Electrical Transfer Characteristics Research Articles

Transport Spectroscopy of Donor/Quantum Dot Interactive System in Silicon Nano‐Transistors

AbstractDonor‐atom‐based nano‐devices in silicon represent a breakthrough for individual control of electrons at atomic scale. Here, a finite‐bias characterization of electrical transport through such a device, fabricated on a silicon‐on‐insulator (SOI) wafer with low phosphorus (P) doping, is presented. In this device, multiple quasi‐periodic current peaks are observed at low temperatures in the electrical transfer characteristics. Such behavior of the transport characteristics is generally observed in devices having high doping concentration or with selective doping in the channel region to form a multi‐donor cluster quantum dot. However, in the present device donor–cluster formation is highly improbable owing to low doping concentration. The observed electrical transport characteristics of the device are explained with a model of two non‐interacting donors coupled in series with an unintentionally larger quantum dot, likely formed within the channel due to roughness. Theoretical simulation is also presented here for such a circuit supporting the experimental observations.

Recording Quality Is Systematically Related to Electrode Impedance.

Extracellular recordings with planar microelectrodes are the gold standard technique for recording the fast action potentials of neurons in the intact brain. The introduction of microfabrication techniques has revolutionized the in vivo recording of neuronal activity and introduced high-density, multi-electrode arrays that increase the spatial resolution of recordings and the number of neurons that can be simultaneously recorded. Despite these innovations, there is still debate about the ideal electrical transfer characteristics of extracellular electrodes. This uncertainty is partly due to the lack of systematic studies comparing electrodes with different characteristics, particularly for chronically implanted arrays over extended time periods. Here a high-density, flexible, and thin-film array is fabricated and tested, containing four distinct electrode types differing in surface material and surface topology and, thus, impedance. It is found that recording quality is strongly related to electrode impedance with signal amplitude and unit yield negatively correlated to impedance. Electrode impedances are stable for the duration of the experiment (up to 12 weeks) and recording quality does not deteriorate. The findings support the expectation from the theory that recording quality will increase as impedance decreases.

ELECTRON TRANSPORT IN GRAPHENE BASED NANOTRANSISTOR AND USE OF NEGATIVE CAPACITANCE FOR STEEPER SUB-THRESHOLD SLOPE

Graphene has demonstrated tremendous promise in recent years as a material that, in the future, could replace silicon-based materials because of its exceptional electrical transfer characteristics. The diffusive MOSFETs suffer from short channel effects caused by their shorter channels, however graphene has numerous unusual features. The strongest material yet tested, Graphene exhibits a significant and nonlinear diamagnetism, has great mobility at room temperature, a low atomic thickness, a high current density, and is almost transparent. A single sheet of carbon atoms organized in a hexagonal lattice makes up graphene, an allotrope form of carbon. It is a semimetal with little short channel effects overall and little overlap between the valence and conduction bands. The Graphene nanoribbon has been incorporated into the ballistic nanotransistor as its channel and differentiate it form the diffusive one.In this review , I have presented the report on the survey of Nanotransistor . It has been divided into three sections : (1) Ballistic transport in Nanotransistor (2) Modelling of GNRFET (Graphene Nano-ribbon FET) using NEGF (Non-equilibrium Greens function) (3) Using ferroelectric capacitance into FET to reduce its sub-threshold regime below 60 mV/decade.The purpose of this review is to understand charge carrier transport phenomenon in the Nanotransistor. This includes the description about the ballistic nanotransister and differentiate it form the diffusive one. The NEGF allows us to characterizing its transfer characteristics in the real lattice space.Also the Id-Vd, sub-threshold regime , log(Id)-Vg , transmission coefficient and their application to drastically enhance the device performance for low energy digital electronics are being studied and modeled. Furthermore, the negative capacitance due to FE (ferroelectric layer) in FET will enhance the switching speed of FET and reduce the sub-threshold swing (SS) below 60 mV/decade which is impossible in case of traditional MOSFET. Thus, improving ION/IOFF ratio for low power digital devices.

Charge Transfer Dynamics of Doped Graphene Electrodes for Organic Light-Emitting Diodes.

Atomically thin graphene has attracted immense attention as a future transparent electrode for flat-panel displays owing to its excellent conductivity, optical transparency, and flexibility. In particular, a graphene doping process is essential for implementing graphene-based high-performance devices, and the development of a transparent cathode with a low work function is required to simplify the integration process of thin-film transistors and organic light-emitting diodes (OLEDs) into active matrix displays. In this study, a transparent n-doped graphene cathode is proposed for implementing inverted OLEDs through two types of cesium (Cs)-based doping techniques: a dipping method using wet chemicals and an evaporation method under a vacuum atmosphere. The changes in the chemical structures and work functions of the n-doped graphene electrodes, as well as their surface morphologies and transmittances, were systematically investigated. The n-type doping mechanism of graphene was investigated, and a close relationship between the electrical charge transfer characteristics of graphene transistors and the formation of C-O-Cs complexes was revealed. Finally, an effective Cs-doped graphene electrode was developed, exhibiting a dramatically decreased work function while maintaining high transmittance; therefore, the Cs-doped graphene cathode was successfully integrated with inverted OLEDs with a bottom-light emission structure that exhibited enhanced external quantum efficiency of graphene cathode-based OLEDs. Thus, our findings provide a better understanding of the doping strategies and potential of n-doped graphene as a transparent cathode for developing high-performance future displays.

Hydrogen Atom Doping—A Versatile Method for Modulated Interface Resistive Switching

AbstractInterface kinetics plays a crucial role in modulating the resistive switching mechanism for memristor devices with a Schottky junction. This study introduces H atoms by catalytic doping and examines the interfacial electrical transfer characteristics of the Pd/Nb‐doped SrTiO3 (Nb‐STO). The I–V measurements show that H+ doping at the Pd/Nb‐STO interface reduces the barrier height by 300 mV compared to the sample before H+ doping. This reduction in barrier height is further correlated with the decrease in built‐in potential by 300 mV and depletion layer thickness from C–V measurements. The underlying reason for such a drastic change in resistive switching characteristics is the reduction of interface layer thickness. The work highlights the easy use of Pd metal to introduce H atoms to oxide materials and provides insight into their effects on switching mechanisms.

Charge distribution in turbostratic few-layer graphene studied by carbon isotope labeling

Elucidating layer-resolved charge distribution in van der Waals stacked crystals is crucial for electronic applications based on 2D materials. Here, we use CVD-grown few-layer graphene (FLG) labeled by carbon isotopes as a prototype, in which Raman features of two isotope components identify distinct layers. Electrical transfer characteristics of graphene field-effect transistors (GFETs) are employed to quantitatively calibrate the correspondence of Fermi level and G-phonon frequency that shifts with the charge-carrier concentration (n) variation. The isotope-assisted spectroscopy reveals previously unprobed characteristics that the n value of both top and bottom layers in FLG is close rather than following an exponential decay law. This negligible gradient likely benefits from the π−π interaction that favors the interlayer diffusion of charges. In addition, each extra layer reduces the degree of charge exchange at the graphene/dopant interface. These results have important implications for FLG nanoelectronics and provide a robust framework by which one can further investigate the critical properties of other 2D systems.

Output power boosting of a photovoltaic panel based on various back pipe structures: a computational study

The efficiency of photovoltaic panels (PV) drops due to the rise in temperature, which leads to a decrease in the PV output power. A PV/Thermal system is therefore used as a solution to increase the output power from the PV panels. Comsol Multiphysics software program, a simulator-based Finite Element Method (FEM) tool, and Matlab program simulations are used to perform this electro-thermal model. The simulation process for different back pipes follows a serpentine, and a new shape of pipes called (square shapes) which are attached under the PV module. These shapes were specifically chosen for higher conversion efficiency and increase the heat transfer of the system. Additionally, a comparison between electrical parameters and heat transfer characteristics of water and CuO/water nanofluid in a PV cooling system has been studied. The new shape leads to improve the photovoltaic (PV) module parameters, such as short circuit current ISC, open-circuit voltage VOC, and maximum power Pmax for a new shape more than the serpentine shape. These parameters are calculated under Air Mass 1.5 G (AM1.5G) with 1000 W/m2 of irradiance which is considered the average irradiance at the MENA (The Middle East and North Africa) region throughout the year. The results exhibit the PV module’s total enhancement by using the new shape with CuO nano-fluid about 24.7 %.

Hysteresis Behavior of the Donor-Acceptor-Type Ambipolar Semiconductor for Non-Volatile Memory Applications.

Donor–acceptor-type organic semiconductor molecules are of great interest for potential organic field-effect transistor applications with ambipolar characteristics and non-volatile memory applications. Here, we synthesized an organic semiconductor, PDPPT-TT, and directly utilized it in both field-effect transistor and non-volatile memory applications. As-synthesized PDPPT-TT was simply spin-coated on a substrate for the device fabrications. The PDPPT-TT based field-effect transistor showed ambipolar electrical transfer characteristics. Furthermore, a gold nanoparticle-embedded dielectric layer was used as a charge trapping layer for the non-volatile memory device applications. The non-volatile memory device showed clear memory window formation as applied gate voltage increases, and electrical stability was evaluated by performing retention and cycling tests. In summary, we demonstrate that a donor–acceptor-type organic semiconductor molecule shows great potential for ambipolar field-effect transistors and non-volatile memory device applications as an important class of materials.

Modulating the Electronic, Optical, and Transport Properties of CdTe and ZnTe Nanostructures with Organic Molecules: A Theoretical Investigation.

In this paper, we systematically investigated the electronic, optical, and transport properties of CdTe and ZnTe nanostructures before and after adsorption with benzyl viologen (BV) and tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) organic molecules based on the first principles calculation. First, the band gaps of CdTe and ZnTe nanostructures obviously decrease after BV and F4-TCNQ adsorptions. Interestingly, the electronic property calculation shows that BV and F4-TCNQ can donate/accept electrons to/from the surface of CdTe and ZnTe nanostructures, leading to an effective n-/p-type doping, respectively. Second, the optical absorption in a broad spectral range (from visible to near-infrared) of CdTe and ZnTe is significantly improved by adsorption of BV and F4-TCNQ molecules, offering great opportunities for the use of CdTe and ZnTe nanostructures in renewable energy fields. Lastly, the electrical transfer characteristics on CdTe and ZnTe nanostructure-based field-effect transistors clearly showed that the conduction of the nanostructures can be rationally tuned into n- and p-type conductivity with BV and F4-TCNQ adsorptions, respectively. Our work clearly demonstrates that the electronic, optical, and transport properties of CdTe and ZnTe nanostructures are effectively modulated by adsorption of BV and F4-TCNQ, which can be used to construct high-performance electronic and optoelectronic devices.

Comparison between Horizontal and Vertical OFETs by Using Poly (3-Hexylthiophene) (P3HT) as an Active Semiconductor Layer

In this paper, a comparison between horizontal and vertical OFET of Poly (3-Hexylthiophene) (P3HT) as an active semiconductor layer (p-type) was studied by using two different gate insulators (ZrO2 and PVA). The electrical performance output (Id-Vd) and transfer (Id-Vg) characteristics were investigated using the gradual-channel approximation model. The device shows a typical output curve of a field-effect transistor (FET). The analysis of electrical characterization was performed in order to investigate the source-drain voltage (Vd) dependent current and the effects of gate dielectric on the electrical performance of the OFET. This work also considered the effects of the capacitance semiconductor on the performance OFETs. The values of current, as calculated using MATLAB simulation, exhibited an increase with increasing source-drain voltage. Also, the organic transistor modeling software was used to evaluate the transconductance calculated. The best results for the vertical OFET were achieved using the gate insulators of ZrO2.

Photo-induced and electrical degradation of organic field-effect transistors

The field of organic field-effect transistors (OFETs) has matured over the past two decades and devices with charge carrier mobilities of several cm2/Vs have been demonstrated. Nevertheless, to enter commercial products, the operational stability of OFET technology also needs to be addressed. Herein, two potential degradation mechanisms occurring in N,N′-di-1-naphthalenyl-N,N′-diphenyl [1,1′:4′,1″:4″,1‴-quaterphenyl]-4,4‴-diamine (4P-NPD)-based OFETs are investigated. Electrical transfer characteristics show that photo-induced oxidation of the organic thin-film decreases the hole mobility and increases the threshold voltage. The inverse hole mobility depends approximately linearly on the concentration of photo-induced defect states, which is in agreement with the Multiple Trapping and Release model. This implies that the created defects act as hole traps located energetically above the highest occupied molecular orbital level. In contrast, electrical stress increases the threshold voltage without affecting the hole mobility. This behavior is related to charge trapping, which probably take place in the gate dielectric as indicated by a relatively long trapping time of ~102 s. Time-resolved photoluminescence spectroscopy, which proved to be sensitive to both mobile and trapped charges, shows that the threshold voltage shift is caused exclusively by charge accumulation. The obtained results broaden the fundamental knowledge about the degradation processes occurring in OFETs, which is highly relevant for increasing their stability.

SiAs2/GeP2 heterostructure for solar cell: A first-principles calculation

The two-dimensional (2D) materials offer tremendous opportunities for efficient, ultrathin solar cells beyond conventional three-dimensional materials. In this work, we study the interfacial electrical properties and charge transfer characteristics of the SiAs2/GeP2 heterostructure by first-principles calculations. The SiAs2/GeP2 heterostructure shows a 2.25 eV bandgap and pronounced solar light absorption. Furthermore, the heterostructure presents a type-II alignment, and possesses a desirable power conversion efficiency (PCE) of up to 12.1%. These results reveal that SiAs2/GeP2 is promising for solar energy conversion in photovoltaic applications, and also provide a possible alternative for experiment scheme.

Interfacial charge behavior modulation in 2D/3D perovskite heterostructure for potential high-performance solar cells

2D/3D perovskite heterostructure can combine the advantages of 2D perovskite with well stability and 3D perovskite with high efficiency. 2D BA2PbI4/3D MAPbI3 heterostructures are constructed to study the interfacial electrical properties and charge transfer characteristics by first-principle calculations. 3D MAPbI3 perovskite have two kinds of contacting interface, i.e., PbI interface and I interface. The 2D/3D interface heterostructures are van der Waals contacting, and their light absorption can be enhanced as compared to pure 2D or 3D perovskite, mainly resulting from 3D perovskite part in the heterostructure. In 2D/I interface heterostructure, the band gap is 1.15 eV, and the charge recombination center is at 2D BA2PbI4 interface, which favor to improve the power conversion efficiency (PCE). While in 2D/PbI heterostructure, the band gap is as small as 0.53 eV, and the charge recombination center is at PbI interface, leading to a large number of recombination and low PCE. The work function difference of 2D BA2PbI4 and 3D MAPbI3 perovskite is the nature of energy level shifting and interface charge oriented movement. These results demonstrate that the construction of 2D BA2PbI4 and 3D I interface heterostructure by interfacial engineering is a potential strategy to enhance the performance of the 2D/3D heterostructured PSCs.

Research and development on composite nanofluids as next-generation heat transfer medium

Nanocomposite is a nanotechnology-based multiphase, high-performance composite material having combination of properties, which has been emerged as one of the promising research and development activities. Recently, nanocomposites have shown significant application opportunities for several sectors of biotechnology, engineering, and medical sciences, and its dispersed fluids (composite nanofluids) have gained huge interest and demand in wide area of engineering applications, particularly for heat transfer intensification. The main aim of the present review is to summarize the recent advances in nanocomposite-dispersed nanofluids. The synthesized methods, characterization, and applications of nanocomposites as well as the preparation, stability analysis, thermophysical, optical and electrical properties, heat transfer and pressure drop characteristics and applications of nanocomposite-dispersed nanofluids are well-grouped and discussed. Present review reveals that the nanocomposite with proper combination of nanomaterials yields superior performance characteristics compared to the individual alone for application in nanofluids, although many related aspects are still unexplored. Hence, the challenges and opportunities for future research are also identified, which will be useful for the newcomers and manufacturers in this field.

Organic Electrochemical Transistors Based on Room Temperature Ionic Liquids: Performance and Stability

Organic electrochemical transistors (OECTs) are becoming a key device in the field of organic bioelectronics. For many applications of OECTs, in particular for enzymatic sensing, a complex mixture of room temperature ionic liquids (RTILs) combined with other electrolytes is used as a gate electrolyte, making the interpretation of experimental trends challenging. Here, the switching mechanism of OECTs using such RTILs is studied. It shows that ions smaller in size than the ions contained in the RTIL (e.g., Na+) have to be added to the ionic liquid to ensure switching of the OECTs. Furthermore, it is shown that OECTs based on RTILs exhibit noticeable gate‐bias stress effects and a hysteresis in the electrical transfer characteristics. A model based on incomplete charging/discharging of the effective gate capacitance during operation of the OECT and a dispersion in the ion mobilities is proposed to explain these instabilities, and thus it shows that the hysteresis can be minimized by optimizing the geometry of the device. Overall, a better understanding of the underlying mechanisms of switching and stability of OECTs based on RTILs is the first step toward various applications such as lactate acid sensors and neurotransmitter recording.

Low-voltage organic thin film transistors (OTFTs) using crosslinked polyvinyl alcohol (PVA)/neodymium oxide (Nd2O3) bilayer gate dielectrics

We have reported here on the design, processing and dielectric properties of pentacene-based organic thin film transitors (OTFTs) with a bilayer gate dilectrics of crosslinked PVA/Nd2O3 which enables low-voltage organic thin film operations. The dielectric characteristics of PVA/Nd2O3 bilayer films are studied by capacitance–voltage (C–V) and current–voltage (I–V) curves in the metal–insulator–metal (MIM) structure. We have analysed the output electrical responses and transfer characteristics of the OTFT devices to determine their performance of OTFT parameters. The mobility of 0.94 cm2/Vs, the threshold voltage of − 2.8 V, the current on–off ratio of 6.2 × 105, the subthreshold slope of 0.61 V/decade are evaluated. Low leakage current of the device is observed from current density–electric field (J–E) curve. The structure and the morphology of the device are studied using X-ray diffraction (XRD) and atomic force microscope (AFM), respectively. The study demonstrates an effective way to realize low-voltage, high-performance OTFTs at low cost.

Sol-Gel PMMA-ZrO2 Hybrid Layers as Gate Dielectric for Low-Temperature ZnO-Based Thin-Film Transistors.

We report a simple sol–gel process for the deposition of poly(methyl methacrylate) (PMMA)–ZrO2 organic–inorganic hybrid films at low temperature and studied their properties as a function of the molar ratios of the precursors in the hybrid sol–gel solution, which included zirconium propoxide as the inorganic (zirconia) source, methyl methacrylate as the organic source, and 3-trimethoxy-silyl-propyl-methacrylate (TMSPM) as the coupling agent to enhance the compatibility between the organic and inorganic phases. The hybrid thin-film deposition was done on glass slide substrates by the dip-coating method. After deposition, the films were heat-treated at 100 °C for 24 h. The analysis of the hybrid films included Fourier transform infrared spectroscopy to identify their chemical groups and thermogravimetric analysis to determine the content of their organic and inorganic components. In addition, capacitance–voltage (C–V) and current–voltage (I–V) curves in metal–insulator–metal structures, using gold as metal contacts, were measured to find the dielectric constant and leakage current of the PMMA–ZrO2 hybrid films. Finally, because of their adequate dielectric characteristics, single hybrid layers were deposited on indium tin oxide-coated glass substrates and were tested as gate dielectric in thin-film transistors (TFTs), using sputtered ZnO layers as the semiconductor active channel. We measured the output electrical response and transfer characteristics of these hybrid dielectric gate-based devices and determined their main electrical parameters as a function of the TMSPM content in the hybrid dielectric gate layer. The better TFT electrical behavior presents field effect mobility of 0.48 cm2/V s, low threshold voltage of 3.3 V, and on/off current ratio of 105, and it was obtained by using PMMA–ZrO2 with 0.3 TMSPM content as the gate dielectric layer. The values obtained for the electrical parameters show that PMMA–ZrO2 hybrid films are quite suitable for dielectric gate applications in TFTs

Highly Ordered Gold Nanopatterned Indium Tin Oxide Electrodes for Simultaneous Optical and Electrochemical Probing Cell Interactions.

The formation of new types of sensitive conductive surfaces for the detection and transduction of cell-extracellular matrix recognition events in a real time, label-free manner is of great interest in the field of biomedical research. To study molecularly defined cell functions, biologically inspired materials that mimic the nanoscale order of extracellular matrix protein fibers and yield suitable electrical charge transfer characteristics are highly desired. Our strategy to achieve this goal is based on the spatial self-organization of patches of cell-adhesive molecules onto a gold-nanoparticle-patterned indium tin oxide electrode. Fibroblast adhesion response to selective ligands for integrins α5β1 and αvβ3, which are both relevant in cancer progression, is investigated by simultaneous electrochemical impedance spectroscopy and optical microscopy. Adhesive cells on α5β1-selective nanopatterns showed enhanced membrane dynamics and tighter binding, compared with cells on αvβ3-selective nanopatterns. The surface of the electrode exhibits high sensitivity to small changes in surface properties, because of the constitution of specific cell-surface interactions. Moreover, such sensitivity enables differentiation between cell types. This is exemplified by analyzing distinct features in the electrochemical readout of MCF-7 breast cancer cells versus MCF-10A mammary epithelial cells, when subjected to individual adhesive nanopatches.

수열합성법으로 성장시킨 ZnO 나노 로드기반 TFT 가스 센서 제조 및 특성평가

In this study, we fabricated a TFT gas sensor with ZnO nanorods grown by hydrothermal synthesis. The suggested devices were compared with the conventional ZnO film-type TFTs in terms of the gas-response properties and the electrical transfer characteristics. The ZnO seed layer is formed by atomic-layer deposition (ALD), and the precursors for the nanorods are zinc nitrate hexahydrate (<TEX>$Zn(NO_3)_2{\cdot}6H_2O$</TEX>) and hexamethylenetetramine (<TEX>$(CH_2)6N_4$</TEX>). When 15 ppm of NO gas was supplied in a gas chamber at <TEX>$150^{\circ}C$</TEX> to analyze the sensing capability of the suggested devices, the sensitivity (S) was 4.5, showing that the nanorod-type devices respond sensitively to the external environment. These results can be explained by X-ray photoelectron spectroscopy (XPS) analysis, which showed that the oxygen deficiency of ZnO nanorods is higher than that of ZnO film, and confirms that the ZnO nanorod-type TFTs are advantageous for the fabrication of high-performance gas sensors.

Variable temperature performance of a fully screen printed transistor switch

This article reports on the variable temperature performance of a flexible printed transistor which works as a current driven switch. In this work, electronic ink is formulated from nanostructured silicon produced by milling polycrystalline silicon. The study of the silicon active layer shows that its conductivity is based on thermal activation of carriers, and could be used as active layers in active devices. We further report on the transistors switching operation and their electrical performance under variable temperature. The reliability of the transistors at constant current bias was also investigated. Analysis of the electrical transfer characteristics from 340 to 10K showed that the printed devices’ current ON/OFF ratio increases as temperature decreases making it a better switch at lower temperatures. A constant current bias on a terminal for up to six hours shows extraordinary stability in electrical performance of the device.