Laboratory for Advanced Materials Science and
Technology (LAMSAT)
Sarath Witanachchi
Associate Professor
Co-Director of LAMSAT
Department of Physics
University of South Florida
Tampa, FL 33620
Tel: (813) 974 2789
FAX: (813) 974 5813
e-mail:[email protected]
Laboratory for Advanced Materials Science and Technology
explores innovations in pulsed laser ablation, plasma processes and laser
–assisted spray pyrolysis for the growth of thin films and nanostructures of
technologically significant materials including super hard materials,
thermoelectric
materials,
magnetic
and
multiferroic
materials,
superconductors, and quantum dots of semiconductors for solar cells.
NSF and DOE sponsored research projects have focused on the
application of a dual-laser ablation process discovered in this laboratory to
grow large-area, particulate-free films of type I clathrate Ba8Ga16Ge30 as a
thermoelectric material, type II clathrate Na24Si136 and SixGe136-x as tunable
optoelectronic material, fabrication of diamond and diamond-like carbon
structures for MEMS applications, growth of vertically aligned nanograined films of super-hard materials by a hybrid process where chemical
self-assembly and physical vapor deposition techniques are combined,
and to fabricate Cu(InGa)Se2 and ZnO thin films for solar cell applications.
Currently, we are also investigating the inclusion of PbSxSe1-x
nanoparticles in organic and inorganic solar cell structures for multiple
exciton generation. Optical spectroscopic techniques such as time-offlight and time-gated CCD imaging are being used to study species
resolved plasma plume dynamics. The research encompasses thin film
growth, nano-structures, nanoparticle films, dynamic optical process
diagnostics, thin film and nanostructure analysis, characterization and
process modeling leading to the fabrication of single-layer and heterostructure devices.
Dual-laser ablation for thin film growth
Current and past NSF & DOE supported research
Time-gated CCD imaging
of plasma dynamics
•
A Fundamental Study of Bulk and Thin-film Type II Clathrate Materials
•
Pulsed Thermal Excitation of Self-Assembled Nanotemplates for
Manufacturing Dimensionally Controlled Nanostructured Films.
•
Low-cost fabrication of thin film solar cells.
•
A Fundamental study of laser-triggered hollow-cathode transient plasma for a
multi-component film manufacturing process.
•
In-situ fabrication of diamond structures for microelectromechanical systems
(MEMS) using a novel pulsed laser process.
•
Experimental and Theoretical Investigation of Dual-laser Ablation for
Stoichiometric Large-area Multicomponent CuInGaSe2 Film Growth.
•
Pulsed Laser Ablation for Manufacturing: A Novel Dual-laser Film Growth Process.
Nanoparticle films by laserassisted spray pyrolysis
Nanostructred films by chemicalphysical hybrid growth process
Graduate Students
Robert is a Ph.D student in
Applied Physics. He has spent most of
his time on the dual-laser ablation
system. It is a unique process for highquality film growth, especially thin films of
multi-component materials. This method
combines the outputs of excimer laser
(UV) and CO2 laser (IR) pulses on the
ablation target. Lasers arrive at the
target with an inter-pulse delay that is
Robert Hyde
Oscilloscope
UV Detector
Excimer
Laser
determined based on the physical
properties of the target material.
Under optimum conditions the
Delay
IR
Generator
plasma plume of the ablated target Detector
material is highly energetic, close
to 70% ionized, and contain very
Rotating
few particulates that are abundant
Target
CO
in the conventional laser ablated
Laser
films. To optimize the process and
to understand the dynamics of the
growth process he has been using
Vacuum
Chamber
an optical Multi-channel Analyzer
(OMA) to conduct optical emission
spectroscopy
and
time-gated,
species resolved CCD imaging.
Dual-laser ablation system
The main focus of his Ph.D project
is the growth, characterization and
investigation of structure-property relationships of type I clathrate (Ba8Ga16Ge30) films
by
the
dual-laser
ablation
process.
(a)
(b
Type I clathrates
that has a cage-like
structure
is
a
semiconductor with the
unique characteristic of
very
low
thermal
conductivity.
Type I
Plasma plume in (a) single laser and (b) dual-laser
clathrates
find
applications in thermoelectric devices. Low thermal conductivity arises as a result of
resonant interaction of guest-host atom vibrations in the structure.
2
Gayan Dedigamuwa
Gayan’s research towards a
Ph.D in Applied Physics involves
the growth of ferromagnetic and
semiconducting nanoparticles and
quantum dots using a laserassisted spray pyrolysis and nearatmospheric pressure microwave
plasma processes. In the laserassisted spray pyrolysis method
precursors that contain the salts in
the same stoichiometric ratios
of the desired nanoparticle
material are nebulized and
injected into a growth
CO2 laser
chamber using SF6 carrier
Heated
gas. A CO2 laser heats the
substrate
SF6 gas and in turn heats the
aerosol to evaporate the
solvent. Lower the
concentration of the starting
SF6
precursor, smaller the size of
the nanoparticles.
Vacuum
Altarnatively, precursors
containing passivated
nanoparticles can also be in
Nebulizer
Precursor
this system to deposit a
nanoparticle coating. He is
N2
currently studying the growth
and the size dependant
magnetic properties of barium
Laser-assisted spray pyrolysis system for
ferrite (BaFe12O19)
nanoparticle growth.
nanoparticle films and
developing methodology to grow PbSSe quantum dots directly on substrates. These
quantum dots will be incorporated into organic and inorganic solar devices to study the
enhancement in device current due to multi-exciton generation-dissociation.
Devajyoti Mukherjee
Devajyoti is a Ph.D student
in Applied Physics. My research
involves the growth of type II
clathrate materials in thin film form.
Type II clathrates have the general
chemical formula Na24Si136 where
the structure consists of a
combination of hexakaidecahedra
and dodecahedra cages that
resemble a soccer ball. This
material is electrically conducting
while lattice thermal conductivity is
low. One of the exciting aspects of
this material is the recent
theoretical prediction that Si-Ge
alloys with the type II clathrate
structure have a tunable direct
band gap of between 1.2 and 2.0
eV. His project is aimed at the
growth characterization and
determination of structure-optical
and electrical property relation of
Na24Si136 and SixGe136-x films.
Ted Wangensteen
Ted is a Ph.D. student in
Applied Physics. His research
involves the growth and
investigation of the thermoelectric
properties of the layered cobalt
(Co) oxide Ca3Co4O9. It is known
that boundaries in thermoelectric
materials promote phonon
scattering and thus reduce the
lattice thermal conductivity. In
addition, enhancements in
Seebeck coefficient in
nanocomposites have also been
observed and have been attributed
to boundary effects. In his
research he is growing
nanoparticles of Ca3Co4O9 using the laser-assisted spray pyrolysis technique to
investigate dependence of electrical properties on the particle size. He will also be
using the microwave plasma spray process to grow nanoparticle films in-situ without
post annealing steps.
Marek is working towards his M.S.
degree in Physics. His thesis
research involves the development
and characterization of a nearatmospheric pressure microwave
plasma spry system. Aim is to
obtain localized, moderate
temperature (300-600 C) plasma of
an inert gas in a quartz tube where
Vacuum
Substrate
Marek Merlak
aerosols of different precursors can be injected into
the hot zone. The plasma temperature should be
high enough to evaporate the solvent of the
injected droplets and cause a reaction between the
chemicals within the drop to form nanoparticles.
However, the temperature should be low enough
not to evaporate the particles. The system is being
constructed with waveguides and directional
couplers to obtain the desired plasma conditions.
Plasma temperature will be measured by optical
emission spectroscopy.
Tunable Wall
Wave-guide
Ar
Nebulizer
Carrier gas
Microwave plasma system for
growth of nanoparticle films
Jason Rejman
Jason is a Ph.D. student in Applied Physics who just joined the LAMSAT research
group. He will be using the laser ablation process to fabricate ferromagnetic and
ferroelectric multilayer structures and investigate the coupling between magnetic
moment and electrical polarization.
His aim is to investigate several material systems that exhibit multiferroic behavior to
develop a fundamental understanding of the structure-property relation that may lead to
novel magneto-electric devices. Current materials of interest are the heterostructures of
BaFe12O19 /Pb(Zr,Ti)O3 (PZT, piezoelectric), BiFeO3/CoFe2O4, BaTiO3/CoFe2O4 .
Collaborators within the University
Prof. Pritish Mukherjee, Physics- Co-Director LAMSAT
Prof. George Nolas, Physics- Clathrate films
Prof. Srikanth Hariharan, Physics- Ferromagnetic and ferroelectric films and
nanostructurs for multiferroic applications.
Prof. Lilia Woods, Physics- Modeling transport in nanostructured films.
Prof. Xiaomei Jiang, Physics- PbSe quantum dots for organic excitonic solar cells
Prof. Matthias Batzill, Physics- Oxide thin films
Prof. Martin Munoz, Physics- Semiconductor films
Prof. Don Morel, Electrical Engineering- Quantum dot based solar cells
Prof. Chris Ferakides, Electrical Engineering- Quantum dot based solar cells
Laser ablation
and diagnostic
facility