Formation and properties of high-dose nitrogen implanted epitaxially grown Gd₂O₃ on silicon

The effects of nitrogen incorporation by high-dose ion implantation in epitaxial Gd₂O₃ films on Si(111) followed by annealing have been investigated. Nitrogen incorporation is believed to occur by filling the oxygen vacancies or by removing hydroxyl group ions in gadolinium oxide (Gd₂O₃). The nitrogen content in the oxide layer has been altered by changing the implantation dose. The impact of nitrogen incorporation on Gd-O bonding is studied using X-ray photoelectron spectroscopy. A shift in the Gd and O peak positions indicate the presence of nitrogen in the layer. Raman spectroscopy reveals heavy structural changes. The newly appearing structure is crystalline, but not in agreement with either the known bixbyite (Gd₂O₃) or rocksalt (GdN) structure. Electron microscopic investigations reveal the formation of cracks and small areas with lower densities or even voids. That structure exhibits similarities with transmission electron microscopy images of gadolinium nitride (GdN) layers. The electronic band gap of Gd₂O₃ estimated from O1s plasmon energy loss measurements was found to decrease significantly by the incorporation of nitrogen. Reduction in the valence band and conduction band offset is obtained as a function of implantation dose.