Grafting of molecular layers to oxidized gallium nitride surfaces via phosphonic acid linkages

The grafting of organophosphonic acids to the oxidized GaN(0 0 0 1) surface was investigated using X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. The stability of the monolayers was characterized by immersion in buffer solutions at pH 5, pH 7, and pH 9 for one week. The results demonstrate excellent stability under acidic and neutral conditions, but decreased stability under basic conditions. While photochemical grafting of alkenes directly to the unoxidized GaN surface appears to provide slightly better stability under basic conditions, the versatility of phosphonic acids makes this approach a potentially attractive alternative method for integrating molecular and/or biomolecular layers with GaN and other wide-bandgap semiconductors.