Charge-Transfer Mapping of Nanostructured GaN/Ag Surfaces using Surface Enhanced Raman Spectroscopy

In this work we present a method for mapping the degree of charge transfer (ρCT) on variously etched GaN surfaces covered by nanoclusters of silver using Raman imaging. The goal was to map ρCT across the surface of a substrate in order to discover the surface features which stimulate relatively large charge transfer from molecule to substrate. These substrates were used because they contain a variety of physical features designed to facilitate surface enhanced Raman spectroscopy (SERS). A clear correlation was found between these features and the degree of charge transfer. To our knowledge no previously published report had used degree of charge transfer as a mapping tool. This type of analysis could lend itself to many applications, such as the evaluation of charge injection across the surface of a light harvesting dye-sensitized solar cell or photovoltaic device.