Size quantization effect in GaAs nanocrystals

GaAs nanocrystals have been synthesized by an electrochemical route from the acidic solutions of metallic gallium and arsenic oxide. Structural analysis by transmission electron microscopy (TEM), reveales the presence of orthorhombic phase, in contrast to the usual cubic phase of bulk GaAs. Well separated GaAs nanocrystals having sizes in the range of 7 to 15 nm are identified in the TEM micrograph. Optical absorption shows a strong excitonic absorption band on account of quantum size effect associated with GaAs nanocrystals. Photo luminescence, recorded at 300 K under ultraviolet excitation (369 nm), shows the HOMO-LUMO transition band as well as the red shifted bands. Micro-Raman analysis shows a phonon mode centered at 250 cm(-1) associated with a point defect. (C) 2004 Elsevier B.V. All rights reserved.