Fullerene irradiation leading to track formation enclosing nitrogen bubbles in GaN material

Gallium nitride was irradiated with fullerene projectiles having an electronic stopping power above the threshold required to promote ion track formation. The structural and chemical changes induced by fullerene irradiation were studied through Transmission Electron Microscopy (TEM). High resolution TEM inquiries were performed to identify the structural order along the ion tracks and the strain induced in the lattice neighboring the ion tracks. The TEM investigation pointed out local amorphization inside the whole tracks and High Resolution TEM studies in the track periphery evidence local stress in the wurtzite structure. Chemical investigations were carried out by STEM Electron Energy Loss Spectroscopy (EELS) to describe the chemical order in the neighboring and inside the ion path. Ga/N stoichiometry is essentially maintained in the track core, whereas an oxidation is detected in the ion track, at the surface. Furthermore, the nitrogen k near-edge fine structure investigation reveals the encapsulation of nitrogen bubbles inside the ion tracks.