Structure of nitrogen – hydrogen complexes from x-ray and synchrotron radiation techniques

This Chapter illustrates the role played by x-ray techniques, in particular synchrotron radiation-based ones, in the analysis of the structure of nitrogen-hydrogen complexes in dilute nitrides. Para-graph 6.2 introduces the x-ray diffraction experiments which gave the first evidence of a modification of the structure driven by hy-drogenation. Paragraph 6.3 provides a theoretical and experimen-tal framework for understanding the main results presented in this chapter, which were obtained by x-ray spectroscopy; the paragraph explains the physics at the basis of x-ray absorption spectroscopy, with specific reference to the application to the subject of impurities in semiconductors, diffraction anomalous fine structure, and x-ray emission spectroscopy. The possibility of achieving both unidimensional and threedimensional information on the local struc- ture around the isoelectronic impurities and the structure of the complexes playing on different analysis strategy is explained; the importance of coupling spectroscopy data analysis with state-of-art theoretical calculations described in Chapter 4 is stressed. Para-graph 6.4 shows the experimental results and data analysis of different x-ray spectroscopy experiments performed on hydrogenated dilute nitrides, focusing on the local structural information ob-tained and placing it in its historical context with respect to the results of different characterization techniques reported at Chapters 5 and 7. The complementarity between different technical approaches is emphasized. Paragraph 6.5 draws the main conclusions of the chapter and future perspectives.