Room-temperature Detectors Research Articles

High detectivity terahertz radiation sensing using frequency-noise-optimized nanomechanical resonators

We achieve high detectivity terahertz radiation sensing using a silicon nitride nanomechanical resonator functionalized with a metasurface absorber. High performances are achieved by striking a balance between the frequency stability of the resonator and its responsivity to absorbed radiation. Using this approach, we demonstrate a detectivity D*≈3.4×109cm⋅Hz/W and a noise equivalent power NEP≈36pW/Hz that outperform the best room-temperature on-chip THz detectors, such as pyroelectric detectors, while maintaining a comparable thermal response time of ≈200 ms. Our optical absorber consists of a 1-mm diameter metasurface, which currently enables a 0.5–3 THz detection range but can easily be scaled to other frequencies in the THz and infrared ranges. In addition to demonstrating high-performance terahertz radiation sensing, our work unveils an important fundamental trade-off between frequency stability and responsivity in thermal-based nanomechanical radiation sensors.

Iodine- and Oxygen-Free Sensitization Process for VPD-PbS:IO Detectors

Uncooled lead salt detectors have significant advantages in developing the next generation of infrared detectors with SWaP3 features. Herein, a one-step pure nitrogen (N2) sensitized process is proposed to simplify the fabrication process for a wafer-scale lead sulfide (PbS) film fabricated by a modified low-temperature vapor physical deposition (VPD). A room-temperature peak detectivity of 4 × 1010 Jones is achieved after one-step pure N2 sensitization process carried out for VPD-PbS:IO films, which is comparable to the detectors fabricated from the standard chemical bath deposition (CBD) process. The VPD fabrication technology with an iodine-free sensitization process provides an available route for promoting the commercial application of uncooled infrared detectors.

Switching On/Off Air Conditioner and Fan Alternately based on IoT Motion Detection and Room Temperature

The Internet of Things (IoT) connects electrical appliances that enable data transfer for communication without human intervention. IoT has evolved, and its implementation has been extended to residential areas. It can be said that all residents use fans as cooling appliances. In Malaysia, having a fan is not sufficient due to its hot temperature throughout the year. Therefore, most of the residents use air conditioners as an additional cooling appliance. Using air conditioners regularly could contribute to high energy consumption. Furthermore, excessive energy consumption occurs when an occupant of a residential building forgets to switch off electrical appliances such as fans and air conditioners. In addition, leaving electrical appliances turning on when nobody is at home just wastes energy. This work aims to develop an IoT-based smart home controlling system for minimizing energy consumption. This system enables automatic control that depends on room temperature and motion detection. Various types of sensors, such as temperature sensor, humidity sensor, and motion sensor, are used to switch on/off the air conditioner and fan. The air conditioner and fan will be alternately switched on and off depending on the ideal room temperature. The testing results show a significant reduction in energy consumption and a promising decrease in the electricity bill. Future works should be focusing on determining the over limit energy consumption. On top of that, this research would be best to try on simulation to get better results.

Band Alignment Semimetal Heterojunction-Based Ultrabroadband Photodetector for Noncontact Gesture Interaction with Low Latency.

Non-contact gesture recognition and interaction (NGRI) revolutionizes the natural user interface, fundamentally transforming human interactions with daily-use technology. Conventional NGRI systems frequently encounter obstacles such as pronounced latency and environmental disturbances, including humidity or lighting conditions, resulting in compromised system fluidity and robustness. This study highlights the utilization of silicon-based semimetal heterojunction photodetectors for precise gesture recognition and seamless human-machine interaction. Through the application of band alignment theory and sophisticated TCAD simulation, heterojunction barriers are successfully optimized by fine-tuning parameters including Si doping concentration and semimetal thickness. By strategically aligning vertical material growth and implementing vertical heterojunction configuration, a room temperature detector with exceptional sensitivity (specific detectivity (D*): ≈1011 Jones), ultra-broad spectral range (405-10600 nm), and rapid response time (≈ µs) is achieved. Harnessing its distinguished speed and sensitivity in detecting human infrared radiation, in conjunction with an advanced spatial-temporal comparison algorithm and a multi-channel high-frequency sampling processing design, a NGRI system with low latency, high precision, minimal energy consumption, and versatility across diverse scenarios has been developed. The results pave the way for non-contact sensor design and may further enhance the practicality and user experience of non-contact human-machine interaction systems.

Au-Loaded WS₂/SnO₂ Heterostructure for Room Temperature Detection of CO at ppb-Level

Au-Loaded WS₂/SnO₂ Heterostructure for Room Temperature Detection of CO at ppb-Level

P-Type AgAuSe Quantum Dots.

Control over the carrier type of semiconductor quantum dots (QDs) is pivotal for their optoelectronic device applications, and it remains a nontrivial and challenging task. Herein, a facile doping strategy via K impurity exchange is proposed to convert the NIR n-type toxic heavy-metal-free AgAuSe (AAS) QDs to p-type. When the dopant reaches saturation at approximately 22.2%, the Femi level shifts down to near the valence band, with the p-type carrier characteristics confirmed through photoluminescence, X-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy analysis. First-principles calculations reveal that K impurities preferentially occupy interstitial positions and form complex defects when combined with the abundant cationic vacancy in AAS caused by the high mobility of Ag, thereby functioning as a shallow acceptor to enhance p-type conductivity. A p-n homojunction based on AAS QDs has been fabricated and served as the active layer in a photodiode device, which demonstrates an excellent room-temperature detectivity of up to 2.29 × 1013 Jones and an outstanding linear dynamic range of over 103 dB. This study provides guidance for future design of the p-n homojunction using the toxic-metal-free Ag-based QDs and further unleashes their potential in advanced optoelectronic device applications.

Spectrally Tunable Ultrafast Long Wave Infrared Detection at Room Temperature.

Room-temperature longwave infrared (LWIR) detectors are preferred over cryogenically cooled solutions due to the cost effectiveness and ease of operation. The performance of present uncooled LWIR detectors such as microbolometers, is limited by reduced sensitivity, slow response time, and the lack of dynamic spectral tunability. Here, we present a graphene-based efficient room-temperature LWIR detector with high detectivity and fast response time utilizing its tunable optical and electronic characteristics. The inherent weak light absorption is enhanced by Dirac plasmons on the patterned graphene coupled to an optical cavity. The absorbed energy is converted into photovoltage by the Seebeck effect with an asymmetric carrier generation environment. Further, dynamic spectral tunability in the 8-12 μm LWIR band is achieved by electrostatic gating. The proposed detection platform paves the path to a fresh generation of uncooled graphene-based LWIR photodetectors for wide ranging applications such as molecular sensing, medical diagnostics, military, security and space.

Characterization of TlBr gamma detector based on electrical charge and Cherenkov light analysis

Thallium Bromide (TlBr) semiconductors have been extensively studied for their potential as room-temperature gamma-ray detectors, owing to their advantageous material properties. Recent advancements have demonstrated that timing performance in TlBr detectors can be enhanced by incorporating Cherenkov photon detection during gamma-ray interactions. In this study, TlBr detector (5 × 5 × 5 mm3) was investigated through a combined analysis of electrical charge and Cherenkov light signals. The depth of interaction (DoI) correction applied to the trapezoidal filter output yielded significant improvements in energy resolution, reducing it from 5.6% to as low as 2.51% FWHM at 511 keV and from 4.6% to as low as 1.94% FWHM at 662 keV, within specific C/A ratio ranges. The drift time, ranging from 2 to 30 μs, was found to be proportional to the C/A ratio, covering 4 to 9 photoelectrons. Furthermore, a time resolution of 511 ps was achieved at 6 photoelectrons, based on the FWHM of the time difference distribution in coincidence measurements at 511 keV using a 22Na source. These results highlight the potential of TlBr detectors for achieving high energy and timing resolution in gamma detection, particularly for Compton-PET systems.

Microstructure evolution of CdZnTe crystals irradiated by heavy ions

Consideration of irradiation effects is important for in-orbit operation and radiation protection in aerospace applications. The configuration of irradiation defects and their impact on deteriorating the carrier transport properties of CZT crystals need to be clarified. In this study, the microdefect evolution mechanism of CdZnTe (CZT) crystals under 10 MeV Chlorine (Cl) ion irradiation at flux of 1×1010∼1×1012 n·cm-2 are investigated. The stacking faults first appear in the CZT crystal at 4.5×10-4 displacement per atom (dpa), which are categorized into slip-type, gap-type and vacancy-type. In order to hinder the further expansion of stacking fault, S-shaped stacking fault dipole appears. When the dpa reaches 4.5×10-2, the local phase transition occurs in the damage zone to form CuPt-A ordered phase with ZnTe/CdTe periodic arrangement because the fluctuation in local composition and strain caused by cascade collisions. The deterioration of electric field distribution and charge collection caused by irradiation damage layer leads to the decrease of γ-ray detection ability. The energy resolution (ER) of the CZT detector for γ-ray can be maintained at 30.6% when the ion flux accumulates to 1×1012 n·cm-2, revealing high irradiation hardness. Consequently, these findings provide a theoretical basis for the radiation damage recovery of CZT detectors, further demonstrating that CZT crystals are the most competitive new generation of room-temperature nuclear radiation detection materials, and can provide radiation protection strategies for similar compound semiconductor materials.

Growth and Performance of Perovskite Semiconductor CsPbX3 (X = Cl, Br, I, or Mixed Halide) for Detection and Imaging Applications.

The material family halide perovskites has been critical in recent room-temperature radiation detection semiconductor research. Cesium lead bromide (CsPbBr3) is a halide perovskite that exhibits characteristics of a semiconductor that would be suitable for applications in various fields. In this paper, we report on the correlations between material purification and crystal material properties. Crystal boules of CsPbX3 (where X = Cl, Br, I, or mixed) were grown with the Bridgman growth method. We describe in great detail the fabrication techniques used to prepare sample surfaces for contact deposition and sample testing. Current-voltage measurements, UV-Vis and photocurrent spectroscopy, as well as photoluminescence measurements, were carried out for material characterization. Bulk resistivity values of up to 3.0 × 109 Ω∙cm and surface resistivity values of 1.3 × 1011 Ω/□ indicate that the material can be used for low-noise semiconductor detector applications. Preliminary radiation detectors were fabricated, and using photocurrent measurements we have estimated a value of the mobility-lifetime product for holes (μτ)h of 2.8 × 10-5 cm2/V. The results from the sample testing can shed light on ways to improve the crystal properties for future work, not only for CsPbX3 but also other halide perovskites.

Pt-modified hollow tube-like polyaniline-based NH3 sensor

Polyaniline (PANI) has significant applications in room-temperature NH3 detection due to its unique and reversible doping-dedoping chemical state, stable electrical conductivity and easy and convenient synthesis process. However, pristine PANI still suffers from poor performance in terms of sensitivity, response speed and detection limit. To address issues of low sensitivity and high detection limit, a platinum (Pt)-modified hollow PANI (Pt-PANI) sensor was designed. The Pt-PANI was fabricated by an in-situ sacrificial template method, and Pt-MnO2 nanowires obtained from hydrothermal combined impregnation methods, utilizing the potential generated during the sacrificial reaction with acid to induce the polymerization of aniline on the nanowires' surfaces. This hollow tube-like structure with the unique inlay of Pt particles provides numerous gas diffusion pathways, facilitating the penetration of the target gas into the internal space, enhancing the utilization of the inner surface and accelerating the electron transfer. Meanwhile, the presence of Pt particles not only forms Schottky junctions that cause large changes in the resistance of the composites, but also catalysis and accelerates the gas sensing reaction between the target gas and the sensitive materials. Gas sensitivity tests revealed that the prepared Pt-PANI-3 gas sensor exhibits a low NH3 detection limit of 20.3 ppb, along with reproducibility and long-term stability. Compared to pure PANI-sensor, the sensitivity to 20 ppm NH3 increased by 17 times. This work offers real-time sensing and monitoring of environmental changes, making it highly promising for future applications.

V2CTx MXene-derived porphyrin-based MOF modified with ZIF-67 as an ultra-stretchable and deformable double-network hydrogel for room temperature detection of dimethylamine

Stretchable and self-adhesive chemical sensors are highly appealing for wearable health and environmental monitoring applications. Here, for the first time, we report V2CTx MXene-derived Porphyrin-based MOF (V-PMOF) modified with Zeolite imidazole framework-67 (ZIF-67) for the room temperature detection of dimethylamine. V-PMOF is synthesized from V2CTx MXene using tetrakis(4-carboxyphenyl)porphyrin (TCPP) as a ligand via a solvothermal route. Thereafter, an optimized wt% ratio (1:1) of ZIF-67 and V-PMOF crosslinked by PVA/polypyrrole (Ppy) is put for lyophilization which yields the V-PMOF@ZIF-67 double-network (DN) hydrogel. Detailed morphological assessment reveals dodecahedron-shaped ZIF-67 particles are evenly distributed on the V-PMOF sheets which are encapsulated in the polymer matrix. This three-dimensional polymeric structure of hydrogel largely enhances the active sites on the surface with abundant oxygen vacancies. The sensor exhibits a dynamic range of 1 ppm to 13 ppm with a low limit of detection (LOD = 3s/σ) of 902 ppb towards dimethylamine detection. Further, quick response/recovery times (3 s/7 s) are observed along with high robustness tosignificant mechanical deformation, including twist (270°), large-range bending, and up to 500% strain without affecting the sensing performance. The remarkable sensitivity is accredited to the abundance of O2 functional groups in polymer chains and the formation of Schottky heterojunction between V-PMOF and ZIF-67, facilitating charge transfer between the heterostructure to dimethylamine during sensing. In addition, the self-adhesive hydrogel-based sensor shows outstanding selectivity against other typical volatile organic compounds (VOCs) such as acetone, ethanol, ammonia, trimethylamine, aniline, and methanol. In overall, this work provides insight into designing extremely flexible sensitive dimethylamine gas sensor as innovative material.

Photodiodes Made of Cascade Perovskite Single Crystals with Passivation Layers for High-Energy-Resolution γ-ray Spectroscopy.

Lead halide perovskite single crystals (LHPSC) are promising for room-temperature γ-ray spectroscopy in radiation detection. While MA(CH3NH3)-based LHPSCs are the most straightforward and cost-effective to synthesize from solution, their performance in γ-ray spectroscopy is hindered by significant noise and ion migration at high bias, which degrades their energy resolution (ER). The work introduced an n-type/intrinsic/n-type photodiode incorporating passivation layers of MA-based LHPSCs, grown through solution-process epitaxial growth. This single-polarity device demonstrated an outstanding ER of 3.6% for 662 keV γ-ray photons. Overall, this work provides useful information for developing room-temperature γ-ray detectors based on solution-processed lead halide perovskites.

Photoelectric H2S Sensing Based on Electrospun Hollow CuO-SnO2 Nanotubes at Room Temperature.

Pure tin oxide (SnO2) as a typical conductometric hydrogen sulfide (H2S) gas-sensing material always suffers from limited sensitivity, elevated operation temperature, and poor selectivity. To overcome these hindrances, in this work, hollow CuO-SnO2 nanotubes were successfully electrospun for room-temperature (25 °C) trace H2S detection under blue light activation. Among all SnO2-based candidates, a pure SnO2 sensor showed no signal, even toward 10 ppm, while the 1% CuO-SnO2 sensor achieved a limit of detection (LoD) value of 2.5 ppm, a large response of 4.7, and a short response/recovery time of 21/61 s toward 10 ppm H2S, as well as nice repeatability, long-term stability, and selectivity. This excellent performance could be ascribed to the one-dimensional (1D) hollow nanostructure, abundant p-n heterojunctions, and the photoelectric effect of the CuO-SnO2 nanotubes. The proposed design strategies cater to the demanding requirements of high sensitivity and low power consumption in future application scenarios such as Internet of Things and smart optoelectronic systems.

Chemiresistive room temperature H2S sensor based on CunO nanoflowers fabricated by laser ablation

Hierarchical CunO nanoflowers were synthesized through the laser ablation of a CuO target in NaOH solutions for room-temperature (27 ℃) H2S detection. Notably, the pH value of NaOH solutions influenced both the micro-morphologies and compositions of the CunO products, as evidenced by XRD, XPS, SEM and TEM. In high pH solutions, the specific surface area of the CunO products increased, their thickness decreased, and the Cu2O content diminished, resulting in enhanced sensitivity, selectivity and stability of the CunO products’ response to H2S. Notably, the pH14# sample synthesized using an NaOH solution with a pH value of 14 featured pure CuO nanoflowers comprising slightly curled nanosheets with a thickness of approximately 10 nm. This sensor demonstrated excellent H2S sensing performance at room temperature, exhibiting a response value of 1.17 for 10 ppb H2S, along with high selectivity and good long-term stability. However, after exposure to H2S, the resistance of the sensor did not recover to its baseline in air at room temperature. Thermogravimetry results revealed that a temperature of 300 °C was effective for recovery of the sensor. Consequently, the operation temperature of the pH14# sensor was controlled using a micro-hotplate. In the pulse heating mode, the sensor’s response to 100 ppb H2S was 1.5, with a response time of 135 s and a recovery time of 137 s.

TexSe1-x Shortwave Infrared Photodiode Arrays with Monolithic Integration.

TexSe1-x shortwave infrared (SWIR) photodetectors show promise for monolithic integration with readout integrated circuits (ROIC), making it a potential alternative to conventional expensive SWIR photodetectors. However, challenges such as a high dark current density and insufficient detection performance hinder their application in large-scale monolithic integration. Herein, we develop a ZnO/TexSe1-x heterojunction photodiode and synergistically address the interfacial elemental diffusion and dangling bonds via inserting a well-selected 0.3 nm amorphous TeO2 interfacial layer. The optimized device achieves a reduced dark current density of -3.5 × 10-5 A cm-2 at -10 mV, a broad response from 300 to 1700 nm, a room-temperature detectivity exceeding 2.03 × 1011 Jones, and a 3 dB bandwidth of 173 kHz. Furthermore, for the first time, we monolithically integrate the TexSe1-x photodiodes on ROIC (64 × 64 pixels) with the largest-scale array among all TexSe1-x-based detectors. Finally, we demonstrate its applications in transmission imaging and substance identification.

Quantum Confinement and End-Sealing Effects for Highly Sensitive and Stable Nitrogen Dioxide Detection: Homogeneous Integration of Ti3C2Tx-Based Flexible Gas Sensors.

The real-time and room-temperature detection of nitrogen dioxide (NO2) holds significant importance for environmental monitoring. However, the performance of NO2 sensors has been hampered by the trade-off between the high sensitivity and stability of conventional sensitive materials. Here, we present a novel fully flexible paper-based gas sensing structure by combining a homogeneous screen-printed titanium carbide (Ti3C2Tx) MXene-based nonmetallic electrode with a MoS2 quantum dots/Ti3C2Tx (MoS2 QDs/Ti3C2Tx) gas-sensing film. These precisely designed gas sensors demonstrate an improved response value (16.3% at 5 ppm) and a low theoretical detection limit of 12.1 ppb toward NO2, which exhibit a remarkable 3.5-fold increase in sensitivity compared to conventional Au interdigital electrodes. The outstanding performance can be attributed to the integration of the quantum confinement effect of MoS2 QDs and the conductivity of Ti3C2Tx, establishing the main active adsorption sites and enhanced charge transport pathways. Furthermore, an end-sealing effect strategy was applied to decorate the defect sites with naturally oxygen-rich tannic acid and conductive polymer, and the formed hydrogen bonding network at the interface effectively mitigated the oxidative degradation of the Ti3C2Tx-based gas sensors. The exceptional stability has been achieved with only a 1.8% decrease in response over 4 weeks. This work highlights the innovative design of high-performance gas sensing materials and homogeneous gas sensor techniques.

Study on the Gas-Chromic Character of Pd/TiO2 for Fast Room-Temperature CO Detection.

As a widely used support, TiO2 has often been combined with Pd to form highly sensitive gas-chromic materials. Herein, we prepared a series of Pd/TiO2 catalysts with different Pd content (from 0.1 to 5 wt.%) by the impregnation method for their utilization in fast room-temperature CO detection. The detection was simply based on visible color change when the Pd/TiO2 was exposed to CO. The sample with 1 wt.% Pd/TiO2 presented an excellent CO gasochromic character, associated with a maximum chromatic aberration value of 90 before and after CO exposure. Systematic catalyst characterizations of XPS, FT-IR, CO-TPD, and N2 adsorption-desorption and density functional theory calculations for the CO adsorption and charge transfer over the Pd and PdO surfaces were further carried out. It was found that the interaction between CO and the Pd surface was strong, associated with a large adsorption energy of -1.99 eV and charge transfer of 0.196 e. The color change was caused by a reduction in Pd2+ to metallic Pd0 over the Pd/TiO2 surface after CO exposure.

Development of SnO2 functionalized In2O3 porous microrods for trace level detection of formaldehyde at room temperature

Room temperature detection is a crucial objective in semiconductor sensor research, given its inherent benefits including reduced energy consumption, extended sensor lifespan, and significant reduction of safety hazards. Herein, novel room temperature sensing materials, SnO2-modified In2O3 porous microrods were synthesized, which exhibited exceptional sensing capability towards formaldehyde at room temperature. Specifically, the 5%-SnO2/In2O3 porous microrods demonstrate an impressive sensing response across varying formaldehyde concentrations, even at sub-ppm levels (0.1 ppm, 5.22), with a theoretical detection limit of 5.47 ppb, thereby enabling the detection of trace amounts of formaldehyde. Moreover, the sensors exhibit superior formaldehyde selectivity, rapid response characteristic, as well as good stability and reproducibility. The exceptional formaldehyde sensing ability of the SnO2/In2O3 sensor primarily arises from the creation of n-n heterojunctions at the SnO2/In2O3 interface, effectively modulating the interfacial potential. Additionally, the presence of SnO2 enhances the amount of surface-adsorbed oxygen species and active sites, thereby boosting sensing response. The porous rod-like structures further facilitate gas adsorption and diffusion, enhancing gas sensing capabilities. This work presents a novel strategy for constructing SnO2-In2O3 heterojunctions to achieve room-temperature formaldehyde detection.

Room temperature detection of n-butanol Ce-doped MOF:ZnO sensor under UV activation

Being one of toxic and flammable volatile organic compounds (VOC), n-butanol has brought about many potential health risks, there is an urgent demand for highly sensitive detection techniques to monitor its concentration in occupational environments and the air. In this paper, Ce-doped MOF:ZnO sensors under UV activation for room-temperature detection of n-butanol were synthesized by the co-precipitation method and systemically characterized by XRD, SEM, HRTEM, and XPS. The sensitive performances were evaluated by the use of a WS-30A gas sensor measurement system. The results showed that Ce doping has significantly enhanced the sensitivity of the MOF:ZnO sensors, and the response value of the 0.08 % Ce-doped ZnO sensor has achieved to 397.30, which was 9.32 times higher than that of the pristine MOF:ZnO. And the response and recovery times were 17 and 117 s respectively, demonstrating a speedy detection capability. In addition, the sensor gained excellent stability and reproducibility with special selectivity for n-butanol. The comprehensive achievements of this research would be promising to promote the development of volatile organic compound detection technology and beneficial to the well application in the fields of environmental monitoring, industrial safety, and public health.