were studied and, for the later, coupling probability between the fast electron and the photon improved by a factor of 200x (AU) | |
| FAPESP's process: | 17/00259-5 - High performance optical system for a scanning tunneling microscope |
| Grantee: | Yves Maia Auad |
| Support Opportunities: | Scholarships in Brazil - Master |