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Optimization of Nanostructures for Electron Emission

Yasrebi, Navid | 2013

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 46057 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Rashidian, Bizhan
  7. Abstract:
  8. The need for better characterization systems (electron microscopes) and high resolution lithography systems, have made electron beams systems an interesting choice for research and development. In fact, all of the above applications require ideal electron beams (beams with minimum energy spread, maximum current density, and minimum spotsize), and electron-optic lenses (simple lenses with minimum aberration). In this research, theoretical aspects of electron emission and lens systems are reviewed. Field emission array (FEA) electron guns are introduced as electron sources with minimum energy spread, and a new simulation method is presented in order to minimize the complexity, and reduce the computational requirements of FEA simulation problems. After that a semi-experimental algorithm for determination of field emission parameters is introduced. Si-FEAs with Molybdenum coatings are fabricated in Nanoelectronics laboratory of department of Electrical engineering of Sharif University. Incorporating the developed simulation method has showed that the ideal field emitter geometry is something between nanotubes and pyramids. In the next part two novel electrostatic electron beam lenses (cubic Einzel, and continuous body electrostatic (CBE) lenses) are presented. It is shown that in almost every case, these new lens systems have better performance (in terms of aberration and sensitivity) comparing to the conventional Einzel and quadrupole lenses. In the next part, an optimized sputtering method is presented for the deposition of minimum resistivity ITO thin film. Finally, ITO nanostructures with controllable size and shape (such as pyramid shaped field emitters) are deposited by means of chemical methods. Different methods such as scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV-Vis spectrometry has been used to characterize the fabricated devices and thin films.
  9. Keywords:
  10. Nanostructure ; Electron Gun ; Electrostatic Lens ; Charged Particles ; Electron Emitters ; Transparent Anodes

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