Current-voltage Analysis Research Articles

Novel Al/CoFe/p-Si and Al/NiFe/p-Si MS-type photodiode for sensing

CoFe and NiFe are used in the construction of Si-based metal-semiconductor-type photodiodes. Thin film layers are sputtered onto thep-Si surface where Al metal contacts are deposited using the thermal evaporation technique. Film characteristics of the layers are investigated with respect to the crystalline structure and surface morphology. Their electrical and optical properties are investigated using dark and illuminated current-voltage measurements. When these two diodes are compared, Al/NiFe/p-Si exhibits better rectification properties than Al/CoFe/p-Si diode. There is also a high barrier height where these values for both diodes increase with illumination. According to the current-voltage analysis, the existence of an interlayer causes a deviation in diode ideality. In addition, the response to bias voltage, the derivation of electrical parameters, and the light sensitivity of diodes are evaluated using current-voltage measurements under different illumination intensities and also transient photosensitive characteristics.

Adsorption of arsenite (As3+) ions pollution by synthesized BC2N graphene-like nanosheets: DFT investigation

Detecting As3+ in urban and industrial wastewater is of paramount importance for maintaining public health. Density functional theory can be utilized to investigate the potential applications of BC2N nanosheets in sensing and removing As3+ ions. The findings of the current study confirm that the adsorption of As3+ ions onto the BC2N nanosheet significantly reduces the band gap, thereby rendering the nanosheet an exceptional sensing platform for As3+ ions. The BC2N nanosheet exhibits the potential to function as both an electronic and φ-type sensor for the detection of toxic As3+ ions. Moreover, this study examines the impact of As3+ ion adsorption on the electronic transport characteristics of the BC2N nanosheet through current-voltage and transmission analyses, utilizing a bias voltage ranging from 0 to 2 V. The results of this study provide theoretical evidence supporting the use of pristine BC2N nanosheets as a viable substrate for efficient sensing and removal of toxic As3+ ions in practical water treatment applications.

Unravelling the effect of soxhlet extracted Pisolithus arhizus fungi in bio-sensitized solar cells in response to diverse polar solvents

The potential application of Pisolithus arhizus fungi as an effective sensitizer in bio-sensitized solar cells (BSSCs) is the first of its kind to investigate the photovoltaic performance of BSSCs in polar protic and aprotic solvents. The soxhlet extraction method was employed to extract dye molecules in organic solvents including chloroform, 2-propanol, acetone, ethanol, methanol and DMSO and named PA1, PA2, PA3, PA4, PA5, PA6 to fabricate BSSCs. TiO2 and Platinum were used as working and counter electrodes. The structural, optical, morphological properties of the extracted dyes and dye anchored TiO2 films were analyzed through FTIR, UV–Vis spectroscopy and FESEM analysis. The optical absorption analysis revealed the presence of pisoquinone pigments in the fungi, from flavonoid family. The current-voltage, electrochemical impedance and cyclic voltammetry analysis showed that the PA4 ethanolic-based BSSC demonstrated the highest power conversion efficiency of 1.31 % compared to other DSSCs, with a Jsc of 3.40 mA cm−2 and Voc of 514 mV and the bandgap energy of 1.8eV. The order of the conversion efficiency for DSSCs with different solvents was ethanol (PA4) > methanol (PA5) > acetone (PA3) > DMSO (PA6) > 2-propanol (PA2) > chloroform (PA1). This finding highlights that selecting optimal, novel sensitizers and extraction solvents is crucial to maximize solar cell efficiency.

Gas phase formaldehyde degradation: Continuous versus duty cycle driven plasma reactor

This study investigated the degradation of formaldehyde (HCHO) using continuous plasma reactor (CPR) and duty cycle driven plasma reactor (DCPR) to obtain insights into reactor selection, optimization strategies, and underlying kinetics. The electrical characteristics of the reactors were analyzed via current-voltage analysis while optical properties were investigated using optical emission spectroscopy (OES). Furthermore, the reactive species concentrations were determined using gas Fourier-transform infrared (FTIR) measurements. The optimization of the degradation focused on varying the applied voltages, resulting in intensified plasma and changes in the surface temperature, electron temperature rotational temperature, and vibrational temperature. CPR demonstrated outstanding efficiency, with an energy yield of 3.60 g kW−1 h−1 and an impressive 89 % removal effectiveness at 5.8 kV. The best removal efficiency of 92 % was observed at 6.2 kV. The degradation kinetics were primarily driven by energetic electrons, along with primary reactive species such as OH ⋅ and O ⋅ with a reaction rate of 6.8 × 10−3 L J−1. This study contributes to advancing the understanding of HCHO degradation kinetics and provides practical insights into enhancing plasma-based environmental cleanup technologies without using any catalyst.

Thermal annealing effect on phase evolution, physical properties of DC sputtered copper oxide thin films and transport behavior of ITO/CuO/Al Schottky diodes

Herein, we report on the post-annealing temperature effect on the transport behavior of p-CuO/Al Schottky barrier diodes. In addition, the transformation of phase from Cu4O3 to CuO phase was studied. Copper oxide thin films were grown on soda lime glass substrates, and post-annealing temperature's influence on the films’ structural, chemical, morphological, and electrical characteristics was comprehensively examined. X-ray diffraction study revealed the development of polycrystalline tenorite phase (CuO) on annealing. Raman analysis also confirmed the formation of the tenorite phase (CuO) at higher annealing temperatures (400 °C and 500 °C). XPS study revealed the occurrence of the Cu4O3 phase for room temperature deposited sample and CuO phase at the higher annealing temperature. Using current–voltage analysis, the Chueng model, and the thermoelectric emission model, the Schottky behavior between the metal and semiconductor were investigated. The fabricated diode showed a rectification ratio of 103 at ± 2 V, with the barrier height ranging from 0.84 to 1.12 eV due to different annealing treatments. The attributes of the power law were employed to elucidate space charge-limited conduction and the process of tunneling across the density of interface traps in p-CuO/Al Schottky diodes. This study provides valuable insights into the behavior of the p-CuO/Al Schottky junction, enhancing our understanding of its characteristics.

Hot carrier photocurrent induced by 0.92 eV photon energy radiation in a Si solar cell

Absorption of the below-bandgap solar radiation and direct pre-thermalizational impact of a hot carrier (HC) on the operation of a single-junction solar cell are ignored by the Shockley-Queisser theory. The detrimental effect of the HC is generally accepted only via the thermalization-caused heating of the lattice. Here, the authors demonstrate experimental evidence of the HC photocurrent induced by the below-bandgap 0.92 eV photon energy radiation in an industrial silicon solar cell. The carriers are heated both through direct free-carrier absorption and by residual photon energy remaining after the electron-hole pair generation. The polarity of the HC photocurrent opposes that of the conventional generation photocurrent, indicating that the total current across the p-n junction is contingent upon the interplay between these two currents. A model of current-voltage characteristics analysis allowing us to obtain a reasonable value of the HC temperature was also proposed. This work is remarkable in two ways: first, it contributes to an understanding of HC phenomena in photovoltaic devices, and second, it prompts discussion of the HC photocurrent as a new intrinsic loss mechanism in solar cells.

Defects Contributing to Hysteresis in Few-Layer and Thin-Film MoS2 Memristive Devices.

Molybdenum disulfide, a two-dimensional material extensively explored for potential applications in non-von Neumann computing technologies, has garnered significant attention owing to the observed hysteresis phenomena in MoS2 FETs. The dominant sources of hysteresis reported include charge trapping at the channel-dielectric interface and the adsorption/desorption of molecules. However, in MoS2 FETs with different channel thicknesses, the specific nature and density of defects contributing to hysteresis remain an intriguing aspect requiring further investigation. This study delves into memristive devices with back-gate modulated channel layers based on CVD-deposited flake-based and thin-film-based MoS2 FETs, with a few-layer (FL) and thin-film (TF) channel thickness. Analysis of current-voltage (I-V) and conductance-frequency (Gp/ω-f) measurements led to the conclusion that the elevated hysteresis observed in TF MoS2 devices, as opposed to FL devices, stems from a substantial contribution from intrinsic defects within the channel volume, surpassing that of interface defects. This study underscores the significance of considering both intrinsic defects within the bulk and the interface defects of the channel when analyzing hysteresis in MoS2 FETs, particularly in TF FETs. The selection between FL and TF MoS2 devices depends on the requirements for memristive applications, considering factors such as hysteresis tolerance and scaling capabilities.

Effect of graphene electrode functionalization on machine learning-aided single nucleotide classification.

Solid-state nanogap-based DNA sequencing with a quantum tunneling approach has emerged as a promising avenue due to its potential to deliver swift and precise sequencing outcomes. Nevertheless, despite significant progress, experimentally achieving single base resolution with a high signal-to-noise ratio remains a daunting challenge. In this work, we have utilized a machine learning (ML) framework coupled with the quantum transport method to assess and compare the nucleotide identification performance of graphene nanogaps functionalized with four different edge-saturating entities (C, H, N, and OH). The optimized ML model, especially the random forest classifier (RFC), demonstrates high accuracy (>90%) in classifying unlabeled nucleotides from their transmission readouts with the four functionalized graphene nanogaps. Additionally, the minor variance in the accuracy of nucleotide classification across the nanogaps highlights that RFC can capture the role of electrode-nucleotide coupling dynamics in their transmission function. Moreover, we have also conducted conductance sensitivity (%) and current-voltage (I-V) analyses of each functionalized nanogap. Among the edge-saturating entities, the nitrogen atom terminated graphene nanogap (NGN) is found to be the most sensitive for distinguishing DNA nucleotides. Our quantum transport combined ML study provides a useful perspective by conducting a comparative analysis of the role of edge-saturating entities in single-molecule DNA sequencing.

Tailoring the temperature coefficient of resistance of flame-formed carbon nanoparticle thin films by electric field-assisted deposition

The electric-field assisted deposition is successfully proposed as a method for the manufacturing of carbon nanostructured films with tunable properties, benefiting from the superimposition of electric fields on the thermophoretic deposition. Morphology, optical, and thermo-resistive properties of the carbon nanoparticle (CNP) films have been studied by UV–vis Absorption Spectroscopy, Scanning Electron Microscopy, Atomic Force Microscopy, and Current-Voltage analysis. In comparison to thermophoresis alone, the introduction of an electric field results in a six-fold increase in the deposition rate characterized by a non-linear film growth influenced by a three-fold augmentation in surface roughness and polarization effects. Notably, the surface morphology of the CNP films undergoes modification, exhibiting larger grains and a reduced optical band gap energy. Moreover, while maintaining a non-ohmic behaviour, the electric field plays a crucial role in increasing by about two orders of magnitude the electrical conductance of CNP films at ambient temperature. This effect is accompanied by a decrease in temperature sensitivity, attributed to the low and nearly temperature-independent activation energy for the tunneling of electrons in the percolative network. In summary, electric-field assisted deposition is a promising approach to tailor the thermal response of CNP films, which could be beneficial for the development of next-generation sensors.

Current-Voltage Analysis Tool for Solar Fuel Production (CATS)

Solar-driven electrochemical devices, such as PV-electrolyzers and photoelectrochemical (PEC) devices, contain multiple components which can make it difficult to pinpoint the failing piece when overall device performance is degrading. The current-voltage analysis tool for solar fuel production (CATS) is a free app that analyzes current-voltage data collected during operation, parameters that are easily accessible for many devices of interest. The program captures the time-dependence of loss mechanisms at play during PEC device operation and opens the door for real-time optimizations of operational parameters like the feed humidity to minimize performance losses. Aside from the possibility of deconvoluting loss mechanisms, this software can also reveal possible performance benefits, such as by convective PV cooling when the photoabsorber is integrated into the electrolysis cell.

Highly efficient tandem organic light-emitting diodes using p-type metal halide copper iodide (CuI)

Efficient charge generation is essential for tandem organic light-emitting diode (OLED) devices. In this study, we introduce a p-type copper iodide (CuI) layer within the charge generation layer (CGL) that exhibits high charge generation efficiency in tandem OLED devices. Briefly, CuI is deposited as a thin layer via thermal evaporation technique. X-ray diffraction (XRD) analysis reveals the formation of γ-CuI, and the ultraviolet-visible (UV-Vis) spectral analysis demonstrates outstanding optical transparency (∼95%) of the deposited CuI films in the visible range. The current-voltage (I-V) and capacitance-voltage (C-V) analyses show that the p-type CuI layer is a vital and excellent charge generator and enhances the current density significantly. The tandem OLED device fabricated using Bphen:Liq/CuI/HAT-CN as the CGL results in a substantial 1.9-fold increase in current efficiency compared to the single-unit OLED device, approaching the theoretical two-fold increase. These findings highlight the potential of CuI as a promising p-type material for CGL design in tandem OLED devices.

The potential of multicylindrical dielectric barrier discharge plasma for diesel-contaminated soil remediation and biocompatibility assessment

This study explored the use of multicylindrical dielectric barrier discharge (MC–DBD) plasma technology to eliminate diesel fuel contamination from the soil. This study also assessed the environmental impact of plasma-generated reactive species on soil properties, plant growth, and the safety of microbial and human skin cells using various analytical methods. MC–DBD plasma was characterized using the current–voltage analysis and optical emission spectroscopy (OES). Gas Fourier transform infrared spectroscopy was employed to detect reactive species, such as O3, NO, NO2, N2O, and HNO3, in the plasma-treated air. The diesel fuel concentration in the soil was measured before and after plasma treatment using a gas chromatography–flame ionization detector. The efficacy of the MC–DBD plasma treatment was evaluated based on soil characteristics (pH and moisture), discharge parameters (power), and reactive species (O3 and NOx). Using only power of 30 W, the MC–DBD achieved a 94.19% removal of diesel fuel from the soil and yielded an energy efficiency of 1.78 × 10−2 m3/kWh within a 60-min treatment period. Neutral soil with a moisture content of 2% proved more effective in diesel fuel removal compared with acidic or alkaline soil with higher moisture content. O3 was the most efficient plasma-generated reactive species for diesel fuel removal and is involved in oxidation-induced fragmentation and volatilization. Overall, the potential of the MC–DBD plasma technology for remediating diesel fuel-contaminated soils is highlighted, and valuable insights for future applications are provided.

Microstructure, ferromagnetic resonance, and electrical analysis of Ho-substituted Li-Ni nanoparticles

The substitution of rare earth ions is a novel approach to vary the dynamic magnetic properties of soft ferrites to such an extent that its electrical properties and ferromagnetic resonance (FMR) response can be set over a broad frequency range. In this work, a complete transmission electron microscopy (TEM), scanning electron microscopy (SEM), ferromagnetic resonance spectroscopy (FMR), X-ray photoelectron spectroscopy (XPS), and current-voltage (I-V) analysis of holmium (Ho) substituted lithium-nickel soft ferrites with composition Li1.2Ni0.4Fe2−xHoxO4 (x = 0, 0.03, 0.06, 0.09, 0.12, and 0.15) is carried out. TEM analysis reveals a spherical shape distribution of nanoparticles with a particle size of ∼ 50 nm. FMR study is carried out to check the role of Ho addition on magnetic energy losses, FMR line position, and shape. The shift in FMR line shape is mainly attributed to the anisotropy contribution, relaxation processes, and ferromagnetic interactions between the magnetic nanoparticles. XPS experiments confirm the presence of all compositional elements along their valence states. The Ho substitution increased the electrical resistivity, whereas the damping of A-B exchange interactions resulted in a decline of Curie temperature (Tc), which is required for high-frequency power applications.

Subthreshold Conduction of Disordered ZnO-Based Thin-Film Transistors.

This study presents the disorderedness effects on the subthreshold characteristics of atomically deposited ZnO thin-film transistors (TFTs). Bottom-gate ZnO TFTs show n-type enhancement-mode transfer characteristics but a gate-voltage-dependent, degradable subthreshold swing. The charge-transport characteristics of the disordered semiconductor TFTs are severely affected by the localized trap states. Thus, we posit that the disorderedness factors, which are the interface trap capacitance and the diffusion coefficient of electrons, would result in the degradation. Considering the factors as gate-dependent power laws, we derive the subthreshold current-voltage relationship for disordered semiconductors. Notably, the gate-dependent disorderedness parameters are successfully deduced and consistent with those obtained by the gm/Ids method, which was for the FinFETs. In addition, temperature-dependent current-voltage analyses reveal that the gate-dependent interface traps limit the subthreshold conduction, leading to the diffusion current. Thus, we conclude that the disorderedness factors of the ZnO films lead to the indefinable subthreshold swing of the ZnO TFTs.

Accelerated Stress Testing of Perovskite Photovoltaic Modules: Differentiating Degradation Modes with Electroluminescence Imaging

Herein, electroluminescence (EL) and thermal imaging are used to examine p–i–n metal halide perovskite (MHP) photovoltaic (PV) mini‐modules (MA0.6FA0.4PbI3, 20 cells, 78 cm2) before and after indoor‐accelerated stress testing or outdoor deployment. Distinct spatial patterns in the EL images emerge, which depend on the external stress conditions experienced by the mini‐module. Imaging results highlight a distribution of dark speckle features that dominate after UV stress, attributed to widespread interfacial contact degradation. Lateral intensity gradients across cells dominate after thermal cycling (TC) stress, attributed to current crowding near scribe defects. While current–voltage analysis alone does not give full insight on the degradation process, this study shows that distinct degradation modes can be further defined by multimodal electro‐optical imaging (i.e., EL combined with photoluminescence and dark lock‐in thermography). Neither UV exposure nor TC‐accelerated stress testing alone replicates the same degradation signatures observed after outdoor deployment, suggesting that multiple degradation modes occur under concurrent stressors outdoors. Spatial characterization of degradation modes in MHP PV mini‐modules before and after accelerated stress testing lays the groundwork for developing targeted accelerated stress testing procedures through comparison with outdoor aging.

Atomic resolution interface structure and vertical current injection in highly uniform MoS2 heterojunctions with bulk GaN

The integration of two-dimensional MoS2 with GaN recently attracted significant interest for future electronic/optoelectronic applications. However, the reported studies have been mainly carried out using heteroepitaxial GaN templates on sapphire substrates, whereas the growth of MoS2 on low-dislocation-density bulk GaN can be strategic for the realization of “truly” vertical devices. In this paper, we report the growth of ultrathin MoS2 films, mostly composed by single-layers (1L), onto homoepitaxial n−-GaN on n+ bulk substrates by sulfurization of a pre-deposited MoOx film. Highly uniform and conformal coverage of the GaN surface was demonstrated by atomic force microscopy, while very low tensile strain (∼0.05%) and a significant p+-type doping (∼4.5 × 1012 cm−2) of 1L-MoS2 was evaluated by Raman mapping. Atomic resolution structural and compositional analyses by aberration-corrected electron microscopy revealed a nearly-ideal van der Waals interface between MoS2 and the Ga-terminated GaN crystal, where only the topmost Ga atoms are affected by oxidation. Furthermore, the relevant lattice parameters of the MoS2/GaN heterojunction, such as the van der Waals gap, were measured with high precision. Finally, the vertical current injection across this 2D/3D heterojunction has been investigated by nanoscale current-voltage analyses performed by conductive atomic force microscopy, showing a rectifying behavior with an average turn-on voltage Von = 1.7 V under forward bias, consistent with the expected band alignment at the interface between p+ doped 1L-MoS2 and n-GaN.

TCAD Analysis of Leakage Current and Breakdown Voltage in Small Pitch 3D Pixel Sensors.

Small-pitch 3D pixel sensors have been developed to equip the innermost layers of the ATLAS and CMS tracker upgrades at the High Luminosity LHC. They feature 50 × 50 and 25 × 100 μm2 geometries and are fabricated on p-type Si-Si Direct Wafer Bonded substrates of 150 μm active thickness with a single-sided process. Due to the short inter-electrode distance, charge trapping effects are strongly mitigated, making these sensors extremely radiation hard. Results from beam test measurements of 3D pixel modules irradiated at large fluences (1016neq/cm2) indeed demonstrated high efficiency at maximum bias voltages of the order of 150 V. However, the downscaled sensor structure also lends itself to high electric fields as the bias voltage is increased, meaning that premature electrical breakdown due to impact ionization is a concern. In this study, TCAD simulations incorporating advanced surface and bulk damage models are used to investigate the leakage current and breakdown behavior of these sensors. Simulations are compared with measured characteristics of 3D diodes irradiated with neutrons at fluences up to 1.5 × 1016neq/cm2. The dependence of the breakdown voltage on geometrical parameters (e.g., the n+ column radius and the gap between the n+ column tip and the highly doped p++ handle wafer) is also discussed for optimization purposes.

Effect of SrTiO3 buffer layer on electrical, ferroelectric memory, and polarization reversal studies of spin-coated ferroelectric 0.6Ba (Zr0·2Ti0.8)O3-0.4(Ba0·7Ca0.3)TiO3 thin film in MFIS structure

This work highlights the effect of SrTiO3 (STO) buffer layer on leakage current, memory, and polarization reversal properties of spin-coated 0.6Ba(Zr0·2Ti0.8)O3-0.4(Ba0·7Ca0.3)TiO3 (BCZT) thin film on Si-substrate in metal-ferroelectric-semiconductor configuration. XRD and Raman analysis confirm the presence of a morphotropic phase of BCZT. Raman and SEM studies suggested that STO enhances the microstructure of BCZT films. The current-voltage (I–V) analysis suggests that the transport mechanism is governed by Schottky – emission model and insertion of STO reduces the leakage current by three orders of magnitude. The capacitance-voltage (C–V) characteristics of Al/BCZT/Si and Al/BCZT/STO/Si structures exhibited a memory window of 1.7 V and 2.6 V respectively. The Al/BCZT/STO/Si structure also showed good retention properties. Further, the peak values of polarization current in the Al/BCZT/STO/Si structure exhibited Mert'z law. The low leakage current, enhanced memory window, high retention characteristics, and faster switching time of the Al/BCZT/STO/Si structure make it attractive for next-generation memory applications.

Simulation of NOx and COx Gas Sensor based on Pristine Armchair Stanene Nanoribbon

AbstractIn this study, the adsorption of the most common hazardous gases (CO, NO, NO2, and CO2) on the stanene armchair nanoribbon of width 6 (H‐ASnNR(6)) is investigated using density functional theory. The most stable adsorption sites, adsorption energies, charge transfer, electronic features, transmission spectra, and current–voltage analysis are explored. All molecules are physisorbed on H‐ASnNR(6) through van der Waals interactions, indicating a potential use for this material in recoverable gas sensors, and all gas molecules act as acceptors. Additionally, the highest and the lowest charge transfer is related to the NO and CO2 molecules, respectively. It is revealed that the adsorption of NO and NO2 affects the electronic properties of the H‐ASnNR(6), and the system displays conducting behavior, while the influence of CO and CO2 gas molecules on the electrical properties of H‐ASnNR(6) is relatively small. The results demonstrate that compared to pristine H‐ASnNR(6), the transmission function of the gas plus H‐ASnNR(6) system undergoes a significant change, particularly after the adsorption of NO and NO2 molecules. The presence and absence of the molecules are shown by current–voltage (I–V) characteristic results. The results suggest that H‐ASnNR(6) has the potential to be used in gas molecule detection applications.

Smartphone-powered, ultrasensitive, and selective, portable and stable multi-analyte chemiresistive immunosensing platform with PPY/COOH-MWCNT as bioelectrical transducer: Towards point-of-care TBI diagnosis

Traumatic Brain Injury, one of the significant causes of mortality and morbidity, affects worldwide and continues to be a diagnostic challenge. The most desirable and partially met clinical need is to simultaneously detect the disease-specific-biomarkers in a broad range of readily available body fluids on a single platform with a rapid, low-cost, ultrasensitive and selective device. Towards this, an array of interdigitated microelectrodes was fabricated on commercially existing low-cost single-side copper cladded printed-circuit-board substrate followed by the bioelectrodes preparation through covalent immobilization of brain injury specific biomarkers on carboxylic functionalized multi-walled carbon nanotubes embedded polypyrrole nanocomposite modified interdigitated microelectrodes. Subsequently, the immunological binding events were transduced as the normalized change in bioelectrode resistance with and without the target analyte via current-voltage analysis. As proof of concept, current-voltage responses were primarily recorded using a conventional probe station, and later, a portable handheld-electronic-readout was developed for the point-of-care application. The data compilation and analysis were carried out using the in-house developed android-based mobile app. Notably, the smartphone powered the readout through a PL-2303 serial connector, avoiding integrating power sources with the readout. Further, this technology can be adapted to other point-of-care biosensing applications.