Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Infrared”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Sulfide treatment passivation of mid-/long-wave dual-color infrared detectors based on type-II InAs/GaSb superlattices

The surface passivation of mid-/long-wave dual-color infrared detectors based on type-II InAs/GaSb superlattices(T2SLs) photodetectors employing diverse voltage and current conditions of sulfide treatment passivation was presented. The superlattices were grown on GaSb substrate by molecular beam epitaxy technology. The circle pixel devices in the diameter of 200 μm with 5 μm at mid-infrared and 14 μm at long-infrared 100% cutoff wavelength were fabricated. Compared to only SiO{sub 2} encapsulation passivation and unpassivated detectors, the dark current density, which takes into account surface leakage current, was reduced by approximately three orders of magnitude and the R0A-product was six times higher by sulfide treatment. Besides, detectors passivated through 22 V 15 mA sulfur treated, the responsivity of was 0.95A/W and QE was 0.44 at 2.6 μm. As for the wavelength of 5.3 μm, the responsivity and QE were 1.95 A/W and 0.45 severally.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Infrared and radar fusion detection method based on heterogeneous data preprocessing

The difficulty in infrared and radar fusion target detection lies in the pre-processing steps such as sample reduction and feature reduction of heterogeneous sensors. For the problem of data volume redundancy, HVS sample reduction is proposed to reduce the amount of data in the infrared data set. Infrared and radar joint feature vectors are constructed through nearest neighbor data association. For the problem of feature redundancy, a weighted mutual information feature selection method based on prior information is proposed according to the difference of feature sources. The fusion data set is then used for classification. The experiments show that the HVS-based sample reduction and the prior weighted feature selection achieved a higher detection probability and a shorter detection time, and improved the robustness in the case of large differences between the training set and the test set.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Millimeter-scale gate-tunable graphene nanoribbon devices as a platform for mid-infrared and bio sensing applications

The experimental observation of graphene plasmon resonance has generated tremendous interest due to numerous potential applications such as photosensors, detectors, biosensors, and switches from THz to mid-infrared regime. However, practical applications require much larger dimensions (mm to cm scale) than that demonstrated in the proof-of-concept devices. Moreover, such devices also require a detailed understanding of ribbon-to-ribbon interaction, which has not been investigated so far. Here in this paper we demonstrate gate tunable plasmon resonance in the mid-infrared spectral region on millimeter-scale graphene nanoribbon (GNR) array devices fabricated using graphene monolayer. Gate dependent Fourier-transform infrared (FTIR) transmission measurements on GNR of various widths were investigated experimentally. The shift in plasmon resonance peaks of wave number 100 cm -1 at applied external gate voltage -100 V was observed. This shift is attributed to strong gate modulation. Our investigation of ribbon-to-ribbon interaction by tuning the aspect ratio reveals strong modulation of surface plasmon resonance peaks in GNR. This suggests that plasmon resonances are coupled as evidenced by blue-shifted plasmon resonance. These studies demonstrate that large-area GNR devices can serve as an ideal platform for ultrasensitive sensing and detector applications.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Near-field infrared microscopy: A novel analytic mapping technique to nanocharacterize calcium silicate-based cement materials

Infrared imaging via scattering-type scanning near-field optical microscopy (s-SNOM) allows chemical mapping of organic and inorganic materials with nanoscale spatial resolution. However, its potential adaptation to the complex multiphase structure of Portland cement is yet to be explored. Here we demonstrate the successful implementation of s-SNOM to spatially resolve coexisting chemical phases in tricalcium silicate, Portland cement's main compound, with 20-nm resolution. We found that s-SNOM is sensitive to different anhydrous polymorphic phases, revealing nanoscale domains that are ‘invisible’ to other microscopic techniques. Furthermore, s-SNOM's ability to distinguish the unhydrated and hydrated phases signifies its great promise as an analytical tool to study the complex hydration process of cement. The key to s-SNOM's application was nano-modifying the surface roughness of the cement samples, allowing nanoscale infrared imaging without topographical artifacts. Our study opens a window for infrared spectral microscopy in cement and other porous inorganic materials.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Understanding the infrared to visible upconversion luminescence properties of Er{sup 3+}/Yb{sup 3+} co-doped BaMoO{sub 4} nanocrystals

In this paper we report the infrared to visible upconversion luminescence properties of Er{sup 3+}/Yb{sup 3+} co-doped BaMoO{sub 4} nanocrystals synthesized via microwave assisted sol–gel processing route. Structural, morphological and upconversion luminescence properties were investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and Upconversion Photoluminescence spectra analysis. Results revealed that the oval shaped BaMoO{sub 4} nanocrystals ranging in size from 40 to 60 nm having tetragonal scheelite crystal structure were obtained by sol–gel route. The infrared to visible upconversion luminescence has been investigated in Er{sup 3+}/Yb{sup 3+} co-doped in BaMoO{sub 4}with different Yb{sup 3+} concentrations. Intense green upconversion emissions around 528, 550 nm, and red emission at 657 nm corresponding to the {sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}, and {sup 4}F{sub 9/2} transitions, respectively to the {sup 4}I{sub 15/2} ground state were observed when excited by CW laser radiation at 980 nm. The green emissions were greatly enhanced after the addition of sensitizer (Yb{sup 3+} ions). The effect of Yb{sup 3+} on the upconversion luminescence intensity was analyzed and explained in terms of the energy transfer process based. The reported work establishes the understanding of molybdates as an alternative host material for upconversion luminescence. - Graphical abstract: Infrared to visible upconversion luminescence of Er{sup 3+}/Yb{sup 3+} co-doped BaMoO{sub 4} nanocrystals. - Highlights: • Nanocrystals were synthesized by microwave assisted sol–gel processing route. • Strong green emissions were observed in Er{sup 3+}/Yb{sup 3+} co-doped BaMoO{sub 4} nanocrystals. • Provides an insight on Upconversion luminescence properties of oxides host materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Ratiometric near infrared luminescent thermometer based on lanthanide metal-organic frameworks

A near infrared luminescent MOFs thermometer (Nd{sub 0.676}Yb{sub 0.324}BTC) was prepared via a simple solvothermal method using Ln{sup 3+} (Ln=Nd, Yb) ions and 1, 3, 5-benznenetricarboxylic acid (H{sub 3}BTC), and characterized by PXRD, TGA, ICP, and photoluminescence (PL) spectrum. These results indicate that the Nd{sub 0.676}Yb{sub 0.324}BTC displays high relative sensitivity and excellent repeatability in the physiological temperature range (288–323 K), and the maximum relative sensitivity is determined to be 1.187% K{sup −1} at 323 K. These NIR luminescent MOFs may have potential applications in physiological temperature sensing. - Graphical abstract: A near infrared luminescent MOFs thermometer (Nd{sub 0.054}Yb{sub 0.946}BTC ) displays high relative sensitivity and excellent repeatability in the physiological temperature range (288–323 K). Display Omitted - Highlights: • A ratiometric near infrared luminescent MOFs thermometer (Nd{sub 0.676}Yb{sub 0.324}BTC) was prepared via a simple solvothermal method. • The maximum relative sensitivity of Nd{sub 0.676}Yb{sub 0.324}BTC is determined to be 1.187% K{sup −1} at 323 K. • Nd{sub 0.676}Yb{sub 0.324}BTC showed excellent repeatability in the physiological temperature range (288–323 K).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Establishment of the correlation law between electron density, infrared absorption and doping concentration in Ga{sup 3+}-doped ZnO

Highlights: ► Synthesis of nanometric A{sup 3+}-doped ZnO by polyol-mediated route. ► Correlation between free electron density and the doping rate of A{sup 3+}-doped ZnO. ► Optimization of infrared absorbing properties of A{sup 3+}-doped ZnO. - Abstract: A polyol-mediated synthesis allows the obtaining of doped zinc oxides nanoparticles with tunable infrared absorption properties via the doping concentration. In a first step the prepared nanoparticles are characterized in terms of chemical composition (purity and homogeneity), crystallite size and agglomerate morphology. A correlation law between the infrared absorbing efficiency, the free electron density and the doping concentration is then clearly established; this law is based on the neighboring probability of the dopant ions in the crystal network.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Sub-10 nm lanthanide doped BaLuF{sub 5} nanocrystals: Shape controllable synthesis, tunable multicolor emission and enhanced near-infrared upconversion luminescence

Highlights: • Sub-10 nm cubic phase BaLuF{sub 5} nanocrystals were synthesized by a hydrothermal method for the first time. • Tunable multicolor from yellow to yellow-green was achieved by controlling Gd{sup 3+} content in BaLuF{sub 5}:Yb/Er system. • Intense near-infrared upconversion luminescence in BaLuF{sub 5}:Gd/Yb/Tm nanocrystal. • The enhancement near-infrared luminescence can be realized by adjusting the content of Gd{sup 3+} in BaLuF{sub 5}:Gd/Yb/Tm system. - Abstract: In this study, sub-10 nm BaLuF{sub 5} nanocrystals with cubic phase structure were synthesized by a solvothermal method using oleic acid as the stabilizing agent. The as-prepared BaLuF{sub 5} nanocrystals were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and analyzed by the upconversion (UC) spectra. The TEM results reveal that these samples present high uniformity. Compared with Gd-free samples, the size of BaLuF{sub 5}:Yb/Er doped with 10% Gd{sup 3+} decreased to 5.6 nm. In addition, BaLuF{sub 5}:Yb/Tm/Gd upconversion nanoparticles (UCNPs) presented efficient near-infrared (NIR)-NIR UC luminescence. Therefore, it is expected that these ultra-small BaLuF{sub 5} nanocrystals with well-controlled shape, size, and UC emission have potential applications in biomedical imaging fields.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Enhanced visible to near infrared downshifting in Ce{sup 3+}/Yb{sup 3+}-co-doped yttrium aluminum garnet through Pr{sup 3+} doping

Graphical abstract: In order to achieve improved near infrared downshifting, we have investigated the effect of Pr{sup 3+} doping on the energy transfer efficiency from Ce{sup 3+} to Yb{sup 3+} in the YAG host. - Highlights: • Synthesis and characterization of tri-doped Y{sub 3}Al{sub 5}O{sub 12} (YAG). • Efficient energy transfer in YAG:Ce{sup 3+}, Pr{sup 3+}, Yb{sup 3+}. • Discussion of mechanism of energy transfer in tri-doped host. • Potential application in c-Si solar cell. - Abstract: Novel YAG:Ce{sup 3+}, Pr{sup 3+}, Yb{sup 3+} phosphors were synthesized using a high temperature solid state reaction method. The XRD patterns revealed that the obtained samples belong to the single phase YAG. The optical spectra demonstrated that Pr{sup 3+} could be a bridge to facilitate the energy transfer from Ce{sup 3+} to Yb{sup 3+} in the YAG host. Blue light excited Ce{sup 3+} and a yellow emission from Ce{sup 3+} together with a near infrared emission of Yb{sup 3+} was obtained. The effect of Pr{sup 3+} doping on the energy transfer efficiency was explored. When the doping concentration of Pr{sup 3+} increased, the yellow emission intensities of Ce{sup 3+} decreased and the near infrared emission intensity of Yb{sup 3+} increased monotonously. Hence, the efficiency of energy transfer from Ce{sup 3+} to Yb{sup 3+} is enhanced by the addition of Pr{sup 3+}, implying that the YAG:Ce{sup 3+}, Pr{sup 3+}, Yb{sup 3+} phosphors are promising downshifting materials and have the potential to be used in Si-based solar cells.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Near-infrared downconversion luminescence of SrMoO{sub 4}:Tm{sup 3+},Yb{sup 3+} phosphors

Graphical abstract: The calculated band structure of SrMoO{sub 4} and the visible and infrared emission spectra of SrMoO{sub 4}:1%Tm{sup 3+},10%Yb{sup 3+} phosphors under 283 nm excitation.▪ - Highlights: • Near-infrared downconversion luminescence of SrMoO{sub 4}:Tm{sup 3+},Yb{sup 3+} phosphors were systematically investigated. • The electronic structure of SrMoO{sub 4} was estimated by density functional theory. • The quenching concentration of Yb{sup 3+} ions approaches 10 mol%. • The energy transfer mechanism was discussed in detail. - Abstract: Tm{sup 3+} and Yb{sup 3+} codoped SrMoO{sub 4} phosphors were synthesized by the high-temperature solid-state reaction method. The structure, ultraviolet-visible diffuse reflectance spectra, photoluminescence, decay properties and theoretical energy transfer efficiency of the phosphors were investigated in detail. The electronic structure and band gap of SrMoO{sub 4} were estimated by density functional theory (DFT) calculation. The XRD results show that all the prepared phosphors can be readily indexed to scheelite-type structure. The strong visible emission around 473 nm from Tm{sup 3+} ({sup 1}G{sub 4} → {sup 3}H{sub 6}) and near-infrared (NIR) emission around 998 nm from Yb{sup 3+} ({sup 2}F{sub 5/2} → {sup 2}F{sub 7/2}) of the SrMoO{sub 4}:Tm{sup 3+},Yb{sup 3+} phosphors were observed under 283 nm excitation. The dependence of the visible and NIR emissions on Yb{sup 3+} concentration have also been investigated. The quenching concentration of Yb{sup 3+} ions approaches 10 mol%. In addition, the energy transfer processes and possible transfer routes were proposed.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Visible and near-infrared excitation spectra from the neptunyl ion doped into a uranyl tetrachloride lattice

We present that visible and near-infrared illumination induces 5f-5f and ligand-to-metal charge-transfer (LMCT) transitions of the neptunyl tetrachloride anion in polycrystalline Cs 2 U(Np)O 2 Cl 4 , and results in near-infrared luminescence from the second electronically excited state to the ground state. This photoluminescence is used as a detection method to collect excitation spectra throughout the near-infrared and visible regions. The excitation spectra of LMCT transitions in excitation spectra were identified in previous work. Here the measurement and analysis is extended to include both LMCT and intra-5f transitions. The results manifest variation in structural properties of the neptunium-oxo bond among the low-lying electronic states. Vibronic intensity patterns and energy spacings are used to compare bond lengths and vibrational frequencies in the excited states, confirming significant characteristic differences between those excited by 5f-5f transitions from those due to LMCT transitions. Lastly, results are compared with recently published RASPT2/SO calculations of [NpO 2 Cl 4 ] 2- .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Decay-Associated Fourier Spectroscopy: Visible to Shortwave Infrared Time-Resolved Photoluminescence Spectra

Here, we describe and implement an interferometric approach to decay-associated photoluminescence spectroscopy, which we term decay-associated Fourier spectroscopy (DAFS). In DAFS, the emitted photon stream from a substrate passes through a variable path length Mach–Zehnder interferometer prior to detection and timing. The interferometer encodes spectral information in the intensity measured at each detector enabling simultaneous spectral and temporal resolution. We detail several advantages of DAFS, including wavelength-range insensitivity, drift-noise cancellation, and optical mode retention. DAFS allows us to direct the photon stream into an optical fiber, enabling the implementation of superconducting nanowire single photon detectors for energy-resolved spectroscopy in the shortwave infrared spectral window (λ = 1–2 μm). We demonstrate the broad applicability of DAFS, in both the visible and shortwave infrared, using two Förster resonance energy transfer pairs: a pair operating with conventional visible wavelengths and a pair showing concurrent acquisition in the visible and the shortwave infrared regime.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Infrared Near-Field Spectroscopy of Gold Nanotriangle Fabry-Pérot Resonances

Here, in this work, we characterize the near-field response of individual gold nanotriangles over a broad, visible-to-infrared, spectral region (200–1500 meV) using high-resolution electron energy-loss spectroscopy (EELS) performed inside of a scanning transmission electron microscope (STEM). We begin by experimentally imaging the spatial and spectral extent of each nanotriangle’s plasmonic Fabry-Pérot modes and measuring the evolution of their resonance energies with increasing edge length; thereby providing detailed information on infrared plasmon dephasing times and dispersion relations. Numerical electromagnetic simulations of the electron probe are used to interpret these experimental results and to compare the near-field electromagnetic enhancement factors of gold nanotriangles and nanorods of equal resonant energy. Taken together, this combined experimental and theoretical study provides unique insights relevant to designing noble metal plasmonic nanoparticle systems for solar energy harvesting and sensing applications in the near- and mid-infrared.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Black Phosphorus for Mid-Infrared Optoelectronics: Photophysics, Scalable Processing, and Device Applications

High efficiency mid-infrared (λ = 3-8 μm) light emitters and photodetectors are pivotal for advancing next-generation optoelectronics. However, narrow-bandgap semiconductors face fundamental challenges such as pronounced nonradiative carrier recombination and thermally generated noise, which impede device performance. Recently, two-dimensional layered black phosphorus (BP) and its alloys have attracted substantial interest for mid-infrared device applications, demonstrating superior performance relative to conventional III-V and II-VI semiconductors with similar bandgaps. In this review, we discuss the optical properties of BP, contrasting these with those of covalent compounds. Owing to its inherently self-terminated surface structure and reduced nonradiative recombination, BP exhibits high performance in light emission and photodetection at room temperature. Furthermore, this review highlights recent advances in the large-area processing of BP thin films, paving the way for practical device applications and integration. Finally, we explore ongoing challenges and emerging opportunities in the utilization of BP for functional mid-infrared devices.

Higashitarumizu, Naoki↗
DOE OSTI2018

Ultrashort Carbon Nanotubes That Fluoresce Brightly in the Near-Infrared

The intrinsic near-infrared photoluminescence observed in long single-walled carbon nanotubes is known to be quenched in ultrashort nanotubes due to their tiny size as compared to the exciton diffusion length in these materials (>100 nm). Here in this study, we show that intense photoluminescence can be created in ultrashort nanotubes (~40 nm length) upon incorporation of exciton-trapping sp 3 defect sites. Using super-resolution photoluminescence imaging at <25 nm resolution, we directly show the preferential localization of excitons at the nanotube ends, which separate by less than 40 nm and behave as independent emitters. Lastly, this unexpected observation opens the possibility to synthesize fluorescent ultrashort nanotubes—a goal that has been long thought impossible—for bioimaging applications, where bright near-infrared photoluminescence and small size are highly desirable, and for quantum information science, where high quality and well-controlled near-infrared single photon emitters are needed.

36 MATERIALS SCIENCE↗
DOE OSTI2021

High Resolution Infrared Spectroscopy of Highly Reactive Chemical Intermediates: Berkeley Inspiration and a C.B. Moore Retrospective

One of the long-standing paradoxes in chemistry is that the molecular species of greatest interest are often highly reactive chemical intermediates and thus present only at vanishingly small concentrations under typical steady state conditions. Here, this has proven both a key frustration and powerful motivation for physical chemists in probing such species, particularly for high resolution laser spectroscopic methods in the infrared. Over the past 4-5 decades, this fundamental sensitivity challenge has stimulated the development of many novel techniques for efficient generation, cooling, and infrared probing of such transient chemical intermediates, achieving increasingly sophisticated levels of spectroscopic detail, chemical insight, and a testbed for comparison with first principles ab initio quantum calculations. Two of the pioneering contributors to this scientific arena have been George Pimentel and C. Bradley Moore, both responsible for nourishing DJN’s own enduring fascination with spectroscopic IR study of elusive chemical intermediates. This chapter is not intended to provide a comprehensive review of this large and enormously successful field, but it rather more simply attempts to capture a few selective “Moore-centric” snapshots of the Nesbitt group scientific evolution, specifically in i) advances by Pimentel for the original development of rapid scan flash kinetic spectroscopy based on spectrometers with rapidly rotating IR gratings, ii) the modernization/extension of these methods in the Moore group toward the first high resolution IR laser spectroscopy of singlet/triplet methylene 1,3 CH 2 diradical, and finally to iii) the development of slit supersonic discharge expansion methods at JILA for sub-Doppler infrared laser study of multiple radicals, jet cooled molecular ions, and highly reactive chemical intermediates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Near-Infrared Photoluminescence Enhancement in Ge/CdS and Ge/ZnS Core/Shell Nanocrystals: Utilizing IV/II-VI Semiconductor Epitaxy

Ge nanocrystals have a large Bohr radius and a small, size-tunable band gap that may engender direct character via strain or doping. Colloidal Ge nanocrystals are particularly interesting in the development of near-infrared materials for applications in bioimaging, telecommunications and energy conversion. Epitaxial growth of a passivating shell is a common strategy employed in the synthesis of highly luminescent II–VI, III–V and IV–VI semiconductor quantum dots. Here, we use relatively unexplored IV/II–VI epitaxy as a way to enhance the photoluminescence and improve the optical stability of colloidal Ge nanocrystals. Selected on the basis of their relatively small lattice mismatch compared with crystalline Ge, we explore the growth of epitaxial CdS and ZnS shells using the successive ion layer adsorption and reaction method. Powder X-ray diffraction and electron microscopy techniques, including energy dispersive X-ray spectroscopy and selected area electron diffraction, clearly show the controllable growth of as many as 20 epitaxial monolayers of CdS atop Ge cores. In contrast, Ge etching and/or replacement by ZnS result in relatively small Ge/ZnS nanocrystals. The presence of an epitaxial II–VI shell greatly enhances the near-infrared photoluminescence and improves the photoluminescence stability of Ge. Ge/II–VI nanocrystals are reproducibly 1–3 orders of magnitude brighter than the brightest Ge cores. Ge/4.9CdS core/shells show the highest photoluminescence quantum yield and longest radiative recombination lifetime. Thiol ligand exchange easily results in near-infrared active, water-soluble Ge/II–VI nanocrystals. We expect this synthetic IV/II–VI epitaxial approach will lead to further studies into the optoelectronic behavior and practical applications of Si and Ge-based nanomaterials.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Terahertz and mid-infrared plasmons in three-dimensional nanoporous graphene

Two-dimensional (2D) graphene emerged as an outstanding material for plasmonic and photonic applications due to its charge-density tunability, high electron mobility, optical transparency and mechanical flexibility. Recently, novel fabrication processes have realised a three-dimensional (3D) nanoporous configuration of high-quality monolayer graphene which provides a third dimension to this material. In this work, we investigate the optical behaviour of nanoporous graphene by means of terahertz and infrared spectroscopy. We reveal the presence of intrinsic 2D Dirac plasmons in 3D nanoporous graphene disclosing strong plasmonic absorptions tunable from terahertz to mid-infrared via controllable doping level and porosity. In the far-field the spectral width of these absorptions is large enough to cover most of the mid-Infrared fingerprint region with a single plasmon excitation. The enhanced surface area of nanoporous structures combined with their broad band plasmon absorption could pave the way for novel and competitive nanoporous-graphene based plasmonic-sensors.

36 MATERIALS SCIENCE↗