Infrared (IR) technology has been widely used in biomedical imaging, non-destructive inspection, environmental monitoring and optical communication. The important mid-far-IR photodetectors are mainly limited to compound semiconductors that normally requires intricate crystal growth process and operation at cryogenic cooling, which results in bulky and expensive system. The emergence of two-dimensional (2D) transition metal dicharcogenides (TMDCs) semiconductors offers new opportunities for optoelectronic applications for their strong quantum confinement and the easiness in forming heterostructures enabled by the out-of-plane van der Waals bonding. The interlayer excitons formed in a TMDC heterostructure possess the inherent large exciton binding from their parent materials and the flexibility in exciton energy tuning. This offers opportunity to realize excitonic devices operable at room temperature at mid- to far-IR range, which are challenging for intraband exciton based 2D devices. This paper will introduce photodetection in mid-IR range by manipulating interlayer excitons generated between two specifically selected TMDCs with appropriate band alignment. The unique band structure in the heterostructure allows the absorption band to be tuned and extended to 20μm under a modest electric field, far beyond the cutoff wavelength of 2D black phosphorous or 2D black arsenic phosphorous. The ab initio simulation suggests the sizeable charge delocalization and accumulation at interface result in greatly enhanced oscillator strength of interlayer excitons and high responsivity of the photodetector. The results provide a promising platform for realizing robust tunable room temperature operating IR photodetectors.
Optical sensing technology is critical for optical communication, defense and security applications.
Advances in optoelectronics materials in the UV, Visible and Infrared, using nanostructures, and use of novel
materials such as CNT and Graphene have opened doors for new approaches to apply device design
methodology that are expected to offer enhanced performance and low cost optical sensors in a wide range of
applications.
This paper is intended to review recent advancements and present different device architectures and
analysis. The chapter will briefly introduce the basics of UV and Infrared detection physics and various wave
bands of interest and their characteristics [1, 2]
We will cover the UV band (200-400 nm) and address some of the recent advances in nanostructures
growth and characterization using ZnO/MgZnO based technologies and their applications. Recent
advancements in design and development of CNT and Graphene based detection technologies have shown
promise for optical sensor applications. We will present theoretical and experimental results on these device
and their potential applications in various bands of interest.
In recent years a substantial amount of research has focused on the mechanical and electro-optical
properties of ZnO nanowires (NWs). Initially, a significant portion of the work involved
developing either single NWs or NW arrays for photo detection at ultraviolet (UV) wavelengths,
and the innovation and performance of such devices have subsequently and progressively
advanced. In addition, several new areas of ZnO NW research have since appeared, with energy
harvesting at the forefront. The piezoelectric potential of nanowires has been a source of
considerable interest, and novel concepts have been reported, including devices that convert
thermal energy and sound waves into electrical power. In this paper we will address recent work
(mostly published within the past couple years) on both ZnO NW based UV photodetectors and
energy harvesting, seeking in the process to identify notable and innovative features that are
advancing ZnO NW technology and nanodevice performance.
Next Generation EO/IR focal plane arrays using nanostructure materials are being developed for a variety
of Defense and Homeland Security Sensor Applications. Several different nanomaterials are being
evaluated for these applications. These include ZnO nanowires, GaN Nanowires and II-VI nanowires,
which have demonstrated large signal to noise ratio as a wide band gap nanostructure material in the UV
band. Similarly, the work is under way using Carbon Nanotubes (CNT) for a high speed detector and focal
plane array as two-dimensional array as bolometer for IR bands of interest, which can be implemented for
the sensors for homeland security applications.
In this paper, we will discuss the sensor design and model predicting performance of an EO/IR focal plane
array and Sensor that can cover the UV to IR bands of interest. The model can provide a robust means for
comparing performance of the EO/IR FPA's and Sensors that can operate in the UV, Visible-NIR (0.4-
1.8μ), SWIR (2.0-2.5μ), MWIR (3-5μ), and LWIR bands (8-14μ). This model can be used as a tool for
predicting performance of nanostructure arrays under development. We will also discuss our results on
growth and characterization of ZnO nanowires and CNT's for the next generation sensor applications. We
also present several approaches for integrated energy harvesting using nanostructure based solar cells and
Nanogenerators that can be used to supplement the energy required for nanostructure based sensors.
Next Generation EO/IR focal plane arrays using nanostructure materials are being developed for a variety
of Defense Applications including Unattended Ground Sensor Applications. Several different
nanomaterials are being evaluated for these applications. These include ZnO nanowires that have
demonstrated large signal to noise ratio as a wide band gap nanostructure material in the UV band.
Similarly, the work is under way using Carbon Nanotubes (CNT) for a high speed detector and focal plane
array as bolometer for IR bands of interest, which can be implemented for the unattended ground sensor
applications.
In this paper, we will discuss the sensor design and model predicting performance of an EO/IR focal plane
array that can cover the UV to IR bands of interest. The model can provide a robust means for comparing
performance of the EO/IR FPA's and Sensors that can operate in the UV, Visible-NIR (0.4-1.8μ), SWIR
(2.0-2.5μ), MWIR (3-5μ), and LWIR bands (8-14μ). This model can be used as a tool for predicting
performance of nanostructure arrays under development. We will also discuss our results on growth and
characterization of ZnO nanowires and CNT's for the next generation sensor applications. Several
approaches for compact energy harvesting using nanostructures will be discussed.
Ultra-high, broadband transmittance through coated glass windows is demonstrated over a wide range of incident angles. Near perfect 100% transmittance through a glass substrate has been achieved over select
spectral bands, and the average transmittance increased to over 97% for photons incident between 0° and 75° with wavelengths between 400 nm and 1600 nm. The measured improvements in transmittance result from coating the windows with a new class of materials consisting of porous SiO2 nanorods.
E-O Sensors are being developed for a variety of Military Systems Applications. These include UV, Visible,
SWIR, MWIR and LWIR Nano Sensors. In this paper, we will discuss growth and characterization of ZnO
Nanowires on a variety of substrates that include Silicon, ZnO and flexible substrates.
The critical technologies being developed include ZnO nanostructures with wide band gap for UV detection
for a variety of threat warning applications. We will present experimental results on the structural, electrical
and optical properties of ZnO nanowire for UV detectors. Experimental results on ZnO based nanostructures
demonstrate enhanced UV sensitivity and path forward for larger arrays.
EO/IR Nanosensors are being developed for a variety of Defense and Commercial Systems
Applications. These include UV, Visible, NIR, MWIR and LWIR Nanotechnology based
Sensors. The conventional SWIR Sensors use InGaAs based IR Focal Plane Array (FPA) that
operate in 1.0-1.8 micron region. Similarly, MWIR Sensors use InSb or HgCdTe based FPA that
is sensitive in 3-5 micron region. More recently, there is effort underway to evaluate low cost
SiGe visible and near infrared band that covers from 0.4 to 1.6 micron.
One of the critical technologies that will enhance the EO/IR sensor performance is the
development of high quality nanostructure based antireflection coating. Prof. Fred Schubert and
his group have used the TiO2 and SiO2 graded-index nanowires / nanorods deposited by obliqueangle
deposition, and, for the first time, demonstrated their potential for antireflection coatings by
virtually eliminating Fresnel reflection from an AlN-air interface over the UV band. This was
achieved by controlling the refractive index of the TiO2 and SiO2 nanorod layers, down to a
minimum value of n = 1.05, the lowest value so far reported
In this paper, we will discuss our modeling approach and experimental results for using oblique
angle nanowires growth technique for extending the application for UV, Visible and NIR sensors
and their utility for longer wavelength application. The AR coating is designed by using a genetic
algorithm and fabricated by using oblique angle deposition. The AR coating is designed for the
wavelength range of 400 nm to 2500 nm and 0° to 40° angle of incidence. The measured average
optical transmittance of an uncoated glass substrate between 1000 nm and 2000 nm is improved
from 92.6% to 99.3% at normal incidence by using a two-layer nanostructured AR coating
deposited on both surfaces of the glass substrate.
Next Generation EO/IR focal plane arrays using nanostructure materials are being developed for a variety of Defense Applications including Unattended Ground Sensor Applications. These include ZnO nanowires that have demonstrated large signal to noise ratio as a wide band gap nanostructure material in the UV band. Similarly, the work is under way using Carbon Nanotubes (CNT) for a high speed detector and focal plane array as bolometer for IR bands of interest, which can be implemented for the unattended ground
sensor applications.
In this paper, we will discuss the sensor design and model predicting performance of an EO/IR focal plane array that can cover the UV to IR bands of interest. The model can provide a robust means for comparing performance of the EO/IR FPA's and Sensors that can operate in the UV, Visible-NIR (0.4-1.8μ), SWIR (2.0-2.5μ), MWIR (3-5μ), and LWIR bands (8-14μ). This model can be used as a tool for predicting performance of nanostructure arrays under development. We will also discuss our results on growth and
characterization of ZnO nanowires and CNT's for the next generation sensor applications.
EO/IR Nanosensors are being developed for a variety of Defense and Commercial Systems Applications.
These include UV, Visible, NIR, MWIR and LWIR Nanotechnology based Sensors. The conventional
SWIR Sensors use InGaAs based IR Focal Plane Array (FPA) that operate in 1.0-1.8 micron region.
Similarly, MWIR Sensors use InSb or HgCdTe based FPA that is sensitive in 3-5 micron region. More
recently, there is effort underway to evaluate low cost SiGe visible and near infrared band that covers from
0.4 to 1.6 micron.
One of the critical technologies that will enhance the EO/IR sensor performance is the development of high
quality nanostructure based antireflection coating. Prof. Fred Schubert and his group have used the TiO2
and SiO2 graded-index nanowires / nanorods deposited by oblique-angle deposition, and, for the first time,
demonstrated their potential for antireflection coatings by virtually eliminating Fresnel reflection from an
AlN-air interface over the UV band. This was achieved by controlling the refractive index of the TiO2 and
SiO2 nanorod layers, down to a minimum value of n = 1.05, the lowest value so far reported.
In this paper, we will discuss our modeling approach and experimental results for using oblique angle
nanowires growth technique for extending the application for UV, Visible and NIR sensors and their utility
for longer wavelength application.
EO/IR Nanosensors are being developed for a variety of Defense and Commercial Systems
Applications. These include UV, Visible, NIR, MWIR and LWIR Nanotechnology based
Sensors. The conventional SWIR Sensors use InGaAs based IR Focal Plane Array (FPA) that
operate in 1.0-1.8 micron region. Similarly, MWIR Sensors use InSb or HgCdTe based FPA that
is sensitive in 3-5 micron region. More recently, there is effort underway to evaluate low cost
SiGe visible and near infrared band that covers performance up to 1.6 micron.
The use of Nanowires for developing high quality antireflection coatings that allows minimizing
the reflection loss is discussed. We have explored the possibility of using nanostructures grown
by oblique angle deposition technique. A graded-index coating with different index profiles has
been investigated for broadband antireflection properties, particularly with air as the ambient
medium. In this paper, we present, modeling and experimental results for nanostructure
AR coatings for UV, Visible and calculations for NIR sensors and also their utility for
longer wavelength application.
EO/IR Sensors have been developed for a variety of Military Systems Applications.
These include UV, Visible, SWIR, MWIR and LWIR Sensors. The conventional SWIR Sensors
using InGaAs Focal Plane Array (FPA) can operate in 0.4 - 1.8 micron region. Similarly, MWIR
Sensors use InSb and HgCdTe based FPA's that are sensitive in 3-5 and 8-14 micron region.
DOD investments in the last 10 years have provided the necessary building blocks for the IR
Sensors that are being deployed in the field.
In this paper, we discuss recent developments and work under way to develop Next
Generation nanostructure based EO/IR detectors that can potentially cover UV, Visible and IR
regions of interest. The critical technologies being developed include ZnO nanostructures with
wide band gap for UV detection and Carbon Nanostructures that have shown the feasibility for IR
detection. Experimental results on ZnO based nanostructures demonstrate enhanced UV
sensitivity and path forward for larger arrays. Similarly, recent works on carbon nanostructures
have shown the feasibility of IR detection. Combining the two technologies in a sensor can
provide multispectral capability.
Next Generation EO/IR Sensors using Nanostructures are being developed for a variety of Defense
Applications. In addition, large area IRFPA's are being developed on low cost substrates. In this paper, we will discuss
the capabilities of a EO/IR Sensor Model to provide a robust means for comparing performance of infrared FPA's and
Sensors that can operate in the visible and infrared spectral bands that coincide with the atmospheric windows - UV,
Visible-NIR (0.4-1.8μ), SWIR (2.0-2.5μ), MWIR (3-5μ), and LWIR (8-14μ).
The model will be able to predict sensor performance and also functions as an assessment tool for single-color
and for multi-color imaging. The detector model can also characterize ZnO, Si, SiGe, InGaAs, InSb, HgCdTe and
Nanostructure based Sensors. The model can predict performance by also placing the specific FPA into an optical
system, evaluates system performance (NEI, NETD, MRTD, and SNR). This model has been used as a tool for
predicting performance of state-of-the-art detector arrays and nanostructure arrays under development. Results of the
analysis can be presented for various targets for each of the focal plane technologies for a variety of missions.
In this Paper we present growth and characterization of ZnO nanowires on wideband gap substrates,
such as SiC and GaN. Experimental results on the ZnO nanowires grown on p-SiC and p-GaN are
presented with growth morphology, structure analysis, and dimensionality control. We also present
experimental results on individual nanowires such as I-V measurements and UV sensitivity
measurements with use of polymer coating on ZnO nanowires. The ZnO nanowires can be used for a
variety of nanoscale optical and electronics applications.
The ZnO nanostructures can be implemented in optoelectronic applications, piezoelectric
pressure sensors, Spintronic devices, transducers and biomedical applications [1-8]. Use of these
nanostructures, will also allow building of nanoscale nanosensors, nanocantilevers, field-effect
transistors and nanoresonators for a variety of military, homeland security and, commercial
applications. In this paper we review growth and characterization of ZnO nanowires on a variety
of substrates. Experimental results on the ZnO nanowires grown on GaN and SiC are presented
with growth morphology, structure analysis, and dimensionality control. We also discuss Raman
and micro-Raman spectroscopy for characterization of ZnO nanostructures.
In this Paper we present growth and characterization of ZnO nanowires on a variety of substrates, such as Silicon and SiC. Experimental results on the ZnO nanowires grown on Si and SiC are presented with growth morphology, structure analysis, and dimensionality control. The ZnO nanowires can be used for a variety of nanoscale optical and electronics sensors.
We report on a bridge structure PZT [Pb(ZrxTi1- x)O3] thin film microtransducer with proof mass that has been fabricated successfully at the Microtechnology Laboratory (MTL) of the University of Minnesota. The bridge microtransducer is made on silicon wafer using bulk micromachining of microelectromechanical systems (MEMS) and special techniques for deposition of a PZT thin film. The bridge is 300 micrometers wide, 1000 micrometers long, and a few micrometers thick. A proof mass made from the silicon wafer is loaded under the bridge at the central region, its area is 300 X 300 square micrometers and its thickness is 475 micrometers (same as the wafer). Used as an accelerometer, the microtransducer is calibrated using a Vibration Test Systems (VTS), which is a commercial accelerometer calibration instrument. The sensitivity of the microtransducer is constant over the range of frequencies from zero to 10 kHz, 240(mu) V/g at 0.5g with a dc bias voltage of 0.2 volts and a deviation of 5%. The Brownian thermal noise equivalent acceleration is 9.072(mu) g/(root)Hz. Design of a bridge structure with mass loading is modeled using ANSYS. Simulation analysis shows that the fundamental natural frequency of the microtransducer is 11.352 kHz, which is close to the measured resonant frequency of 12.28 kHz.
The US Office of Naval Research is funding a multi- disciplinary team to consolidate progress made in earlier programs towards self-contained microsensors to be embedded in a composite structure and queried using methods that methods that do not require physical connections. The sensors are to be left in place for the lifetime of the structure, are powered by the querying apparatus, and require no penetrations through the surface of the structure. This paper describes the integrated approach taken to realize the goal of an interrogatable strain rosette that is embedded 0.25' below the surface of a graphite composite plate. It also describes the progress to date of the sensor system itself.
Joel Dubow, Wenjia Zhang, Yijang Lu, Jeremy Bingham, F. Syammach, Donald Krantz, John Belk, Paul Biermann, Ramesh Harjani, Susan Mantell, Dennis Polla, Philip Troyk
Pressed PZT Piezoelectric disks were embedded in a range of materials and their properties monitored under a wide range of conditions. The output depends on the temperature and pressure exerted on the PZT by the surrounding material and by the mechanical impedance mismatch between the embedded PZT and the surroundings. By monitoring the `Q' of the PZT (the ratio of energy stored to energy dissipated) it was found that the PZT discs could be used as cure monitors, strain gauges, and as embedded dynamic mechanical property estimators. This latter property is a means of gauging the `health of the material', and its degradation with time. These sensors were part of the MTS/US Navy embedded sensor program, so the sensors could be addressed and read remotely. The techniques, the data and the applications are discussed in this paper.
Sensors embedded in structural composites have been a topic of research in recent years. Embedded sensors can be used to monitor and optimize the manufacturing process, to monitor performance during use, and for structural health monitoring in high-performance applications. For several years, embedded optical fibers were the predominant type of sensor. There are well-known reasons that optical fiber sensors have not yet been fully embraced in industry including primarily the cost of equipment and sensors, the fragility of the optical fiber itself, and the need to provide ingress and egress from the structure. Recent work by the authors and others has produced prototype wireless electronic sensors of various types that address these shortcomings. The US Office of Naval Research is funding a multi-disciplinary team to consolidate progress made in earlier programs towards self- contained microsensors to be embedded in a composite structure and queried using methods that do not require physical connections. The sensors are to be left in place for the lifetime of the structure, are powered by the querying apparatus, and require no penetrations through the surface of the structure. This paper describes the integrated approach taken to realize the goal of an interrogatable strain rosette that is embedded 0.25' into a graphite composite plate. It also describes the progress to date of the sensor system itself.
Piezoelectric thin films have been integrated with silicon microfabrication methods in the formation of both sensors and actuators (commonly called MEMS). This work describes several applications of merged PZT thin film technology, solid-state micromachining, and silicon-based integrated circuit fabrication methods in the formation of acoustic emission microsensors, cantilever microbeam accelerometers, diaphragm micropumps, and cantilever microvalves. When combined with CMOS-based integrated circuits, these sensors and actuators form smart microelectromechanical systems with potentially low-cost and high performance.
Solid-state micromachining techniques have been used in the fabrication of low-stress silicon nitride thermal isolation structures for pyroelectric detectors. Thin films of PbTiO(subscript 3/ and other related Perovskite materials are integrated on these structures. Process compatibility with NMOS electronics is demonstrated.
Ferroelectric thin films have been integrated with silicon-based microelectromechanical systems, commonly called MEMS. Several thin films of the PZT family have been used in the formation of both microsensors and microactuators in processes compatible with silicon nitride, surface-micromachined, membranes and analog CMOS technology. Back-end micromachining of MEMS structures based on PZT-type electroceramic thin films is described. Several ferroelectric MEMS examples are described including (1) cantilever beam micro- accelerometer, (2) acoustic pressure sensor, (3) uncooled pyroelectric infrared imaging array, (4) integrated acoustic sensor, (5) micro- positioner, and (6) simple cantilever flap actuators. Major issues of merging technologies with ferroelectric thin films with microelectromechanical structures and on-chip electronics are described.
Piezoelectric thin film actuator-based fiber-optic switches are introduced as low loss, high interchannel optical isolation 1 X 2 and 2 X 2 fiber-optic switches. A macroscale PZT actuator is built and tested. Preliminary results from a microscale actuator are given. Optical switch configurations and fabrication procedures are highlighted.
The paper describes the integration of sol-gel ferroelectric thin films into micromachined sensors and optical detectors, devices which are based on the piezoelectric and pyroelectric effects in Pb(Zr(x)Ti(1-x))O3 and PbTiO3 thin films, respectively. The ferroelectric and surface-micromachining technologies are described, which are compatible with 3-micron CMOS technology. At 297 K and a chopping frequency of 50 Hz, the measured blackbody voltage responsivity of a pyroelectric element with an active area of 7 x 10 exp -4 sq cm was 4.2 x 10 exp 4 V/W and the measured normalized detectivity was 1.0 x 10 exp 9 cm sq-rt Hz/W.
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