Why So Colourful? On the Optical Properties of Silicon Nanocrystals

• Author / Creator

  Regina Sinelnikov

• Owing to their rich, tailorable surface chemistry, low toxicity, and elemental abundance,silicon nanocrystals (SiNCs) present an attractive alternative to fluorescentorganic dyes and traditional quantum dots for bioimaging, optoelectronics, and chemicalsensors. These applications capitalize on the optical properties of SiNCs, which arenot fully understood. Thus, the aim of this thesis was to gain a fundamental insightinto the optical response of SiNCs and the factors that affect it. Size, surface chemistry,oxidation, and attachment of conjugated surface groups were taken into considerationwhen evaluating factors influencing the photoluminescence (PL) of SiNCs.First, temperature-dependent steady-state and time-resolved PL measurements ofSiNCs of different sizes and surface functionalities were carried out. A general emissionmechanism based on the observed phenomena was proposed, suggesting that surfacegroups play a crucial role in SiNC PL. Next, the effect of oxidation on the stabilityof the SiNC optical response was evaluated. The convergence of the SiNC PL to thesame region of the visible spectrum, regardless of the initial SiNC PL, was postulated tooccur due to the formation of surface suboxide species. Lastly, the effect of interfacingSiNCs with conjugated surface groups was explored. Scanning tunneling spectroscopyrevealed the formation of in-gap states, which accounted for the observed red-shift inSiNC PL, thus illustrating another way to tune SiNC PL via surface chemistry.Overall, the research presented in this thesis demonstrated the intricate relationshipthat exists between size and surface when it comes to SiNC optical response, whichshould be taken into consideration for any future application design.

• Subjects / Keywords

  • silicon nanocrystals, photoluminescence, surface chemistry

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-bxyh-vg39

• License

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