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Synthesis, Passivation and Charging of Silicon Nanocrystals


Boer, Elizabeth A. (2001) Synthesis, Passivation and Charging of Silicon Nanocrystals. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/ZB66-SN79.


Silicon nanocrystals are intriguing from both a fundamental and an applied physics point of view. The efficient room temperature luminescence exhibited by Si nanocrystals (as compared to bulk silicon) and the apparent size-dependent bandgap of Si nanocrystals are two incompletely explained phenomena. Meanwhile, the applied physicist may take advantage of the optical and electronic properties of small Si structures to build devices not possible with only bulk silicon.

In this thesis, nanocrystal samples produced by aerosol techniques were investigated. The aerosol samples were size-classified in the size range of 2-50 nm with a size variation of 15-20%. Conducting tip atomic force microscopy (AFM) was used to manipulate and investigate the samples' charging characteristics. The AFM was used to inject charge into single Si nanocrystals and to observe the dissipation.

The charging characteristics of samples made by ion implantation and annealing were also explored. An atomic force microscope was used to locally inject, detect and quantify the amount and location of charge in SiO2 films containing Si nanocrystals (size 2-6 nm). By comparison with control samples, charge trapping was shown to be due to nanocrystals and not ion implantation-induced defects in these samples.

Two models were developed for quantitative charge imaging with an atomic force microscope, one appropriate for non-contact mode and the other for intermittent contact (tapping) mode imaging. From the models, estimates of the best charge sensitivity of an unbiased standard AFM cantilever were found to be on the order of a few electrons. The models were used to estimate the amount of charge injected in the charging experiments: in typical experiments, on the order of 60 electrons were injected in an isolated Si nanoparticle, and a few hundred electrons were injected in SiO2 films containing Si nanocrystals.

Finally, for optical studies, nanocrystal passivation with hydrogen and SiO2 were briefly investigated using photoluminescence and X-ray photoelectron spectroscopy.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:nanoparticle manipulation; nanoparticles; quantum dots
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Libbrecht, Kenneth George
Thesis Committee:
  • Quake, Stephen R. (chair)
  • Atwater, Harry Albert
  • Vahala, Kerry J.
  • Flagan, Richard C.
  • Libbrecht, Kenneth George
  • Crocker, John C.
Defense Date:9 February 2001
Non-Caltech Author Email:eboer (AT)
Funding AgencyGrant Number
Record Number:CaltechETD:etd-01132002-032219
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:145
Deposited By: Imported from ETD-db
Deposited On:10 May 2002
Last Modified:01 Dec 2022 23:48

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