Atomic Force Microscopy Characterization of Hydrogen Terminated Silicon (100) 2x1 Reconstruction

• Author / Creator

  Huff,Taleana R

• Non-contact Atomic Force Microscopy (NC-AFM) is a Scanning Probe Microscopy tool offering unique non-perturbative analysis of surfaces and adsorbates at the atomic scale. AFM precisely oscillates a sharp tip above a sample. By monitoring the shift in resonance frequency of a quartz tuning fork caused by local changes in the tip-sample interaction potential, distinct forces due to electrostatic, van der Waals, or chemical interactions can be extracted and quantitatively analyzed. Hydrogen terminated silicon (100) 2×1 (H:Si(100)) has already been explored as a surface for nano-electronic applications using other analysis techniques such as STM, where exploitation of dangling bonds acting as atomic silicon quantum dots have been investigated for uses in quantum cellular automata based nano-electronics, [1][2] [3], ultra-fast wires [4] [5], and logic gates [6]. H:Si(100) also provides a promising platform for electronically decoupled examination of adsorbed atoms, physisorbed molecules [7] [8] [9], and chemisorbed molecular structures with organic electronics applications [10]. Despite these potential uses, studies of H:Si(100) using AFM have been rarely done in the literature, and only once has it been experimentally imaged [11]. NCAFM is a valuable complementary form of analysis that would give access to unique information on H:Si(100) such as unperturbed surface charge distributions, chemical bonding, and surface forces. Therefore, this thesis presents atom resolution images of H:Si(100) achieved in both constant frequency shift and constant height modes of NC-AFM. As part of this analysis, AFM capabilities first had to be developed in our lowtemperature ultra-high-vacuum system, and were optimized over many months of research, trial, and error. Stable operation was attained, and constant frequency shift images of H:Si(100) were taken first to compare to the one published image result [11]. Constant height AFM analysis had never been published on H:Si(100), and was explored next. Constant height scans taken at incremented tip-sample distances above the surface, a novel analysis, demonstrate the evolution from attractive to repulsive surface forces, with repulsive forces showing the first observation of the chemical bond structure of H:Si(100). Furthermore, site-specific force spectroscopy reveals unique force profiles for different surface locations. These differences have application in subtraction of background forces for aformentioned molecule or atom examination, as well as strongly contribute to our understanding of the surface structure of H:Si(100). Imaging of the inert H:Si(100) surface highlights the sensitivity of our system, and opens the door for many other high-resolution AFM experiments.

• Subjects / Keywords

  • Constant height
  • Terminated
  • QPlus
  • UHV
  • Silicon
  • H:Si(100)
  • Atomic force microscopy
  • FIM
  • Hydrogen
  • Si(100)
  • Force spectroscopy
  • AFM

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3CZ32K4F

• 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.