J.J. Talghader

University of Minnesota Duluth, Duluth, Minnesota, United States

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Publications (72)92.36 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: Most thermoluminescent materials are created using crystal growth techniques; however, it would be of great utility to identify those few thermoluminescent materials that can be deposited using simpler methods, for example to be compatible with the early portions of a silicon integrated circuit or microelectromechanical fabrication process. In this work, thin films of yttrium oxide with a terbium impurity (Y2O3:Tb) were deposited on silicon wafers by electron beam evaporation. The source for the Y2O3:Tb was made by combining Y2O3 and Tb4O7 powders. The approximate thicknesses of the deposited films were 350 nm. After deposition, the films were annealed at 1100 °C for 30 s to improve crystallinity. There is a strong correlation between the x-ray diffraction (XRD) peak intensity and the thermoluminescent glow curve intensity. The glow curve displays at least two peaks at 140 °C and 230 °C. The emission spectra was measured using successive runs with a monochromator set to a different wavelength for each run. There are two main emission peaks at 490 nm and 540 nm. The terbium impurity concentration of approximately 1 mol% was measured using Rutherford backscattering spectrometry (RBS). The Y2O3:Tb is sensitive to UV, x-ray, and gamma radiation. The luminescent intensity per unit mass of UV irradiated Y2O3:Tb was about 2 times that of x-ray irradiated TLD-100.
    Journal of Luminescence. 01/2014; 148:225–229.
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    ABSTRACT: It is well known that thermal gradients penetrating deep into a material can preserve a memory of the temperature history of the surface. To date, this concept has been largely applied in the earth sciences, but there are many applications where a memory of rapid thermal events would be useful. For example, multiple layers of thermoluminescent films could serve as temperature sensors that indicate temperature versus depth in a microfabricated structure. As an advance toward this goal, this paper examines the effect of nonuniform temperature profiles on the thermoluminescence of heterogeneous multilayers. A Nd:YAG laser is used to create a known thermal event and apply pulses of heat energy of varying duration to a metalized thermoluminescent multilayer composed of LiF:Mg,Ti and CaF2:Dy. The thermoluminescence of the system is measured before and after the applied laser pulse. To model the process, a finite-difference time-domain method is used to calculate the dynamic heat transfer, and the temperature distribution is plugged into a first order kinetics model of the thermoluminescence of each film to get a final luminescent intensity. A thermal contact conductance between the critical layers is also introduced. Dynamic temperatures in durations of hundreds of milliseconds are resolved with the technique, and simulation curves match experimental measurements to within 6% at 250 ms.
    Journal of Applied Physics 08/2013; 114(5). · 2.21 Impact Factor
  • Wing S. Chan, Mika J. Saarinen, Joseph J. Talghader
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    ABSTRACT: Vertical electrostatic wedge actuators are described that control nanometer-scale gaps between surfaces. Standard parallel-plate electrostatic actuators become difficult to stabilize across extremely small gaps because the nature of the forces and the force laws that describe them often deviate from a Coulomb's law dependence. In this work, a nanometer-scale air gap between a collapsed cantilever structure formed by two facing In0.53Ga0.47As surfaces, with areas of tens of microns, was controlled by a wedge electrostatic actuator. Upon actuation, the gap spacing between the surfaces was tuned over a maximum range of 55 nm with an applied voltage of 60 V.
    Applied Physics Letters 06/2013; 102(24). · 3.79 Impact Factor
  • A.S. Gawarikar, R.P. Shea, J.J. Talghader
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    ABSTRACT: Fabrication and characterization of high detectivity thermopile infrared detectors with spectrally selective absorption operating at room temperature is described. The detector architecture consists of a Johnson noise limited thermoelectric readout scheme integrated with a resonant cavity coupled absorber and a low thermal conductance support structure. A resonant responsivity enhancement of 4.3 and a peak detectivity of 1.3×109 cm Hz1/2 Watt-1 at 10.5 μm wavelength are demonstrated.
    Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS & EUROSENSORS XXVII), 2013 Transducers & Eurosensors XXVII: The 17th International Conference on; 01/2013
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    ABSTRACT: Thermoluminescent LiF:Mg, Ti (TLD-100) micro- particle sensors are demonstrated to record the thermal history of the environment around a high-explosive detonation. Microparticles are gamma-irradiated to fill their charge-carrier traps and then exposed to the detonation of 20 g of a plastic bonded HMX and Al explosive formulation at a test distance of approximately 22 cm from the center of the detonation. The thermal history of the microparticles is reconstructed by iteratively matching the degree of trap depopulation, derived from luminescence measurements, with that projected by theoretical simulations using appropriate models. Measurements and modeling indicate that the particles experienced a maximum temperature of 240°C, then cooled to 1°C above ambient temperature within 0.4 seconds. The resulting glow curve intensity is calculated to match the observed post-detonation signal to 3% averaged over the comparison values used for reconstruction.
    IEEE Sensors Journal 01/2013; 13(5):1742-1747. · 1.48 Impact Factor
  • A.S. Gawarikar, R.P. Shea, J.J. Talghader
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    ABSTRACT: A spectrally selective uncooled long wave infrared detector with peak detectivity between 3×109 cm Hz1/2/W and 4.4×109 cm Hz1/2/W is reported. The detector is fabricated using silicon microfabrication techniques and integrates a thermoelectric readout with a resonant optical cavity to achieve wavelength selective absorption.
    Optical MEMS and Nanophotonics (OMN), 2013 International Conference on; 01/2013
  • A.S. Gawarikar, R.P. Shea, J.J. Talghader
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    ABSTRACT: We describe uncooled thermal detectors with a peak detectivity of at least 3 ×109 cm √{Hz}/W with spectrally selective absorption in the long-wave infrared. The spectral selectivity in absorption is achieved through resonant cavity coupling of a thin metal film with a low-order air-gap optical cavity. The electrical readout uses thermoelectric thin films with a Johnson noise limited performance. The detectors are of multiple sizes but those with 100- μm2 area have time constants of 58 ms and thermal conductances of 2.3 ×10-7 W/K.
    IEEE Transactions on Electron Devices 01/2013; 60(8):2586-2591. · 2.06 Impact Factor
  • M.L. Mah, P.R. Armstrong, J.J. Talghader
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    ABSTRACT: The thermoluminescence characteristics of a thin film of terbium-doped yttrium oxide change upon repeated stress application through electrostatic actuation. A maximum 42% decrease in the intensity of two thermoluminescent peaks is seen when voltage is applied in 5V increments to 25V, translating to 0.15 μm of center deflection. While the overall intensity decreases, the higher temperature peak - corresponding to deeper traps - is affected more than the lower temperature one. Two possible physical explanations for the behavior are mechanical stress and dielectric charging.
    Optical MEMS and Nanophotonics (OMN), 2013 International Conference on; 01/2013
  • Source
    Joseph J Talghader, Anand S Gawarikar, Ryan P Shea
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    ABSTRACT: A review is made of the physics and technology of spectrally selective thermal detectors, especially those operating at non-cryogenic temperatures. The background radiation noise fluctuations are rederived for arbitrary spectral characteristics. Infrared absorption due to phonons and free carriers is discussed followed by a review of published works on artificial infrared absorption materials such as patterned grids, nanoparticles, plasmonic structures, metamaterials and others. Subsequently, the literature of the spectral characteristics of broadband thermal detectors and spectrally selective thermal detectors is reviewed. Finally, the authors speculate on the directions that future research and development in the area will take regarding architectures, sensitivity and spectral characteristics.
    Light: Science & Applications. 08/2012; 1(8).
  • Source
    Anand S. Gawarikar, Ryan P. Shea, Joseph J. Talghader
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    ABSTRACT: The far field radiation efficiency achievable in narrowband thermal emitters is investigated, taking into account the full spatial and spectral variation of the emissivity. A coupled Fabry-Perot cavity model is used to develop an insight into the efficiency variation with cavity coherence and device temperature. It is found that the spatial variation of emissivity has to be explicitly included in the radiation power calculations to accurately estimate the achievable power efficiencies. The calculated radiation efficiencies of an ideal coherent cavity coupled emitter were found to vary from 0.1% to 9%, with a corresponding increase in the emission linewidth from 6.3 nm to 930 nm, and were much lower than that estimated without accounting for effects of spatial coherence. The analysis presented here can be used to determine the optimal operating temperature of a coherent thermal emitter once its emission characteristics and conduction losses are known and it is demonstrated that this optimum temperature is different from the temperature of peak blackbody emission at the resonant absorption wavelength.
    AIP Advances. 07/2012; 2(3).
  • Kyle D Olson, Joseph J Talghader
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    ABSTRACT: The optimum transition wavelength between high absorption and low emissivity for selective solar absorbers has been calculated in several prior treatises for an ideal system, where the emissivity is exactly zero in the infrared. However, no real coating can achieve such a low emissivity across the entire infrared with simultaneously high absorption in the visible. An emissivity of even a few percent radically changes the optimum wavelength separating the high and low absorption spectral bands. This behavior is described and calculated for AM0 and AM1.5 solar spectra with an infrared emissivity varying between 0 and 5%. With an emissivity of 5%, solar concentration of 10 times the AM1.5 spectrum the optimum transition wavelength is found to be 1.28 µm and have a 957K equilibrium temperature. To demonstrate typical absorptions in optimized solar selective coatings, a four-layer sputtered Mo and SiO₂ coating with absorption of 5% across the infrared is described experimentally and theoretically.
    Optics Express 07/2012; 20 Suppl 4:A554-9. · 3.55 Impact Factor
  • A.S. Gawarikar, R.P. Shea, J.J. Talghader
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    ABSTRACT: This paper presents the design and fabrication of narrowband resonant cavity absorbers in the long wave infrared. Absorption in multiple spectral bands is demonstrated with a structure whose thermal mass is compatible with thermal detectors.
    Optical MEMS and Nanophotonics (OMN), 2012 International Conference on; 01/2012
  • W.S. Chan, J.J. Talghader, M.J. Saarinen
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    ABSTRACT: An actuator was designed and fabricated to actively tune the nanometer-scaled gap between quantum wells in a collapsed cantilever structure. Maximum actuation of 55nm was achieved. Photoluminescence from the quantum wells at the collapsed cantilever was observed at cryogenic temperature, indicating that the wells remained intact after fabrication.
    Optical MEMS and Nanophotonics (OMN), 2012 International Conference on; 01/2012
  • Source
    Nicholas T. Gabriel, Joseph J. Talghader
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    ABSTRACT: Hafnia-alumina nanolaminates show improved smoothness and reduced crystallinity relative to pure hafnia in films formed by atomic layer deposition (ALD). However, typical nanolaminates also show reduced cross-plane thermal conductivity due to the much larger interface density relative to continuous films. We find that the interface thermal resistance in hafnia-alumina nanolaminates is very low and does not dominate the film thermal conductivity, which is 1.0 to 1.2 W/(m K) at room temperature in 100 nm thin films regardless of the interface density. Measured films had a number of interfaces ranging from 2 to 40, equivalent to interface spacing varying from about 40 to 2 nm. The degree of crystallinity of these films appears to have a much larger effect on thermal conductivity than that of interface density. Cryogenic measurements show good agreement with both the minimum thermal conductivity model for disordered solids and the diffuse mismatch model of interface resistance down to about 80 K before diverging. We find that the films are quite smooth through a 400:5 ratio of hafnia to alumina in terms of ALD cycles, and the refractive index scales as expected with increasing alumina concentration.
    Journal of Applied Physics 08/2011; 110(4):043526-043526-8. · 2.21 Impact Factor
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    ABSTRACT: Thermoluminescent (TL) particles show promise as robust direct-contact thermal history sensors for explosive events. Research with microheaters has shown that TL microparticles can measure temperature excursions of hundreds of degrees; however, microheaters do not generate the severe pressure and shock stimuli present in post- detonation environments. To address this, TL particles were tested under conditions produced by the detonation of an aluminized explosive formulation. TLD-100 (LiF:Mg,Ti) powder was irradiated with 220 Gy of gamma radiation from a ^167Cs source before being exposed to the free field detonation of a 20 gram charge. Particles were recovered post-detonation from two separate tests and their TL glow curves measured. At least two TL emission peaks 50 ^oC apart are clearly distinguishable in both samples, with peak intensity ratios decreasing 33.7% and 60.0% from an original 8.88:1, indicative of distinct carrier traps emptying at rates depending on the trap energy. These ratios agree well with thermocouple measurements from within the post-detonation fireball.
    06/2011;
  • [show abstract] [hide abstract]
    ABSTRACT: Thermoluminescent LiF:Mg,Ti (TLD-100) microparticle sensors are demonstrated to record the thermal history of the region near a detonated high explosive. Microparticles were gamma-irradiated to fill their charge-carrier traps and then exposed to the detonation of 20 g of a plastic bonded explosive formulation containing HMX and Al particles at a test distance of approximately 22 cm from the center of the detonation. The thermal history was reconstructed by measuring the thermoluminescent signature of the traps and matching it to appropriate models. The trap populations derived from luminescence measurements and modeling indicate that the particles experienced a maximum temperature of 240 °C, then cooled to 1 °C above ambient temperature within 0.4 seconds. The resulting glow curve intensity is calculated to match the observed post-detonation signal to 3% averaged over the comparison values used for reconstruction.
    Sensors, 2011 IEEE; 01/2011
  • W.S. Chan, M.J. Saarinen, J.J. Talghader
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    ABSTRACT: A nanomechanical actuator was fabricated to control the electron states of quantum wells coupled across air gaps. This actuator was composed of a collapsed cantilever containing quantum wells and a set of parallel plate electrostatic actuators. The actuators were designed to alter the coupling distance between the wells by a few nanometers over a 200nm gap. The actuation region is separated from the quantum coupling regions so that Stark effect interference is avoided. Preliminary raw data suggests actuator motion. Such an actuator may be applied to infrared photodetectors with wide tuning ranges.
    Optical MEMS and Nanophotonics (OMN), 2011 International Conference on; 01/2011
  • [show abstract] [hide abstract]
    ABSTRACT: Mechanical position is used to control the wavelength of light emission of semiconductor heterostructures. The heterostructures are coupled across a gap that varies with position to tune electron states in much the same manner that optical cavities can be coupled across a tunable reflectivity mirror to control photon states. In the experiments, a Si<sub>x</sub>N/InP cantilever containing an InGaAs surface well collapses over another InGaAs quantum well. The spacing between the wells varies along the cantilever, such that the heterostructure band gap is determined by the mechanical bending of the cantilever. Photoluminescence measurements of the coupled 200° A surface wells show a wavelength shift of up to 22 nm. Associated theory shows that mechanical quantum coupling enables interband or intersubband devices with unprecedented spectral tuning ranges for gain or absorption.
    IEEE Journal of Quantum Electronics 10/2010; · 1.83 Impact Factor
  • Ryan P Shea, Anand S Gawarikar, Joseph J Talghader
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    ABSTRACT: The performance of thermal detectors is derived for devices incorporating materials with non-uniform spectral absorption. A detector designed to have low absorption in the primary thermal emission band at a given temperature will have a background-limited radiation noise well below that of a blackbody absorber, which is the condition typically assessed for ultimate thermal detector performance. Specific examples of mid-wave infrared (ʎ ∼ 3-5 μm) devices are described using lead selenide as a primary absorber with optical cavity layers that maximize coupling. An analysis of all significant noise sources is presented for two example room-temperature devices designed to have detectivities up to 4.37 × 10(10) cm Hz(1/2) W(-1), which is a factor 3.1 greater than the traditional blackbody limit. An alternative method of fabricating spectrally selective devices by patterning a plasmonic structure in silver is also considered.
    Optics Express 10/2010; 18(22):22833-41. · 3.55 Impact Factor
  • Nicholas T. Gabriel, Sangho S. Kim, Joseph J. Talghader
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    ABSTRACT: Thermal expansion mismatch between the layers of an optical coating and its substrate alters the shape of an optical element. We demonstrate predictable coating behavior using atomic layer deposition and apply to high-reflectivity mirror design.
    06/2010;

Publication Stats

71 Citations
92.36 Total Impact Points

Institutions

  • 2002–2014
    • University of Minnesota Duluth
      • Department of Electrical Engineering
      Duluth, Minnesota, United States
  • 2000–2013
    • University of Minnesota Twin Cities
      • Department of Electrical and Computer Engineering
      Minneapolis, Minnesota, United States