We investigated by Raman spectroscopy (RS) the crystalline quality of CeO 2 thin films radio frequency magnetron sputtered on n-type (111) Si substrates from CeO 2 target. The deposition temperature was in the range of 200-800 • C. We also realized structural investigations on CeO 2 layers after Rapid Thermal Annealing (RTA) performed in the range of 750-1000 • C for 30 s under nitrogen atmosphere. So this study displays that a high-growth temperature and a high post-growth-RTA temperature improves the crystalline structure of the film.In fact, the best crystalline quality, which is close to the CeO 2 target taken as a reference, is obtained for a CeO 2 layer deposited at 800 • C and post-annealed at 1000 • C for 30 s.
Mg + ions were implanted at room temperature in n-type hexagonal GaN for the device isolation purposes. The implantation dose varied from 7.5 × 10 12 to 10 16 ions cm −2 . We performed resonance Raman spectroscopy and DC electrical measurements in order to monitor the structural and electrical changes of non-annealed and annealed implanted GaN samples. Annealing was carried out at 900 • C for 30 s, these conditions being used to achieve good Ohmic contacts. The aim was to determine, on the one hand, the influence of ion doses on the device isolation and, on the other, to establish the order of the technological steps which should be made between ion implantation and Ohmic contact annealing. On increasing the implantation dose from 7.5 × 10 12 to 2 × 10 14 ions cm −2 , an increase in the electrical isolation and a decrease in the photoluminescence (PL) were observed. For the highest dose, the implanted layer became conductive owing to a hopping mechanism and only the first-order phonon lines remained observable. After annealing, the implanted samples became conductive and the PL reappeared or increased compared with the nonannealed samples at same implantation doses, except for the sample implanted at the highest dose, which became insulating. Then, it is possible to achieve device electrical isolation by using a lower ion dose without thermal annealing or using a higher ion dose with thermal annealing.
Ar + ions were implanted at room temperature in n-type hexagonal GaN for device isolation purpose. We performed electrical measurements and resonance Raman spectroscopy in order to monitor the electrical and structural changes of non-annealed and annealed implanted GaN samples. On increasing the implantation dose from 3.4 × 10 12 to 3.4 × 10 14 ions cm −2 , an increase in the electrical isolation and a decrease in the photoluminescence were observed. For a 10 16 ions cm −2 dose, the implanted layer became conductive owing to a hopping mechanism and only the first-order phonon lines remained observable. After annealing at 900 • C for 30 s, the implanted samples became conductive and the photoluminescence reappeared or increased compared with the non-annealed samples at same implantation doses, except for the sample implanted at the highest dose, which became insulating.
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