Synthesis and tailoring of GaN nanocrystals at room temperature by RF magnetron sputtering

We report here the synthesis of hexagonal GaN nanocrystals on p-silicon substrates by Radio-Frequency (RF) magnetron sputtering without substrate heating or by post-deposition annealing treatment. GaN nanocrystals are synthesized and tailored as a function of RF power at constant Ar and N-2 flow rates (working pressure). The observed reduction in grain sizes as a function of RF power has been correlated with an increase in compressive strain. The effect of RF power on crystallite orientation has been determined by diffraction intensities using the degree of c-axis orientation. Atomic force microscopy shows uniform lateral nanocrystal sizes with spherical in shape by insignificant difference in Root-Mean-Square (RMS) roughness values for all the deposited thin films. Transmission electron microscope and field emission-scanning electron microscope studies have been performed to understand the surface morphologies and grain sizes. Thus, tailoring the size of the nanocrystals has been discussed by correlating RF powers, working pressures and cathode voltages on lattice vibrations.