LOW TEMPERATURE OPTICAL PROPERTIES OF AMORPHOUS OXIDE NANOCLUSTERS IN POLYMETHYL METHACRYLATE MATRIX
V. V. Volkova, Wang Zhong-lin (王中林)b, Zou Bing-suo (邹炳锁)ac, Xie Si-shen (解思深)c
a School of Chemistry and Biochemistry, Georgia Institute of Technology Atlanta, G. A. 30332; b School of Materials Science and Engineering, Georgia Institute of Technology Atlanta, G. A. 30332; c Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
Abstract We studied the temperature-dependent steady-state and time-resolved fluorescence properties of very small (1-2 nm) ZnO, CdO, and PbO amorphous nanoclusters prepared in AOT reverse micelles and imbedded in polymethyl methacrylate(PMMA) films. X-ray diffraction and electron diffraction and imaging indicate that these structures are amorphous. These amorphous oxide nanoclusters demonstrate similar structural, electronic, and optical properties. Properties of steady-state fluorescence spectra indicate the unique localization of electronic states due to the amorphous structure. ZnO and CdO show double-band fluorescence structure, which is due to the spin-orbital splitting, similar to Cu2O. Time-resolved fluorescence studies of the nanoclusters in the polymer reveal two lifetime components, as found in solution. The slow component reflects relaxation processes from band-tail states while the fast component may be related to high-lying extended states. The temperature dependence of fast fluorescence component reveals the presence of exciton hopping between anharmonic wells at temperatures higher than 200K. We correlate the barrier height between two wells formed around local atoms with the inter-atomic distance and bond ionicity.
Received: 02 March 2000
Revised: 30 May 2000
Accepted manuscript online:
V. V. Volkov, Wang Zhong-lin (王中林), Zou Bing-suo (邹炳锁), Xie Si-shen (解思深) LOW TEMPERATURE OPTICAL PROPERTIES OF AMORPHOUS OXIDE NANOCLUSTERS IN POLYMETHYL METHACRYLATE MATRIX 2000 Chinese Physics 9 767
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