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The imperative to meet the energy needs of contemporary electronic devices has spurred extensive exploration into self‐powered systems. Given the anticipated ubiquity of sensor networks in future cities, a novel battery‐free sensing paradigm, rooted in triboelectric nanogenerators (TENG), has gained prominence. Utilizing mechanical energy otherwise wasted daily for electricity generation presents a promising alternative to conventional sensors. Embedding the sensing electrode within the TENG structure enables the creation of gas sensors suitable for portable and wireless applications. This study focuses on fabricating a 3D microporous sponge of polydimethylsiloxane (PDMS) using sugar cubes and graphene oxide (GO) nanosheets. Leveraging the hydrophilic properties of the GO enhances moisture absorption, elevating the humidity sensor's responsivity. In addition, the porous structure not only improves sensitivity to high humidity but also mitigates surface saturation issues prevalent in nonporous sensors. The porous self‐powered sensor, composed of PDMS with 0.5 wt% of GO, exhibits a response of up to 2500%, quantified as ((ΔV/V) × 100%), to relative humidity changes from 20% to 99%. Furthermore, the response and recovery times stand at 1.2 and 2.3 s, respectively. These findings underscore the feasibility of integrating TENG electrodes, utilizing a porous PDMS–GO nanocomposite, to create various types of integrated gas sensors. [ABSTRACT FROM AUTHOR]

Respiration stands as a vital process reflecting physiological and pathological human health status. Exhaled breath analysis offers a facile, non-invasive, swift, and cost-effective approach for diagnosing and monitoring diseases by detecting concentration changes of specific biomarkers. In this study, we employed Polyethylene oxide/copper (I) oxide composite nanofibers (PCNFs), synthesized via the electrospinning method as the sensing material to measure ethanol levels (1–200 ppm) in an exhaled breath simulator environment. The integrated contact-separation triboelectric nanogenerator was utilized to power the self-powered PCNFs exhaled breath sensor. The PCNFs-based gas sensor demonstrates promising results with values of 0.9 and 3.2 for detecting 5 ppm and 200 ppm ethanol, respectively, in the presence of interfering gas at 90% relative humidity (RH). Notably, the sensor displayed remarkable ethanol selectivity, with ratios of 10:1 to methanol and 25:1 to acetone. Response and recovery times for 200 ppm ethanol at 90 RH% were rapid, at 2.7 s and 5.8 s, respectively. The PCNFs-based exhaled breath sensor demonstrated consistent and stable performance in practical conditions, showcasing its potential for integration into wearable devices. This self-powered breath sensor enabling continuous monitoring of lung cancer symptoms and facilitating compliance checks with legal alcohol consumption limits. [ABSTRACT FROM AUTHOR]

Harvesting solar energy, as a clean and abundant resource, in the photothermal process, is the winning point of solar steam generation (SSG) systems. Herein, copper plasmonic nanoparticles were synthesized through a green method via red sanders extraction on the cotton fabric as the reducing matrix. The prepared fabrics were analyzed using FESEM, EDS, XRD, PL, Raman, and contact angle. The treated fabric on the stitched PU foam with cotton yarns with bio-inspired jellyfish structure was used for heat localization and water transmission, simultaneously. The evaporation rate, enhancement, and conversion efficiency of the plasmonic SSG were 1.73 kg m−2 h−1, 179%, and ~ 98%, under one sun irradiation, respectively. The quality of the collected water was investigated via induced coupled plasma which presents the proper solar desalination (> 99.83% for filtration of Na+ ion). Regenerating features of the treated fabric along with the simple and cost-effective preparation method promises viable aspects of our system for large-scale applications. [ABSTRACT FROM AUTHOR]

Due to the favorable properties of two-dimensional materials such as SnS2, with an energy gap in the visible light spectrum, and InSe, with high electron mobility, the combination of them can create a novel platform for electronic and optical devices. Herein, we study a tunable gain SnS2/InSe Van der Waals heterostructure photodetector. SnS2 crystals were synthesized by chemical vapor transport method and characterized using X-ray diffraction and Raman spectroscopy. The exfoliated SnS2 and InSe layers were transferred on the substrate. This photodetector presents photoresponsivity from 14 mA/W up to 740 mA/W and detectivity from 2.2 × 108 Jones up to 3.35 × 109 Jones by gate modulation from 0 V to +70 V. Light absorption and the charge carrier generation mechanism were studied by the Silvaco TCAD software and the results were confirmed by our experimental observations. The rather high responsivity and visible spectrum response makes the SnS2/InSe heterojunction a potential candidate for commercial visible image sensors. [ABSTRACT FROM AUTHOR]

Self-powered detectors based on triboelectric nanogenerators (TENG) have been considered because of their capability to convert ambient mechanical energy to electrical out-put signal, instead of conventional usage of electrochemical batteries as power sources. In this regard, the self-powered photodetectors have been designed through totally two lay out called passive and active circuit. in former model, impedance matching between the TENG and the resistance of the circuit's elements is crucial, which is not investigated systematically till now. In this paper, a cost effective novel planar photodetector (PD) based on heterojunction of SnS2 sheets and Cs0.05(FA0.83 MA0.17)0.95Pb(I0.83Br0.17)3 three cationic lead iodide based perovskite (PVK) layer fabricated which powered by graphene oxide (GO) paper and Kapton based contact-separated TENG (CS-TENG). To achieve the high performance of this device, the proper range of the load resistances in the circuit regards to TENG's characterization has been studied. In the next steps, the integrated self-powered photo-detection system was designed by applying Kapton/FTO and hand/FTO TENG, separately, in the proposed impedance matching circuit. The calculated D* of integrated self-powered SnS2/PVK supplied by tapping the Kapton and hand on FTO is 2.83 × 1010 and 1.10 × 1013 Jones under the 10 mW/cm2 of white light intensity, the investigations determine that for designing significate performance of self-powered PD supplied by TENG, the existence of the load resistance with the well match amount to the utilized TENG is crucial. Our results which can be generalized to other types of passive self-powered sensors, are substantial to both academia and industry concepts. [ABSTRACT FROM AUTHOR]

Self-powered detectors based on triboelectric nanogenerators (TENG) have been considered because of their capability to convert ambient mechanical energy to electrical out-put signal, instead of conventional usage of electrochemical batteries as power sources. In this regard, the self-powered photodetectors have been designed through totally two lay out called passive and active circuit. in former model, impedance matching between the TENG and the resistance of the circuit's elements is crucial, which is not investigated systematically till now. In this paper, a cost effective novel planar photodetector (PD) based on heterojunction of SnS2 sheets and Cs0.05(FA0.83 MA0.17)0.95Pb(I0.83Br0.17)3 three cationic lead iodide based perovskite (PVK) layer fabricated which powered by graphene oxide (GO) paper and Kapton based contact-separated TENG (CS-TENG). To achieve the high performance of this device, the proper range of the load resistances in the circuit regards to TENG's characterization has been studied. In the next steps, the integrated self-powered photo-detection system was designed by applying Kapton/FTO and hand/FTO TENG, separately, in the proposed impedance matching circuit. The calculated D* of integrated self-powered SnS2/PVK supplied by tapping the Kapton and hand on FTO is 2.83 × 1010 and 1.10 × 1013 Jones under the 10 mW/cm2 of white light intensity, the investigations determine that for designing significate performance of self-powered PD supplied by TENG, the existence of the load resistance with the well match amount to the utilized TENG is crucial. Our results which can be generalized to other types of passive self-powered sensors, are substantial to both academia and industry concepts. [ABSTRACT FROM AUTHOR]

Evaporation is the main outflow of many water bodies. In hypersaline Lake Urmia (LU), which has experienced significant shrinkage during the last 3 decades, evaporation is the only water outflow. The 15-year daily saline water evaporation pan data collected near the lake indicate that approximately 71% of the annual evaporation occurred from May to September, about 4.15 billion m3/year. To reduce this water loss, three self-assembled layer coatings—fatty alcohols of stearyl and cetyl with stearic acid in hexane solvents, stearyl and cetyl alcohols with stearic acid powder, and stearyl and cetyl alcohols in ethanol solvents—were tested on pools and evaporation pans adjacent to LU in July, when the lake had the highest evaporation rate. Results of 60 h of experiments for each test showed that the coating composed of stearyl and cetyl alcohols with stearic acid in hexane had the best performance and could reduce evaporation by about 52%. This suggests that applying this coating to LU for 5 months/year could reduce the lake evaporation by about 1.5 billion m3 , which is more than the total annual supply of the main river flowing into the lake. A short-term study of Artemia urmiana indicated that the coatings did not have a significant effect on their length and weight. However, long-term side effects on human health and the environment need further investigation. [ABSTRACT FROM AUTHOR]

The room temperature polar vapor sensing behavior of a graphene-TiS3 heterojunction material and TiS3 nanoribbons is described. The nanoribbons were synthesized via chemical vapor transport (CVT) and their structure was investigated by scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Raman and Fourier transform infrared spectroscopies. The gas sensing performance was assessed by following the changes in their resistivities. Sensing devices were fabricated with gold contacts and with lithographically patterned graphene (Gr) electrodes in a heterojunction Gr-TiS3-Gr. The gold contacted TiS3 device has a rather linear I-V behavior while the Gr-TiS3-Gr heterojunction forms a contact with a higher Schottky barrier (250 meV). The I-V responses of the sensors were recorded at room temperature at a relative humidity of 55% and for different ethanol vapor concentrations (varying from 2 to 20 ppm). The plots indicate an increase in the resistance of Gr-TiS3-Gr due to adsorption of water and ethanol with a relatively high sensing response (~495% at 2 ppm). The results reveal that stable responses to 2 ppm concentrations of ethanol are achieved at room temperature. The response and recovery times are around 8 s and 72 s, respectively. Weaker responses are obtained for methanol and acetone. [ABSTRACT FROM AUTHOR]

In this research, inorganic copper thiocyanate (CuSCN) hole transport layer (HTL) was applied in conventional structure of perovskite solar cells (PSCs). Besides, mixed halides perovskite (Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3) was utilized as the light absorbing layer and deposited on FTO/compact TiO2 substrates through a one-step coating method in ambient condition. The mentioned perovskite is more stable against high temperature, high irradiation and humidity compared to commonly applied MAPbI3 perovskite. Nevertheless, the CuSCN could not be well dissolved in usual dipropyl sulfide solution and should be deposited for several times to achieve suitable thickness, this could reduce the quality of CuSCN layer and corresponding interfaces with the other layers. Here, Acetonitrile was applied as a co-solvent to increase the CuSCN concentration in mixed solvent. Consequently, the proper thickness was achieved for just one step of spin coating process. In addition, the CuSCN layer seemed smooth and pinholes free and the interfaces were well-formed. The PSCs with CuSCN HTLs prepared by usual low concentration CUSCN solution were also fabricated and characterized. The results show that the PSCs with improved CuSCN layer deposited from the acetonitrile assisted solution demonstrated a power conversion efficiency (PCE) 11%. This value was nearly close to that of the reference cell with Spiro-OMeTAD organic HTL. The corresponding stabilities were also comparable according to the carried out measurements. In addition, the PCE was increased about 45% compared to the optimized situation of the PSCs with CuSCN layer prepared from low concentration CuSCN solution. [ABSTRACT FROM AUTHOR]

Titanium trisulfide (TiS3), a transition metal chalcogenide, bears the potential to replace silicon, when taking the form of nanoflakes, due to its favorable band gap and optical response. In this paper, we investigate the response of TiS3 nanoflakes to gas detection through a careful quantum computational approach and a few succinct measurements. The computations are benchmarked and compared with a relevant experiment at each step, where their results/conclusions are discussed. The most stable surface of TiS3 particles is determined as (001), in agreement with the literature. The adsorption of 5 gas molecules is characterized through formulating and estimating their adsorption intensity values, rather than using singled-out values of binding energies. This formulation, which is rooted in a statistical view of the gas adsorption process, distinguishes H2 and CH4 molecules from H2O and O2 explicitly and unambiguously through comparing their adsorption profiles. The difference in the adsorption intensities thus predicts and elucidates the difference in the sensing behaviour of TiS3 particles. This work suggests that the computationally obtained profile for the adsorption spectrum of gas molecules serves as a tool/criterion to predict the selectivity of their detection by TiS3. [ABSTRACT FROM AUTHOR]

CuInS nanoparticles as the visible (wurtzite, 1.67 eV) or near infrared (chalcopyrite, 1.50 eV) light absorbing material in thin film solar cells, were synthesized using facile, one step heating up method by dissolving of CuCl, InCl and SC(NH) as precursors in oleylamine (OLA) alone or in combination with oleic acid (OA) and 1-octadecene (ODE) as solvent. The phase, size, morphology, and size distribution were controlled by the coordination ability between solvent molecules and metal precursors, reaction temperature and time. The presence of higher amounts of thiourea or OA to OLA led to the formation of chalcopyrite phase in comparison to wurtzite structure. Also, higher reaction temperatures (>240 °C) resulted in favour of more chalcopyrite phase and higher crystallinity but the nanoparticles got agglomerated. As synthesized nanoparticles was characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, high resolution-transmission electronic microscopy, ultraviolet-visible-near infrared, photoluminescence. The high resolution TEM confirmed the existence of chalcopyrite structure along with wurtzite structure in the nanocrystal (polytypism). Well controlled chalcopyrite CuInS triangular pyramidal shape with an average size ranging from ~10-20 nm size was obtained by using 20 ml OLA or 20 ml OLA along with 4 ml OA and ODE, respectively, with 210 °C heating up and 4 h annealing time. [ABSTRACT FROM AUTHOR]

The structural, electrical, optical, and photovoltaic properties of aggregated submicron nitrogen-doped TiO particles (NTiO) and the influence of utilizing them, in comparison with undoped ones, as the light-scattering layer of dye-sensitized solar cells were investigated. Field emission scanning electron microscope, X-ray diffraction, and diffuse reflectance spectra showed that both type samples have similar morphology, crystal phase, and scattering feature. Moreover, photoluminescence, Mott-Schottkey, and photovoltaic characteristics such as IMPS/IMVS and charge extraction analysis indicated that the NTiO layer is an efficient scatterer in two aspects: enhancement of light-harvesting efficiency by having submicron-size centers and modification of the electrical properties such as charge collection efficiency in photoanode. As a result, the overall conversion efficiency reached 7.34 % upon employing NTiO as the light-scattering layer, which is 13 % higher than undoped one. This improvement is a consequence of trap density reduction, electrons transfer enhancement in the interface of photoactive/scattering layer, and shunt resistance increment at photoelectrode/electrolyte interface. [ABSTRACT FROM AUTHOR]

We present fabrication, characterization, and experimental results describing electrical actuation and readout of the mechanical vibratory response of electrospun ZnO nanofibers. For a fiber with an approximate radius of 200 nm and a length of 70 μm, a resonance frequency around 3.62 MHz with a quality factor (Q) of about 235 in air at ambient conditions is observed. It is shown that the measured frequency of the resonance is consistent with results from finite element simulations. Also, the measurements were performed in an enclosed chamber with controlled levels of ethanol vapor. The adsorption of ethanol causes a shift in the resonance frequency of the fibers, which can be related to the concentration of ethanol vapor for sensing purposes. [ABSTRACT FROM AUTHOR]

Gas sensors have been fabricated based on field ionization from titanium oxide nanotubes grown on titanium foil. Ordered nanaotube arrays of titanium oxides were grown by the anodization method. We measured breakdown voltages and discharge currents of the device for various gases. Our gas ionization sensors (GIS) presented good sensitivity, selectivity, and short response time. The GISs based on TiO nanotube arrays showed lower breakdown voltage, higher discharge current, and good selectivity. An excellent response observed for Ar compared to other gases. Besides, by introducing 2 % CO and 4 % H to N flow gas, the amount of breakdown voltage shifts about 20 and 70 volts to the lower values, respectively. The GIS works at room temperature and has the ability of detect inert gases with high stability and good linearity. Besides, short response time of about 1 second for the GISs based on TiO nanotube arrays makes them excellent for gas sensing applications. Sharp edges of the nanotubes, through enhancing the applied electric field, reduce operating voltage to the reasonable values and power consumption. [ABSTRACT FROM AUTHOR]

Pd doped WO3 fibers were synthesized by electro-spinning. The sol gel method was employed to prepare peroxopolytungstic acid (P-PTA). Palladium chloride and Polyvinyl pyrrolidone (PVP) was dissolved in the sol Pd:WO3 = 10% molar ratio. The prepared sol was loaded into a syringe connected to a high voltage of 18.3 kV and electrospun fibers were collected on the alumina substrates. Scanning electron microscope (SEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques were used to analyze the crystal structure and chemical composition of the fibers after heat treatment at 500 °C. Resistance-sensing measurements exhibited a sensitivity of about 30 at 500 ppm hydrogen in air, and the response and recovery times were about 20 and 30 s, respectively, at 300 °C. Hydrogen gas sensing mechanism of the sensor was also studied. [ABSTRACT FROM AUTHOR]

In this work, we report on fabrication and characterization of dye-sensitized solar cells based on TiO2 nanotube/nanoparticle (NT/NP) composite electrodes. TiO2 nanotubes were prepared by anodization of Ti foil in an organic electrolyte. The nanotubes were chemically separated from the foil, ground and added to a TiO2 nanoparticle paste, from which composite NT/NP electrodes were fabricated. In the composite TiO2 films the nanotubes existed in bundles with a length of a few micrometres. By optimizing the amount of NT in the paste, dye-sensitized solar cells with an efficiency of 5.6% were obtained, a 10% improvement in comparison to solar cells with pure NP electrodes. By increasing the fraction of NT in the electrode the current density increased by 20% (from 11.1 to 13.3 mA cm−2), but the open circuit voltage decreased from 0.78 to 0.73 V. Electron transport, lifetime and extraction studies were performed to investigate this behavior. A higher fraction of NT in the paste led to more and deeper traps in the resulting composite electrodes. Nevertheless, faster electron transport under short-circuit conditions was found with increased NT content, but the electron lifetime was not improved. The electron diffusion length calculated for short-circuit conditions was increased 3-fold in composite electrodes with an optimized NT fraction. The charge collection efficiency was more than 90% over a wide range of light intensities, leading to improved solar cell performance. [ABSTRACT FROM AUTHOR]

ZnO nanostructures were synthesized through arc discharge of zinc electrodes in deionized (DI) water. X-ray diffraction (XRD) analysis of the prepared nanostructures indicates formation of crystalline ZnO of hexagonal lattice structures. Transmission electron microscopy (TEM) images illustrate rod-like as well as semi spherical ZnO nanoparticles with 15–20 nm diameter range, which were formed during the discharge process with 5 A arc current. The average particle size was found to increase with the increasing arc current. X-ray photoelectron spectroscopy (XPS) analysis confirms formation of ZnO at the surface of the nanoparticles. Surface area of the sample prepared at 5 A arc current, measured by BET analysis, was 34 m/g. Photodegradation of Rhodamine B (Rh. B) shows that the prepared samples at lower currents have a higher photocatalytic activity due to larger surface area and smaller particle size. [ABSTRACT FROM AUTHOR]

We report a simple, inexpensive and one-step synthesis route of colloidal gold nanoparticles using arc discharge between titanium electrodes in HAuCl4 solution achieving long-time stability. Gold nanoparticles of 8 nm diameter were formed during reduction of HAuCl4 in the plasma discharge zone. The resulting nanoparticles were characterized using UV–Vis spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Optical absorption spectroscopy of as prepared samples at 15 A arc current in HAuCl4 solution shows a surface plasmon resonance around 550 nm. It was found that sodium citrate acts as a stabilizer and surface capping agent of the colloidal nanoparticles. SEM images exhibit the increase of reduced nanoparticles in 4 minutes arc duration compared with 1 minute arc duration. A TEM image of the sample prepared at 4 minutes arc duration shows a narrow size distribution with 8 nm mean particle size. The plasmonic peak intensity of as prepared gold nanoparticles in 1 minute arc duration gradually increases due to seed mediation up to 6 hours. [ABSTRACT FROM AUTHOR]

In this study WO x films were deposited by laser ablation of ultra-pure (5N) tungsten trioxide targets onto SiO2 or silicon substrates at 250°C temperature, 100 mTorr oxygen partial pressure and 1×10−5 Torr vacuum. Surface chemical states and compositions of the deposits were determined by X-ray photoelectron spectroscopy. The results showed that deposits in oxygen partial pressure contain W6+ with x∼3.1, while vacuum-deposited films have different W states with various percentage distributions as W4+>W5+>W6+>W0, and x∼1. We used fast electrical resistance measurement as a probe to study the deposition process. Film resistance as a function of deposition time in vacuum revealed some microsecond fluctuations modulated on the time variation curve of electrical resistance. We attribute these data to surface absorption and desorption of oxygen during layer deposition. Finally, the effect of the laser beam on the target’s structure, surface morphology and chemical state was studied. Our results revealed that in spite of structural variation by laser irradiation, the O/W ratio remained about 3. [ABSTRACT FROM AUTHOR]

Here in this research, room temperature ethanol and humidity sensors were prepared based on two dimensional (2D) hybrid nanostructures of tungsten di-sulfide (WS2) nanosheets and graphene oxide nanoribbons (GONRs) as GOWS. The characterization results based on scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (ESD), Raman spectroscopy and X-ray diffraction (XRD) analysis confirmed the hybrid formations. Ethanol sensing of drop-casted GOWS films on SiO2 substrate indicated increasing in gas response up to 5 and 55 times higher compared to pristine GONRs and WS2 films respectively. The sensing performance of GOWS hybrid nanostructures was investigated in different concentrations of WS2, and the highest response was about 126.5 at 1 ppm of ethanol in 40% relative humidity (R.H.) for WS2/GONRs molar ratio of 10. Flexibility of GOWS was studied on Kapton substrate with bending radius of 1 cm, and the gas response decreased less than 10% after 30th bending cycles. The high response and flexibility of the sensors inspired that GOWS are promising materials for fabrication of wearable gas sensing devices. [ABSTRACT FROM AUTHOR]

A high‐performing, lightweight, and flexible asymmetric supercapacitor (ASC) using NiCo‐layered double hydroxide (NiCo LDH) supported on 3D nitrogen‐doped graphene (NG) as a positive electrode and NG as a negative electrode is demonstrated. Highly conductive NG provides fast electron transfer and facilitates (dis)charging of NiCo LDH deposited on it. The composite electrode of NiCo LDH@NG exhibits a high specific capacitance of 1421 F g−1 at 2 A g−1. Moreover, the as‐obtained hybrid electrode shows an excellent rate capability with a specific capacitance of 1397 F g−1 at a high current density of 10 A g−1, which is about 98% of the capacitance obtained at 2 A g−1. The flexible ASC device shows a specific capacitance of 109 F g−1 at 0.5 A g−1 and a maximum energy density of 49 W h kg−1, which is comparable with or superior to previously reported electrodes based on nickel‐cobalt hydroxides. Furthermore, an excellent mechanical stability is obtained. Under repeated mechanical bendings, the ASC demonstrates high bending stability up to 450 bending cycles at a 90° angle. Hence, this flexible NiCo LDH@NG electrode that is free of binders and conductive agents shows superior performance and stability, and is a promising candidate for the future wearable energy storage devices. [ABSTRACT FROM AUTHOR]

Unidirectional current flow is at the heart of modern electronics, which has been conceived by making p–n junctions or Schottky barriers between different kinds of materials. Within such elements, however, synthesis of thin film lateral heterostructures has so far remained challenging. Here, a one‐step simple synthesis of p‐type, n‐type, and metallic lateral heterostructures using bipolar electrodeposition (BPE) technique is reported. Molybdenum oxides and sulfides with gradient of oxygen and sulfur are deposited at a metallic substrate. A lateral heterostructure is achieved with electrical properties that change from p‐ to n‐type semiconductor and then to metal by moving in the plane of the layer. This effect is observed due to an increase in MoO-2 and reduction of MoSx from one side to the other side of the structure. Finally, by transferring the layer onto a dielectric substrate, the current–voltage (I–V) characteristic of the layer is found to show a rectifying behavior with a low threshold of 0.45 V and a rectification of about 10 at relatively low applied voltages. A simple one‐step synthesis of semiconductive lateral heterostructures is presented. Gradients of molybdenum sulfides and oxides through bipolar electrodeposition technique are obtained with rectifying current–voltage characteristics at relatively low voltage limits. Scanning tunneling spectroscopy indicates that type I and II band alignments are formed in p–n and n–n lateral heterostructures. [ABSTRACT FROM AUTHOR]