dmitri a. tenne...dmitri a. tenne department of physics, boise state university office: mp 312a,...
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© 2015 Boise State University 1
Looking into the nanoworld with the help of lasers
(Laser spectroscopy of novel nanomaterials)
Department of physicsDmitri A. Tenne
© 2015 Boise State University 2
What are nanomaterials ? Artificially engineered structures at nanometer
(one billionth of a meter) scale in one, two, or all three dimensions
2D nanostructures: ultrathin films and multilayered structures
1D nanostructures: nanowires, nanotubes
0D nanostructures: nanocrystals (aka quantum dots)
M. Varela et al. in Scanning Transmission Electron Microscopy, ed. by S.J. Pennycook and P.D. Nellist (Springer, 2011)
Luo et al. Appl. Phys. Lett. 83, 440 (2003)
S. Adireddy et al. Chem. Mater. 22, 1946 (2010)
© 2015 Boise State University 3
Complex oxides: functional properties and applications
Image from A. Rothschild, http://matwww.technion.ac.il/Rothschild/Research.html#
high-temperature superconductivity (YBa2Cu3O7) ferroelectricity and piezoelectricity (PbZrxTi1-xO3,
BaxSr1-xTiO3); giant permittivity (CaCu3Ti4O12); colossal magnetoresistance (La1-xSrxMnO3); ionic (YxZr1-xO2), electronic (AlxZn1-xO2),
and mixed ionic-electronic conductivity (SrTi1-xFexO3);
semiconductors (ZnO) photocatalytic activity (TiO2); gas sensitivity (SnO2);
• • •⇒ many electronic, optical and
electrochemical devices including:• nonvolatile memories • sensors and actuators • transparent electrodes
• solar cells • chemical sensors • fuel cells and batteries
• electro-optic modulators • electrochromic windows • catalysts and photocatalysts
© 2015 Boise State University 4
Physical science of nanomaterials: many participants involved
• Theoretical modeling (our collaborators)
• Samples synthesis (more collaborators)
• Structural characterization (collaborators and BSU facilities)
• Studies of physical properties (that’s where we belong!)
• … device design and fabrication
© 2015 Boise State University 5
Boise State University: Departments of Physics, Electrical and Computer Engineering, Materials
Science and Engineering
Cornell University
Oak Ridge National Laboratory
COLLABORATORS
University of Wisconsin -
Madison
Temple University
Penn State University
Argonne National Laboratory
© 2015 Boise State University 6
Our part: probing the physical behavior by laser spectroscopy methods
emitted andscattered
light
incidentlight
z
x
y
reflectedlight
• a material is illuminated by light which characteristics are known;
• light can be: - reflected (reflectivity, ellipsometry)
- absorbed by a material(absorption spectroscopy)
- re-emitted from material (photoluminescence)
- scattered by a material (light scattering)
Raman spectroscopy
© 2015 Boise State University 7
Photoluminescence
350 400 450 500 550
102
103
104
105
3.5 3.4 3.3 3.2 3.1 3 2.9 2.8 2.7 2.6 2.5 2.4 2.3
Inte
nsity
(arb
.uni
ts)
Wavelength (nm)
T=10 Kλi = 325 nm
Energy (eV)
• Pure ZnO emits in the near UV range• Defects such as vacancies, interstitials, or impurities lead to the
light emission in the visible range – great for biological applications (can see them in optical microscope)
Example: zinc oxide, ZnO
© 2015 Boise State University 8
Raman spectroscopy
Chandrasekhara Venkata Raman
The Nobel Prize in Physics 1930
• a material or a molecule scatters irradiant light from a source • Most of the scattered light is at the same wavelength as the laser
source (elastic, or Raileigh scattering) • but a small amount of light is scattered at different wavelengths
(inelastic, or Raman scattering)
Stokes Raman
Scatteringωi- Ω(q)
Anti-Stokes Raman Scatteringωi+ Ω(q)
ωi
Elastic (Raileigh) Scattering
ω
I
0
αβ
ћΩ
ћωiћωsStokes
0
αβ
ћΩ
ћωi
Raileigh
ћωsAnti-Stokes
Analysis of scattered light energy, polarization, relative intensity provides information on properties of material under study (e.g. vibrations of atoms in a crystal or molecule)
© 2015 Boise State University 9
Contact: Dmitri A. TenneDepartment of Physics, Boise State University Office: MP 312A, Lab: MP 302
Tel: 208-426-1633 Email: [email protected]