Progress in Materials Synthesis and Processing of Barium 

Titanium Oxide (BaTiO3) and Barium Strontium Titanium 

Oxide (BaTiSrO3) Films for Uncooled Infrared (IR) Detector 

Applications

by Wendy L. Sarney, Kimberley A. Olver, John W. Little

Frank E. Livingston, Krisztian Niesz, and Daniel E. Morse

ARL-TR-5853 December 2011

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Army Research Laboratory

Adelphi, MD 20783-1197

ARL-TR-5853 December 2011

Progress in Materials Synthesis and Processing of Barium 

Titanium Oxide (BaTiO3) and Barium Strontium Titanium 

Oxide (BaTiSrO3) Films for Uncooled Infrared (IR) Detector 

Applications

Wendy L. Sarney, Kimberley A. Olver, and John W. Little

Sensors and Electron Devices Directorate, ARL

Frank E. Livingston

The Aerospace Corporation

and

Krisztian Niesz and Daniel E. Morse

Institute for Collaborative Biotechnologies

University of California Santa Barbara

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Progress in Materials Synthesis and Processing of Barium Titanium Oxide 

(BaTiO3) and Barium Strontium Titanium Oxide (BaTiSrO3) Films for 

Uncooled Infrared (IR) Detector Applications

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Wendy L. Sarney, Kimberley A. Olver, John W. Little, Frank E. Livingston, 

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14. ABSTRACT

This report describes the highlights and summary of the year 2, quarter four (Y2Q4) progress for the 6.2 project “Improved 

Sensitivity Low-Cost Uncooled IR Detector Focal-Plane Arrays.” This work occurred during the January 2010–May 2010 

time period. The program goals for Y2Q4 corresponded to the continued expansion of our barium titanium oxide (BaTiO3) 

nanomaterial synthesis capabilities and deposition methods; laser-induced pyroelectric phase conversion studies and nanoscale 

characterization of the pyroelectric activation process; and fabrication of infrared (IR) test heterostructures for pyroelectrical 

analysis, along with the development of a technique for generating the requisite IR absorbing layer. 

15. SUBJECT TERMS

Uncooled infrared

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Wendy L. Sarney

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(301) 394-5761

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iii

Contents

List of Figures iv

List of Tables v

Acknowledgments vi

1. Introduction 1

2. Progress by the Aerospace Corporation (Aerospace) 2

2.1 Laser-scripted Direct-write Processing of BaTiO3 and BaSrTiO3 Thin Films for 

Electrical Analysis...........................................................................................................2

2.1.1 CAD-CAM Patterning of Pixel Arrays...............................................................2

2.1.2 Laser-induced Pixelation/Pyroelectric Activation...............................................4

2.2 Nanoscale Ferroelectric Characterization of Laser-induced Pyroelectric Activation 

in ICB Perovskite Thin Films..........................................................................................6

2.3 Measurement of Optical Band Gap Energies for CeO2-doped Perovskite Thin Films...9

3. Progress by the Institute for Collaborative Biotechnologies (ICB) 11

3.1 BaTiO3 and BaSrTiO3 Sample Preparation with Varying Compositions and 

Thickness; Surface Stabilization Studies with PVP......................................................11

4. Progress by ARL 11

4.1 Nanostructured IR Absorbing Layer Development.......................................................11

4.2 Frequency and Temperature Dependent Capacitance/Conductance Measurements.....13

4.3 Nanoscale Characterization of BSTO Particles.............................................................14

5. Plans and Goals for Year 3, Quarter 1 15

6. Metrics for Year 2 Quarter 4 16

6.1 Publications...................................................................................................................16

6.2 Conferences and Symposia ...........................................................................................16

List of Symbols, Abbreviations, and Acronyms 17

Distribution List 19
iv

List of Figures

Figure 1. Project schedule...............................................................................................................1

Figure 2. CAD illustration of a single 8x8 sub-array comprising 64 individual pixels, where 

the pixel dimensions are 100 m x 100 m with a center-to-center spacing of 200 m. 

Each 8x8 pixel sub-array is enclosed in a 2.2 mm x 2.20 mm frame for visual reference 

and deposition mask alignment..................................................................................................3

Figure 3. CAD illustration of a 4x4-(8x8) master array comprising 1024 pixels and sixteen 

8x8 pixel sub-arrays...................................................................................................................4

Figure 4. Low (left) and high (right) magnification photomicrographs acquired following 

the laserscripted pixelation of 4x4-(8x8) arrays on a Kapton film on quartz at = 

355 nm. ......................................................................................................................................5

Figure 5. Low (left) and high (right) magnification photomicrographs of an individual 8x8 

pixel array acquired following the laser-scripted patterning of a Kapton film at = 

355 nm. The inset (upper right) shows a single 100 m x 100 m pixel element. ..................5

Figure 6. Low (left) and high (right) magnification photomicrographs acquired following the 

laser scripted pixelation and pyroelectric activation of 4x4-(8x8) arrays on a pure,

undoped BaTiO3 thin-film at = 355 nm. The inset (upper right) shows a single 100 m 

x 100 m pixel element. ............................................................................................................6

Figure 7. PFM concept where the mechanical response of the thin film is measured during 

local high frequency excitation by the AFM probe tip. The topography and piezoresponse 

profiles can be simultaneously acquired and decoupled to provide surface roughness and 

ferroelectric phase contrast information. ...................................................................................7

Figure 8. PFM images (in-plane polarization) of BaTiO3 thin films that were acquired 

(a) prior to laser exposure and (b) following laser-scripted patterning and pyroelectric 

phase conversion at = 355 nm. The image sizes are 5 m x 5 m.........................................8

Figure 9. PFM images (out-of-plane polarization) of BaTiO3 thin films that were acquired 

(a) prior to laser exposure and (b) following laser-scripted patterning and pyroelectric

phase conversion at = 355 nm. The image sizes are 5 m x 5 m. (c) High 

magnification PFM image showing typical ferroelectric domain sizes of 50‒500 nm. ............8

Figure 10. Optical transmission spectra measured for pure and CeO2-doped BaTiO3 and 

BaSrTiO3 films with thicknesses of 550 nm. The inset shows the cerium (Ce4+) 

absorption spectrum.................................................................................................................10

Figure 11. The absorption (relative to a bare Si wafer) at different wavelengths as a function 

of the etch time for the currently-developed IR absorption layer............................................12

Figure 12. Transmission electron microscope (TEM) images of as-prepared BaTi 

nanoparticles stabilized with PVP. ..........................................................................................13

Figure 13. Capacitance test structure............................................................................................14

Figure 14. SEM image of an 8x8 array (one column is for ground plane contact) of 100 x 

100 m Ti/Pt-SiO2 capacitors.................................................................................................15
v

List of Tables

Table 1. Summary of the optical results for the pure and CeO2-doped BaTiO3 and BaSrTiO3

films. ........................................................................................................................................10
vi

Acknowledgments

We acknowledge support by the Institute for Collaborative Biotechnologies through grant 

DAAD19-03-D-0004 from the U.S. Army Research Office and The Aerospace Corporation 

Independent Research and Development (IR&D) Program and the Product and Development 

Program (PDP).
1

1. Introduction 

This report describes the highlights and summary of the year 2, quarter four (Y2Q4) progress for 

the 6.2 project “Improved Sensitivity Low-Cost Uncooled IR Detector Focal-Plane Arrays.” This 

work occurred during the January 2010–May 2010 time period. The project schedule for year 2 

is summarized in figure 1. 

Figure 1. Project schedule.

The program goals for Y2Q4 corresponded to the continued expansion of our barium titanium 

oxide (BaTiO3) nanomaterial synthesis capabilities and deposition methods; laser-induced 

pyroelectric phase conversion studies and nanoscale characterization of the pyroelectric 

activation process; and fabrication of infrared (IR) test heterostructures for pyroelectrical 

analysis, along with the development of a technique for generating the requisite IR absorbing 

layer. Respective team highlights include the following:
2

• Aerospace: This team conducted laser-scripted pixelation and pyroelectric activation of 

8x8 pixel subarrays and 4x4-(8x8) pixel master arrays on Institute for Collaborative 

Biotechnologies (ICB) perovskite thin-film test structures for electrical characterization by 

the U.S. Army Research Laboratory (ARL). We successfully implemented piezoresponse 

force microscopy (PFM) techniques for the nanoscale ferroelectric analysis of the laserinduced pyroelectric phase activation process in perovskite thin films. Efforts also focused 

on the optical analysis and laser scripted processing of cerium (Ce)-doped perovskite 

nanoparticle thin films for enhanced laser-induced phase conversion efficiency.

• ICB: This team extended the bio-inspired vapor diffusion catalytic methods to include the 

synthesis, functionalization and deposition of perovskite nanoparticle (BaTiO3, 

Ba1-xSrxTiO3) thin films comprising different compositions and thickness, along with the 

inclusion of Ce-dopant for enhanced ultraviolet (UV) absorption and improved laserinduced pyroelectric phase activation. Surface stabilization of the BaTiO3 nanoparticles 

was also achieved using polyvinylpyrrolidone (PVP), which was found to facilitate the 

formation of stable colloids of BaTiO3 and thereby mitigate the need for additional predeposition dispersion steps with carboxylic acids.

• ARL: This team continued with the development and refinement of the nanostructured IR 

absorbing layer, including optical absorption analysis of the nanostructures as a function of 

etch time. We established an electrical measurement system for frequency and temperature 

dependent capacitance/conductance measurements on native and laser-processed 

perovskite thin films, and fabricated 8x8 standard reference (titanium platinum [Ti/Pt]-

silicon dioxide [SiO2]) capacitor structures for baseline electrical testing. High resolution 

nanoscale characterization of re-dispersed barium strontium titanium oxide (Ba1-xSrxTiO3

or BSTO) nanoparticles was also accomplished.

All project teams have accomplished their respective planned milestones for Y2Q4. Highlights 

of the major activities are provided in sections 2 through 4.

2. Progress by the Aerospace Corporation (Aerospace) 

2.1 Laser-scripted Direct-write Processing of BaTiO3 and BaSrTiO3 Thin Films for 

Electrical Analysis

2.1.1 CAD-CAM Patterning of Pixel Arrays

Our recent efforts in year 2 have focused on the digitally scripted laser genotype direct-write 

processing of ICB-provided BaTiO3 and BaSrTiO3 thin films, with particular emphasis on the 

systematic correlation of the laser processing parameters with the (pyro)electrical properties and 

IR responsiveness of the perovskite test structures. Based on the existing and preferred ARL 

mask geometries for metal contact deposition, our recent studies include laser processing 
3

exposure patterns that comprise 8x8 pixel sub-arrays and 4x4-(8x8) pixel master arrays, as 

depicted in figures 2 and 3. Figure 2 shows a computer-assisted design (CAD) representation of a 

single 8x8 sub-array comprising 64 individual pixels, where the pixel dimensions are 100 m x 

100 m with a lateral spacing of 100 m and a center-to-center spacing of 200 m. Each pixel is 

laser patterned using a sequential line fill with a lateral step-over that is comparable to the laser 

spot size (1–3 m). Equivalent laser processing parameters—in the form of laser pulse “scripts” 

that are “linked” on a per spot basis to the tool path geometry in Cartesian space and contain 

specific information on laser pulse energy, polarization, wavelength, etc.—are applied to a series 

of four pixels so that 16 sets of laser processing parameters or “scripts” are administered to each 

64 pixel set. 

Figure 2. CAD illustration of a single 8x8 sub-array comprising 64 individual pixels, where the pixel dimensions 

are 100 m x 100 m with a center-to-center spacing of 200 m. Each 8x8 pixel sub-array is enclosed 

in a 2.2 mm x 2.20 mm frame for visual reference and deposition mask alignment.
4

Figure 3. CAD illustration of a 4x4-(8x8) master array comprising 1024 pixels and sixteen 8x8 pixel sub-arrays.

Figure 3 displays a CAD illustration of a 4x4 master array of the 8x8 sub-arrays patterned on a 

standard 10 mm x 10 mm substrate, where the 16 8x8 pixel sub-arrays are processed using 

equivalent laser parameters and correspond to a total of 1024 laser-pixelated regions per sample. 

This laser-scripted redundancy can be implemented to assess the reproducibility of pyroelectric 

phase activation and film homogeneity across the entire spin-cast perovskite sample. 

For visual reference and to facilitate the mask alignment procedure for metal contact deposition 

by ARL, each of the 16 8x8 pixel sub-arrays is enclosed by a 2.200 m x 2.200 m frame with a 

100 m width. The frames are created using laser-controlled ablative patterning and the laser 

power is set to gently ablate or desorb the perovskite thin film without damage to the underlying 

Ti/Pt:silicon (Si) substrate. The distance from the outer edge of each of the four frame corners to 

the nearest corners of the four adjacent pixels (i.e., pixels 1, 8, 57, and 64) is 350 m.

2.1.2 Laser-induced Pixelation/Pyroelectric Activation

Preliminary laser-scripted patterning and pixel array fabrication experiments were performed on 

organic polyimide thin films, such as KaptonTM. These polymer-based films retain a very low 

thermal ablation threshold and are therefore useful in verifying high precision control of incident 
5

photon flux and revealing the possible existence of excessive heat loading effects and residual 

thin-film damage. Additionally, low fluence laser exposure patterning of the organic thin films 

can be used to compare the laser-scripted pattern dimensions with the CAD-computer aided 

manufacturing (CAM) geometries and help elucidate any deviations or discrepancies. 

Figures 4 and 5 show a series of low and high magnification photomicrographs of composite 

4x4-(8x8) pixel arrays and 8x8 pixel sub-arrays that were laser patterned on a Kapton thin film. 

The 1024 individual pixel elements, along with the sub-array frames and sample identification 

label, were fabricated using laser irradiation at =355 nm, a pulse repetition rate of 80 MHz, and 

a pulse duration of 10 ps. The per-pulse fluence employed for pixelation and frame/ID were 

E=0.88 mJ·cm–2and E=2.00 mJ·cm–2, respectively. A non-contact white light optical 

profilometer was used to measure the laser-fabricated pixels, lateral pixel spacing distances, and 

frame dimensions. The standard deviation between the laser-scripted pattern dimensions and the 

user-defined CAD geometries was measured to be less than 0.05% and is consistent with the 

nominal resolution and repeatability of the XYZ air bearing translation stage encoders of 40 nm. 

Figure 4. Low (left) and high (right) magnification photomicrographs acquired 

following the laserscripted pixelation of 4x4-(8x8) arrays on a Kapton film 

on quartz at  = 355 nm.

Figure 5. Low (left) and high (right) magnification photomicrographs of an individual 

8x8 pixel array acquired following the laser-scripted patterning of a Kapton 

film at  = 355 nm. The inset (upper right) shows a single 100 m x 100 m 

pixel element.
6

During the fourth quarter, digitally scripted laser genotype processing techniques were also 

implemented to create patterned and pyroelectrically active pixel arrays on ICB undoped and 

CeO2-doped BaTiO3 and Ba1–xSrxTiO3 thin films deposited on Ti/Pt:Si substrates. Laser-scripted 

direct-write laser pulse modulation was used to convert pixelated regions (100 m x 100 m) of 

the perovskite thin-films from the pyroelectrically inactive cubic polymorph to the 

pyroelectrically active tetragonal polymorph. Figure 6 shows several photomicrographs of an 

undoped BaTiO3 thin film sample following laser pixelation and pyroelectric phase activation 

at = 355 nm (80 MHz, 10 ps full width at half maximum [FWHM]). The BaTiO3:Ti/Pt:Si 

sample was 10 mm x 10 mm in size, and contained sixteen 8x8 pixel sub-arrays for a total of 

1024 laser-pixelated regions. The pixelated regions were patterned using 16 sets of laser 

processing parameters—i.e., genotype laser pulse “scripts”—for each 8x8 pixel sub-array. The 

large laser processing parameter set will help to optimize the pyroelectric phase activation

protocol and facilitate the correlation of the laser processing conditions with the electrical 

properties of the pixel domains. The variation in pixel contrast uniformity and darkness arise 

from the diverse set of laser processing pulse scripts that were implemented for patterning, and 

do not correspond to inhomogeneities or variegations in the perovskite thin film.

A set of laser-pixelated BaTiO3:Ti/Pt:Si and BaTiO3-CeO2:Ti/Pt:Si samples have been shipped 

to ARL, and electrical analysis and pyroelectrical responsiveness tests are now underway.

Figure 6. Low (left) and high (right) magnification photomicrographs acquired 

following the laser scripted pixelation and pyroelectric activation of 4x4-

(8x8) arrays on a pure, undoped BaTiO3 thin-film at  = 355 nm. The inset 

(upper right) shows a single 100 m x 100 m pixel element.

2.2 Nanoscale Ferroelectric Characterization of Laser-induced Pyroelectric Activation in 

ICB Perovskite Thin Films

Our fourth quarter efforts for year 2 have also focused on the nanoscale characterization of the 

ferroelectric properties of laser-processed barium titanate thin films. We are continuing to 

develop the use of scanning PFM techniques for nanoscale analysis of the laser-induced BaTiO3

cubic-to-tetragonal pyroelectric phase transformation, along with an assessment of the relative 
7

magnitudes of the ferroelectric phase contrasts of the respective nonferroelectric (nFE)/

ferroelectric (FE) domains. As noted in our prior quarterly reports, PFM permits direct imaging 

of ferroelectric domain structures with nanometer-scale resolution (~3–10 nm) and is ideally 

suited for post-laser-processing examination of the perovskite thin films due to its relative 

insensitivity to topography and ease of implementation. We have successfully augmented and 

tailored our traditional atomic force microscopy (AFM) instrument for PFM operation, where the 

mechanical response of the sample is measured during local electrical excitation by the AFM 

probe tip. A modulated AC voltage is applied between the underlying Ti/Pt:Si substrate and 

conductive AFM/PFM tip during contact mode scanning. Using lock-in amplifier techniques, the 

local electromechanical displacement can be decoupled from the topographical displacement via 

the phase shift between the rapidly oscillating ac field and the slow cantilever displacement 

feedback (figure 7). The static cantilever deflection corresponds to the surface profile variations 

and topography, while the modulated cantilever oscillations are related to the piezoresponse of 

the perovskite sample.

Figure 7. PFM concept where the mechanical response of the thin film is measured during local high frequency 

excitation by the AFM probe tip. The topography and piezoresponse profiles can be simultaneously 

acquired and decoupled to provide surface roughness and ferroelectric phase contrast information.

Figure 8a displays a PFM image of a BaTiO3 thin-film sample that was acquired prior to laserscripted exposure at  = 355 nm and shows no in-plane (polarization parallel to sample surface) 

ferroelectric phase contrast for the as-received cubic crystalline BaTiO3 thin film. Following 

laser-scripted exposure at =355 nm (~1x106pulses, per-pulse fluence = 2.5 mJ·cm–2), the PFM 

results in figure 8b reveal appreciable ferroelectric phase contrast and confirm successful 

pyroelectric conversion to the tetragonal phase. Figures 9a and 9b show similar PFM contrast 

behavior for the unexposed and laser-processed BaTiO3 thin film, where the measured 
8

piezoresponse signals correspond to polarization dipoles that are aligned perpendicular to the 

sample surface. The laser-structured and pyroelectrically activated regions appear uniform and 

retain ferroelectric domain sizes of ~50–500 nm.

Figure 8. PFM images (in-plane polarization) of BaTiO3 thin films that were acquired (a) prior 

to laser exposure and (b) following laser-scripted patterning and pyroelectric phase 

conversion at  = 355 nm. The image sizes are 5 m x 5 m.

Figure 9. PFM images (out-of-plane polarization) of BaTiO3 thin films that were acquired 

(a) prior to laser exposure and (b) following laser-scripted patterning and pyroelectric 

phase conversion at  = 355 nm. The image sizes are 5 m x 5 m. (c) High 

magnification PFM image showing typical ferroelectric domain sizes of 50‒500 nm.
9

2.3 Measurement of Optical Band Gap Energies for CeO2-doped Perovskite Thin Films

Expanding upon our prior detailed studies concerning the influence of perovskite film thickness 

on the intrinsic optical bandgap energies of the nanostructured films, we are now examining the 

optical properties of doped perovskite nanoparticle thin films. The intent is to incorporate the 

appropriate photo-active constituents (e.g., CeO2) into the perovskite nanoparticles to enhance 

the UV absorption in the native thin films and thereby improve the laser-induced pyroelectric 

phase conversion efficiency and reduce the incident laser energy required for pyroelectric 

activation. The prudent selection of dopant type and concentration will also facilitate the finetuning of the electrical properties of the perovskite thin films and may enable a broader range of 

pyroelectric responsiveness.

Our prior optical transmission studies indicated that for the thicker micron-sized BaTiO3 films 

(>1 m), inter-band transitions occur at wavelengths of λ<450‒500 nm, and the transmission 

falls rapidly to less than 10% at wavelengths of λ<400 nm. In contrast, inter-band transitions 

occur at wavelengths of λ<300 nm for the thinner 200–500 nm-thick films, and the 10% cut-off 

occurs at UV wavelengths of <260 nm. Consequently, the absolute bandgap energies for the 

thinner and functionalized BaTiO3 films are significantly blue-shifted compared with the thicker 

micrometer scale films. The calculated bandgap energies displayed the following trend with film

thicknesses denoted in parentheses: E=3.27±0.4 eV (3–5 m), 3.84±0.2 eV (0.5–1 m), 

3.95±0.1 eV (300–500 nm), and 4.12±0.05 eV (200–300 nm). The film-thickness dependent 

behavior of the bandgap energy severely impacts the selection of the appropriate laser processing 

wavelengths and other laser parameters that are requisites for efficient laser energy-material 

coupling and optimal pyroelectric phase conversion. For low-cost rapid prototype manufacture of 

the IR sensor components, the use of a readily available commercial solid-state laser system is 

preferred.

Accordingly, and with our ICB collaborators, we have explored the effect of incorporating CeO2

into the perovskite nanoparticles during synthesis as a means to red-shift the absorption band 

edge of the nanostructured films, thereby lowering the optical bandgap energies and reducing the 

total incident laser irradiation required for complete pyroelectric phase transformation. Figure 9 

shows the optical transmission spectra that were measured for pure BaTiO3 and CeO2-doped 

(0.03 wt%) BaTiO3 thin films. The BaTiO3 samples correspond to 1-layer spin coatings with a 

nominal film thickness of ~550 nm. The optical results presented in figure 10 are encouraging,

and reveal that low impurity doping with CeO2 can be used to reduce the UV transmission for 

<350 nm and induce a red-shift in the band gap energy. For example, the bandgap energy and 

10% T cut-off wavelength for the pure undoped 550-nm-thick BaTiO3 films were measured to be 

E=4.02±0.05 eV and =264.5 nm, respectively. However, the bandgap energy has been reduced to 

E=3.87±0.05 eV and the 10% T cut-off has been shifted to a longer wavelength of  = 300 nm 

for the CeO2- doped BaTiO3 film of comparable thickness. The optical results for the pure and

CeO2-doped BaTiO3 and BaSrTiO3 films are summarized in table 1.
10

Figure 10. Optical transmission spectra measured for pure and CeO2-doped BaTiO3 and 

BaSrTiO3 films with thicknesses of 550 nm. The inset shows the cerium (Ce4+) 

absorption spectrum.

Table 1. Summary of the optical results for the pure and CeO2-doped BaTiO3 and BaSrTiO3 films.

The inset in figure 10 shows the absorption spectrum that is associated with the Ce chromophore, 

and was derived from the difference between the CeO2-doped and undoped perovskite thin-film. 

The primary spectral feature is an absorption peak located near =230–235 nm and corresponds to 

the Ce4+ oxidation state of Ce. A broad featureless absorption is also observed and extends 

beyond 250 nm. There is a rapid absorption fall-off for wavelengths >300 nm, and this behavior 

is likely responsible for the negligible change in absorption characteristics for the thicker 

(>1 m) CeO2-doped BaSrTiO3 films.
11

3. Progress by the Institute for Collaborative Biotechnologies (ICB)

3.1 BaTiO3 and BaSrTiO3 Sample Preparation with Varying Compositions and

Thickness; Surface Stabilization Studies with PVP

The ICB efforts focused on three critical areas regarding perovskite sample synthesis and thinfilm preparation:

• Based on our previous experiences, samples with different compositions (BaTiO3, 

Ba1–xSrxTiO3), with and without using additional Ce dopant were synthesized, 

functionalized with oleic acid and deposited from colloidal suspensions onto different types 

of substrates (quartz, Pt/Ti:Si). The depositions were carried out by layer-by-layer spinning 

using different numbers of deposition/annealing cycles to vary the perovskite film 

thickness. The samples were then sent to our collaborating partners at Aerospace and ARL 

for further investigations.

• Comprehensive sets of pure (undoped) and CeO2-doped (0.03 wt%) BaTiO3 and

Ba1–xSrxTiO3 thin films were prepared and sent to Aerospace for laser-scripted processing 

and pixelation/activation studies, as well as optical analysis. These samples included 

systematic variation of the film thickness from 550 nm (1-layer spin coat) to 1440 nm 

(3-layer spin coat). BaTiO3 and Ba1–xSrxTiO3 samples—in their nascent nanoparticle 

form—were synthesized and sent to ARL for thin-film test structure fabrication and 

electrical characterization.

• Experiments were conducted using PVP as surface stabilizing agent to form BaTi

nanoparticles as stable colloids. Performing the synthesis this way the additional stabilizing 

step with oleic acid before depositions could be avoided. Adding PVP to the BaTi double 

alkoxide molecules dissolved in butanol (2:1 molar ratio of PVP-monolayer to BaTiprecipitate) indeed resulted in the formation of BaTiO3 nanocrystals stable against 

aggregation (see figure 10).

4. Progress by ARL

4.1 Nanostructured IR Absorbing Layer Development

As explained in the prior quarter’s report, thermal detectors require a layer similar to a thin 

coating of black paint that absorbs a wide range of wavelengths and heats up. The heat is 

transferred to the BT layer and the pyroelectric voltage is generated. We are developing a lowcost technique that is temperature-compatible with the bio-inspired BaTiO3 films and with 

readout integrated circuit (ROIC) technology. The details of the process were given in the 
12

previous quarterly report, but the main features of the technique involve forming nanoparticles of 

metal (e.g., gold [Au]) on an evaporated Si film and subsequently etching the Si with a dry etch. 

The Au particles mask the surface resulting in nanopilars of Si that have been shown to trap and 

absorb light strongly. We formed the particles on a Si wafer by heating a 5-nm evaporated Au 

film to 350 °C and etched pieces in a carbon tetrafluoride (CF4) plasma for various times.

Figure 11 shows the absorption (relative to a bare Si wafer) at different wavelengths as a 

function of the etch time. Note that for this first set of samples, the highest absorption was 

obtained for a 20 s and was peaked at 1.5 m wavelength. This wavelength is ideal for enhancing 

the near IR photoresponse of solar cells, and we are transitioning this technology to our quantum 

dot solar cell program. 

Figure 11. The absorption (relative to a bare Si wafer) at different wavelengths as a function of 

the etch time for the currently-developed IR absorption layer.

We are modifying the nanostructure to push the wavelength into the thermal imaging part of the 

spectrum (3–12 m) and maximize the absorption strength. A new set of samples is being 

prepared with larger scale and deeper nanostructures and the results will be given in a subsequent 

report.
13

4.2 Frequency and Temperature Dependent Capacitance/Conductance Measurements

We have begun establishing a measurement system that will characterize the temperature and 

frequency dependence of the capacitance/conductance of the BaTiO3 films (in order to determine 

the pyroelectric properties of the films). A Hewlett Packard 4280A precision fixed frequency 

(1 MHz) capacitance meter and a variable frequency (1 Hz–1 MHz) function 

generator/quadrature lock-in amplifier is used to measure the capacitance/conductance of our test 

samples. The system has been calibrated with a precision capacitance bridge. A variable 

temperature sample mount will be added soon.

Figures 12 and 13 show an 8 x 8 array (one column is for ground plane contact) of Ti/Pt–SiO2 

capacitors (100 x 100 microns) that we fabricated as a standard reference for the measurement 

system (this test structure has a known capacitance). These samples have the same configuration 

as the laser-modified BT films.

TiPt

SiO2

TiPt

SiO2 coated Si wafer

92 microns

100 microns

Figure 12. Transmission electron microscope (TEM) images of 

as-prepared BaTi nanoparticles stabilized with PVP.
14

Figure 13. Capacitance test structure.

4.3 Nanoscale Characterization of BSTO Particles

In this quarter, the ICB sent vials of BSTO nanoparticles to ARL. As detailed in the prior report, 

BSTO has several desirable properties for both IR detector and laser processing applications.

These include a relatively large dielectric constant, good pyroelectric response near room 

temperature, low dielectric loss and leakage current, and phase transition temperature 

controllable by the amount of strontium (Sr) incorporated. 

The nanoparticles were capped with oleic acid, and then were precipitated and dried. At ARL,

we re-dispersed the nanoparticles into isopropanol to prepare TEM grids. 

Figure 14 is a TEM image of the barium strontium titanate (BST) powder (KN238). As with the 

previously examined BaTiO3 nanoparticles, the TEM images show high-quality, singlecrystalline nanoparticles. The particles in this particular vial measured around 6–7 nm.
15

Figure 14. SEM image of an 8x8 array (one column 

is for ground plane contact) of 100 x 100 m

Ti/Pt-SiO2 capacitors.

5. Plans and Goals for Year 3, Quarter 1

In the coming quarter, we will continue to expand our nanomaterial synthesis capabilities, laser 

processing techniques and pyroelectric phase conversion studies, and perovskite thin-film

electrical characterization efforts:

• ICB: This team will finalize construction of the large-scale reactor and pursue trials of 

continuous-flow production with automated control, further investigate the in situ

stabilization of BaTiO3 nanoparticles using PVP, and continue to provide pure and doped 

BaTiO3 and Ba1–xSrxTiO3 nanoparticle thin films to Aerospace and ARL for laser-scripted 

pixelation/pyroelectric activation studies and electrical characterization of thin-film test 

structures.

• Aerospace: This team will continue fabrication of laser-pixelated perovskite thin-film array 

test structures for electrical analysis and IR responsiveness measurements by ARL;

measure local PFM hysteresis curves for unexposed and laser-processed perovskite thin

films to extract piezoelectric constants and assess uniformity of phase conversion and 

intrinsic/residual stresses in the IR test structures; and explore the laser scripted processing 

of the IR absorbing overlayer to induce patterned pyroelectric phase conversion of the

underlying perovskite thin film.

• ARL: This team will modify the IR nanostructures that comprise the absorbing layer to shift 

absorption into the thermal imaging region (3–12 m) and optimize the absorption strength 

and integrate variable temperature sample mount into electrical measurement system for 

frequency and temperature dependent capacitance/conductance studies on native and laseractivated BaTiO3 and Ba1–xSrxTiO3 thin-film test structures.
16

6. Metrics for Year 2 Quarter 4

6.1 Publications

1. Niesz, K.; Morse, D. E. Sonication-accelerated Catalytic Synthesis of Oxide Nanoparticles. 

Nano Today 2010, 5, 99–105. 

6.2 Conferences and Symposia

1. Livingston, F. E.; Sarney, W. L.; Niesz, K.; Morse, D. E. Laser Direct-write Activation of 

Perovskite Nanoparticle Films for Thermal Detector Applications. Presented Poster at the

National Defense Industrial Association (NDIA) – 11th Annual Science & Engineering

Technology Conference/DoD Tech. Exposition, Charleston, SC, Apr. 12–15, 2010. 

2. Niesz, K.; Reji, C.; Vargas, R. C.; Neilson, J.; Ould Ely, T.; Livingston, F. E.; Sarney, W. L.;

Morse, D. E. Fabrication of Simple and Complex Oxide Nanoparticles by Sonication 

Assisted Vapor Diffusion Catalysis: Synthesis, Characterization and Applications. Presented 

poster at the 239th ACS National Meeting and Exposition, San Francisco, Mar. 21, 2010.

3. Livingston, F. E.; Sarney, W. L.; Niesz, K.; Little, J. W.; Olver, K. A.; Morse, D. E. Laser 

Tailoring of Bio-inspired Thin-films for Improved Sensitivity, Low-cost Uncooled IR

Detector FPAs. Presented poster at the 2010 Institute for Collaborative Biotechnologies

(ICB) Army-Industry Collaboration Conference, UC Santa Barbara, CA, Mar. 3–4, 2010.
17

List of Symbols, Abbreviations, and Acronyms

AFM atomic force microscopy

ARL U.S. Army Research Laboratory 

Au gold 

BaTiO3 barium titanium oxide

BST barium strontium titanate

BSTO barium strontium titanium oxide 

CAD computer-assisted design

CAM computer aided manufacturing

Ce cerium

CF4 carbon tetrafluoride 

FE ferroelectric

FWHM full width at half maximum

ICB Institute for Collaborative Biotechnologies

IR infrared

IR&D Independent Research and Development

nFE nonferroelectric

PDP Product and Development Program

PFM piezoelectric force microscopy

PVP polyvinylpyrrolidone

ROIC readout integrated circuit 

Si silicon

SiO2 silicon dioxide

Sr strontium

TEM transmission electron microscope
18

Ti/Pt titanium platinum

UV ultraviolet

Y2Q4 year two, quarter four
19

NO. OF

COPIES ORGANIZATION

1 ADMNSTR

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CMND

ARMAMENT RSRCH DEV & ENGRG 

CTR

ARMAMENT ENGRG & TECHNLGY 

CTR

ATTN AMSRD AAR AEF T J MATTS

BLDG 305

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1 COMMANDER

US ARMY RDECOM

ATTN AMSRD AMR 

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1 US GOVERNMENT PRINT OFF

DEPOSITORY RECEIVING SECTION

ATTN MAIL STOP IDAD J TATE

732 NORTH CAPITOL ST NW

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2 INSTITUTE FOR COLLABORATIVE 

BIOTECHNOLOGIES UNIVERSITY 

OF CALIFORNIA, SANTA BARBARA

ATTN D MORSE

ATTN K NIESZ

SANTA BARBARA CA 93106-5100

1 THE AEROSPACE CORPORATION

MICRO/NANOTECHNOLOGY

DEPARTMENT

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ATTN RDRL SEE I K OLVER

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INTENTIONALLY LEFT BLANK.