Nanocrystals of ZnO formed by the hot isostatic pressure method

Abstract

We present here a novel and simple physical method for obtaining ZnO nanocrystals, using the pressure cycle method and the membrane diamond anvil cell (MDAC) up to 13 GPa at 500 K. The recovered nanocrystals in the wurtzitic ZnO phase (w-ZnO) were characterized by the high-resolution Raman scattering and X-ray diffraction. A single crystal of w-ZnO was used in this work. The high-pressure cell was a MDAC specifically designed for high-temperature studies. The Raman spectra of the high-quality ZnO single crystal and nanocrystals were compared, and we observed both a softening and an asymmetric broadening of the Raman peaks, which are in good agreement with the effect of relaxation of the q-vector selection rule due to quantum size confinement effects. The experimental results confirm the existence of ZnO nanocrystals in the w-ZnO phase with an average diameter of 17 nm.

Keywords:

• nanocrystals
• Raman scattering
• phase transitions
• large gap semi-conductors

Acknowledgements

Financial support from the Spanish MEC (Project No. MAT2005-00099) and MALTA INGENIO-CONSOLIDER 2010 (Ref. CDS2007-0045) are acknowledged. J.G, J.M and Ch.P are grateful to the PCP Carbon Nanotubes (France)–MCT(Venezuela) for financial support.