Temperature-Dependent Photoluminescence of Surface-Passivated 2D-Layered Silicon Carbide Nanocrystals

Ligand-passivated 2D-layered SiC nanocrystals (NCs) are suspended in a cross-linked polymer to measure their cryogenic photoluminescence (PL). Three scenarios are queried based on surface chemistry as dictated by sample history. Samples exposed to oxygen during processing are dominated by nonradiative recombination despite full passivation, showing broad PL and relatively low (10–20%) quantum yields (QYs) that increase only modestly with cooling. In contrast, both fully and partially passivated samples shielded from oxygen show much stronger radiative recombination with bright narrow blue PL and higher QYs that increase markedly under cryogenic conditions. We compare these results to room-temperature radiative rates measured for size-purified fractions derived from analogous colloidal parents. From the multipeak PL structure exhibited by the shielded nanocomposites under cryogenic conditions, we invoke a Franck–Condon argument to link the bright narrow emission to surface SiCH_x, while the weak PL in exposed samples is linked to surface bridging oxygen. The results have important implications for visible light emission from all forms of nanostructured SiC.