Single-step fabrication of luminescent GaAs nanocrystals by pulsed laser ablation in liquids

Optical absorption and emission properties of gallium arsenide nanocrystals can be tuned across the visible spectrum by tuning their size. The surface of pure GaAs nanocrystals tends to oxidize, which deteriorates their optical properties. In order to prevent the oxidization, surface passivation has been previously demonstrated for GaAs nanocrystals larger than the Bohr exciton radius. In this paper, we study synthesis of small GaAs nanocrystals by pulsed laser ablation in liquids combined with simultaneous chemical surface passivation. The fabricated nanocrystals are smaller than the Bohr exciton radius and exhibit photoluminescence peaked near 530 nm due to quantum confinement. The photoluminescence properties are stable for at least six months, which is attributed to successful surface passivation. The chemical structure of the nanocrystals and changes caused by thermal annealing are elucidated with Raman spectroscopy, transmission electron microscopy and x-ray photoelectron spectroscopy. (C)2012 Optical Society of America