Phonon dynamics of Zn(Mg,Cd)O alloy nanostructures and their phase segregation

Ghosh, Manoranjan ; Dilawar, Nita ; Banyopadhyay, A. K. ; Raychaudhuri, A. K. (2009) Phonon dynamics of Zn(Mg,Cd)O alloy nanostructures and their phase segregation Journal of Applied Physics, 106 (8). 084306 _1-084306 _6. ISSN 0021-8979

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In this paper we report phonon dynamics in chemically synthesized Zn1−xMgxO (0≤x≤0.07) and Zn1−yCdyO (0≤y≤0.03) alloy nanostructures of sizes ∼10 nm using nonresonant Raman and Fourier transformed infrared spectroscopy. Substitution by Mg makes the unit cell compact while Cd substitution leads to unit cell expansion. On alloying, both A1(LO) and E1(LO) mode of wurtzite ZnO show blueshift for Zn1−xMgxO and redshift for Zn1−yCdyO alloy nanostructures due to mass defect and volume change induced by the impurity atoms. Significant shift has been observed in E1(LO) mode for Zn1−xMgxO (73 cm−1 for x=0.07) and Zn1−yCdyO (17 cm−1 for y=0.03) nanostructures. The variation in Zn(Mg,Cd)-O bond length determined from the blue- (red-) shift of IR bands on alloying with Mg (Cd) is consistent with their respective ionic sizes and the structural changes predicted by X-ray diffraction study. However, on progressive alloying one can detect phase segregation (due to presence of interstitial Mg and Cd ions) in the alloy nanostructures for relatively higher Mg and Cd concentrations. This is confirmed by the gradual absence- of the characteristic IR and Raman bands of wurtzite ZnO near 400-600 cm−1 as well as by X-ray and TEM studies.

Item Type:Article
Source:Copyright of this article belongs to American Institute of Physics.
Keywords:Bond Lengths; Cadmium Compounds; Fourier Transform Spectra; II-VI Semiconductors; Impurities; Infrared Spectra; Interstitials; Magnesium Compounds; Nanofabrication; Nanostructured Materials; Phonons; Raman Spectra; Segregation; Transmission Electron Microscopy; Wide Band Gap Semiconductors; X-ray Diffraction; Zinc Compounds
ID Code:42631
Deposited On:04 Jun 2011 12:49
Last Modified:04 Jun 2011 12:49

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