Materials and Electronics for Space Applications
Investigators: Félix E. Fernández (Group Leader), Luis Fonseca, Weiyi Jia, Ram S.
Katiyar, Huimin Liu, Antonio Martínez, Rafael Rodríguez-Solís.
1. General Overview
1.1 Description of the MESA Group
The MESA group conducts research on materials with potential for new or improved
electronic or optoelectronic devices. It has seven faculty members (three from Physics
and one from Electrical Engineering at UPR-Mayaguez, and three from Physics at UPRRío Piedras). Very substantial infrastructure has been developed by this group with
support from NASA and other federal agencies. Eight students (6 undergraduate, 2
graduate) participating in MESA projects were directly supported by TCESS during this
extension period or part of the period.
1.2 Relevance to NASA
Because of the potential technological applications of the materials and devices
developed and studied by the MESA group, all are in principle relevant to NASA.
However, some materials and device designs are of more immediate interest for
application in NASA projects related to advanced microwave communications. These
aspects of the MESA group work are highlighted below, particularly in relation to
microwave antennas to support satellite communications by providing multiband
operation with a single antenna or receiver, which would also provide a reduction of
footprint area required to place antennas for multiple systems by using a single antenna,
eliminating the problem of co-site interference. Continuing collaboration with NASA –
GRC in development of ferroelectric electroceramic thin films resulted in a joint
publication during this period.
1.3 Benefits to Society
All materials produced and studied by MESA scientists have been chosen because of
possible technological impact, and could therefore have societal impact. Of particular
note in this respect are novel phosphor materials studied by MESA scientists, which have
potential for applications in field emission display applications. Work with new antenna
designs raise the possibility of lower cost phased array antennas for communications
applications.
1.4 MESA Goals
Specific goals of the MESA group during this last project period have focused on several
projects which included:
Study of new scintillator materials for detection of high-energy radiation.
Development of new phosphor materials with enhanced properties for miniature
LED solid state lighting sources.
Development and study of VO2 thin films as a material of interest for optical
limiting and ultrafast optical switching.
Design and numerical simulation characterization of tunable antennas and circuits
for Ka band radiation.
1.5 MESA Accomplishments
A total of 14 scientific papers were published in peer-reviewed journals and peerreviewed conference proceedings, and 7 technical presentations were offered in national
or international scientific meetings.
A systematic investigation was performed on sulfide phosphors, including CaS;Ce,Na,
CaS:Ce,Eu, ZnS:Ce,Li and ZnS:Te/Se/Mn. These phosphors can be used for miniature
LED solid state lighting sources.
An extensive study of the ultrafast nonlinear optical response of VO2 thin films was
completed. The films were deposited by Pulsed Laser Deposition and studied with
femtosecond and picosecond laser techniques. This material is of interest for passive
nonlinear optical device applications.
Tunable folded-slot and aperture coupled microstrip patch antennas using BSTO were
designed for operation between 29 GHz and 31.5 GHz and a bandwidth of approximately
3 GHz.
1.6 Student Accomplishments
TCESS-supported student Teddy Rodríguez (graduate, Physics) co-authored two peerreviewed articles. Formerly supported students Víctor Rodríguez Santiago (graduate,
Physics), Luz Díaz (undergraduate, Engineering) and Ming Ye (undergraduate,
Engineering) co-authored one peer-reviewed article each.
TCESS-supported student Antonio Amador (graduate, EE) completed statistical design of
annular slot ring antennas and is presenting his results at the IEEE Antennas and
Propagation International Symposium at Albuquerque, NM (July 2006). He also begun
application of findings to design of a tunable antenna using thin-film ferroelectric
materials.
Doctoral student Joaquín Aparicio (Chemical Physics), formerly supported by TCESS,
achieved growth of epitaxial ZnO and p-type N-doped ZnO thin films as part of his
dissertation work. He is currently studying these materials with a variety of techniques in
order to understand the stability of dopant species.
1.7 Summary of Accomplishments
IPEG Statistical Data.
# Investigators (Total # faculty and research associates)
# Investigators (Total # faculty and research associates)
# Undergrad students supported (total)
# Undergrad students supported (US Citizen, UMD only)
# Undergraduate degrees awarded (US Citizen, UMD only)
# Masters students supported
# Masters students supported (U.S. Citizen, UMD only)
# Doctoral Students Supported
# Doctoral Students Supported (U.S. Citizen, UMD only)
# Grad students supported (total)
# Grad students supported (U.S. Citizen, UMD only)
# Masters degrees awarded (US Citizen, UMD only)
# Doctoral degrees awarded (U.S. Citizen, UMD only)
# Post-docs supported (total)
# Post-docs supported (U.S. Citizen, UMD only)
# Refereed Papers and Book Chapters Accepted/Published
# of student authors or co-authors
# Refereed Papers and Book Chapters submitted but not yet accepted
or published
# of student authors or co-authors
# Presentations at NASA Installations
# Presentations national/international research conferences
# given by students
# Presentations at Faculty seminars
# Presentations to K-12 Schools
# K-12 Students Contacted
# K-12 Educators Contacted
# Patents applied/awarded
# NASA MUREP Panels served on (peer review, advisory, etc.)
# Other NASA Panels served on (peer review, advisory, etc.)
Total research $ awarded by NASA other than URC
Total research $ awarded by other Agencies
Infrastructure $ leveraged from NASA sources other than URC
Infrastructure $ leveraged from other Agencies during 2003 as a direct
result from URC
UMD = Underrepresented Minority and Disabled
7
6
6
****
2
2
0
0
2
2
0
0
0
0
14
4
2
0
0
7
1
0
0
0
0
0
0
0
0
0
0
0
2. Technical Summary
Intensity (a.u.)
Emission of Pr3+ from two sites in CaHfO3 perovskite
In the last decades, many new scintillators have been investigated due to the urgent need
for detection of high-energy radiation. Among them, aluminate perovskites, such as
YAlO3:Ce (YAP), GdAlO3:Ce (GAP) and LuAlO3:Ce (LuAP), have shown very promising
performance for scintillation. These perovskites demonstrate high light yield, fast response
time, and high radiation hardness. In search of new scintillators, hosts consisting of
elements with high
atomic number are
1000
CaHfO3:0.2%Pr
more attractive. They
(1400C
in
N
+5%H
)
potentially have higher
(a)
2
2
density and effective
(a)Monitoring
at
490nm
800
(b)Monitoring at 610nm
atomic number, and
therefore, have shorter
600
radiation
distance.
From this consideration,
(b)
400
alkali-earth
hafnates
with
perovskite
x10
structure
(ABO
3) have
200
been
proposed
as
candidates
for
0
scintillator hosts. Ce200
250
300
350
400
450
500
doped
alkali
earth
Wavelength (nm)
hafnates were reported
very recently and quite
3+
efficient emission
Figure 1 Excitation spectra of Pr from two sites: (a) From Pr(Ca) site,
monitored at 490.5 nm; and (b) from Pr(Hf) site, monitored at 610 nm.
from Ce3+ was
observed. However, it was suspected from consideration of the crystal structure and ionic
sizes that Ce3+ may also replace Hf at the B-site, and may consequently lead to a reduction
in quantum efficiency. In work by MESA researchers, Pr-doped CaHfO3 was investigated.
Compared to Ce3+, Pr3+ is more sensitive to the host environment, and can be used to obtain
more spectroscopic information and site distribution of the doping ions within the host
system. CaHfO3 is an interesting host for rare earths. It was found that Pr ions could
replace both Ca and Hf sites. Strong UV emission bands from 5d state and visible emission
lines from 3P0 and 1D2 states of Pr3+ were observed. It is estimated from the emission
intensity that about 15% Pr is on the Hf site in CaHfO3:0.2%Pr3+. Co-doping with charge
compensation ions will re-distribute Pr on the two sites. In3+ (Hf) and Al3+ (Hf) tend to
increase the population of Pr on B site, while Na+(Ca) tends to reduce the population of Pr
on B site.
UV Excitation and trapping centers in CaTiO3:Pr3+
Intensity (a.u.)
The
phosphor
3+
CaTiO3:Pr
has
been shown to be
300
attractive for various
3+
(a)CaTiO3:0.2%Pr
display applications
(b)CaTi
Al
O
:0.2%Pr
in recent years. The
250
0.9 0.1 3
dominant transition
in the phosphor
ex=355nm
200
originates from the
em=612nm
1
D2 state to the 3H4
150
ground state with an
emission wavelength
100
near 612 nm, which
is ideal as the red
(b)
color component for
50
various color display
(a)
technologies.
0
Moderate
intrinsic
conductivity
makes
it
150
200
250
300
350
400
especially interesting
Temperature (K)
3+
for field emission
Figure 2. Thermoluminescence of polycrystalline CaTiO3:0.05%Pr (a) and
CaTi0.9Al0.1O3:0.05%Pr3+ (b), after excitation for two minutes at 355 nm and
displays (FED). Its
monitored at 612 nm.
UV
excitation
spectrum consists of
three bands at 279, 330 and 360 nm, which are assigned to the Pr3+ 4f to 5d transition, the
valence-to-conduction band transition Ti4+-O2- to Ti3+-O- and the charge transfer transition
Pr3+-Ti4+ to Pr4+-Ti3+, respectively. 3P0 luminescence under UV excitation is completely
quenched to 1D2 through a strong coupling with the charge transfer state at room
temperature. However, quite strong 3P0 emission was observed at low temperatures when
the 3P2 state was excited at 457.9nm. In addition, the phosphor showed a red afterglow. The
traps are associated with electron-trapping, and are possibly related to Pr4+ and oxygen
vacancies existing in the samples. Incorporation of Al3+ was found to increase the
brightness and persistence time, as shown in Figure 2.
Ultrafast optical response in pulsed laser-deposited vanadium dioxide thin films
Vanadium dioxide (VO2) is the object of increasing interest due to its potential applications
in storage devices, ultrafast optical or field-controlled switches and bistable optoelectronic
units. In spite of numerous experimental and theoretical approaches, the problem of
determining the phase transition (PT) mechanisms in VO2 is still open. Vanadium dioxide
exhibits a first order insulator-to-metal (I-M) phase transition at a temperature of about 340
K. The extremely fast I-M transition can also be induced by laser illumination. A
ferroelastic structural deformation of the lattice symmetry from a monoclinic to a
tetragonal (rutile) structure produces a significant change in optical constants. The
transition to the monoclinic phase is characterized by pairing and tilting of the V ions from
cr rutile axis. That motion of the V ions leads to a doubling of the unit cell. The formation
of the VO2 band gap is related both to electron-lattice interaction and electron-electron
correlations. The first-order PT appears as a spatial displacement of vanadium ions. It is
expected that the intra-atomic electron-electron correlations stabilize the insulator phase at
low temperatures. One can expect that the Mott-Hubbard mechanism initiates the lattice
distortion. So far, however, this is not entirely confirmed experimentally. Thus, study of
post-transition electron-phonon interactions is important in order to clarify the relaxation
160 nm
Epump~ 30 mJ/cm
2
140 nm
R/RS
0.0
100 nm
90 nm
50 nm
25 nm
-0.5
70 nm
0.0
0.5
1.0
1.5
2.0
2.5
Time delay (ns)
Figure 3. Normalized change of light-induced transient reflectivity versus probe delay for various
thicknesses of VO2 films. The film thickness is indicated for each curve. Note prompt reflectivity response
at onset of illumination.
processes accompanying the I-M PT in VO2.
Detailed investigations of electron-electron and electron-phonon relaxation properties
during the phase transition in VO2 require ultrafast experimental techniques which allow
real-time observation of the processes. Recently, optical experiments with laser pulse
durations from 1.5 ps to 15 fs at 650 nm have shown that the PT occurs at a time scale of
less than 100 fs, which cannot be associated with the lattice temperature effect. A strong
electron-phonon coupling was found in the picosecond time scale after the ultrafast PT in
VO2. Further study of time resolved electron and phonon relaxations may yield more
information about the transition mechanisms. We have presented results of transient
reflection and transmission measurements through the PT induced by femtosecond laser
pulses in VO2 thin films. A model to interpret the PT process involving electron-phonon
coupling, electron diffusion, and heat transfer processes was also discussed.
By laser excitation, ultrafast I-M PT in VO2 films was confirmed to be light-induced in
nature. Due to optical absorption by the film, phonon-associated thermal effects, which are
slow processes in the nanosecond scale, can also lead to PT in the film volume. The sign
of the transient reflectivity depends on film thickness due to wave interference in the thin
films. The investigations of VO2 films with different thicknesses have shown the different
stepwise formation of the metallic phase after optical pumping. Interaction of 30 mJ/cm2
femtosecond pulses with 50 nm and thinner films produces complete ultrafast light-induced
I-M PT within 500 fs (see Figure 3).
The mechanism of the
light-induced PT can be
understood as the optical
transition
to
an
intermediate Wannier-Mott
exciton state in the
insulator phase, followed
by the transition to the
metallic state.
The
experimental data was
fitted using a proposed
analytical approximation.
The general properties of
the films with thickness
greater than 50 nm under
moderate pump power are
described by an ultrafast (~
500 fs) light-induced phase
transition in the nearsurface
layers;
the
consequent heat transfer
produced
by
light
absorption causes a slower
PT in the film volume.
Figure 4. Schematic band structure of light-induced ultrafast I-M phase
transition and related processes. The main channel of PT is via vibronic
Wannier-Mott exciton clusters.
Slot ring antenna designs for microwave applications
CPW fed slot ring antennas (SRA) have been studied recently because they are simple to
fabricate, have low cost, light weight, are compact in size, can radiate at low elevation
angles and can be easily integrated to microwave circuits. These characteristics make them
attractive for mobile communications. An eccentric microstrip fed annular SRA has been
presented in the literature, where it was shown that by moving the inner circular conductor,
the bandwidth of the antenna was improved. Using this technique it is possible to design a
wide-band CPW fed circular antenna. We have used the DOE technique to determine the
effect of the design parameters in the impedance and radiation characteristics of a CPW fed
annular SRA. Figure 5 shows the antenna configuration and Figure 6 shows the design
parameters.
Figure5. Annular slot ring antenna configuration. The
yellow region correspond to metal and the red region
corresponds to the dielectric substrate.
Figure 4. Schematic of an Annular Slot
Ring Antenna with its design parameters.
The annular slot ring antenna has six design parameters. To make the statistical
characterization possible, some parameters were maintained constant. The relative
permittivity of the substrate was chosen as 6.15 and its width was 1.28 mm, to keep the
CPW fed line cross-section with a center conductor of 1.02 mm and a slot width of 0.2 mm.
A full 24 factorial design with one central point was used for the DOE design. Initially, an
antenna was designed for a resonance frequency around 10 GHz. The antenna parameters
were adjusted to achieve input impedance with a value close to 50 ohms. The parameter
values of this initial design are used as the central point values. Central points are used to
determine the linearity of the statistical model. The factors in the design were Ro, Ri, d and
s. The experiment was perfomed twice, each time using a different electromagnetic
simulator: Designer, which uses the method of moments, and HFSS, which uses the finite
element method.
The factorial design was analyzed for the effects in each response: resonant frequency,
input impedance at the resonant frequency, bandwidth and gain. As a result of this
statistical characterization it was shown that increasing the separation between circles and
decreasing the inner radius lowers the impedance. Adjusting the antenna dimensions in this
way also increases the resonant frequency and lowers the gain of the antenna at broadside,
showing that the impedance of slot rings and folded slots can be decreased by increasing
the slot width at the side opposite to the feed line. A typical response of the annular slot
ring antenna is shown in Figure 7. Future work will include a higher order model to
increase the accuracy of the results and a tunable version using thin ferroelectric films.
Figure 5. Typical response of an annular slot ring antenna: a) radiation pattern in the E-plane (-o-) and Hplane (-x-), and b) input impedance.
3. Personnel
Students Funded by TCESS under MESA projects
Name
Major
DegreeDegree completion
Teddy Rodríguez
Physics
MS
6/2007
Antonio Amador
EE
MS
6/2007
Legna Torres
Physics
BS
6/2006
Griselle Miranda
Physics
BS
Leyra Cuadrado Caraballo Physics
BS
Verónica Hernández Ortíz EE
BS
Antonio Castañer Padró
Lorna Alvarez Mártir
Physics?
EE
BS
BS
4. Outcomes
4.1 Publications in peer-reviewed journals
1.
Novel PLD -VO2 thin films for ultrafast applications
H. Liu, O. Vázquez, V.R. Santiago, L. Díaz, A.J. Rua, and F.E. Fernández
Journal of Electronic Materials 34 (2005) 491.
2.
The model of metal-insulator phase transition in vanadium oxide
V.S. Vikhnin, S. Lysenko, A. Rua, F. Fernandez, H. Liu
Physics Letters A 343 (2005) 446.
3.
The model of ultrafast light-induced insulator-metal phase transition in vanadium
oxide
V.S. Vikhnin, S. Lysenko, A. Rúa, F. Fernández, and H. Liu
Journal of Physics C 21 (2005) 44.
4.
Laser excitation and excited state dynamics in vanadium dioxide thin film
H. Liu, S. Lysenko, A. Rua, V. Vikhnin, G. Zhang, O. Vásquez and F.E. Fernández
Journal of Luminescence, Volumes 119-120 (2006) 404.
5.
Eu-emission quenching by electron screening in VO2 thin films
H. Liu, S. Lysenko, A. Rua, V. Vikhnin, O. Vásquez and F.E. Fernández
Journal of Luminescence, Volumes 119-120 (2006) 388.
6.
The model of ultrafast light-induced insulator-metal phase transition in VO2
V.S. Vikhnin, S. Lysenko, A. Rua, F. Fernández and H. Liu
Solid State Communications 137 (2006) 615.
7.
Light-induced Ultrafast Phase Transitions in VO2 Thin Film
S. Lysenko, A. J. Rúa, V. Vikhnin, J. Jiménez, F. Fernández, H. Liu
Applied Surface Science 252 (2006) 5512.
8.
Emission of Pr3+ from two sites in CaHfO3 perovskite
W.Jia, D. Jia, T. Rodriguez, Y. Wang, H. Jiang and K. Li,
Journal of Luminescence, in press, 2006.
9.
UV Excitation of Pr3+ and Trapping Centers in CaTiO3
W. Jia, D. Jia, T. Rodriguez, D. Evans, W.M. Yen, and R. Meltzer
Journal of Luminescence, Volumes 119-120 (2006) 13.
10.
Quantum Splitting and its Dynamics in GdLiF4:Nd
W. Jia, Y. Zhou, S.P. Feofilov, R.S. Meltzer, J. Y. Jeong and D. Keszler
Phys. Rev. B 72 (2005) 075114.
11.
Stress-Induced Mechanoluminescence in SrAl2O4:Eu2+,Dy3+
Yi Jia, Ming Ye, and Weiyi Jia
Optical Materials 28 (2006) 974.
12.
Investigations on Sol-Gel Derived Highly (100) Oriented Ba0.5Sr0.5TiO3:MgO
Composite Thin Films for Phase Shifter Applications
M. Jain, S.B. Majumder, R.S. Katiyar, A.S. Bhalla, F.A. Miranda, and F.W. van
Keuls
Applied Physics A A80 (2005) 645.
13.
Local Symmetry Breaking in PbxSr1-xTiO3 Ceramics and Composites Studied by
Raman Spectroscopy
M. Jain, Yu. I. Yuzyuk, R.S. Katiyar, Y. Somiya, and A.S. Bhalla
Journal of Applied Physics 98 (2005) 24116.
14.
Dielectric and Tunable Properties of BaZr1-xO3 Thin Films
A. Dixit, S.B. Majumder, R.S. Katiyar, and A.S. Bhalla
Ferroelectrics Letters 32 (2005) 131.
4.2 Technical Presentations in national or international conferences
1.
Sulfide phosphors for LED white light sources
Weiyi Jia et al.
Symposium of Solid State Lighting Materials and Devices
2006 Spring Meeting of Materials Research Society
April 7-21, 2006, San Francisco CA.
2.
Analysis of a CPW Fed Annular Slot Ring Antenna Using DOE
A. Amador-Pérez
IEEE Antennas and Propagation International Symposium
July 2006, Albuquerque, NM.
3.
Light-induced Ultrafast Phase Transitions in VO2 Thin Film
S. Lysenko, A.Rúa, V.Vikhnin, F.Fernández, H. Liu
13th International Congress on Thin Films/8th International Conference on
Atomically Controlled Surfaces, Interfaces and Nanostructures
June 19-23, 2005, Stockholm, Sweden.
4.
Eu-emission quenching by electron screening in VO2 thin films
H. Liu, S. Lysenko, A. Rua, V. Vikhnin, O. Vasquez, F.E. Fernandez
15th International Conference on Dynamical Processes in Exited States of Solids
Aug. 1-5, 2005, Shanghai, China
5.
Laser excitation and excited state dynamics in vanadium dioxide thin film
H. Liu, S. Lysenko, A. Rua, V. Vikhnin, G. Zhang, O. Vasquez, F.E. Fernandez
15th International Conference on Dynamical Processes in Exited States of Solids
Aug. 1-5, 2005, Shanghai, China
6.
Insulator to Metal Phase Transformation of VO2 Films upon Femtosecond Laser
Excitation
S. Lysenko, V. Vikhnin, A. Rua, Z. Guangjun, F. Fernandez, H. Liu
TMS 2006 Annual Meeting, March 12-16, San Antonio, TX
7.
Photoinduced Reflectivity Transients in Vanadium Dioxide
S. Lysenko, V. Vikhnin, A. Rua, Z. Guangjun, F. Fernandez, H. Liu
TMS 2006 Annual Meeting, March 12-16, San Antonio, TX
4.5 Submitted Proposals
Center for Advanced Functional Materials
F.E. Fernández et al.
Submitted to: NSF-CREST
Requsted: $ 4,960,000
Status: Pending
Structural health monitoring in high-temperature environments via strain sensors
M. Jimenez, O. Ducodray, F.E. Fernández, Y. Jia
Submitted to: PR DEPSCoR
Requested: $ 1,050,000
Status: Declined