Bottom Contact Research Articles

Reliability aspects in repulsive steric hindrance approach: Selectivity and sensitivity investigations

Dual metal regulated bottom gate top contact structured Organic Thin Film Transistor based biosensor (Bio-OTFT) for recognition of breast cancer cell lines along with the non-tumorigenic epithelial cell line is presented here. A feasible fabrication scheme for Bio-OTFT has been demonstrated. Repulsive steric hindrance (RSH) consideration inside the cavity zone directs more practical and realistic sensing mechanisms. The insightful electrostatic analysis regarding electric field, energy band diagram, transfer characteristics (IDS-VGS), and transconductance (gm) has been described. Alteration of the dielectric constant (k) of these cancerous and healthy cell lines stated the recognition scheme in this reported Bio-OTFT. The efficiency of the recommended model has been assessed thoroughly with the reported OTFT literatures. The sensitivity is examined respecting drain current (IDS) in (A/μm), gm in (μS/μm), threshold voltage (VTH) in Voltage and sub-threshold swing (SS) in (mV/dec) and reaches to the maximum value of 2.3 × 108, 1.85 × 1010, 0.68, and 0.08 for T-47D cell line at VGS = −1.25 V. The recommended model thus suggests an enormous reliability and possibility for biosensing purposes.

Experimental Characterisation of BGBC OTFT for Indoor CO<sub>2</sub> Gas Sensing

Global warming is a concern nowadays due to excessive release of harmful gasses to the environment, leading to greenhouse effect phenomena worldwide. Based on the data provided by global pollution agencies, the release of greenhouse gasses to the atmosphere is the main cause of pollution and the increase in atmospheric temperature due to warming. Greenhouse gasses (GHGs) contents released to the environment is worrying, with carbon dioxide (CO2) is reported at the highest concentration compared to other gasses. There are many studies conducted to develop and evaluate the performance of harmful gas sensors incorporating inorganic and organic semiconductive materials. Organic semiconductors (OSCs) are environmentally friendly materials, relatively cheaper technology, and comprised of a wide range of materials with good carrier mobility. Therefore, in this work, Organic Thin Film Transistor (OTFT) is developed for gas sensor application. As global warming is becoming more serious, this solution is instead a sustainable solution to the environment, as organic molecules which are held together via Van der Waals bond are easily processed via low-temperature deposition and solution processing as compared to more complicated processes involved in conventional inorganic counterpart. In addition, the developed sensor is generally robust due to the ability to withstand high humidity conditions and can be fabricated on flexible substrates. In this work, suitable materials are identified in basic OTFT construction, which are the electrodes, dielectric and substrate. The scope is mainly focusing on the development of bottom gate OTFT construction, incorporating p-type active material which are Trisisopropylsilylethynyl Pentacene (TIPS Pentacene), Aluminium (Al) as drain and source electrodes, PEDOT: PSS as gate electrode and Polyvinyl alcohol (PVA) as gate dielectric. The materials in bottom gate bottom contact (BGBC) configuration, fabricated via screen printing technique is experimentally tested towards CO2 detection. CO2 is initially detected at 1618 ppm with contact resistance of 15 kΩ, and at 10 ml/minute flow rate, the developed configuration is demonstrated able to achieve sensitivity of 2.069 Ω/ppm. In conclusion, the studied BGBC OTFT has demonstrated suitability and applicability in CO2 gas sensing for sustainable environmental condition monitoring, that could lead to safer environment for the living things on earth. With the proposed dimensions, in the future it is possible to proceed with this work to be fabricated by using more advanced techniques such as photolithography and many others.

All Solution Processable OTFT-Based on Direct-Written Printing Method Towards Flexible Electronics Applications

Development of organic electronics, particularly organic thin film transistors (OTFTs), have been centred of discussion among researchers due to their potential uses in flexible electronics applications. Conventionally, an inkjet printing method has been deployed to fabricate the OTFTs due to its simplicity in fabrication steps and applicability to diverse substrates and solution-processable materials. Nonetheless, this technique has a major drawback which requires low viscosity materials to prevent clogging issue at the printer’s nozzle. This in return limits the material selections and requires additional steps i.e. modification of the selected materials to fit the printer’s requirement or in other words, to avoid clogging at the nozzle. Therefore, this paper proposes a method to fabricate a bottom gate bottom contact (BGBC) OTFT by using a direct-write printing technique which is compatible with a commercial conductive ink that can be directly used without any further modification. This technique does not compromise the fabricated devices overall performance and can fabricate the devices up to micrometre scale. The proposed OTFT achieved a saturation mobility of 4.28x10-5 cm2/Vs, a threshold voltage of -0.4 V, an on/off current ratio of 102, and a subthreshold swing of 10 V/dec with overall fabrication temperature is less than 150 ℃, hence, makes it suitable for flexible electronics applications.

Oxygen reduction reaction induced electrode effects in polymer light-emitting electrochemical cells

The perceived diminished sensitivity of Polymer Light-Emitting Electrochemical Cells (LECs) to electrode material and active layer thickness compared to Organic Light-Emitting Diodes (OLEDs) due to electrochemical doping, positions them as a focal point in emerging electronic applications. However, empirical evidence reveals the electrode still influences device performance. Simultaneously, electrochemical doping involves side reactions at the cathode, predominantly with oxygen. Nevertheless, the impact of oxygen reduction reaction on the device performance concerning electrode effects remains underexplored. This study centers on the pivotal influence of oxygen reduction reaction on the electrode effect in LECs. The investigation of the doping process for various electrodes and active layer thicknesses was conducted using photoluminescence imaging. Through controlling temperatures and vacuum levels, obtained time-current curves undergo fitting procedures, which enables quantitative analysis of oxygen reduction reaction effects on both electrode and film thickness. The results underscore the impact of oxygen reduction reaction on the performance of the device induced by electrodes, emphasizing the pronounced effect on the activation energy of the reduction reaction dictated by both the electrode work function and oxygen concentration. In addition, this study elucidates that the utilization of a low-work-function bottom contact in conjunction with a thicker active layer exerts a discernible influence on the device's current magnitude.

Growth of CuAlO2 on SiO2 under a layer-by-layer approach conducted by digitally processed DC sputtering and its transistor characteristics

A CuAlO2 (CAO) bottom gate top contact p-type thin film transistor (TFT) is demonstrated. The CAO thin film is synthesized through a digitally processed DC sputtering (DPDS) technique, employing a precise layer-by-layer (LBL) deposition strategy. X-ray diffraction analysis exhibited distinct peaks beyond 600 °C. The CAO film shows a dominant phase along the (004) plane at the elevated temperature of 990 °C. The fabricated CAO p-TFT exhibits field effect mobility of 4.1 cm2 V−1 s−1. In addition, the p-TFT characteristics were observed even in the as-deposited CAO film. The DPDS-assisted LBL approach offers a promising pathway for controlled stacking deposition routes in the growth of CAO thin films, enabling enhanced performance and device integration.

Effect of source and drain electrode positions on the performance of bottom gate organic thin film transistor

In recent years several novel technologies have emerged on commercial level. Organic electronics is one such technology that has created new avenues for the development of flexible, robust, and cost-effective electronic devices. Transistor developed using organic materials are called organic thin film transistors (OTFT). Transistor is elementary component of any electronic device, any variation in the size or performance of the transistors reflects directly on the overall performance of the electronic devices. Bottom gate bottom contact (BGBC) OTFT is commonly employed single gate organic transistor owing to its simple architecture and easy fabrications. Since in organic semiconductor material carrier mobility of charges is lower, hence its overall performance declines. As a result, its application in electronic circuits becomes limited. Therefore, to enhance the performance of BGBC OTFT and facilitate the optimal charge mobilisation inside organic semiconductor layer i.e., OSC, improvement in the architecture of BGBC is deemed necessary. In this research article the performance of BGBC OTFT is analysed for different positions of electrodes viz. source and drain embedded inside the OSC layer. The study signifies the effect of electrode positions on performance optimization of BGBC OTFT without changing the materials, dimensions, or the operating voltage regime. It has been found that for 30 nm thick OSC layer, the electrodes should ideally be placed between 5 nm to 10 nm above the junction of OSC and dielectric layer inside OSC layer for optimal results.

Drain-Induced Multifunctional Ambipolar Electronics Based on Junctionless MoS2.

Applying a drain bias to a strongly gate-coupled semiconductor influences the carrier density of the channel. However, practical applications of this drain-bias-induced effect in the advancement of switching electronics have remained elusive due to the limited capabilities of its current modulation known to date. Here, we show strategies to largely control the current by utilizing drain-bias-induced carrier type switching in an ambipolar molybdenum disulfide (MoS2) field-effect transistor with Pt bottom contacts. Our CMOS-compatible device architecture, incorporating a partially gate-coupled p-n junction, achieves multifunctionality. The ambipolar MoS2 device operates as an ambipolar transistor (on/off ratios exceeding 107 for both NMOS and PMOS), a rectifier (rectification ratio of ∼3 × 106), a reversible negative breakdown diode with an adjustable breakdown voltage (on/off ratio exceeding 109 with a maximum current as high as 10-4 A), and a photodetector. Finally, we demonstrate a complementary inverter (gain of ∼24 at Vdd = 1.5 V), which is highly facile to fabricate without the need for complex heterostructures and doping processes. Our study provides strategies to achieve high-performance ambipolar MoS2 devices and to effectively utilize drain bias for electrical switching.

Does Minimizing Seabed Contact Alleviate the Impacts of Bottom Trawling? An Experimental Study on Bycatch from North-western Bay of Bengal

In light of the ecological concerns associated with bottom trawling in tropical multispecies fisheries, an attempt was undertaken to implement operational modifications in experimental trawling practices aimed at reducing bottom contact. This endeavour was pursued to investigate the resulting effects on bycatch biomass and diversity along the north-western Bay of Bengal. The average total catch rate and bycatch rate in 66 hauls from January 2017 to December 2019 were 35.46 kg/h and 9.70 kg/h respectively. Bycatch biomass was mainly contributed by Teleostei (77.90%), of which the dominant species was Equuilites lineolatus. Temporal variations in bycatch composition were recorded, and average seasonal dissimilarity ranged between 35.03% and 59.61%. Juvenile percentages varied among six commercial species from 1.42 to 28.0, and their occurrences were related to their peak spawning seasons. The trophic index of bycatch calculated was 3.65. Species diversity and richness in bycatch were higher during post-monsoon and summer seasons. Biomass and abundance plots indicated the bycatch fauna to be relatively unstressed during most seasons. Trawling marginally above the bottom had improved ecological outcomes; as evident from the decreased proportion of bycatch to total trawl catch, reduced growth overfishing from lower juvenile proportions and within optima for various diversity indicators.

Implementation of Highly Reliable Contacts for RF MEMS Switches.

A contact is the key structure of RF MEMS (Radio Frequency Microelectromechanical System) switches, which has a direct impact on the switch's electrical and mechanical properties. In this paper, the implementation of highly reliable contacts for direct-contact RF MEMS switches is provided. As a soft metal material, gold has the advantages of low contact resistance, high chemical stability, and mature process preparation, so it is chosen as the metal material for the beam structure as well as the contacts of the switch. However, a Pt film is used in the bottom contact area to enhance the reliability of the contact. Three kinds of contacts with various shapes are fabricated using different processes. Particularly, a circular-shaped contact is obtained by dry/wet combined processes. The detailed fabrication process of the contacts as well as the Pt film on the bottom contact area are given. The experimental test shows that the contact shape has little effect on the RF performance of the switches. However, the circular contact shows better reliability than other contacts and can work well even after 1.2 × 109 cycles.

Resistive Memory-Switching Behavior in Solution-Processed Trans, trans-1,4-bis-(2-(2-naphthyl)-2-(butoxycarbonyl)-vinyl) Benzene-PVA-Composite-Based Aryl Acrylate on ITO-Coated PET.

Resistive switching memories are among the emerging next-generation technologies that are possible candidates for in-memory and neuromorphic computing. In this report, resistive memory-switching behavior in solution-processed trans, trans-1,4-bis-(2-(2-naphthyl)-2-(butoxycarbonyl)-vinyl) benzene-PVA-composite-based aryl acrylate on an ITO-coated PET device was studied. A sandwich configuration was selected, with silver (Ag) serving as a top contact and trans, trans-1,4-bis-(2-(2-naphthyl)-2-(butoxycarbonyl)-vinyl) benzene-PVA-composite-based aryl acrylate and ITO-PET serving as a bottom contact. The current-voltage (I-V) characteristics showed hysteresis behavior and non-zero crossing owing to voltages sweeping from positive to negative and vice versa. The results showed non-zero crossing in the devices' current-voltage (I-V) characteristics due to the nanobattery effect or resistance, capacitive, and inductive effects. The device also displayed a negative differential resistance (NDR) effect. Non-volatile storage was feasible with non-zero crossing due to the exhibition of resistive switching behavior. The sweeping range was -10 V to +10 V. These devices had two distinct states: 'ON' and 'OFF'. The ON/OFF ratios of the devices were 14 and 100 under stable operating conditions. The open-circuit voltages (Voc) and short-circuit currents (Isc) corresponding to memristor operation were explained. The DC endurance was stable. Ohmic conduction and direct tunneling mechanisms with traps explained the charge transport model governing the resistive switching behavior. This work gives insight into data storage in terms of a new conception of electronic devices based on facile and low-temperature processed material composites for emerging computational devices.

Inkjet printing high mobility indium-zinc-tin oxide thin film transistor

Metal oxide thin film transistor has been widely used in flat panel display industry because of its low leakage current, high mobility and large area uniformity. Besides, with the development of printed display technology, inkjet printing process can fabricate the customizable patterns on diverse substrates with no need of vacuum or lithography to be used, thus significantly reducing cost and receiving more and more attention. In this paper, we use inkjet printing technology to prepare a bottom gate bottom contact thin film transistor (TFT) by using indium-zinc-tin-oxide (IZTO) semiconductor. The surface morphology of the printed IZTO film is modified by adjusting the solvent composition and solute concentration of the printing precursor ink. The experimental result show that the use of binary solvents can effectively overcome the coffee ring shape caused by the accumulation of solute edge in the volatilization process of a single solvent, ultimately presenting a uniform and flat contour surface. Further increase in solute concentration is in favor of formation of convex surface topology. The reason for the formation of the flat surface of the oxide film is the balance between the inward Marangoni reflux of the solute and the outward capillary flow during volatilization. In addition, IZTO thin film transistor printed with binary solvents exhibits excellent electrical properties. The ratio of width/length = 50/30 exhibits a high on-off ratio of 1.21×10<sup>9</sup>, a high saturation field-effect mobility is 16.6 cm<sup>2</sup>/(V·s), a low threshold voltage is 0.84 V, and subthreshold swing is 0.24 V/dec. The uniform and flat active layer thin film pattern can form good contact with the source leakage electrode, and the contact resistances of TFT devices with different width-to-length ratios are less than 1000 Ω, which can reach the basic conditions of high mobility thin film transistors prepared by inkjet printing. Therefore, using solvent mixture provides a universal and simple way to print oxide films with required surface topology, and present a visible path for inkjet printing of high-mobility thin film transistors.

A Chelating‐Agent‐Passivated Electron Transport Layer for Efficient Perovskite Solar Cells with Enhanced Reproducibility

AbstractSubstandard printing quality of electron transport layers (ETLs) always leads to non‐ideal nucleation crystallization and bottom interface contact of the perovskite, followed by the formation of poor‐quality perovskite films with severe heterogeneity, which is the major source of non‐radiative recombination loss and environmental sensitivity of perovskite solar cells (PVSCs). These often result in serious photovoltaic performance loss, significant instability, and negative fabrication reproducibility. Herein, sodium phytate is proposed as a chelating agent for passivating the tin oxide (SnO2) ETLs to enable the stabilization of SnO2 nanoparticles and facilitate the printing of pinhole‐free films, thereby realizing the controlled nucleation crystallization in perovskite precursor. Thus, the printed PVSCs exhibit a champion power conversion efficiency up to 23.77% with negligible hysteresis effect. The unencapsulated devices demonstrate outstanding long‐term stability, which maintains over 80% of their initial efficiency under exposure to atmospheric environment (50% relative humidity) for 1500 hours, and a consistent and centralized distribution of efficiencies across all seasons, indicating their good reproducibility in diverse climatic atmospheres.

Negative Differential Interlayer Resistance in WSe2 Multilayers via Conducting Channel Migration with Vertical Double-Side Contacts.

The inherent interlayer resistance in two-dimensional (2D) van der Waals (vdW) multilayers is expected to significantly influence the carrier density profile along the thickness, provoking spatial modification and separation of the conducting channel inside the multilayers, in conjunction with the thickness-dependent carrier mobility. However, the effect of the interlayer resistance on the variation in the carrier density profile and its direction along the thickness under different electrostatic bias conditions has been elusive. Here, we reveal the presence of a negative differential interlayer resistance (NDIR) in WSe2 multilayers by considering various contact electrode configurations: (i) bottom contact, (ii) top contact, and (iii) vertical double-side contact (VDC). The contact-structure-dependent shape modification of the transconductance clearly manifests the redistribution of carrier density and indicates the direction of the conducting channel migration along the thickness. Furthermore, the distinct characteristic of the electrically tunable NDIR in 2D WSe2 multilayers is revealed by the observed discrepancy between the top- and bottom-channel resistances determined by four-probe measurements with VDC. Our results provide an optimized device layout and further insights into the distinct carrier transport mechanism in 2D vdW multilayers.

Large area polymer thin film towards high-sensitivity BGBC-OFET based phototransistor

With the expansion of organic electronics, organic field-effect transistors (OFETs) are broadly used in electronic devices and logic circuits. In these, OFET-based phototransistors were recently developed for detecting the light signal. Developing better field-effect mobility and sensitivity in bottom gate bottom contact (BGBC) OFET-based phototransistors, however, is still a difficulty. This is because the low mobility of most organic photoresponsive materials limits the efficiency of transporting and collecting charge carriers. In the current work, a poly (3-hexyl thiophene) based organic phototransistor was studied. For increasing the device performance, a thin layer of Self-assembled monolayer (SAM) is formed on the dielectric interface of SiO2. The ribbon-shaped floating film transfer method (FTM) is utilized in the fabrication of thin film. The prepared film shows the average OFETs mobility, Ion/Ioff ratio (μ) 2 × 10−2 Cm2/Vs, 104 respectively under air and dark conditions. This result is more than one order higher in the BGBC configuration reported by the conventional FTM. Further, illumination of light (λ = 550 nm, Pin = 1 mW/cm2) shows photosensitivity of ∼100 and responsivity of 22 AW1.

Contact metamorphic reactions and fluid–rock interactions related to magmatic sill intrusion in the Guaymas Basin

Abstract. Igneous basaltic intrusions into young organic-rich sedimentary basins have a major impact not only on the carbon cycle but also on major and trace element transfers between deep and superficial geological reservoirs. The actively rifting Guaymas Basin in the Gulf of California, which was drilled by the International Ocean Discovery Program during Expedition 385, represents the nascent stage of an ocean characterized by siliceous organic-rich sediments (diatom ooze) intruded by a very dense network of basaltic sills. This study focuses on Site U1546 where the relatively high geothermal gradient (over 200 ∘C km−1) induces early diagenetic transformations in both pore waters and sediments, involving sulfide, carbonate and silica. Geochemical and mineralogical characterizations of the sediment at sill contacts indicate that sulfides and silica polymorphs are the main phases impacted by contact metamorphism, being evident by a transition from opal-CT to quartz and pyrite to pyrrhotite, respectively. Mass balance calculations have been used to estimate mass transfers in metamorphic aureoles. In the top contact aureole, predominantly isochemical metamorphism is reflected by the presence of authigenic quartz and disseminated 20–50 µm sized pyrrhotite crystals, filling primary interstitial space, and partial dissolution of detrital feldspar grains. In the bottom contact aureole, quartz and euhedral pyrrhotite crystals occur, which are up to 4 times larger than those at the top contact. Significant metamorphism of sediments is observed in the lower contact aureole, where plagioclase recrystallizes around the detrital feldspars and locally euhedral pyroxenes are included in patches of carbonate cement; this suggests precipitation from carbon-rich fluids at temperatures (T) higher than 300 ∘C. The lower contact aureole also is more enriched in CaO, Na2O, Fe2O3 and trace elements (Cu, As, Zn, etc.) compared to the upper contact. Based on these petrological investigations, a conceptual model of magma–sediment–fluid interaction is proposed distinguishing top and bottom contact processes. Initial contact metamorphism due to sill emplacement is characterized by dehydration reactions in sediments and crystallization of new minerals. It was followed by carbonate precipitation from the released fluids. At a final stage, the temperature re-equilibrated with the geothermal gradient and the rocks were further altered by hydrothermal fluids.

Bottom fishing beyond trawling. Spatio-temporal trends of mobile and static bottom fisheries on benthic habitats

The effective implementation of the Marine Strategy Framework Directive (MSFD) and formulation of spatial management policies rely heavily on a good understanding of the extent, distribution and intensity of human pressures and their overlap with benthic habitats. However, little research has quantified the pressure and impact on the seabed of bottom contact gears other than trawling. This study analyzes the spatio-temporal trends of fishing pressure of bottom-contact gear, including mobile and static gears, and asseses its relative importance within each benthic habitat. To achieve this, a set of pressure indicators was calculated using vessel monitoring system information from the Bay of Biscay for 2009–2020. Nested General Linear Models were conducted to assess the temporal fluctuation of fishing activities. While trawlers exhibited wider and higher levels of fishing intensity over sedimentary habitats, set gillnet and set longliners were distributed among more sensitive habitats, such as biogenic reef habitats. Additionally, there was a significant decrease in fishing effort in recent years along Offshore circalittoral habitats, particularly with respect bottom trawling, in contrast to increasing fishing intensity in deeper areas. These results emphasize that from a conservation perspective and MSFD implementation, there is a need to quantitatively analyze the fishing footprint of all fishing gears, including static gears in the regional assessments, and the necessity to progress in adapting impact indicators to these fishing activities. The findings are discussed based on the potential impacts of policies such as the MSFD and can assist managers in developing spatial protection measures.

Research on the conceptual design and performance analysis of a 10 MW SPIC concept floating wind turbine foundation in intermediate water depth

The sea area in China demands high requirements for water depth adaptability, stability, structural integrity, dynamic response characteristics, and economic performance of large-scale floating wind turbines (FWTs). The aim of the research is to propose the 10 megawatts (MW) SPIC concept (Semi-submersible platform with Partially Inclined Columns, SPIC for short) FWT in intermediate water depth, providing guidance for the concept design of large-scale FWT. The SPIC concept FWT incorporates partially tilted outward side columns, which effectively minimize the risk of bottom contact and significantly enhance the stability of the floating wind turbine. This is achieved by increasing the inertia moment of the waterplane without increasing the displaced water or water surface area. The 10 MW SPIC concept FWT exhibits superior performance in terms of smaller static heeling angle, motion amplitude response function, and wave force transfer function. It also features lower steel consumption and less displaced water, achieving good stability, hydrodynamic performance, and low cost. The rationality of the concept design and the accuracy of the numerical simulation process were validated in this study using experimental results. The study assessed the extreme responses of the 10 MW SPIC concept FWT in its six degrees of freedom (DOFs) under various scenarios, including power production, power production with faults, parked condition, and parked condition with faults, thus verifying the safety of the SPIC concept.

Ditch incorporated organic thin film transistor based organic all-p inverter: a novel approach

This paper demonstrates the static and dynamic characteristics of all-p organic inverter employing a bottom gate bottom contact organic thin film transistor with a ditch incorporated into the OSC and additional p+ doping done to its S/D nearing area. Various configurations of OTFT have been experimented with and it is found that as compared to an OTFT without extra p+ doping, the devices having additional doping show better responses. Where, for SG OTFT, ID is derived to be 18 μs, yet the one with extra doping illustrates a swooping 16.67% increased output current of 21 μs. To enhance the performance of the device further, a ditch of 30 nm, embedded 10 nm into the OSC is incorporated, further augmenting the performance of the device by 55.5% as compared to the conventional BGBC. Besides, the proposed inverter presents a considerably elevated performance in terms of robustness and low and high noise margins. This paper further compares the inverter using Diode Load Logic and Zero Vgs Load Logic topologies, wherein it was found that DLL shows an exceptional 211% less propagation delay τ p of 27 μs, as compared to 84 μs delay experienced by ZVLL. But comparing the two topologies in terms of the static response, ZVLL are way better and preferred over the counterparts since ZVLL configuration displays 20.5% augmented Noise Margin, improved gain, and overall robustness. Owing to the performance parameters achieved, such organic inverters may be incorporated into integrated circuits rendering trustworthiness to digital operations in electronic circuits and numerous cascading applications. Since the organic inverters made using the proposed OTFT exhibit a decent gain hence have an apparent prospective of driving myriad-stage logic like ring oscillators and memory blocks. Moreover, these may be employed in the areas of biosensors and wearable electronics as well wherever.

Midwave resonant cavity infrared detectors (RCIDs) with suppressed background noise.

We report a resonant cavity infrared detector (RCID) with an InAsSb/InAs superlattice absorber with a thickness of only ≈ 100 nm, a 33-period GaAs/Al0.92Ga0.08As distributed Bragg reflector bottom mirror, and a Ge/SiO2/Ge top mirror. At a low bias voltage of 150 mV, the external quantum efficiency (EQE) reaches 58% at the resonance wavelength λres ≈ 4.6 µm, with linewidth δλ = 19-27 nm. The thermal background current for a realistic system scenario with f/4 optic that views a 300 K scene is estimated by integrating the photocurrent generated by background spanning the entire mid-IR spectral band (3-5 µm). The resulting specific detectivity is a factor of 3 lower than for a state-of-the-art broadband HgCdTe device at 300 K, where dark current dominates the noise. However, at 125 K where the suppression of background noise becomes critical, the estimated specific detectivity D* of 5.5 × 1012 cm Hz½/W is more than 3× higher. This occurs despite a non-optimal absorber cut-off that causes the EQE to decrease rapidly with decreasing temperature, e.g., to 33% at 125 K. The present RCID's advantage over the broadband device depends critically on its low EQE at non-resonance wavelengths: ≤ 1% in the range 3.9-5.5 µm. Simulations using NRL MULTIBANDS indicate that impact ionization in the bottom contact and absorber layers dominates the dark current at near ambient temperatures. We expect future design modifications to substantially enhance D* throughout the investigated temperature range of 100-300 K.

Signature of correlated electron–hole pair tunneling in multilayer WSe2 at room temperature

Van der Waals (vdW) heterostructures provide a promising platform for high-temperature exciton condensates due to a strong Coulomb interaction, but the fabrication of very clean interface structures with precisely aligned 2D crystals is challenging. Here, we propose that correlated electron–hole pair tunneling can occur at room temperature in a monolithic multilayer WSe2 device with bottom Au contacts. Electron and hole conducting channels separated by an intrinsic, insulating region in the center of the crystal are defined by doping. The monolithic vertical homojunction formed naturally in the bulk vdW crystal provides a defect-free interface structure which shows clear indications of correlated tunneling at room temperature. We interpret zero-bias peaks in the differential conductance curves as a signature of electron–hole pairing when their densities balance. The conductance peak vanishes when the electron and hole densities are unbalanced, which can be controlled by the external electrical field, magnetic field, or temperature. Our results open an opportunity for realization of room-temperature superfluidity in vdW materials with a simple, clean, and effective approach.