Showing papers on "Biasing published in 2019"

Tunable all-dielectric metasurface for phase modulation of the reflected and transmitted light via permittivity tuning of indium tin oxide

Abstract: We propose an electrically tunable metasurface, which can achieve relatively large phase modulation in both reflection and transmission modes (dual-mode operation). By integration of an ultrathin layer of indium tin oxide (ITO) as an electro-optically tunable material into a semiconductor-insulator-semiconductor (SIS) unit cell, we report an approach for active tuning of all-dielectric metasurfaces. The proposed controllable dual-mode metasurface includes an array of silicon (Si) nanodisks connected together via Si nanobars. These are placed on top of alumina and ITO layers, followed by a Si slab and a silica substrate. The required optical resonances are separately excited by Si nanobars in reflection and Si nanodisks in transmission, enabling highly confined electromagnetic fields at the ITO-alumina interface. Modulation of charge carrier concentration and refractive index in the ITO accumulation layer by varying the applied bias voltage leads to 240° of phase agility at an operating wavelength of 1696 nm for the reflected transverse electric (TE)-polarized beam and 270° of phase shift at 1563 nm for the transmitted transverse magnetic (TM)-polarized light. Independent and isolated control of the reflection and transmission modes enables distinctly different functions to be achieved for each operation mode. A rigorous coupled electrical and optical model is employed to characterize the carrier distributions in ITO and Si under applied bias and to accurately assess the voltage-dependent effects of inhomogeneous carrier profiles on the optical behavior of a unit cell.

Switchable Broadband Dual-Polarized Frequency-Selective Rasorber/Absorber

Abstract: This letter presents a switchable dual-polarized frequency-selective rasorber/absorber at low microwave frequency based on double-layered metallic resonant structure array loaded with lumped elements. It consists of an absorbing layer and a bandpass frequency-selective surface layer loaded with PIN diodes, sandwiched with an air-spacer between them. The operating principle is analyzed with the help of an equivalent circuit model. By biasing the PIN diodes on or off , it can be easily switched between the rasorber and absorber modes. When in the rasorber mode, it exhibits a passband at 1.6 GHz with 1.7 dB insertion loss between two neighboring absorption bands. While switched to the absorber mode, it achieves more than 80% absorptivity ranging from 0.8 to 3.4 GHz, corresponding to a fractional bandwidth of 124%. The total thickness is less than 8% of the free-space wavelength at the lowest operating frequency. A prototype of the proposed structure is fabricated and measured, where reasonable agreements between simulations and measurements are observed.

Broadband Frequency-Selective Rasorber With Varactor-Tunable Interabsorption Band Transmission Window

Abstract: In this paper, we present a frequency-selective rasorber with tunable transmission window located within the absorption band. The rasorber maintains a low reflectivity, which is less than −10 dB in broadband during the tuning process. An equivalent circuit model is provided as a guideline for the tunable rasorber design. Based on the model, a varactor-tunable rasorber composed of three stacked metallic layers is constructed and investigated. These layers include a frequency selective surface (FSS) loaded with resistors and varactors, a wire grid and a varactor-loaded bandpass FSS. The wire grids in the middle and bottom layers in combination with metallic vias provide the bias and grounding for the varactors, respectively. This configuration avoids using two separated bias networks for varactors on different layers, thus, averting undesirable responses associated with having more bias grids. A tunable rasorber prototype was fabricated and measured, showing that the passband can be tuned from 2.2 to 3.3 GHz by changing bias voltage from 4 to 22 V, with an insertion loss between 6.6 and 3.3 dB. A wide low-reflectivity band under normal incidence for double polarizations from 1.9 to 5.4 GHz is realized. This tunable rasorber has promising applications in broadband stealth facilities with integrated hopping communication functionality.

Bias-Voltage Driven Switching of the Charge-Density-Wave and Normal Metallic Phases in 1T-TaS2 Thin-Film Devices.

Abstract: We report on switching among three charge-density-wave phases, commensurate, nearly commensurate, incommensurate, and the high-temperature normal metallic phase in thin-film 1T-TaS2 devices induced...

Energetic Ions during plasma-enhanced atomic layer deposition and their role in tailoring material properties

Abstract: Plasma-enhanced atomic layer deposition (PEALD) has obtained a prominent position in the synthesis of nanoscale films with precise growth control. Apart from the well-established contribution of highly reactive neutral radicals towards film growth in PEALD, the ions generated by the plasma can also play a significant role. In this work, we report on the measurements of ion energy and flux characteristics on grounded and biased substrates during plasma exposure to investigate their role in tailoring material properties. Insights from such measurements are essential toward understanding how a given PEALD process at different operating conditions can be influenced by energetic ions. Ion flux-energy distribution functions (IFEDFs) of reactive plasmas typically used for PEALD (O2, H2, N2) were measured in a commercial 200-mm remote inductively-coupled-plasma ALD system equipped with RF substrate biasing. IFEDFs were obtained using a gridded retarding field energy analyzer and the effects of varying ICP power, pressure and bias conditions on the ion energy and flux characteristics of the three reactive plasmas were investigated. The properties of three material examples – TiOx, HfNx and SiNx – deposited using these plasmas were investigated on the basis of the energy and flux parameters derived from IEDFs. Material properties were analyzed in terms of the total ion energy dose delivered to a growing film in every ALD cycle, which is a product of the mean ion energy, total ion flux and plasma exposure time. The properties responded differently to the ion energy dose depending on whether it was controlled with RF substrate biasing where ion energy was enhanced, or without any biasing where plasma exposure time was increased. This indicated that material properties were influenced by whether or not ion energies exceeded energy barriers related to physical atom displacement or activation of ion-induced chemical reactions during PEALD. Furthermore, once ion energies were enhanced beyond these threshold barriers with RF substrate biasing, material properties became a function of both the enhanced ion energy and the duration for which the ion energy was enhanced during plasma exposure. These results have led to a better insight into the relation between energetic ions and the ensuing material properties, e.g., by providing energy maps of material properties in terms of the ion energy dose during PEALD. It serves to demonstrate how the measurement and control of ion energy and flux characteristics during PEALD can provide a platform for synthesizing nanoscale films with the desired material properties.

High-Performance WS2 Monolayer Light-Emitting Tunneling Devices Using 2D Materials Grown by Chemical Vapor Deposition.

Abstract: The solid progress in the study of a single two-dimensional (2D) material underpins the development for creating 2D material assemblies with various electronic and optoelectronic properties. We introduce an asymmetric structure by stacking monolayer semiconducting tungsten disulfide, metallic graphene, and insulating boron nitride to fabricate numerous red channel light-emitting devices (LEDs). All the 2D crystals were grown by chemical vapor deposition (CVD), which has great potential for future industrial scale-up. Our LEDs exhibit visibly observable electroluminescence (EL) at both 5.5 V forward and 7.0 V backward biasing, which correlates well with our asymmetric design. The red emission can last for at least several minutes, and the success rate of the working device that can emit detectable EL is up to 80%. In addition, we show that sample degradation is prone to happen when a continuing bias, much higher than the threshold voltage, is applied. Our success of using high-quality CVD-grown 2D materials for red light emitters is expected to provide the basis for flexible and transparent displays.

X-Ray Detector Based on All-Inorganic Lead-Free Cs 2 AgBiBr 6 Perovskite Single Crystal

Abstract: In this paper, single crystals (SCs) of the Cs2AgBiBr6 double perovskite were grown using the method of crystallization from a supersaturated solution. It was shown that the natural crystal growth surface of the perovskite with perfect crystal quality is along the (111) plane by X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM) analyses. The fabricated high-sensitivity X-ray detector based on the Cs2AgBiBr6 SCs with vertical structure achieved detection sensitivity up to $316~\mu $ CGyair−1 cm−2 under bias voltage of 18 V. Furthermore, the frequency noise characteristics of the device under different posttreatment processes were systematically analyzed, which indicated that the combination of thermal annealing and isopropanol rinsing can suppress field-driven ion migration and surface conduction channel, thereby increasing the resistivity of the perovskite material and reducing the noise current of the device. Our results revealed that the Cs2AgBiBr6 SCs-based X-ray detector with high sensitivity and low cost has a great potential for application in manufacturing lead-free and stable radiation detection electronics in the future.

Active Frequency Selective Surface With Wide Reconfigurable Passband

Abstract: This paper presents an active frequency selective surface (AFSS) with a wide reconfigurable passband. The tuning mechanism was investigated with an equivalent circuit which consists of a parallel L-C resonant circuit and a series L-C resonant circuit. A cross-loop slot was selected as a unit cell, and varactor diodes were added across the slot to tune the passband. The effects of various bias configurations on the transmission coefficients were studied. The simulation results showed that a reconfigurable passband ranged from 2.92 to 5.74 GHz was obtained with a variable capacitance from 0.8 to 0.1 pF. A prototype of the proposed AFSS was fabricated and measured. The measurement results showed that the passband was altered from 2.94 to 5.66 GHz if the biasing voltage of varactor diodes was increased from 4 to 18V. The measurement and simulation results agree well with each other.

Gas-Phase Photoelectrocatalysis for Breaking Down Nitric Oxide.

Abstract: Photoelectrocatalysis (PEC) produces high-efficiency electron–hole separation by applying a bias voltage between semiconductor-based electrodes to achieve high photocatalytic reaction rates. Howeve...

Active Frequency Selective Surface to Switch Between Absorption and Transmission Band With Additional Frequency Tuning Capability

Abstract: This study realized a polarization-insensitive active frequency selective surface (AFSS) that simultaneously exhibited mode switching and frequency tunable capacity. Its geometry comprised periodic metallic patterns printed on opposite sides of a dielectric substrate, with varactors and p-i-n diodes mounted on the top and bottom layers, respectively. The proposed AFSS switches between transmission and absorption modes by regulating the p-i-n diodes (OFF and ON states). Transmission and absorption frequencies can also be continuously tuned by changing the bias voltage across the varactor diodes. To realize polarization independence, metallic patterns, lumped components, and biasing configurations were symmetrically patterned. The equivalent circuit and parametric studies were considered to explain AFSS switching and tuning behaviors. The proposed multifunction and frequency tuning responses were experimentally demonstrated by fabricating a prototype with $17 \times 17$ unit cells. The bandpass frequency can be tuned from 3.70 to 4.27 GHz with a 1.96–4.30 dB insertion loss in the transmission mode, and the absorption frequency can be regulated from 4.28 to 5.12 GHz with 78.77%–90.78% absorptivity.

Tunable Frequency-Selective Rasorber Based on Varactor-Embedded Square-Loop Array

Abstract: This paper presents a varactor-based tunable frequency-selective rasorber (FSR) with embedded bias grid. The proposed structure consists of a lossy layer based on square-loop arrays and a lossless layer. Each layer has an embedded wire grid that provides the bias voltage for the varactors through metallic vias. This arrangement can avoid unnecessary effects associated with the additional biasing network. An equivalent circuit model is developed to explain how the structure can provide a tunable transmission window within the absorption band. Simple design guidelines for the tunable FSR are then provided. The performance of the proposed structure is measured in a parallel-plate waveguide setup. Both simulated and measured results show that by changing the bias voltage from 16 to 4 V, the center transmission frequency of the FSR can be tuned from 5.2 to 3.8 GHz continuously. The insertion loss of the FSR within the transmission window is only 0.59 dB at 5.2 GHz and a fractional bandwidth of 93.1% (2.4-6.58 GHz) for -10 dB reflectivity is achieved under the normal incidence.

An Electronically Controlled Leaky-Wave Antenna Based on Corrugated SIW Structure With Fixed-Frequency Beam Scanning

Abstract: A novel electronically controlled (EC) leaky-wave antenna (LWA) based on corrugated substrate integrated waveguide (CSIW) with fixed-frequency beam-steerable capability is presented in this letter. This structure is based on a CSIW structure with rectangular ring slots and metallic vias to the ground, which realizes two isolated dc equipotential planes. Each slot of the rectangular ring is loaded with a varactor diode, and thus the series and shunt capacitance are tunable by adjusting the dc bias voltage, which eventually results in beam scanning at a fixed frequency. The proposed antenna is a single-layer structure and has a simplified dc bias network, which merely needs an inductor and a short microstrip line. An EC beam-steerable CSIW LWA is designed and experimentally validated. It is experimentally demonstrated that the radiation angle ranges from −40.66° to 31.32° as the bias voltage is tuned from 32 V to 7.5 V at 4.5 GHz.

Electrically Triggered Tunable Terahertz Band-Pass Filter Based on VO 2 Hybrid Metamaterial

Abstract: We demonstrate an electrically triggered tunable terahertz (THz) band-pass filter based on vanadium dioxide (VO2) embedded hybrid metamaterials. The unit cell of the filter consists of two cross resonators and a central bar. The phase transition of VO2 is induced by the ohmic heating of the central bar. The transmission can be modulated by the applied currents. The mechanism of tunability is that the conductivity of the VO2 film changes with the applied currents. The relation between the upper cut-off frequency and the geometries is investigated using finite integration time domain method. The sample is fabricated by a thin film process, and characterized using a THz time domain spectroscopy system. The results show that, when the bias current rises from 0 to 0.27 A, the transmission decreases from 0.85 to 0.01. The maximum modulation depth reaches 96%, and the full width at half maximum is about 0.44 THz. This tunable THz band-pass filter has potential applications in THz communication, imaging, and spectroscopy systems.

Tunable Liquid Crystal Filter in Nonradiative Dielectric Waveguide Technology at 60 GHz

Abstract: This letter presents a continuously tunable nonradiative dielectric waveguide three-pole bandpass filter based on liquid crystal (LC) technology at 60 GHz. LC is used as tunable material to obtain a continuous tunable center frequency. For the LC’s orientation, an electrode network with parasitic mode suppressive structure is realized. The measurements are performed with magnetic and electric biasing to verify the performance of the filter design. A maximum fractional bandwidth of 1% and a tunability of 2.5% were measured with electrical biasing. Furthermore, the filter’s insertion loss is between 4.9 and 6.2 dB over the tuning range. The extracted unloaded quality factor for electrical biasing ranges from 96 to 141.

Magnetic tunnel junctions based on ferroelectric Hf0.5Zr0.5O2 tunnel barriers

Abstract: A ferroelectric tunnel barrier in between two ferromagnetic electrodes (multiferroic tunnel junction, MFTJ), is one of the most promising concepts for future microelectronic devices. In parallel, Hafnia based ferroelectrics are showing great potential for device miniaturization down to the nanoscale. Here we utilize ferroelectric Hf0.5Zr0.5O2 (HZO) with thickness of only 2 nm, epitaxially grown on La0.7Sr0.3MnO3 (LSMO) ferromagnetic electrodes, as a large band-gap insulating barrier integrated in MFTJs with cobalt top electrodes. As previously reported for other MFTJs with similar electrodes, the tunneling magnetoresistance (TMR) can be tuned and its sign can even be reversed by the bias voltage across the junction. We demonstrate four non-volatile resistance states generated by magnetic and electric field switching with high reproducibility in this system.

Improved electrical performance of a sol-gel IGZO transistor with high-k Al2O3 gate dielectric achieved by post annealing.

Abstract: We have explored the effect of post-annealing on the electrical properties of an indium gallium zinc oxide (IGZO) transistor with an Al2O3 bottom gate dielectric, formed by a sol–gel process. The post-annealed IGZO device demonstrated improved electrical performance in terms of threshold variation, on/off ratio, subthreshold swing, and mobility compared to the non-annealed reference device. Capacitance–voltage measurement confirmed that annealing can lead to enhanced capacitance properties due to reduced charge trapping. Depth profile analysis using X-ray photoelectron spectroscopy proved that percentage of both the oxygen vacancy (VO) and the hydroxyl groups (M–OH) within the IGZO/Al2O3 layers, which serve as a charge trapping source, can be substantially reduced by annealing the fabricated transistor device. Furthermore, the undesired degradation of the contact interface between source/drain electrode and the channel, which mainly concerns VO, can be largely prevented by post-annealing. Thus, the facile annealing process also improves the electrical bias stress stability. This simple post annealing approach provides a strategy for realising better performance and reliability of the solid sol–gel oxide transistor.

Atomic-Scale Fluidic Diodes Based on Triangular Nanopores in Bilayer Hexagonal Boron Nitride

Abstract: Nanofluidic diodes based on nanochannels have been studied theoretically and experimentally for applications such as biosensors and logic gates. However, when analyzing attoliter-scale samples or enabling high-density integration of lab-on-a-chip devices, it is beneficial to miniaturize the size of a nanofluidic channel. Using molecular dynamics simulations, we investigate conductance of nanopores in bilayer hexagonal boron nitride (h-BN). Remarkably, we found that triangular nanopores possess excellent rectifications of ionic currents while hexagonal ones do not. It is worth highlighting that the pore length is only about 0.7 nm, which is about the atomic limit for a bipolar diode. We determined scaling relations between ionic currents I and pore sizes L for small nanopores, that are I ∼ L1 in a forward biasing voltage and I ∼ L2 in a reverse biasing voltage. Simulation results qualitatively agree with analytical ones derived from the one-dimensional Poisson–Nerst–Planck equations.

Ultra-low-power sub-photon-voltage high-efficiency light-emitting diodes

Abstract: Conventional light-emitting diodes (LEDs) face an efficiency droop at low current due to non-radiative recombination overtaking radiative recombination at low carrier density. To overcome this universal problem, we develop LEDs with high efficiency at ultralow current and voltage, using a novel quantum well design and high-quality interfaces to suppress non-radiative recombination and enhance radiative recombination. The device exhibits close to unity internal quantum efficiency at a low current density of <1 × 10−4 A cm−2, more than three orders of magnitude lower than conventional LEDs. The LED bias voltage is reduced to ~30% below the photon voltage (hν/q). Wireless communication is demonstrated at these low-power conditions, which enables new applications in smart dust and sensor networks 1–6 , low-cost block chain and authentication 7–9 , medical applications 10,11 and wherever high efficiency at low power is needed. New phenomena such as high-efficiency electroluminescent cooling becomes possible as the LED unity internal quantum efficiency extends to smaller voltage and current. By using a single-quantum-well active region with a unique well–cladding design to suppress non-radiative recombination and enhance radiative recombination, light-emitting diodes with close to unity internal quantum efficiency at a low current density of <10−4 A cm−2 are demonstrated.

Accessing MHz Operation at 2 V with Field-Effect Transistors Based on Printed Polymers on Plastic.

Abstract: Organic printed electronics are suitable for the development of wearable, lightweight, distributed applications in combination with cost-effective production processes. Nonetheless, some necessary features for several envisioned disruptive mass-produced products are still lacking: among these radio-frequency (RF) communication capability, which requires high operational speed combined with low supply voltage in electronic devices processed on cheap plastic foils. Here, it is demonstrated that high-frequency, low-voltage, polymer field-effect transistors can be fabricated on plastic with the sole use of a combination of scalable printing and digital laser-based techniques. These devices reach an operational frequency in excess of 1 MHz at the challengingly low bias voltage of 2 V, and exceed 14 MHz operation at 7 V. In addition, when integrated into a rectifying circuit, they can provide a DC voltage at an input frequency of 13.56 MHz, opening the way for the implementation of RF devices and tags with cost-effective production processes.

Electrically tunable liquid crystal terahertz device based on double-layer plasmonic metamaterial.

Abstract: In this paper, a nematic liquid crystal (NLC)-based tunable terahertz (THz) plasmonic metamaterials (MMs) with large modulation depth (MD) and low insertion loss (IL) is designed and experimentally verified at THz frequencies. The proposed structure includes two-layered MM that is immersed in LC. The metal MM is used directly as electrode. The tunable device with a 46×46 array of sub-wavelength circular air loops was fabricated on a quartz glass substrate, with 2×2 cm2 area and 220 µm thickness. The obtained results show that the amplitude MD and IL for normally incident electromagnetic (EM) waves are about 96% and 1.19 dB at 421.2 GHz, respectively, when the bias voltage applied to the NLC layer varies from 0 to 16 V. Meanwhile, the transmission peak frequency gradually decreases from 421.2 to 381.8 GHz, and the frequency tunability (FT) of the proposed structure is greater than 9.35%. This study provides a potential solution for THz modulators, filters, and switches.

High-performance UV detectors based on room-temperature deposited amorphous Ga2O3 thin films by RF magnetron sputtering

Abstract: Room-temperature-fabricated amorphous Ga2O3 is an inexpensive and highly sensitive material for high-performance solar-blind ultraviolet (UV) (220–280 nm) detectors, which are extremely useful given the widespread use of solar-blind UV photoelectronic technology in multiple areas. The UV detection characteristics of room-temperature deposited amorphous Ga2O3 thin films fabricated by a simple RF magnetron sputtering method were studied, and the deposition Ar pressure of an a-Ga2O3 thin film was varied to determine the mechanism underlying high-performance UV detection and to develop an ideal a-Ga2O3 thin film for UV detection. A high-response amorphous Ga2O3-based UV detector was made at 0.5 Pa, and the maximum response of the device reached 436.3 A W−1 under 240 nm UV light with a 25 V bias voltage, which is near the maximum values for a single-crystal β-Ga2O3 material deposited at a high temperature. An amorphous Ga2O3-based UV detector with a low Idark noise level (4.9 nA at 25 V) and a high Iuv/Idark ratio (107314.4) was made at 1.2 Pa, and the Iuv/Idark ratio of the device was near that of a UV detector based on single-crystal β-Ga2O3 with a complex metal-oxide–semiconductor field-effect transistor (MOSFET) structure. Through a comparative analysis of the electrical characteristics and the gain mechanism within amorphous Ga2O3 thin films deposited at different Ar pressures, the high UV response of the amorphous Ga2O3 detector at 0.5 Pa is found to mainly result from the quasi-Zener tunneling multiplication phenomenon between different resistance components. The low Idark value and the high signal-to-noise ratio of the amorphous Ga2O3-based detector deposited at 1.2 Pa were mainly due to more high-resistance components and a relatively higher tunneling gain in the device. In addition, the amorphous Ga2O3-based detectors showed a much shorter response time (0.08 μs for the device deposited at 0.65 Pa) and recovery time (td1 = 0.21 ms, td2 = 5.88 ms for the device deposited at 1.2 Pa) than the reported crystal semiconductor-based devices and multiple complex structure devices. Thus, the room-temperature-fabricated amorphous Ga2O3 thin film could quickly and effectively detect a faint UV light signal in the presence of a very noisy background, which is extremely important in the applications of UV detectors in wearable, flexible photoelectronic devices.

Upgrade of a low-temperature scanning tunneling microscope for electron-spin resonance

Abstract: Electron spin resonance with a scanning tunneling microscope (ESR-STM) combines the high energy resolution of spin resonance spectroscopy with the atomic scale control and spatial resolution of STM. Here we describe the upgrade of a helium-3 STM with a 2D vector-field magnet (Bz = 8.0 T, Bx = 0.8 T) to an ESR-STM. The system is capable of delivering radio frequency (RF) power to the tunnel junction at frequencies up to 30 GHz. We demonstrate magnetic field-sweep ESR for the model system TiH/MgO/Ag(100) and find a magnetic moment of (1.004 ± 0.001) μB. Our upgrade enables to toggle between a DC mode, where the STM is operated with the regular control electronics, and an ultrafast-pulsed mode that uses an arbitrary waveform generator for pump-probe spectroscopy or reading of spin-states. Both modes allow for simultaneous radiofrequency excitation, which we add via a resistive pick-off tee to the bias voltage path. The RF cabling from room temperature to the 350 mK stage has an average attenuation of 18 dB between 5 and 25 GHz. The cable segment between the 350 mK stage and the STM tip presently attenuates an additional 34−3+5 dB from 10 to 26 GHz and 38−2+3 dB between 20 and 30 GHz. We discuss our transmission losses and indicate ways to reduce this attenuation. We finally demonstrate how to synchronize the arrival times of RF and DC pulses coming from different paths to the STM junction, a prerequisite for future pulsed ESR experiments.

Template based sintering of WO3 nanoparticles into porous tungsten oxide nanofibers for acetone sensing applications

Abstract: Porous WO3 nanofibers have been synthesized by electrospinning polyvinylpyrrolidone (PVP) nanofibers embedded with semiconducting WO3 nanoparticles followed by annealing in air. PVP serves as a template in sintering of WO3 nanoparticles into nanofibrous morphology. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations have revealed a highly porous structure of WO3 nanofibers with diameters in the range of 800–1200 nm. Fourier transform infrared spectroscopy (FTIR) confirms complete removal of the polymer from the porous WO3 NFs after annealing. Amperometry based sensing performance of porous WO3 nanofibers is evaluated toward low concentrations (1.8–12.5 ppm) of acetone and further improved via light excitation (365 nm UV) and applied bias voltage (3–7 V). The applied bias voltage has a significant effect on sensor characteristics with a remarkably enhanced response at a higher bias voltage. A maximum response (Igas–Iair) of 1.79 μA is obtained at 7 V bias voltage toward 12.5 ppm acetone at 350 °C under UV irradiation. The porous WO3 nanofibers are able to detect 700 ppb of acetone with 3 V bias voltage using photo-activation with a response/recovery time of 33 s/42 s and excellent repeatability. The experimental results confirm the potential usage of the developed sensor based on electrospun porous WO3 nanofibers for acetone sensing applications.