Direct Observation of Transition from Solid-State to Molecular-Like Optical Properties in Ultrasmall Silicon Carbide Nanoparticles

Beke, Dávid and Fučíková, Anna and Jánosi, Tibor Z. and Károlyházy, Gyula and Somogyi, Bálint and Lenk, Sándor and Krafcsik, Olga and Czigány, Zsolt and Erostyák, János and Kamarás, Katalin and Valenta, Jan and Gali, Ádám (2018) Direct Observation of Transition from Solid-State to Molecular-Like Optical Properties in Ultrasmall Silicon Carbide Nanoparticles. JOURNAL OF PHYSICAL CHEMISTRY C, 122 (46). pp. 26713-26721. ISSN 1932-7447

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Abstract

We employ time-dependent photoluminescence (PL) and steady-state PL excitation (PLE) measurements to study the size-dependent optical properties of ultrasmall silicon carbide (SiC) nanoparticles (NPs). We find that the nature of the optical transition transforms from solid-state indirect gap to molecular-like as the diameter of spherical SiC NPs is reduced from 4-6 to 1-3 nm with a smooth transition in between. We deduce the radiative lifetimes of SiC NPs that are well supported by ab initio time-dependent density functional theory calculations on realistically large SiC NPs with realistic surface terminations, including the solvation effects.

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