Conducting polymer hydrogels represent a unique class of materials that synergizes the advantageous features of hydrogels and organic conductors and have been used in many applications such as ...bioelectronics and energy storage devices. They are often synthesized by polymerizing conductive polymer monomer within a nonconducting hydrogel matrix, resulting in deterioration of their electrical properties. Here, we report a scalable and versatile synthesis of multifunctional polyaniline (PAni) hydrogel with excellent electronic conductivity and electrochemical properties. With high surface area and three-dimensional porous nanostructures, the PAni hydrogels demonstrated potential as high-performance supercapacitor electrodes with high specific capacitance (∼480 F·g ⁻¹), unprecedented rate capability, and cycling stability (∼83% capacitance retention after 10,000 cycles). The PAni hydrogels can also function as the active component of glucose oxidase sensors with fast response time (∼0.3 s) and superior sensitivity (∼16.7 μA·mM ⁻¹). The scalable synthesis and excellent electrode performance of the PAni hydrogel make it an attractive candidate for bioelectronics and future-generation energy storage electrodes.
ZnO-nanorods/graphene heterostructure was synthesized by hydrothermal growth of ZnO nanorods on chemically reduced graphene (CRG) film. The hybrid structure was demonstrated as a biosensor, where ...direct electron transfer between glucose oxidase (GOD) and electrode was observed. The charge transfer was attributed to the ZnO nanorod wiring between the redox center of GOD and electrode, and the ZnO/graphene heterostructure facilitated the transport of electrons on the hybride electrode. The glucose sensor based on the GOD-ZnO/CRG/Pt electrode had a high sensitivity of 17.64 μA mM(-1), which is higher than most of the previously reported values for direct electron transfer based glucose biosensors. Moreover, this biosensor is linearly proportional to the concentration of glucose in the range of 0.2-1.6 mM. The study revealed that the band structure of electrode could affect the detection of direct electron transfer of GOD, which would be helpful for the design of the biosensor electrodes in the future.
In this letter, high-performance Al2O3/Formula Omitted-Ga2O3 (001) metal-insulator-semiconductor (MIS) capacitor has been demonstrated. The capacitance-voltage (C–V) curves of the Al2O3/Formula ...Omitted-Ga2O3 (001) MIS capacitor remain stable under different measurement frequencies. The leakage current density is lower than Formula Omitted A/cm2 when the gate voltage is in the range of −5~13 V. The fixed charge and trapped charge densities in Al2O3 film are Formula Omitted and Formula Omitted cm−2, respectively. Average and minimum interface trapped charge density (Formula Omitted) for Al2O3/Formula Omitted-Ga2O3 (001) interface has been extracted to be as low as Formula Omitted and Formula Omitted cm−2 eV−1 via the Terman method, respectively. The low Formula Omitted is probably attributed to the modification of vacancy defects and the introduction of hydroxyl groups at the Al2O3/Formula Omitted-Ga2O3 (001) interface after piranha solution pretreatment for Formula Omitted-Ga2O3.
Glucose enzyme biosensors have been shown useful for a range of applications from medical diagnosis, bioprocess monitoring, to beverage industry and environmental monitoring. We present here a highly ...sensitive glucose enzyme sensor based on Pt nanoparticles (PtNPs)-polyaniline (PAni) hydrogel heterostructures. High-density PtNPs were homogeneously loaded onto the three-dimensional (3D) nanostructured matrix of the PAni hydrogel. The PtNP/PAni hydrogel heterostructure-based glucose sensor synergizes the advantages of both the conducting hydrogel and the nanoparticle catalyst. The porous structure of the PAni hydrogel favored the high density immobilization of the enzyme and the penetration of water-soluble molecules, which helped efficiently catalyze the oxidation of glucose. In addition, the PtNPs catalyzed the decomposition of hydrogen peroxide that was generated during the enzymatic reaction. The transferred charges from these electrochemical processes were efficiently collected by the highly conducting PtNP/PAni hydrogel heterostructures. The glucose enzyme sensor based on this heterostructure exhibited unprecedented sensitivity, as high as 96.1 μA·mM–1·cm–2, with a response time as fast as 3 s, a linear range of 0.01 to 8 mM, and a low detection limit of 0.7 μM.
Alloy scattering in a sSi/Si 0.5 Ge 0.5 /strained Silicon on Insulator (SOI) (sSOI) quantum-well (QW) p-MOSFET is investigated by hole density modulation through applying back-gate biases. The hole ...mobility under negative back-gate biases is found degraded by intensified alloy scattering at low electrical field because more holes are distributed in the bulk Si 0.5 Ge 0.5 . At higher electrical field, the higher density of holes populated at the Si/ Si 0.5 Ge 0.5 interface and less holes in the bulk Si 0.5 Ge 0.5 result in less pronounced alloy scattering, leading to mobility enhancement under negative back-gate biases. This confirms experimentally that alloy scattering does not play a significant role in the hole mobility of sSi/ Si 0.5 Ge 0.5 /sSOI QW p-MOSFETs under normal operating mode.
High-performance β-Ga2O3-based Schottky barrier diodes (SBDs) and metal-semiconductor field-effect transistors (MESFETs) are fabricated on a non-delta-doped high doping level (>1018 cm−3) epitaxial ...wafer. Their electrical properties and stabilities after annealing at 200–400 °C are investigated. The ON/OFF ratios for all the SBDs are over 108. The ideality factors and Schottky barrier heights for the Au/β-Ga2O3 SBDs with different annealing temperatures range from 1.5 to 2.5 and from 0.8 eV to 1.0 eV, respectively. There are obvious pinch-off and saturation characteristics for the β-Ga2O3 MESFETs. The maximum drain current (ID,max) for the as-fabricated β-Ga2O3 MESFET is 46.8 mA/mm at anode voltage of 2.0 V. They are much higher than the previously reported values of non-delta-doped and nanobelt β-Ga2O3 MESFETs. Threshold voltages for the β-Ga2O3 MESFETs shift to the negative direction with the increase of annealing temperature. This study is meaningful to push forward the development of β-Ga2O3-based electronic devices for practical applications.
•High-performance β-Ga2O3-based Schottky diodes and metal-semiconductor field-effect transistors (MESFETs) are fabricated on a non-delta-doped high doping level (>1018 cm−3) epitaxial wafer.•Maximum drain current (ID,max) for the as-fabricated β-Ga2O3 MESFET is 46.8 mA/mm at gate voltage of 2.0 V. They are much higher than the previously reported values of non-delta-doped and nanobelt β-Ga2O3 MESFETs.
A novel thermal oxidation method for growing a thin SiO2 layer is proposed for improving the Al2O3/4H-SiC-based MOS structure characteristics. The method combines low oxygen partial pressure and high ...temperature oxidation during the SiO2 layer growth process. Compared with the conventional thermal oxidation method, the experimental results show that the proposed method can effectively reduce the density of trapped charges in the oxide and at the gate dielectric/4H-SiC epilayer interface, and improve the breakdown characteristic of the MOS structure. The interface trap density (Dit) at energy level of 0.2 eV below the conduction band edge (EC) of 4H-SiC in the sample by our proposed method is reduced to 6.6 × 1012 cm−2 eV−1, which is about 4 times lower than the as deposited Al2O3/4H-SiC sample. The core reason underlying the improvement is the reduced SiO2 layer thickness and lower SiCxOy component concentration, as shown by X-ray photoelectron spectroscopy measurements.
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•Low oxygen partial pressure oxidation method can grow high-quality thin SiO2.•Reduced fixed oxide charge leads to lower flat-band voltage shift of MOS.•Reduced oxide trapped charge leads to smaller CV hysteresis of MOS.•The proposed oxidation method can improve the breakdown characteristic of MOS.
An Al 2 O 3 thin film is assembled on an unin- tentionally doped ZnO for metal-insulator-semiconductor (MIS) capacitors. Leakage current density (<inline-formula> <tex-math notation="LaTeX">{J} ...</tex-math></inline-formula>), capacitance-voltage (<inline-formula> <tex-math notation="LaTeX">{C} - {V} </tex-math></inline-formula>) properties, and their thermal stabilities are investigated. The <inline-formula> <tex-math notation="LaTeX">{J} </tex-math></inline-formula>-values for the MIS capacitors before and after annealing at 300 °C are lower than <inline-formula> <tex-math notation="LaTeX">2.0 \times 10^{-7} </tex-math></inline-formula> A/cm 2 at a gate voltage of −10.0~10.0V. Frequency-dependent <inline-formula> <tex-math notation="LaTeX">{C}-{V} </tex-math></inline-formula> characteristic shows a stable maximum capacitance for the MIS capacitor before annealing. However, it decreases dramatically at 1 MHz for that after annealing at 300 C, which is attributed to the change of ZnO channel resistance. Flat band voltage shifts in the-curves after annealing at 300 C are one order lower than those before annealing, indicating the decrease of positive fixed charge density in the Al 2 O 3 film. There are ledge phenomena for hysteresis characteristics in the curves, which result possibly from the delayed evacuation of minority carriers in deep depletion region. By considering the Fowler-Nordheim tunneling model, band configurations of the Al 2 O 3 /ZnO heterojunctions are clarified to be straddling gap structures with conduction band offsets larger than 1.3 eV.
Conductance method and capacitance-voltage (C-V) measurements are used to detect and analyze the characteristics of traps in thermally oxidized and NO-annealed SiO2/4 H-SiC-based ...metal-oxide-semiconductor (MOS) structures, which have energy levels near the conduction band edge (EC) of 4 H-SiC. The near-interface traps (NITs) located within SiO2 near the SiO2/4 H-SiC interface, which have a strong effect on the mobility and reliability of the MOS devices, are separated from the interface traps. According to the bias state of the MOS capacitors, two types of electron exchange mechanisms between the energy level of NITs and EC of 4 H-SiC are proposed. The influence of NITs on the (C-V) and conductance characteristics of the MOS capacitors is studied. The possible effect of NITs on the performance of electronic devices containing a MOS capacitor is predicted.
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