Abstract
In this work, a systematic first‐principles study of the quasi‐band structure of silicon nanocrystals (Si‐NCs) is provided, focusing on bandgap engineering by combining quantum confinement of the electronic states with OH surface‐functionalization. A mapping between the bandgap, Si‐NC diameter, and the degree of hydroxide coverage is provided, which can be used as a guideline for bandgap engineering. Complementary to first‐principles calculations, the photoluminescence (PL) wavelength of Si‐NCs in the quantum‐confinement regime is measured with well‐defined diameters between 1 and 4 nm. The Si‐NCs are prepared by means of a microplasma technique, which allows a surfactant‐free engineering of the Si‐NCs surface with OH groups. The microplasma treatment technique allows us to gradually change the degree of OH coverage, enabling us, in turn, to gradually shift the emitted light in the PL spectra by up to 100 nm to longer wavelengths. The first‐principles calculations are consistent with the experimentally observed dependence of the wavelengths on the OH coverage and show that the PL redshift is determined by the charge transfer between the Si‐NC and the functional groups, while on the other hand surface strain plays only a minor part.
Highlights
Bohr radius for silicon was estimated to be merely 4.2 nm,[2] which brings another silicon nanocrystals (Si-NCs) is provided, focusing on bandgap engineering important feature at nanometer size: the by combining quantum confinement of the electronic states with OH surface- large surface to bulk ratio
Bandgap tuning by the quantum confinement effect that gives the use of atmospheric pressure plasmas for the surface treatluminescent properties at room temperature with a photo ment of Si-NCs prepared by electrochemical etching is advanluminescent quantum yield of up to 60–75%.[1]
Where it has to be noted that the experimentally observed PL shift is the average over the particle size of the optical active Si-NCs as it is not possible in experiment to resolve the PL shift individually for each particle size present
Summary
We analyze the size of the Si-NC studied in this work. The Si-NCs diameter is a critical feature that directly influences the bandgap of the Si-NCs and can determine the outcome of the OH functionalization through the microplasma processing technique. For methyl-passivated silicon nanocrystals it has been suggested that the latter effects can lead to large variations of the optical properties,[6] for the polar OH groups it is on the other hand reasonable to assume that the former effect may play a decisive role To quantify both effects we calculated the charge distribution on the Si-NC[38] (Figure 5a) and the absolute strain relative to the bulk Si-Si distance (Figure 5b), both averaged over nearest neighbor shells. For the OH-functionalized Si-NCs studied here the change of the optical properties is induced by the changes of the surface electronic structure caused by charge transfer between the polar OH groups and the Si-NC rather than by mechanical strain
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
