Semiconductor Physics, Quantum Electronics & Optoelectronics, 24 (2), P. 124-130 (2021).

EPR study of paramagnetic centers in SiO2:C:Zn nanocomposites obtained by infiltration of fumed silica with luminescent Zn(acac)2 solution
D.V. Savchenko1,2,*, V.S. Memon1, A.V. Vasin1,3, D.V. Kysil3, A.V. Rusavsky3, O.P. Kuz1, F.M. Gareeva1, E.N. Kalabukhova3

1National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”
37, prosp. Peremohy, 03056 Kyiv, Ukraine
2Institute of Physics of the CAS,
2, Na Slovance, 18221 Prague, Czech Republic
3V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine
41, prosp. Nauky, 03680 Kyiv, Ukraine

Abstract. Silica-carbon with zinc (SiO2:C:Zn) nanocomposites obtained via infiltration with aged luminescent zinc acetylacetonate (Zn(acac)2) ethanol solution of two concentrations (1 or 4%) into the fumed silica (SiO2) matrix have been studied using EPR within the temperature range 6…296 K before and after thermal annealing. The EPR spectrum of SiO2:C:Zn nanocomposites consists of three signals with the Lorentzian lineshape corresponding to paramagnetic centers with S = 1/2, which are related to carbon dangling bonds (CDB) (g = 2.0029(3)), silicon dangling bonds (g = 2.0062(3)) and oxygen-centered carbon-related radicals (CRR) (g = 2.0042(3)). A small EPR linewidth (<1 mT) observed for CDB and oxygen-centered CRR allows us to conclude that they are in the sp3-hybridized state. It was found that the temperature dependence of the EPR signal integrated intensity of the CDB and oxygen-centered CRR follows the Curie–Weiss law with a small positive value of the Curie–Weiss constant, which indicates that the weak ferromagnetic exchange interaction takes place in the spin system of CDB and oxygen-centered CRR. It was supposed that the carbon-related centers are clustered in SiO2:C:Zn nanocomposites. We assume that the oxygen-centered CRR in the sp3-hybridized state are associated with luminescent centers in previously reported aged Zn(acac)2/C2H5OH solution.

Keywords: silica-carbon nanocomposites, carbon-related centers, dangling bonds, exchange interaction, electron paramagnetic resonance.

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