Grisel Rivera Batista Science Undergraduate Laboratory Internship Program August 12 2010 Advantages of AXRD Sensitive to N eighboring elements in the periodic table Specific crystallographic phase ID: 624500
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Slide1
Anomalous X-ray Diffraction Studies for Photovoltaic Applications
Grisel Rivera BatistaScience Undergraduate Laboratory Internship ProgramAugust 12, 2010.Slide2
Advantages of AXRD
Sensitive to:Neighboring elements in the periodic table.Specific crystallographic phase.Specific crystallographic site in a phase.Slide3Slide4
AXRD
– Combination of Structural & Chemical Technique
Structural (XRD)
Chemical (XAS)X-rays diffract from specific planesDiffraction peak
Near resonant absorption energy
X-raysabsorbed
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, 2010Slide5
f
n = f0(Q) + f ′(E
) + i f ′ ′(E)f0(Q) = normal (E independent)f ’(
E) = anomalous (E dependent)f ’’(E) = absorption (E dependent)
fn is the atomic scattering factor
x
n
,
y
n
,
z
n
are the (fractional) positions of the n
th
atom
Atomic scattering strength (
f
n
) varies near X-ray absorption edge
Varying X-ray energy near absorption edge →
total intensity changes
f
n
depends
on oxidation state of the element
Anomalous X-ray
Diffraction (AXRD
)
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, 2010Slide6
ZnO loaded with Gallium
Zinc
oxygen
Tetrahedral sites in
ZnO
cellSlide7Slide8
Peak 100Slide9Slide10Slide11Slide12
Spinel: ZnCo2O4
Zn, Co
OxygenSlide13
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.
MixedSpinel (0 <n < 1)
Normal spinel (
n
= 0)
(
Co
)
(
Zn
)
(
Co
)
B A B
Inverse spinel (
n
= 1)
(
Co
) (
Co
)
(
Zn
)
B A B
Degree of Inversion ContinuumSlide14
Peak 311Slide15Slide16Slide17Slide18
Conclusion
AXRD is an effective technique to characterize bulk and nanomaterials.Slide19
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, Sumohan Misra, 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.Slide20
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.Slide21
Questions
?