Study of the relationship between crystal structure and luminescence in rare-earth-implanted Ga2O3 nanowires during annealing treatments
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A systematical analysis of the correlation between the crystalline quality and the luminescence of rare-earth-implanted β-Ga2O3 nanostructures with potential applications in visible and ultraviolet photonics is presented. Europium ions led to red emission while gadolinium ions are efficient ultraviolet emitters. Different degrees of lattice recoveries of the nanostructures have been achieved after implantation by rapid thermal annealing treatments carried out at different temperatures. The recovery process has been analyzed by transmission electron microscopy (TEM), high-resolution TEM, and Raman techniques. High-fluence implantation with either of the two rare earth ions induces partial amorphization of the structures. Partial recrystallization of the nanostructures above 500 °C is revealed by Raman analysis. Nearly complete recovery of the crystal structure is obtained in the annealing temperature range 900–1100 °C, coincident with the expected value for bulk Ga2O3. Cathodoluminescence and photoluminescence allowed comparison of the Eu3+ and Gd3+ intraionic luminescence lines after annealing at different temperatures and their correlation with the crystallinity. It has been found that the width of the Eu3+ luminescence lines clearly correlates with the width of the Raman peaks, both decreasing with annealing temperature, which shows the possibility of using the luminescence of this rare earth as a probe for lattice disorder. On the other hand, our results suggest that Gd3+ lines are much less sensitive to disorder.
KeywordsGa2O3 Rapid Thermal Annealing Select Area Electron Diffraction Pattern Crystalline Quality Gallium Oxide
This work has been supported by MICINN through Project MAT 2012-31959, and Consolider CSD 2009-00013. The authors are grateful to Dr. Luca Gregoratti at the Sincrotrone Elettra Trieste for useful advice on XPS measurements. We thank Sérgio Miranda (IST/ITN) for the RTA treatments. Financial support by FCT Portugal is acknowledged (PTDC/CTM/100756/2008; PTDC/CTM-NAN/2156/2012).
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