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Anomalous X-ray Diffraction Studies for Photovoltaic Applications

Grisel Rivera Batista Science Undergraduate Laboratory Internship Program August 12, 2010. Anomalous X-ray Diffraction Studies for Photovoltaic Applications. Advantages of AXRD. Sensitive to: N eighboring elements in the periodic table. Specific crystallographic phase.

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Anomalous X-ray Diffraction Studies for Photovoltaic Applications

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  1. Grisel Rivera Batista Science Undergraduate Laboratory Internship Program August 12, 2010. Anomalous X-ray Diffraction Studies for Photovoltaic Applications

  2. Advantages of AXRD • Sensitive to: • Neighboring elements in the periodic table. • Specific crystallographic phase. • Specific crystallographic site in a phase.

  3. AXRD– Combination of Structural & Chemical Technique Chemical (XAS) Structural (XRD) • X-rays • absorbed • Near resonant absorption energy • X-rays diffract from specific planes • Diffraction peak RESULT Diffracted peak intensity ↓ depending on elements present on diffracting planes Misra, S., Bettinger J., Anomalous X-ray Diffraction (AXRD), 5thAnnual SSRL School on Synchrotron X-ray Scattering Techniques in Materials and Environmental Sciences: Theory and Application. June 1st, 2010

  4. Anomalous X-ray Diffraction (AXRD) • Atomic scattering strength (fn) varies near X-ray absorption edge • Varying X-ray energy near absorption edge → total intensity changes • fn depends on oxidation state of the element fn = f0(Q) + f ′(E) + if ′ ′(E) f0(Q) = normal (E independent) f ’(E) = anomalous (E dependent) f ’’(E) = absorption (E dependent) • fn is the atomic scattering factor • xn, yn, zn are the (fractional) positions of the nth atom Misra, S., Bettinger J., Anomalous X-ray Diffraction (AXRD), 5thAnnual SSRL School on Synchrotron X-ray Scattering Techniques in Materials and Environmental Sciences: Theory and Application. June 1st, 2010

  5. ZnO loaded with Gallium Zinc oxygen Tetrahedral sites in ZnO cell

  6. Peak 100

  7. Spinel: ZnCo2O4 Zn, Co Oxygen

  8. B A B B A B (Co) (Co) (Zn) (Co) (Zn) (Co) Mixed Spinel (0 <n < 1) Inverse spinel (n = 1) Normal spinel (n = 0) Degree of Inversion Continuum Spinel Inversion • Inversion determines the amount of each cation found on either the tetrahedral or octahedral site, and has a big effect on the electrical properties.

  9. Peak 311

  10. Conclusion AXRD is an effective technique to characterize bulk and nanomaterials.

  11. Acknowledgments • U.S. Department of Energy, Office of Science, through the Summer Undergraduate Laboratory Internship Program (SULI) • Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC National Accelerator Laboratory. • My mentors Michael Toney, SumohanMisra, and Joanna Bettinger for their guidance during the realization of my project. • Stephen Rock and all the SULI staff at SLAC for give me the opportunity to work during this summer under their program.

  12. References • Bettinger, J., Misra, S. Anomalous X-ray Diffraction (AXRD), California. 2010. • Bettinger, J. Probing the Effects of Dopants, Defects, and Crystal Structure in Spinel Transparent Conducting Oxides for Photovoltaic Applicationsi, California. • Granqvist, C. G., Transparent conductors as solar energy materials: A panoramic review, Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, Uppsala, Sweeden. 2007. • Introduction to X-ray Diffraction, Materials Research laboratory, University of California, Santa Barbara. 2010. • Thomas, R.K., Simple Solids and their Surfaces [Online]. Available: http://rkt.chem.ox.ac.uk/tutorials/surfaces/solids.html • Pecharsky, V. K., Zavalij, P.Y., Fundamentals of Powder Diffraction and Structural Characterization of Materials, Page 146-152, Springer, New York. 2005. • Cullity, B.D., Stock, S.R., Elements of X-Ray Diffraction, Page 31-47, Prentice Hall, New Jersey. 2001.

  13. Questions?

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