Identification of Surface Structures on 3C-SiC Nanocrystals with Hydrogen and Hydroxyl Bonding by Photoluminescence

Abstract

SiC nanocrystals (NCs) exhibit unique surface chemistry and possess special properties. This provides the opportunity to design suitable surface structures by terminating the surface dangling bonds with different atoms thereby boding well for practical applications. In this article, we report the photoluminescence properties of 3C-SiC NCs in water suspensions with different pH values. Besides a blue band stemming from the quantum confinement effect, the 3C-SiC NCs show an additional photoluminescence band at 510 nm when the excitation wavelengths are longer than 350 nm. Its intensity relative to the blue band increases with the excitation wavelength. The 510 nm band appears only in acidic suspensions but not in alkaline ones. Fourier transform infrared, X-ray photoelectron spectroscopy, and X-ray absorption near-edge structure analyses clearly reveal that the 3C-SiC NCs in the water suspension have Si-H and Si-OH bonds on their surface, implying that water molecules only react with a Si-terminated surface. First-principle calculations suggest that the additional 510 nm band arises from structures induced by H(+) and OH(-) dissociated from water and attached to Si dimers on the modified (001) Si-terminated portion of the NCs. The size requirement is consistent with the observation that the 510 nm band can only be observed when the excitation wavelengths are relatively large, that is, excitation of bigger NCs.

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“…Among the reported functionalities, those in photonics, optics, sensors [1], nano and micro-electromechanical systems (NEMS, MEMS) [2], electronics [3], quantum computing [4] are most promising. Some of these architectures are potentially suitable for technological applications such as solar cells, high temperature energy conversion systems, heat engine, gas turbines, optical modulators or switches, sensors and waveguide material in refractometric or fluorescence detection [5][6][7][8].…”

“…In addition, low weight, low wear, high corrosion resistance and chemical inertness make silicon carbide novel material for biophysics and biomedical applications [7]. These materials are extensively playing great role in ceramic materials for increasing the thermal as well as mechanical properties of reinforced composite materials.…”

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