Structural and raman scattering studies of ZnO Cu nanocrystals grown by spray pyrolysis

Estudios estructurales y de dispersión de raman de nanocristales de ZnO-Cu crecidos por spray pirólisis

B. El Filali¹*, T. V. Torchynska², A.I. Díaz Cano¹, M. Morales Rodríguez¹

¹ UPIITA-Instituto Politécnico Nacional, México D.F.07738, México. Corresponding author. E-mail: braelf@hotmail.com

² ESFM-Instituto Politécnico Nacional, México D.F.07738, México.

Received October 29, 2014;
Accepted May 21, 2015.

Abstract

The paper presents a simple method to produce the ZnO nanocrystals (NCs) doped with Cu atoms by means of the spray pyrolysis using Zinc acetylacetonate hydrate, copper acetylacetonate and chloroform as solvent. ZnO nanocrystals with 5?20 wt % Cu were deposited on the glass substrates at 400°C using the spray pyrolysis technique and then thermal annealed at 500°C for 2 hours in ambient atmosphere. The crystallinity and morphology of the films were characterized by SEM, XRD and Raman scattering methods. The XRD study indicates that ZnO films have a hexagonal wurtzite structure and the Cu addition enhances the preferential orientation along the (100). The Raman scattering spectrum of Cu doped ZnO nanocrystals thermal annealed at 500°C for 2 hours in ambient atmosphere demonstrates a set of Raman peaks related to the vibrational modes in ZnO for small Cu concentration (5-10%). In ZnO nanocrystals with higher Cu concentrations (15-20%) the CuO phase was detected by the XRD and Raman scattering methods. It was shown that the quality of ZnO NC films can be improved by copper doping with concentration less than 10%.

Keywords: zinc oxide, SEM, XRD, Raman scattering.

Resumen

Este artículo presenta un método simple para producir nanoestructuras de ZnO con la inclusión de nanocristales metálicas de Cu por medio de spray pirolisis utilizando hidrato de acetilacetonato de zinc, acetilacetonato de cobre y cloroformo como disolvente. Las nanocristales de ZnO con un peso atómico de 5-20% de Cu se depositaron a una temperatura de 400°C sobre los sustratos de vidrio utilizando la técnica de spray pirolisis, después a las muestras se le aplico tratamiento térmico a 500°C en atmósfera ambiente. La cristalinidad y la morfología de las películas se caracterizaron por las técnicas de SEM, XRD y dispersión Raman. El estudio XRD indica que las películas de ZnO tienen una estructura de wurtzita hexagonal y que la adición de Cu mejora la orientación preferencial a lo largo de (100). El espectro de dispersión Raman de las muestras de ZnO dopadas con Cu después del tratamiento térmico a 500°C en atmósfera ambiente demuestran un conjunto de picos relacionados con los modos activos Raman de las nanopartículas de ZnO a niveles bajos de concentración de Cu (5-10%). En las nanocristales de ZnO con alta concentración de Cu (15-20%) se detectó la presencia de la fase secundaria de CuO por la técnica de difracción de rayos X. Además se demostró que la calidad de las nanopartículas de ZnO se puede mejorar con un nivel de dopaje con Cu inferior al 10%.

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