anomalous x-ray diffraction studies for photovoltaic applications
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
Anomalous X-ray Diffraction Studies for Photovoltaic ApplicationsGrisel Rivera BatistaScience Undergraduate Laboratory Internship ProgramAugust 12, 2010.
Advantages of AXRD
Sensitive to: Neighboring
elements in the periodic table.
Specific crystallographic phase.
Specific crystallographic site in a phase.
AXRD – Combination of Structural & Chemical TechniqueStructural (XRD) Chemical (XAS)
X-rays diffract from specific
planes
Diffraction peak
Near resonant absorption
energy
X-raysabsorbed
RESULT
Diffracted peak intensity ↓ depending on elements present on diffracting planes
0.0
0.2
0.4
0.6
0.8
1.0
2.182.23
2.289600 9650 9700 9750 9800
Inten
sity,
I (a.u
.)
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
fn = f0(Q) + f ′(E) + i f ′ ′(E)f0(Q) = normal (E independent)f ’(E) = anomalous (E dependent)f ’’(E) = absorption (E dependent)
atoms
n
lzkyhxinlkh
nnneEfF1
2),,( )(
• fn is the atomic scattering factor• xn, yn, zn are the (fractional) positions of the nth atom
• 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 elementVariation for Zn
Energy, E (eV)9000 9200 9400 9600 9800 10000 10200
Scatt
erin
g Stre
ngth
10
12
14
16
18
20
22
24
Scatt
erin
g Stre
ngth
0
2
4
6
8
10
f0+ f'f''
Anomalous X-ray Diffraction (AXRD)
2hklhkl FI
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
ZnO loaded with Gallium
Zinc
oxygen
Tetrahedral sites in ZnO cell
Q (Å -1)2.0 2.5 3.0 3.5 4.0
Inten
sity (
a.u.)
0.020.040.060.080.100.120.140.160.18
(101)
(002)
(102)
(110)
(100)
(103)
(200)
(112)(201)
ZnO loaded with Ga
Peak 100
Spinel: ZnCo2O4
Zn, Co
Oxygen
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 Continuum
Peak 311
ConclusionAXRD is an effective technique to characterize bulk and nanomaterials.
AcknowledgmentsU.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.
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.
Questions?