IR Detectors Research Articles

An Investigation of Structural, Optical and Pyroelectrical Properties of LiTaO3

In this study, structural, optical, and pyroelectric properties of Z-cut single crystal LiTaO3 bulk materials with thicknesses of 27 µm and 250 µm are analyzed. XRD results show characteristic diffraction peaks of Z-cut LiTaO3 at (012), (006), and (202), along with a Ta2O5 peak due to Li-deficiency. The strong (006) peak confirms a high c-orientation, indicating pyroelectric potential. Raman spectroscopy confirms agreement with known vibration modes of bulk LiTaO3. Band gap values for the 27 µm and 250 µm samples are determined as 4.44 eV and 4.65 eV, respectively, with both showing a direct band gap. Temperature changes from 30 ℃ to 180 ℃ were applied at rates of 50 ℃, 100 ℃, and 150 ℃. As temperatures rose, negative pyroelectric currents were observed; with cooling, currents shifted positive. The 250 µm thick, 24 mm² LiTaO3 wafer produced about 4 nA at 50 ℃ rate, rising to 12-13 nA at 150 ℃. With larger surface areas yielding higher currents, measurements on three wafers at a 50 ℃ change showed the highest-area sample producing ~7.5 nA, while the smallest yielded ~0.5 nA. The mean pyroelectric current density was higher in 27 µm (180 µA/m²) than in 250 µm (125 µA/m²), and the pyroelectric coefficient increased with decreasing thickness, measured at 33.43 µC/m²∙K (27 µm) and 23.22 µC/m²∙K (250 µm). These results suggest the potential of LiTaO3 crystals in IR detectors and self-powered deep UV detector applications due to their wide band gap.

Controlling the Mott–Peierls transition in epitaxial VO2 (M1) film grown by PLD for near-IR photodetection

Vanadium dioxide (VO2) (M1) exhibits a unique metal–insulator transition (MIT) near room temperature, garnering considerable attention for its applications in bolometer, terahertz/infrared detectors, and microelectronic devices. Here, we explore the potential of epitaxially grown VO2 (M1) thin films for near-infrared (IR) detection by optimizing the growth conditions, followed by structural characterization and device fabrication. Alongside the VO2 (M1) phase, two other oxides from the vanadium oxide family, VO2 (A) and V2O5, were also grown on a c-cut sapphire substrate using a pulsed laser deposition (PLD) system. In-depth analysis using temperature-dependent XRD and Raman spectroscopy confirmed the crystalline structure and the quality of epitaxial thin film formation of VO2 (M1), while also unveiling structural phase transition (SPT) behavior and the critical temperature of transition. At elevated temperatures during electrical measurement, the VO2 (M1) epilayer exhibits a first-order phase transition from the metallic to the insulating state, accompanied by a significant change in resistance exceeding three orders of magnitude unveiling its potential in thermal switches, memory-based devices etc. In depth, electrical analysis on all the grown oxides shows that VO2 (M1) and V2O5 exhibit a higher temperature coefficient of resistance (TCR) (3%/K and 2%/K) and a lower 1/f noise (in the order pA/Hz at 0.1 Hz) as compared to VO2 (A), paving scope for further analysis of these two oxides toward important applications in the domain of thermal sensors. Additionally, VO2 (M1) exhibited good bolometric response (in the order of ms) to IR radiation, proving its candidature for the application in IR detectors as well.

Tunable MEMS-based meta-absorbers for nondispersive infrared gas sensing applications

In conventional nondispersive infrared (NDIR) gas sensors, a wide-spectrum IR source or detector must be combined with a narrowband filter to eliminate the interference of nontarget gases. Therefore, the multiplexed NDIR gas sensor requires multiple pairs of narrowband filters, which is not conducive to miniaturization and integration. Although plasmonic metamaterials or multilayer thin-film structures are widely applied in spectral absorption filters, realizing high-performance, large-area, multiband, and compact filters is rather challenging. In this study, we propose and demonstrate a narrowband meta-absorber based on a planar metal–insulator–metal (MIM) cavity with a metallic ultrathin film atop. Nearly perfect absorption of different wavelengths can be obtained by controlling the thickness of the dielectric spacer. More significantly, the proposed meta-absorber exhibits angle-dependent characteristics. The absorption spectra of different gases can be matched by changing the incident angle of the light source. We also preliminarily investigate the CO2 gas sensing capability of the meta-absorber. Afterward, we propose a tunable meta-absorber integrated with a microelectromechanical system (MEMS)-based electrothermal actuator (ETA). By applying a direct current (DC) bias voltage, the inclination angle of the meta-absorber can be controlled, and the relationship between the inclination angle and the applied voltage can be deduced theoretically. The concept of a tunable MEMS-based meta-absorber offers a new way toward highly integrated, miniaturized and energy-efficient NDIR multigas sensing systems.

Dwarf Galaxies with Radio-excess Active Galactic Nuclei in the Very Large Array Sky Survey

We present a systematic search for radio active galactic nuclei (AGNs) in dwarf galaxies using recent observations taken by the Very Large Array Sky Survey (VLASS). To select these objects, we first establish a criterion to identify radio-excess AGNs using the infrared-radio correlation parameter, q, that describes the tight relation between radio and IR emission in star-forming galaxies. We find a 2σ threshold of q < 1.94 to select radio-excess AGNs, which is derived from a sample of ∼7000 galaxies across the full mass range in the NASA-Sloan Atlas that have radio and IR detections from VLASS and the Wide-Field Infrared Survey Explorer, respectively. We create catalogs of radio-excess AGNs and star-forming galaxies and make these available to the community. Applying our criterion to dwarf galaxies with stellar masses M ⋆ ≲ 3 × 109 M ⊙ and redshifts z ≤ 0.15, and carefully removing interlopers, we find 10 radio-excess AGNs with radio-optical positional offsets between ∼0″ and 2.′3 (0–2.7 kpc). Based on statistical arguments and emission line diagnostics, we expect the majority of these radio-excess AGNs to be associated with the dwarf host galaxies rather than background AGNs. Five of the objects have evidence for hosting AGNs at other wavelengths, and five objects are identified as AGNs in dwarf galaxies for the first time. We also identify eight variable radio sources in dwarf galaxies by comparing the VLASS epoch 1 and epoch 2 observations to Faint Images of the Radio Sky at Twenty-centimeters detections presented in A. E. Reines et al. (2020).

Termografia Infravermelha:

Thermographic imagery technology applied to search and identification of infrared radiation signatures is an area which follows in a high development. The technology has two application fields: military and civilian. Both of them use the same sensors and data processing. In the civilian area this technology is used in agriculture, environmental control, health and others. The military area uses the same technology in the Defense systems like as air-air, surface-air and air-surface missile seekers, biological and chemical warning systems and night vision. Research and development of cryogenic and no-criogenic infrared sensors give to the countries a know-how to make an advanced and superiority missile. This technology is not sold and therefore if someone wants to have the same technology needs to reinforce the technological and industrial areas. The production of sensors in the semiconductor detector form is already a known technology and it is available in some research labs form Brazilian Research Institutes or Universities. The great challenge is to transform those semiconductor detector in final components for assemblies that will be used under severe environmental conditions. The aim of this paper is to show the theoretical bases on the IR detection, the more widely used sensor types and the evolution brought with the use of new detection devices and IR cameras for detection and identification of targets that emit infrared energy.

Ultrahigh-gain colloidal quantum dot infrared avalanche photodetectors.

Colloidal quantum dots (CQDs) are promising for infrared photodetectors with high detectivity and low-cost production. Although CQDs enable photoinduced charge multiplication, thermal noise in low-bandgap materials limits their performance in IR detectors. Here we present a pioneering architecture of a CQD-based infrared photodetector that uses kinetically pumped avalanche multiplication. By applying a strong electric field to a thick CQD layer (>540 nm), electrons acquire kinetic energy beyond the bandgap of the CQD material, initiating kinetically pumped charge multiplication. Optimizing the dot-to-dot distance to approximately 4.1 nm improves performance by balancing impact ionization and electron hopping. Our optimized CQD-based infrared photodetector achieved a maximum multiplication gain of 85 and a peak detectivity of 1.4 × 1014 Jones at 940 nm. This architecture offers potential for single-photon detection and ultrahigh detectivity applications.

(Invited) Heterogeneous Integration of IR Detectors with CMOS and Thin Film Transistors

Colloidal quantum dots (CQDs) show promising performance in IR detection because of their many unique advantages, including high material quality, flexibility in operation wavelength, easy fabrication process and suitability for heterogeneous integration with CMOS. Our presentation will cover three areas about colloidal quantum dot detectors: (a) the physical model of CQDs, (b) integration of CQDs with electronics, and (c) strategies of overcoming the limit of dark current for uncooled IR detection. For (a), we will present a physical model considering the unique transport properties of ligand connected quantum dot detectors. The model shows how the CQD detectors perform differently than conventional p-i-n detectors and why those popular parameters derived from Shockley’s diode model such as reverse saturation current and ideality factor cannot model the CQD detectors. For (b), we will show how CQD detectors can be integrated with IGZO thin film transistors on glass substrate, GaN LEDs for wavelength converters, and Si CMOS in a back-end-of-line process. For (c), we will discuss designs of colloidal quantum dot detectors for longer IR wavelengths with minimal effects of dark current to support uncooled operation.

In-flight calibration of the MEDA-TIRS instrument onboard NASA's Mars2020 mission

In-flight calibration of the MEDA-TIRS instrument onboard NASA's Mars2020 mission

Calibration of MAJIS (Moons and Jupiter Imaging Spectrometer). IV. Radiometric calibration (invited)

The MAJIS (Moons and Jupiter Imaging Spectrometer) instrument is an imaging spectrometer on-board the JUICE (JUpiter ICy moons Explorer) spacecraft. MAJIS covers the spectral range from 0.5 to 5.54 μm with two channels [visible–near infrared (VISNIR) and IR]. A comprehensive campaign of on-ground MAJIS calibration was conducted in August and September 2021 in the IAS (Institut d’Astrophysique Spatiale, CNRS/Université Paris-Saclay) facilities. In this article, we present the results relevant for the radiometric calibration of MAJIS. Due to the specific characteristics of the MAJIS detectors (H1RG from Teledyne), an extensive detector characterization campaign was implemented for both the VISNIR and IR detectors before integration so as to validate readout procedures providing precision and accuracy. The characterization also provided critical information on linearity and operability as a function of the integration time and operating temperature. The radiometric calibration of the integrated MAJIS instrument focused on the determination of the instrument transfer function in terms of DN output per unit of radiance for each MAJIS data element as a function of its position in the field of view of MAJIS and its central wavelength. The radiometric calibration of the VISNIR channel required a specific procedure due to stray light at short wavelengths. Observations of an internal calibration source during calibration and after launch (April 14, 2023) showed that there were minor changes in both the VISNIR and IR channels. The instrument transfer functions to be used in flight have been updated on this basis.

Recent Advancements in Nanomaterials for Near‐Infrared to Long‐Wave Infrared Photodetectors

AbstractNanomaterials have superior electronic, optical, and mechanical properties making them highly suitable for a range of applications in optoelectronics, biomedical fields, and photonics. Nanomaterials‐based IR detectors are rapidly growing due to enhanced sensitivity, wide spectral range, and device miniaturization compared to commercial photodetectors. This review paper focuses on the significant role of nanomaterials in infrared detection, an area critical for enhancing night vision and health monitoring technologies. The latest advancements in IR photodetectors that employ various nanomaterials and their hybrids are discussed. The manuscript covers the operational mechanisms, device designing, performance optimization strategies, and material challenges. This review aims to provide a comprehensive overview of the current developments in nanomaterial‐based IR photodetectors and to identify key directions for future research and technological advancements.

Graphene-Liquid Crystal Synergy: Advancing Sensor Technologies across Multiple Domains.

This review explores the integration of graphene and liquid crystals to advance sensor technologies across multiple domains, with a focus on recent developments in thermal and infrared sensing, flexible actuators, chemical and biological detection, and environmental monitoring systems. The synergy between graphene's exceptional electrical, optical, and thermal properties and the dynamic behavior of liquid crystals leads to sensors with significantly enhanced sensitivity, selectivity, and versatility. Notable contributions of this review include highlighting key advancements such as graphene-doped liquid crystal IR detectors, shape-memory polymers for flexible actuators, and composite hydrogels for environmental pollutant detection. Additionally, this review addresses ongoing challenges in scalability and integration, providing insights into current research efforts aimed at overcoming these obstacles. The potential for multi-modal sensing, self-powered devices, and AI integration is discussed, suggesting a transformative impact of these composite sensors on various sectors, including health, environmental monitoring, and technology. This review demonstrates how the fusion of graphene and liquid crystals is pushing the boundaries of sensor technology, offering more sensitive, adaptable, and innovative solutions to global challenges.

Development of Polarization-Insensitive THz-to-IR Converters for Low-IR-Signature Target Detection and Imaging.

A THz-to-IR converter can be an effective solution for the detection of low-IR-signature targets by combining the advantages of mature IR detection mechanisms with high atmospheric transmittance in the THz region. A metallic metasurface (MS)-based absorber with linear polarization dependence based on a split-ring resonator (SRR) unit cell has been previously studied as a preliminary example of a THz-to-IR converter structure in the literature. In this simulation-based study, a new cross-shaped unit cell-based metallic MS absorber structure sensitive to dual polarization is designed to eliminate linear polarization dependency, thereby allowing for incoherent detection of THz radiation. A model is developed to calculate the temperature difference and the response time for this new cross-shaped absorber structure, and its performance is compared to the SRR structure for both coherent and incoherent illumination. This model allows for understanding the efficiency of these structures by considering all loss mechanisms which previously had not been considered. It is found that both structures show similar performance under linearly polarized coherent illumination. However, under incoherent illumination, the IR emittance efficiency as gauged by the temperature difference for the cross-shaped structure is found to be twice as high as compared to the SRR structure. The results also imply that calculated temperature differences for both structures under coherent and incoherent illumination are well above the limit of the minimum resolvable temperature difference of the state-of-the-art IR cameras. Therefore, dual-polarized or multi-polarization-sensitive MS absorber structures can be crucial for developing cost-effective THz-to-IR converters and be implemented in THz imaging solutions.

Parallel coupling of gas chromatography to mass spectrometry and solid deposition Fourier transform infrared spectroscopy: an innovative approach to address challenging identifications.

The request for novel hyphenated instruments and techniques, capable of affording exhaustive information and results, is a focus continuously watched out. In this context, the present work aimed at the development of an integrated system combining gas chromatographic (GC) separation with mass spectrometry (MS) and (solid deposition) Fourier transform infrared spectroscopy (FTIR) detection. An external transfer line was designed inthelab for the parallel coupling of the two detectors, in such a way toobtain complementary analytical information consisting of anMS spectrum, anIR spectrum and linear retention indices (LRI), within a single analysis. The instrument performance was demonstrated for the analysis of a commercial mixture consisting of 139 hydrocarbons, comprising linear, branched, unsaturated and aromatic compounds. A 100-m poly(dimethylsiloxane) column was employed for the separation, and the outlet flow was split 95:5 between the IR and MS detectors using two uncoated capillaries. The IR spectra were acquired from solid deposits on a zinc selenide disc (-90 °C), over a spot (detector area) of about 0.1 mm2, in the range of 4000-700 cm-1 and at a resolution of 4 cm-1. Final identification of the separated compounds by alibrary search was achieved by excluding incorrect results, sequentially using a three-filter approach (85% similarity against reference MS and IR library spectra and ±10 LRI unit tolerance). Based on these preliminary results, the GC-MS/sd-FTIR system is a promising tool for the characterization of complex matrix constituents, for which identification is cumbersome, by using only one detection technique.

The Tobin Coefficient: A Relevant Photodetector Performance Metric for IR Imaging

The well-known Rule07 is a simple thus efficient way to compare available technologies for IR imaging detectors in terms of dark current. The noise is then often estimated using a shot noise approximation on the dark current. Both II–VI and III–V communities use this rule of thumb as a reference for well-performing IR photodiodes. For HOT applications, a dark current close to this rule07 is considered a necessary condition but not a sufficient one to obtain a high-performance IR imager. Indeed, when limited by shot noise, rule07 describes well the noise behavior of the considered device. However, when considering low-frequency noise, it fails to describe the expected performances. In this paper, we focus on another figure-of-merit, dedicated to detector low-frequency noise rather than dark current. Systemic 1/f noise investigation in an IR detector was first reported by Tobin et al. in 1980. There is today a relative consensus on the fact that measured 1/f noise is proportional to the dark current. The ratio between the amplitude of the 1/f noise and the dark current of the same devices may therefore be used as a figure-of-merit for a given technology. This ratio (called the Tobin factor αT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\alpha }_{\ ext{T}}$$\\end{document}) therefore appears adequate to compare different technologies as a figure-of-merit qualifying 1/f noise properties. This dimensionless ratio can also be very useful for optimizing a particular technology or process. However, in order to be relevant, this figure-of-merit must be estimated carefully as it appears, for instance, pixel pitch-dependent. Different examples of Tobin coefficient extraction are presented in this paper. We show that, depending on the technologies, the values of the Tobin coefficient can spread over several orders of magnitude. However, only low values result in high-quality IR imagers. Today, the best results we obtained show that αT=10-5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\alpha }_{\ ext{T}}={10}^{-5}$$\\end{document} is a state-of-art value to be compared with.

Effect of solvent type on chemical composition distribution analysis of polyolefins using crystallization elution fractionation (CEF)

Effect of solvent type on chemical composition distribution analysis of polyolefins using crystallization elution fractionation (CEF)

Use of Electron Beam-Induced Current Technique to Characterize Transport Properties of Narrow-Gap-Energy Materials for IR Detection

The electron beam-induced current technique (EBIC) developed at CEA-Leti has been a valuable tool for studying the transport properties of minority carriers in HdCdTe. Indeed, previous work has demonstrated the use of this technique for estimating diffusion length from the exponential decay of EBIC as a function of junction distance, as well as direct measurement of the modulation transfer function (MTF) of small pixel pitch diodes. In this work, a modulated electron beam and a lock-in amplifier are used to measure the variation in current and phase shift with the scan distance to the junction. This work is focused on the estimation of the minority carrier lifetime from the linear evolution of the phase shift as a function of junction distance.

Portable Medication Reminder System for Elderly and Alzheimer's Patients

As healthcare demands rise and the senior population grows, innovative results are essential for cases with habitual ails and memory-related conditions like Alzheimer's. Introduces a movable drug memorial System designed for hospitals, old age homes, and independent elderly citizens. The system, erected around an Arduino UNO microcontroller, integrates an IR detector, buzzer, TV display, RTC module, keypad, LED, and GSM module, working together to give timely drug monuments. In hospitals, it integrates into patient care routines, driving visual and audile monuments for nursing staff to insure timely drug delivery. This integration helps drug crimes and ensures that cases are cleaved to their prescribed treatment plans. Old age homes profit from the stonerfriendly device, allowing residents to manage their drug schedules via the TV display and keypad. The system's simplicity and trust ability can significantly ameliorate the quality of life for senior residents. For independent seniors, the movable system provides monuments through the TV display and buzzer, with the GSM module transferring SMS cautions to family members or caregivers if boluses are missed. This point is particularly precious for those who live alone, offering peace of mind to both the seniors and their families. Alzheimer's cases, floundering with memory loss and drug adherence, gain significantly from this system. The combination of visual and audile monuments, along with the straightforward keypad and TV display, offers an effective tool for managing their drug needs. By icing timely drug input, alleviates the progression of symptoms and enhances the overall well-being of Alzheimer's cases.

Tuning band gaps in lead chalcogenides under pressure: implications for infrared detection applications

This study employs first-principle calculations within density functional theory (DFT) to explore the structural, electronic, optical, and thermoelectric properties of lead chalcogenides (PbS, PbSe, and PbTe). The investigation focuses on their potential application as infrared photodetectors, leveraging their narrow-band gap semiconductor characteristics. The influence of pressure on the band gap and various electronic, optical, and thermoelectric properties is thoroughly analyzed. The calculated band gap values for PbS, PbSe, and PbTe are determined to be 0.29 eV, 0.18 eV, and 0.18 eV, respectively, aligning well with experimental data. Notably, the study reveals non-linear changes in band gap values under pressure, with phase transitions observed at specific pressure thresholds in PbS and PbSe, but not in PbTe. Under varying pressure conditions, the optical peaks shift towards lower energy levels with increased intensity. The static dielectric constant of PbS, PbSe, and PbTe exhibits distinct variations within pressure ranges of 0–8 GPa. Transport coefficients (S, σ, ke) are calculated using semi-classical Boltzmann theory across different temperatures and pressures, indicating that heavier compounds exhibit higher electrical and thermal conductivity values. At 300 K, the maximum ZT values are determined to be 0.85, 0.8, and 0.52 for PbS, PbSe, and PbTe, respectively. The study suggests enhanced thermoelectric properties of these structures at lower temperatures, particularly highlighting PbS and PbSe as promising candidates for thermoelectric applications below 500 K. Exploring the impact of pressure on the thermoelectric parameters of lead chalcogenides reveals interesting trends, with PbTe demonstrating higher thermoelectric efficiency under increased pressure compared to PbS and PbSe. These findings provide valuable insights into the potential applications and performance of lead chalcogenides in IR detection and thermoelectric systems.

Revelation of luminescence-thermometry, light generation in first biological window and IR detection capabilities of sodium yttrium fluoride co-doped with Yb3+ and Er3+ ions synthesized by low-cost approach

Revelation of luminescence-thermometry, light generation in first biological window and IR detection capabilities of sodium yttrium fluoride co-doped with Yb3+ and Er3+ ions synthesized by low-cost approach

Effect of sintering condition and Ca2+-substitution on structural and electrical properties of lead-free Ba0.46Sr0.54TiO3 piezoceramics for uncooled IR detectors application

Effect of sintering condition and Ca2+-substitution on structural and electrical properties of lead-free Ba0.46Sr0.54TiO3 piezoceramics for uncooled IR detectors application