Blocking Layer Research Articles

Numerical analysis of an ultralow switching loss IGBT with super junction and blocking junction

In order to reduce the switching loss (ESW) and enhance the breakdown voltage (BV), in this paper, an insulated gate bipolar transistor with an internal blocking junction and super junction (SJBJ-IGBT) is proposed and investigated. By inserting P-pillar and N-pillar on both sides of the drift region, a drift area with auxiliary depletion function can be formed. The junction of the primary blocking layer (JPB) is located internally in the device’s drift region. The JPB is reverse biased and withstand the main E-field during device turn-off. Meanwhile, the JPB is surrounded by P-pillar and N-pillar, reducing the E-field(E-field) peak value of device, and making E-field distribution more uniform. Furthermore, during device turn-on, the reduction of the effective area of drift region makes it easier for the JPB side of the P-drift region to accumulate excess holes. So that the SJBJ-IGBT is easier to turn-on. The snapback phenomenon of SJBJ-IGBT is eliminated. Simulation results demonstrate that, under the same forward conduction voltage (VON) condition, the proposed device exhibits a significantly lower turn-on energy loss (EON) compared to the traditional super junction(SJ-IGBT), and is 44.5% lower than that of IPBJ-IGBT, while their turn-off energy losses (EOFF) are almost equivalent.Besides, the optimized E-field distribution in the SJBJ-IGBT shows 13.2% improvement of BV. Researching results can provide important reference for reducing the ESW of IGBT.

A Convolutional Neural Network for Automated Detection of Cervical Ossification of the Posterior Longitudinal Ligament using Magnetic Resonance Imaging.

Retrospective cohort study. We aimed to develop and validate a convolutional neural network (CNN) model to distinguish between cervical ossification of posterior longitudinal ligament (OPLL) and multilevel degenerative spinal stenosis using Magnetic Resonance Imaging (MRI) and to compare the diagnostic ability with spine surgeons. Some artificial intelligence models have been applied in spinal image analysis and many of promising results were obtained; however, there was still no study attempted to develop a deep learning model in detecting cervical OPLL using MRI images. In this retrospective study, 272 cervical OPLL and 412 degenerative patients underwent surgical treatment were enrolled and divided into the training (513 cases) and test dataset (171 cases). CNN models applying ResNet architecture with 34, 50, and 101 layers of residual blocks were constructed and trained with the sagittal MRI images from the training dataset. To evaluate the performance of CNN, the receiver operating characteristic curves of 3 ResNet models were plotted and the area under the curve were calculated on the test dataset. The accuracy, sensitivity, and specificity of the diagnosis by the CNN were calculated and compared with 3 senior spine surgeons. The diagnostic accuracies of our ResNet34, ResNet50, and ResNet101 models were 92.98%, 95.32%, and 97.66%, respectively; the area under the curve of receiver operating characteristic curves of these models were 0.914, 0.942, and 0.971, respectively. The accuracies and specificities of ResNet50 and ResNet101 models were significantly higher than all spine surgeons; for the sensitivity, ResNet101 model achieved better values than that of the 2 surgeons. The performance of our ResNet model in differentiating cervical OPLL from degenerative spinal stenosis using MRI is promising, better results were achieved with more layers of residual blocks applied.

Evaluation of Organic and Inorganic Foulant Interaction Using Modified Fouling Models in Constant Flux Dead-End Operation with Microfiltration Membranes.

The goal of this study was to elucidate the interaction of complex feed solutions under modified membrane fouling models for constant flux operation. The polyvinylidene fluoride membrane (PVDF) was tested for three types of solutions containing inorganic foulants (Al, Mn, and Fe), organic foulants, and suspended solids at 0.5 mM Ca2+ ionic strength. The membrane's performance was evaluated by measuring the increase in transmembrane pressure (TMP) during two different filtration scenarios: continuous filtration lasting 1 h and cyclic filtration lasting 12 min, with 3 min backwashing cycles included. Statistical analysis (linear regression results (R2), p-value) was used to verify the fouling model propagation along with the determination of the contributing constant of each fouling model. An increasing TMP percentage of 164-302%, 155-300%, and 208-378% for S1 (HA + Ca2+), S2 (inorganics + kaolin + Ca2+), and S3 (HA + inorganics + kaolin + Ca2+) was recorded for 1 h filtration, respectively. Furthermore, a five percent increase in irreversible resistance was noted for the S3 solution due to the strong adsorption potential of foulants for the PVDF membrane caused by the electrostatic and hydration forces of foulants. In addition to that, the participation equation elucidated the contribution of the fouling model and confirmed that complete blocking and cake layer contribution were dominant for the S1 and S3 solutions, while standard blocking was dominant for the S2 solution with a high significance ratio. Moreover, R2 and cyclic filtration analysis also confirmed the propagation of these fouling models. The statistical confirmation and regression results analysis of the modified model gave comparative results and satisfied the filtration mechanism and can be used for the constant flux dead filtration analysis of water treatment.

Estimation of charge injection at Al/LDPE interface based on space charge and external current measurement

Space charge accumulation in polymer is a key problem for the electrical aging of insulation under DC condition. Space charge accumulation is strongly determined by the charge injection rate. The estimation of charge injection with steady state current contains the extraction current and is not accurate. This paper proposes a quantitative estimation method of the charge injection at the metal/polymer interface with space charge and current simultaneous measurement. A double-layer sample with a blocking layer is employed to make a quasi-unipolar condition to remove the extraction current. In addition, the displacement current is removed by considering the change in electric field on the electrode. The relationship between the electrode electric field and the pure injection current is analyzed. It is found that the square root of electric field intensity and the logarithm of injection current at the Al/LDPE (low density polyethylene) interface are linear with each other. The coefficients β for negative and positive charge injection at Al/LDPE interface are about 8.44 × 10−24 and 8.32 × 10−24, respectively. It indicates that both negative and positive charge injection at Al/LDPE interface fit the mathematical relationship of the Poole–Frenkel effect, rather than the Schottky effect which is mostly used in the study on the charge transport at polymer/metal. The negative and positive charge injection barriers are 1.23 and 1.24 eV, respectively.

Advancements in Complementary Metal-Oxide Semiconductor-Compatible Tunnel Barrier Engineered Charge-Trapping Synaptic Transistors for Bio-Inspired Neural Networks in Harsh Environments.

This study aimed to propose a silicon-on-insulator (SOI)-based charge-trapping synaptic transistor with engineered tunnel barriers using high-k dielectrics for artificial synapse electronics capable of operating at high temperatures. The transistor employed sequential electron trapping and de-trapping in the charge storage medium, facilitating gradual modulation of the silicon channel conductance. The engineered tunnel barrier structure (SiO2/Si3N4/SiO2), coupled with the high-k charge-trapping layer of HfO2 and high-k blocking layer of Al2O3, enabled reliable long-term potentiation/depression behaviors within a short gate stimulus time (100 μs), even under elevated temperatures (75 and 125 °C). Conductance variability was determined by the number of gate stimuli reflected in the maximum excitatory postsynaptic current (EPSC) and the residual EPSC ratio. Moreover, we analyzed the Arrhenius relationship between the EPSC as a function of the gate pulse number (N = 1-100) and the measured temperatures (25, 75, and 125 °C), allowing us to deduce the charge trap activation energy. A learning simulation was performed to assess the pattern recognition capabilities of the neuromorphic computing system using the modified National Institute of Standards and Technology datasheets. This study demonstrates high-reliability silicon channel conductance modulation and proposes in-memory computing capabilities for artificial neural networks using SOI-based charge-trapping synaptic transistors.

Valorization of phenolic compounds from brewery wastewater: Performances assessment of ultrafiltration and nanofiltration process with application of HPLC coupled with antioxidant analysis tool

Phenolic-rich brewery alkaline wastewater sustainable valorization with membrane technology was investigated. Intensified process of preselected ceramic 15 kDa ultrafiltration and 200 Da nanofiltration membranes was studied at pH 4, 6.5, 10 and 13.5 to prospect the best operation conditions of phenolic compounds (PC) recovery and water reclamation process regarding fouling inclination, productivity and selectivity performances. Flux-limiting phenomena propensity according to pH were investigated. HPLC coupled with online antioxidant capacity innovative analysis was used to assess PC selectivity behavior and its subsequent impact on antioxidant properties of concentrated wastewater. Flux-limiting phenomena consisted of PC, carbohydrates and proteins pore blocking and cake layer during ultrafiltration and was corroborated to pH acidity. Osmotic pressure due to ions concentration polarization was predominant during nanofiltration and was lower during pH 4 and 13.5 due to membrane characteristics. PC selectivity by ultrafiltration and nanofiltration membranes was determined with compounds size and chemistry, along with pH effect on molecules and membrane charges. The chemical structure of single PC led to differential segregation through the valorization process, and thus to modification of the antioxidant profile of concentrated wastewater. pH 13.5 showed controlled fouling development and advantageous selectivity and productivity performance, and nanofiltration yielded concentrated PC retentate for resource recovery and clarified permeate for water and alkalis reclamation.

Polarization Engineered p-Type Electron Blocking Layer Free AlGaN Based UV-LED Using Quantum Barriers with Heart-Shaped Graded Al Composition for Enhanced Luminescence.

In this paper, in order to address the problem of electron leakage in AlGaN ultra-violet light-emitting diodes, we have proposed an electron-blocking free layer AlGaN ultra-violet (UV) light-emitting diode (LED) using polarization-engineered heart-shaped AlGaN quantum barriers (QB) instead of conventional barriers. This novel structure has decreased the downward band bending at the interconnection between the consecutive quantum barriers and also flattened the electrostatic field. The parameters used during simulation are extracted from the referred experimental data of conventional UV LED. Using the Silvaco Atlas TCAD tool; version 8.18.1.R, we have compared and optimized the optical as well as electrical characteristics of three varying LED structures. Enhancements in electroluminescence at 275 nm (52.7%), optical output power (50.4%), and efficiency (61.3%) are recorded for an EBL-free AlGaN UV LED with heart-shaped Al composition in the barriers. These improvements are attributed to the minimized non-radiative recombination on the surfaces, due to the progressively increasing effective conduction band barrier height, which subsequently enhances the carrier confinement. Hence, the proposed EBL-free AlGaN LED is the potential solution to enhance optical power and produce highly efficient UV emitters.

Optimized Doping of Diffusion Blocking Layers and Their Impact on the Performance of Perovskite Photovoltaics.

The roll-to-roll printing production process for hybrid organic-inorganic perovskite solar cells (PSCs) demands thick and high-performance solution-based diffusion blocking layers. Inverted (p-i-n) PSCs usually incorporate solution-processed PC70BM as the electron-transporting layer (ETL), which offers good electron charge extraction and passivation of the perovskite active layer grain boundaries. Thick fullerene diffusion blocking layers could benefit the long-term lifetime performance of inverted PSCs. However, the low conductivity of PC70BM significantly limits the thickness of the PC70BM buffer layer for optimized PSC performance. In this work, we show that by applying just enough N-DMBI doping principle, we can maintain the power conversion efficiency (PCE) of inverted PSCs with a thick (200 nm) PC70BM diffusion blocking layer. To better understand the origin of an optimal doping level, we combined the experimental results with simulations adapted to the PSCs reported here. Importantly, just enough 0.3% wt N-DMBI-doped 200 nm PC70BM diffusion blocking layer-based inverted PCSs retain a high thermal stability at 60 °C of up to 1000 h without sacrificing their PCE photovoltaic parameters.

Interfacial engineering boosted narrow-band ultraviolet LED based on n-PtNPs@ZnO:Ga microwire/AlN/p-GaN heterojunction

Low-dimensional ZnO micro/nanocrystals having high optical gain, self-constructed microcavity and large-bandgap, is the largest potential constituent for constructing droop-free and high-brightness ultraviolet light sources. In this study, we reported a workable scheme to construct high-monochromatic ultraviolet electroluminescence devices including a Ga-doped ZnO microwire decoated with platinum nanoparticles (PtNPs@ZnO:Ga MW), an AlN electron blocking layer and p-GaN layer substrate. The device exhibits a robust narrow-band ultraviolet electroluminescence peaking at around 374.8 nm and a narrowing bandwidth ∼ 13.5 nm. The electroluminescence profile is comparable with photoluminescence spectrum of ZnO:Ga MW. The device properties can be interpreted by the working mechanism of plasmonic effects, heterojunction interface engineering and optimization strategies. The AlN intermediate layer appeared in the optimized device enables effectively to tune the paths of current traveling and carrier recombination, yielding the band-edge luminescence of ZnO:Ga MW. As the device is further modified using PtNPs with desired plasmons, the optimization of heterojunction interface is significantly boosted, like the observable enhancement of holes injection efficiency, electroluminescence efficiency and interface contact, etc. Thereby, the boosted band-edge luminescence of ZnO:Ga MW can contribute to the well-being of the enhanced ultraviolet electroluminescence in our constructed LED devices. The findings are looking forward to bringing new opportunities toward the implementation of ultra-bright and high-efficiency narrow-band ultraviolet light sources, especially for the achievement of electrically-pumped microlaser devices.

In Situ Generated Electron-Blocking Lih Enabling An Unprecedented Critical Current Density of Over 15Ma Cm-2 for Solid-State Hydride Electrolytes.

LiBH4 is a promising solid-state electrolyte due to its thermodynamic stability to Li. However, poor Li-ion conductivities at room temperature, low oxidative stabilities and severe dendrite growth hamper its application. Herein, weadopted a partial dehydrogenation strategy to in situ generate an electronic blocking layer dispersed of LiH, addressing the above three issues simuteneously. The electrically insulated LiH reduces the electronic conductivity by two orders of magnitude, leading to a 32.0-times higher critical electrical bias for dendrite growth on the particle surfaces than that of the counterpart. Additionally, this layer not only promotes the Li-ion conductance by stimulating coordinated rotations of BH4 - and B12 H12 2- , contributing to a Li-ion conductivity of 1.38 × 10-3 S cm-1 at 25 °C, but also greatly enhances oxidation stability by localizing the electron density on BH4 - , extending its voltage window to 6.0V. Consequently, this electrolyte exhibits an unprecedented critical current density of 15.12mA cm-2 at 25 °C, long-term Li plating and stripping stability for 2700h, and a wide temperature window for dendrite inhibition from -30 to 150 °C. Its Li-LiCoO2 cell displayed high reversibility within 3.0 to 5.0V. We believe this work provides a clear direction for solid-state hydride electrolytes. This article is protected by copyright. All rights reserved.

Realizing high efficiency and luminance in green, yellow and blue organic light emitting diode by deoxyribonucleic acid

Although the effect of the electron blocking layer (EBL) material, deoxyribonucleic acid (DNA), on the electroluminescence (EL) performance of organic light-emitting diodes (OLEDs) has been studied, the process of DNA regulation of exciton recombination region within the device is still unclear. Herein, devices with and without EBL were fabricated using different DNA spin-coating speeds, and the photoelectric performance of device were measured. By using DNA compounded with cetyltrimethyl ammonium (CTMA) as the EBL and hole buffer layer, so-called BioLEDs. The DNA-based green Alq3 BioLEDs achieve higher luminance (39 000 cd m−2) and higher current efficiency (8.4 cd A−1), which are increased by 49% and 54%, respectively, compared to the reference OLEDs without the addition of DNA. Similarly, the maximum luminance and efficiency of yellow Rubrene BioLEDs is increased by 64% (from 12 120 to 19 820 cd m−2) and 74% (from 1.36 to 2.36 cd A−1), the luminance and efficiency of blue TCTA BioLEDs is increased by 101% and 245%. Specifically, we found that as the thickness of DNA-CTMA increases, the exciton recombination region moves towards the interface between the emitting layer (EML) and the hole transport layer (HTL). By better confining excitons within the EML, the current efficiency of the BioLEDs is effectively improved. Accordingly, we provide a possible idea for achieve high performance DNA-based BioLEDs by adding DNA-CTMA EBL and hole buffer layers. Meanwhile, as the DNA thickness increases, the exciton recombination region moves towards the EML/HTL interface, thereby enhancing the efficiency of the DNA-based BioLEDs.

Triboxidation and softening induced by dry sliding of copper coupling with steel at 3.36 m s−1 speeds

In this paper, the copper coupled with steel under dry sliding are comparatively sdudied at 0.56 m s−1 and 3.36 m s−1 condition from the morphology, structure and composition of tribolayer of the copper. It is found that the wear rate of Cu at 3.36 m s−1 is twice that at 0.56 m s−1, and the temperature of Cu block at 3.36 m s−1 (240 °C) is much higher than that at 0.56 m s−1 (75 °C). The results show that when the grinding speed is 0.56 m s−1, the grain distortion occurs in the top area of the subsurface layer of Cu block. When the grinding speed is 3.36 m s−1, the grain refinement zone appears below the subsurface layer of Cu block wear. The study further proves that the softening caused by friction heat occurs in the grain refinement zone, and a large number of softened metal copper tends to transfer to the opposite side. At the same time, the friction heat changes the mechanical and thermal deformation, material transfer and friction oxidation of the contact surface, which has a great influence on the dry sliding behavior of Cu.

Partial Point Cloud Registration With Deep Local Feature

How to accurately register partial point cloud still remains a challenging task, because of its irregular and unordered structure in a non-Euclidean space, noise, outliers, and other unfavorable factors. In this paper, an effective partial point cloud registration network is proposed, by devising a two-stage deep local feature extraction process and an outlier filtering strategy. To be specific, on the one hand, to effectively capture geometric interdependency in low-level space, a local attention feature extraction module is explored to extract local contextual attention features, by highlighting different attention weights on neighborhoods. On the other hand, in local feature aggregation module, two position encoding blocks are applied to increase the receptive field of each point in high-level space. Of these, an attentive pooling can automatically learn important local features to alleviate the possible information loss. Furthermore, to derive the weight of the putative correspondence, an outlier filtering module is designed by consisting of point context normalization block, differentiable pooling and differentiable unpooling layer. Moreover, in order to enhance robustness, a weighting point cloud registration model is formulated to alleviate outliers, by considering the contribution of each correspondence. Experiments on multiple datasets demonstrate that the proposed approach is competitive to several state-of-the-art algorithms. Code is publicly available at <uri>https://github.com/zhlSunLab/DLF</uri>.

High‐Performance Filterless Blue Narrowband Organic Photodetectors

AbstractModern image sensors necessitate three color‐selective photodetectors: red, green, and blue (RGB) sensing units. Among those, blue light‐specific photodetectors are comparably much less reported. Here, a fully thermal‐evaporated organic photodetector (OPD) with narrowband blue detection based on exploring the dual role of the hole‐transporting layer is elegantly demonstrated. By incorporating a MoO3‐doped underlayer, the narrowband OPD achieves high external quantum efficiency up to 50% at 0 V with thin‐film devices. By adopting an intrinsic underlayer in planar junction configuration along with efficient hole and electron blocking layers, an ultralow dark current (2.46 × 10−12 A cm−2 at −0.1 V) is achieved. The device has a calculated specific detectivity (D*) reaching a record‐high value of 6.35 × 1014 Jones, outperforming commercial silicon photodetectors, and an ultrahigh linear dynamic range of 205 dB. This work paves the way for high‐sensitivity narrowband organic photodetectors in the visible spectral region.

Electrical characteristics of in situ Mg-doped β-Ga2O3 current-blocking layer for vertical devices

The lack of p-type doping has impeded the development of vertical gallium oxide (Ga2O3) devices. Current blocking layers (CBLs) using implanted deep acceptors have been used to demonstrate vertical devices. This paper presents a pioneering demonstration of in situ Mg-doped β-Ga2O3 CBLs grown using metal–organic chemical vapor deposition. The Mg-doping density during growth was calibrated by quantitative secondary ion mass spectroscopy. Electrical test structures were designed with in situ Mg doped layers with various targeted Mg doping concentrations. The effectiveness of the CBL is characterized by using temperature-dependent current–voltage measurements using n-Mg-doped-n structures, providing crucial insight into the underlying mechanisms. Pulsed measurements show similar blocking characteristics as DC. To further validate the experimental results, a TCAD simulation is performed, and the electrically active effective doping is found to be dependent on the Mg-doping density, offering an alternate perspective on the optimization of CBL performance. Breakdown measurements show a peak 4 MV/cm field strength.

Improvement of critical current properties and irreversibility lines by metal substitution in Ca-free Hg-based double-layered cuprates

Ca-free Hg-based double-layered cuprates with Sr ions separating the two CuO2 planes, Hg(Sr Ba)2SrCu2O y and its metal-substituted analogue of (Hg, M)(Sr Ba)2SrCu2O y (, Re, and Pb), were successfully synthesized under high pressure. These novel materials exhibit bulk superconductivity at a critical temperature above 100 K. The superconducting properties, including critical current density and irreversibility field , were investigated through magnetic hysteresis loop measurements. Our results revealed that the M substitution with and Re improves the J c and B irr properties, which is likely associated with a decrease in the thickness of the blocking layer. Furthermore, a comparison of the irreversibility lines between Ca-free and representative Ca-containing Hg-based compounds highlighted that the replacement of Ca by Sr in the CuO2 planes does not significantly impact the temperature dependence of B irr. Notably, we found that (Hg, Re)Sr2SrCu2O y has an irreversibility line as high as that of the reported triple-layered (Hg, Re)Sr2Ca2Cu3O y cuprate.

Mitigation of Potential‐Induced Degradation in Glass‐Encapsulated Perovskite Solar Cells Using a NiOx Barrier Layer

While the efficiency of perovskite solar cells has been increasing rapidly in recent years, studies on potential‐induced degradation (PID) in these devices have so far been very limited. Herein, the first successful mitigation of PID in glass‐encapsulated perovskite solar cells is reported. A thin NiOx blocking layer between the indium tin oxide and the self‐assembled monolayer is proposed to suppress the PID in these solar cells. Two groups of devices are fabricated, with and without the presence of the NiOx layer. When −1000 V is applied between the short‐circuited solar cell and the front glass pane, the original devices without NiOx only retain about 27% of the initial efficiency, and the modified devices with NiOx retained ≈65% after an extended stress duration of 96 h. The Na+ ions from the glass pane occupy NiOx vacancies under high voltage stress and, as a result, the Nax ion migration toward the perovskite layer is heavily suppressed due to the introduction of NiOx. The modified devices also demonstrate good long‐term stability, retaining more than 80% of initial efficiency after the PID stress test. The results of this work are helpful on the journey toward successful commercialization of perovskite solar cells.

Practical Blind Image Denoising via Swin-Conv-UNet and Data Synthesis

While recent years have witnessed a dramatic upsurge of exploiting deep neural networks toward solving image denoising, existing methods mostly rely on simple noise assumptions, such as additive white Gaussian noise (AWGN), JPEG compression noise and camera sensor noise, and a general-purpose blind denoising method for real images remains unsolved. In this paper, we attempt to solve this problem from the perspective of network architecture design and training data synthesis. Specifically, for the network architecture design, we propose a swin-conv block to incorporate the local modeling ability of residual convolutional layer and non-local modeling ability of swin transformer block, and then plug it as the main building block into the widely-used image-to-image translation UNet architecture. For the training data synthesis, we design a practical noise degradation model which takes into consideration different kinds of noise (including Gaussian, Poisson, speckle, JPEG compression, and processed camera sensor noises) and resizing, and also involves a random shuffle strategy and a double degradation strategy. Extensive experiments on AGWN removal and real image denoising demonstrate that the new network architecture design achieves state-of-the-art performance and the new degradation model can help to significantly improve the practicability. We believe our work can provide useful insights into current denoising research. The source code is available at https://github.com/cszn/SCUNet.

High CO and sulfur tolerant proton exchange membrane fuel cell anodes enabled by “work along both lines” mechanism of 2,6-dihydroxymethyl pyridine molecule blocking layer

Proton exchange membrane fuel cells (PEMFCs) are hindered by their poor tolerance to CO and H2S poisoning. Herein, we report an effective method, via engineering 2,6-dihydroxymethyl pyridine (DhmPy) molecule blocking layers on Pt surface, aiming to save the poisoning issue for PEMFC anode reaction. The PEMFCs assembled by this catalyst produce a power density of 1.18 W cm−2 @ 2.0 A cm−2 and 1.32 W cm−2 @ 2.0 A cm−2, far exceeding commercial Pt/C after H2/10 ppm CO poisoning and H2/5 ppm H2S poisoning tests, respectively. Density functional theory (DFT) indicates that a coronal molecule layer with a steric confinement height (1.82 Å), constructed by DhmPy, emerges more intensive adsorption energy compared to 2,6-pyridinedicarboxamide (DcaPy) and 2,6-diacetylpyridine (DAcPy), thereby more effectively inhibits the adsorption of large-sized CO and H2S on Pt surface without affecting H2 traverse. This “work along both lines” mechanism with the resistance of both CO and H2S provides a new and promising design thought for high CO and sulfur tolerant PEMFC anodes.

Stability of thiol-based self-assembled monolayer functionalized electrodes in EG-OFET-based applications

The surface passivation of thermally deposited Au using n-alkanethiol self-assembled monolayers (SAMs) as insulating monolayers in electrolyte-gated organic-field effect transistor (EG-OFET) and its impact on EG-OFET operation has been clarified. We used three different n-alkanethiols derivates, namely propanethiol (P-SAM), hexanethiol (H-SAM), and octanethiol (O-SAM), with different chain lengths (C3, C6, and C8). The non-uniform distribution of the used SAMs on the inhomogeneous Au surface significantly affects the net capacitance, i.e., the serial capacitance of the double layer (CDL) and blocking layer (CBL) capacitance of the functionalized gate. The SAM-functionalized gates were exposed to cyclic electrical stress (forward and reverse) for 128 cycles with gate voltage (VG) sweep from 0.1 to −0.4 V at constant drain voltage (VD = -0.4 V) and compared to a bulk-gold reference gate electrode. The registered transfer curves showed increased drain currents that saturated during prolonged cycling. Two figures of merit, i.e., threshold voltage (Vth) and hysteresis, were extracted from the recorded transfer curves, and their responses were studied separately. We found that both Vth and hysteresis increase with cycling. The change is small but constantly increases for the short-chain P-SAM, while for the longer-chain H- and O-SAM, the initial change is more prominent, reaching saturation after approximately 25 cycles. We have investigated the surface roughness of different gate electrodes through Atomic Force Microscopy (AFM) to confirm the packing density of thiol molecules. We also performed 80 h long-term stability data using cyclic voltammetry measurements for each thiol-functionalized electrode. No signs of desorption could be found, as evidenced by XPS. The results are consistent with previously suggested models for electrical transport across such SAMs, confirming that these monolayers restrict faradic processes at the electrodes by passivating the Au surface.