Comparative study on the growth of silver nanoplates on GaAs substrates by electron microscopy, synchrotron X-ray diffraction, and optical spectroscopy

We have recently developed a simple and efficient approach involving the galvanic reaction between a pure aqueous solution of AgNO3 and GaAs wafers to directly grow high-quality Ag nanoplates with chemical clean surfaces on the GaAs wafers [Chem. Mater. 2007, 19, 5845; Small 2007, 3, 1964]. The capability to finely control the dimensions (i.e., size and thickness) of the Ag nanoplates and the time-dependent characterizations have not been explored yet. In this article, time-dependent evolutions of the Ag nanostructures grown on highly doped n-type GaAs wafers through the reactions with AgNO3 solutions, which have concentrations varying in the range of 1 - 10 M, for different times have been systematically investigated by employing various powerful techniques including electron microscopy, synchrotron X-ray diffraction, and optical microscopy. The results indicate that the sizes of Ag nanoplates can be tuned in the range from tens of nanometers to half a micrometer and their thicknesses can be varied from similar to 20 to similar to 160 nm by simultaneously controlling the concentration of AgNO3 Solution and the growth time. The as-grown Ag nanoplates exhibit tunable strong extinction peaks in the ultraviolet-visible-near-infrared spectral regimes, where the GaAs substrates intensively interact with the light.