Synthesis and characterization of pure and Co-doped gallium nitride nanocrystals

Abstract

Pure and Co-doped gallium nitride (GaN) (5 and 8 mol%) nanocrystals were synthesized by nitridation of Ga–EDTA.NH4 and Co–Ga–EDTA.NH4 complexes. Pure and 5 mol% cobalt-doped GaN did not show any impurity phases in the X-ray diffraction and Raman analysis, whereas 8 mol% Co-doped GaN show secondary phase formation. Transmission electron microscopic study revealed the broad crystal size distribution ranging from 10 to 140 nm. Cathodoluminiscence spectra measured at 20 K shows the suppression of GaN band edge emission with increasing Co concentration. Magnetic measurements of Co-doped GaN revealed a ferromagnetic behavior up to room temperature. The saturation magnetization value increases with increasing impurity phase separation. X-ray photoelectron spectroscopy revealed evidence on the oxidation states of cobalt and excludes the possibility of Co clusters in the doped samples.