Plasmon excitation in electron energy-loss spectroscopy for determination of indium concentration in (In,Ga)N/GaN nanowires

We demonstrate the potential of low-loss electron energy-loss spectroscopy in transmission electron microscopy as a quick and straightforward method to determine the local indium compositions in (In,Ga)N/GaN nanowires. The (In,Ga)N/GaN nanowire heterostructures are grown by plasma assisted molecular beam epitaxy on Si(111) substrates in a self-assembled way, and on patterned GaN templates in an ordered way. A wide range of indium contents is realized by varying the substrate temperatures. The plasmon peak in low-loss electron energy-loss spectroscopy exhibits a linear relation with respect to indium concentration in (In,Ga)N nanowires, allowing for a direct compositional analysis. The high spatial resolution of this method in combination with structural information from transmission electron microscopy will contribute to a basic understanding of the lattice pulling effect during (In,Ga)N/GaN nanowire growth.