Nano-scale studies of the assembly, structure and properties of hybrid organic-silicon systems

• Author / Creator

  Sinha, Shoma

• Advancements in the field of electronics might be achieved by future molecular scale devices. Hybrid organic-silicon structures have the potential to overcome many challenges facing the use of molecules as devices while maintaining the ability to interface with traditional silicon technology. The objective of this dissertation was to advance our base knowledge of the interactions, behaviour and properties of simple molecular systems and the Si(100):2x1 surface. Experimental studies conducted with scanning tunneling microscopy (STM) and complemented with theoretical investigations, primarily density functional theory (DFT), were utilized to investigate three principle areas of interest: (1) the transport behaviour of monolayers, patterned regions, or nanostructures, (2) surface diffusion and (3) properties of self-assembled molecular lines. The tunneling current versus applied bias behaviour of the clean, the monohydride and the styrene passivated Si(100):2x1 surfaces were studied. An energy band model was formed that incorporates surface dipole characteristics and band bending to describe transport. The transport behaviour from patterns of clean, styrene covered, and 4-fluorostyrene covered Si(100):2x1 on otherwise monohydride terminated Si(100):2x1 were subsequently studied. Comparison with the observations from the full monolayers provided evidence for conduction through surface states. Studies of the transport behaviour from styrene molecular lines were also performed. Surface diffusion is an important aspect of self-assembly. A novel experimental method for studying aspects of diffusion that removes STM tip effects was developed and used to study the diffusion anisotropy of styrene and 4-fluorostyrene on H-Si(100):2x1. These studies were complemented with DFT energy calculations and Monte Carlo methods to incorporate dynamic effects. Various studies were conducted on self-assembled molecular lines. In addition to studying the electron-transport of styrene lines mentioned above, the transport of lines terminated on one end by a silver island was explored. The effect of line growth due to surface exposure to 1,4-cyclohexadiene was considered. Finally, a study of ordering phenomena of molecules within molecular lines was conducted. Lines composed of 1-vinylnaphthalene were particularly interesting. They demonstrated the ability to form lines with double the normal periodicity but which can transform into normal lines. Using theoretical calculations, a T-like model was proposed.

• Subjects / Keywords

  • Molecular lines
  • Nanoelectronics
  • STM
  • Transport
  • Molecular scale devices
  • Si(100)
  • Surface diffusion

• Graduation date

  Fall 2011

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R34747308

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.