High Field Effect Research Articles

Optimisation of trench filling in GaN towards vertical HEMT structures

In this work we present studies how to fill epitaxially trenches in a GaN layer in order to form a current aperture for use in 3D high power field effect transistors. By optimising various growth parameters in our metal organic vapour phase epitaxy, we achieved an almost complete and smooth filling of 5 μm wide and 500 nm deep trenches etched into a GaN:Mg layer by reactive-ion etching. By using GaN:Si marker layers, the filling process could be excellently monitored. Eventually, a high electron mobility transistor structure was deposited on top of the optimized structures enabling an electrical assessment of this process.

High Magnetic Field Effects on Cu-precipitation Behavior of Fe-1mass%Cu at 773 K

High Magnetic Field Effects on Cu-precipitation Behavior of Fe-1mass%Cu at 773 K

Features of the electronic transport of topological semimetal PtSn4 and WTe2 single crystals

PtSn4 and WTe2 single crystals were grown, and the resistivity was studied in the temperature range from 4.2 to 80 K in various magnetic fields up to 10 T in detail. It is suggested that the observed quadratic temperature dependence of the electrical resistivity at low temperatures in zero field can be due to, in addition to electron-electron scattering, the “electron-phonon-surface” interference scattering mechanism. The transition from high effective magnetic fields to weak ones, which is observed in compensated conductors with a closed Fermi surface, was proposed as a possible explanation for the minimum on the temperature dependence of the resistivity of PtSn4 and WTe2 in a magnetic field. The values of the mean free path of current carriers were estimated in these materials.

Carrot (Daucus carota L.) Seed Germination Was Promoted by Hydro-Electro Hybrid Priming Through Regulating the Accumulation of Proteins Involved in Carbohydrate and Protein Metabolism.

Asynchronized and non-uniform seed germination is causing obstacles to the large-scale cultivation of carrot (Daucus carota L.). In the present study, the combination of high voltage electrostatic field treatment (EF) with hydropriming (HYD), namely hydro-electro hybrid priming (HEHP), significantly improved all germination indicators of carrot seeds, and the promoting effect was superior to that of the HYD treatment. A tandem mass tags (TMT)-based proteomic analysis identified 4,936 proteins from the seeds, and the maximum number of differentially abundant proteins (DAPs) appeared between CK and HEHP. KEGG analysis revealed that the upregulated DAPs were mainly enriched in the pathways related to protein synthesis and degradation such as “ribosome” and “proteasome,” while the downregulated DAPs were mainly enriched in photosynthesis-related pathways. Furthermore, the maximum DAPs were annotated in carbohydrate metabolism. Some proteins identified as key enzymes of the glyoxylate cycle, the tricarboxylate cycle, glycolysis and the pentose phosphate pathway showed enhanced abundance in priming treatments. The activities of several key enzymes involved in carbohydrate metabolism were also enhanced by the priming treatments, especially the HEHP treatment. Real-time quantitative PCR (qRT-PCR) analysis revealed that the effect of priming is mainly reflected before sowing. In conclusion, the optimal effect of HEHP is to regulate the synthesis and degradation of proteins in seeds to meet the requirements of germination and initiate the utilization of seed storage reserves and respiratory metabolism. The present work expanded the understanding of the response mechanism of carrot seed germination to priming and the biological effects of high voltage electrostatic field.

High performance and illumination stable In2O3 nanofibers-based field effect transistors by doping praseodymium

Although different kinds of one dimensional (1D) metal oxide nanofibers (MO-NFs) based field effect transistors (FETs) have been developed in recent years, their intrinsic deficiency in illumination instability are not addressed yet, which further prevented their application in practical life. In this work, due to the outstanding performance of suppressing oxygen vacancies and the blue light down-conversion with low charge transfer transition energy, praseodymium (Pr) is demonstrated an ideal candidate to dope into In2O3 NFs for both transferring the depletion mode to the enhancement mode and enhancing the illumination stability of the FETs. The optima In2O3 NFs-based FET was achieved by doping with 3 mol% Pr and exhibited an excellent electrical performance with a carrier mobility of 6.92 cm2V−1s−1, an on/off current ratio of ∼5.4 × 107, threshold voltage of 5.2 V, and subthreshold swing of 0.37 V/dec. Moreover, the FETs exhibited good illumination stability under 3600 s negative gate bias stress test with illumination (NBIS). Finally, the FET was also used as a switch to bright the LED in this work, demonstrating its great promise of Pr-doped In2O3 NFs in future one-dimensional electronic devices.

The proton flux influence on electrical characteristics of a dual-channel hemt based on GaAs

The results of the simulation the influence of the proton flux on the electrical characteristics of the device structure of dual-channel high electron mobility field effect transistor based on GaAs are presented. The dependences of the drain current ID and cut-off voltage on the fluence value and proton energy, as well as on the ambient temperature are shown.

High Performance P-Type Perovskite Lagao3 Thin Film Field Effect Transistor Prepared by Solution-Processed

Metal oxide semiconductor (MOS) is essential to compose high-performance electronic devices, however, the investigation on p-type MOS is relatively rare compared with its n-type counterpart. In this work, LaGaO3 thin films with superior p-type conductivity have been prepared via a facile solution process. Moreover, we have implemented Al2O3 and SiO2 as the dielectric of the p-channel LaGaO3 thin film transistors (TFTs) annealed at different temperatures. Particularly, the LaGaO3/Al2O3 TFTs annealed at 700 °C exhibit an ultrahigh hole mobility of 12.4 cm2V-1s-1, Under the same conditions, LaGaO3/Al2O3 thin film transistor is two orders of magnitude higher than LaGaO3/SiO2 thin film transistor. The advanced p-type characteristics of the LaGaO3 thin film, along with its facile low-cost fabrication process can shed new light on future design of high-performance complementary MOS circuit with other optimized facile-integrated dielectrics.

Mechanism of High Magnetic Field Effect on the D03-L12 Phase Transition in Fe-Ga Alloys

Mechanism of High Magnetic Field Effect on the D03-L12 Phase Transition in Fe-Ga Alloys

Investigations of microscopic mechanisms in exciplex-based devices with isomers of mCBP and CBP as donors via magneto-electroluminescence

The mCBP and CBP are two kinds of isomers containing carbazole groups and often used as the device hosts for fluorescence and phosphorescence emission. However, there are little studies on the microscopic mechanisms of exciplex-type devices based on mCBP or CBP. In this paper, the isomers of mCBP and CBP are used as donors and the PO-T2T is selected as an acceptor. The two kinds of exciplex-based devices are fabricated according to a mass ratio of 1∶1, which are respectively referred to as device 1 (Dev. 1) and device 2 (Dev. 2). Their magneto-electroluminescence (MEL) curves are measured at different working temperatures and various injection currents. It is found that the low field effects of the MEL curves from Dev. 1 are dominated by the <i>B</i>-mediated reverse intersystem crossing (RISC) process at room temperature, and as the operational temperature decreases, the MEL line-shapes change gradually from RISC to the intersystem crossing (ISC) process. Conversely, the low field effects of the MEL curves of Dev. 2 are governed by the <i>B</i>-mediated ISC process at room temperature, and the ISC process first weakens then strengthens with temperature decreasing. The high field effects of the MEL curves of Dev. 1 and Dev. 2 are both dominated by the <i>B</i>-mediated triplet-charge annihilation (TQA) process at room temperature, but those of Dev. 2 at 20 K present the <i>B</i>-mediated triplet-triplet annihilation (TTA) process. The completely opposite low-field line-shapes of MEL traces from Dev. 1 and Dev. 2 can be attributed to their different structures of mCBP and CBP, which lead to the higher and lower triplet state exciton energy, respectively. The higher triplet exciton energy of the mCBP donor causes the triplet exciplex energy to be confined effectively, which promotes the RISC process (EX<sub>1</sub> ← EX<sub>3</sub>) in Dev.1. Contrarily, the lower triplet exciton energy of the CBP donor causes the triplet exciplex to experience an energy loss process (EX<sub>3</sub> → T<sub>1</sub>, CBP) , resulting in the suppressed RISC process in Dev. 2. Consequently, the overlapped effects of the ISC process of polaron pairs and the RISC process of exciplex in Dev. 2 under the action of external magnetic field display the ISC-determined process at room temperature. Moreover, the temperature-dependent change in the microscopic process of Dev. 1 such as the conversion from RISC to ISC is because decreasing temperature is not conducive to the occurrence of the RISC process of exciplex states due to its endothermic property. The low-temperature TTA process occurring in Dev. 2 is due to the suppressed energy loss process of triplet exciplex via the Dexter energy transfer from the triplet exciplex to the triplet exciton of CBP donor. In addition, when the mass ratio of mCBP donor to PO-T2T acceptor varies from 1∶4 to 1∶1 to 4∶1, the RISC process of MEL curves of devices turns stronger and stronger, which is because the devices tend more to balance, favoring the RISC process. A higher external quantum efficiency is obtained in the mCBP:PO-T2T host than in the CBP:PO-T2T host when fluorescent guest material of TBRb is used as a dopant in these two exciplex-based devices, which verifies the importance of the effective confinement of triplet exciplex energy in improving the luminescence efficiency. Note that via the MEL detection technology, the current- and temperature-dependent microscopic processes and their reasonable interpretations and device performances from exciplex-based devices with the isomers of mCBP and CBP as donors have not been reported in the literature. This work provides experimental and theoretical references for fabricating the high-efficiency exciplex-based organic light-emitting devices.

Self-assembled dipoles of o-carborane on gate oxide tuning charge carriers in organic field effect transistors

A novel self-assembled monolayer of o-carborane on gate oxide not only realized p-channel organic field effect transistors with low threshold voltage and high field effect mobility, but also enabled ambipolar charge transport in a typical n-type organic semiconductor.

Orientation in Polymer Thin Film Towards High Field-Effect Mobility and High-Sensitivity Phototransistor

Orientation in Polymer Thin Film Towards High Field-Effect Mobility and High-Sensitivity Phototransistor

Effects of High Magnetic Fields on the Diffusion of Biologically Active Molecules

The diffusion of biologically active molecules is a ubiquitous process, controlling many mechanisms and the characteristic time scales for pivotal processes in living cells. Here, we show how a high static magnetic field (MF) affects the diffusion of paramagnetic and diamagnetic species including oxygen, hemoglobin, and drugs. We derive and solve the equation describing diffusion of such biologically active molecules in the presence of an MF as well as reveal the underlying mechanism of the MF’s effect on diffusion. We found that a high MF accelerates diffusion of diamagnetic species while slowing the diffusion of paramagnetic molecules in cell cytoplasm. When applied to oxygen and hemoglobin diffusion in red blood cells, our results suggest that an MF may significantly alter the gas exchange in an erythrocyte and cause swelling. Our prediction that the diffusion rate and characteristic time can be controlled by an MF opens new avenues for experimental studies foreseeing numerous biomedical applications.

Effect of High Static Magnetic Fields on Biological Activities and Iron Metabolism in MLO-Y4 Osteocyte-like Cells.

There are numerous studies that investigate the effects of static magnetic fields (SMFs) on osteoblasts and osteoclasts. However, although osteocytes are the most abundant cell type in bone tissue, there are few studies on the biological effects of osteocytes under magnetic fields. Iron is a necessary microelement that is involved in numerous life activities in cells. Studies have shown that high static magnetic fields (HiSMF) can regulate cellular iron metabolism. To illustrate the effect of HiSMF on activities of osteocytes, and whether iron is involved in this process, HiSMF of 16 tesla (T) was used, and the changes in cellular morphology, cytoskeleton, function-related protein expression, secretion of various cytokines, and iron metabolism in osteocytes under HiSMF were studied. In addition, the biological effects of HiSMF combined with iron preparation and iron chelator on osteocytes were also investigated. The results showed that HiSMF promoted cellular viability, decreased apoptosis, increased the fractal dimension of the cytoskeleton, altered the secretion of cytokines, and increased iron levels in osteocytes. Moreover, it was found that the biological effects of osteocytes under HiSMF are attenuated or enhanced by treatment with a certain concentration of iron. These data suggest that HiSMF-regulated cellular iron metabolism may be involved in altering the biological effects of osteocytes under HiSMF exposure.

Staphylococcus aureus biofilm inhibition by high voltage prick electrostatic field (HVPEF) and the mechanism investigation

The study was to investigate the inhibitory effect and mechanism of high voltage prick electrostatic field (HVPEF) on Staphylococcus aureus biofilms. Results showed that HVPEF effectively inactivated 24-h and 48-h established S. aureus biofilms, and the effect was verified on different food-contact materials. Confocal laser scanning microscopy and scanning electron microscopy analysis suggested that HVPEF disintegrated the established biofilms by killing the embedded bacteria, but it hardly reduced the bacteria adhesion. HVPEF also effectively inhibit the formation of S. aureus biofilms, the effects varied with electric voltage, treatment time and biofilm culture conditions. The direct effect of HVPEF on planktonic S. aureus was a possible mode of biofilm formation inhibition. HVPEF also suppressed biofilm formation by reducing the release of key compositions of extracellular polymeric substance, including extracellular DNA (eDNA), protein and polysaccharide intercellular adhesion (PIA), and regulating the expression of biofilm formation related genes (icaA, ebh, cidA, sarA, icaR and sigB). We propose HVPEF as a novel method to inhibit bacteria biofilm, based on the results, HVPEF has positive effects to prevent biofilm-associated contamination of S. aureus.

Asymmetric Hybrid Siloxane Side Chains for Enhanced Mobility and Mechanical Properties of Diketopyrrolopyrrole-Based Polymers.

High performance organic field effect transistor devices based on intrinsically scalable materials are of great significance in wearable electronics. In this work, an exclusive approach is reported to rationale the carrier mobility and stretchability of the conjugate polymers (CPs) by modifying the symmetry of the side chains species. Semiconductor CPs with symmetrical alkyl side chains (P(C-C)), symmetrical siloxane side chains (P(Si-Si)), and asymmetrical silicon-carbon side chains (P(C-Si)) are synthesized to investigate the influence of these side chains on the carrier mobility and mechanical behavior. The result shows that silicon-carbon asymmetric side chains can modulate the aggregation degree of polymer chains with a coherence length of 134 Å and maintain the mobility at 0.90 cm2 V-1 s-1 . P(C-Si) exhibits superior tensile properties that even elongation up to 100% the value of mobility retains a majority properties. The main reason is that the lowest coherence length of P(C-Si) polymer leads to an increased proportion of amorphous zones in its polymer film, which efficiently dissipates mechanical stresses. This study provides an efficient strategy for the design and synthesis of the CPs with high carrier transport properties-mechanical stability.

High Field-Effect Mobility Two-Channel InGaZnO Thin-Film Transistors for Low-Voltage Operation

In this study, two-channel thin-film transistors (TC TFTs) using sputtered-deposited amorphous indium–gallium–zinc oxide (a-IGZO) as a channel layer and atomic-layer-deposition Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> as gate insulator (GI) are proposed for wearable and portable device application. Symmetric-TC (S-TC) TFT structure consisted of conventional bottom gate (BG) TFT stacked on top of top gate (TG) TFT. Asymmetric-TC (A-TC) TFT contained BG TFT with tandem structure on the TG TFT. It was shown that the TC TFTs exhibited excellent performance such as high field-effect mobility ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{\text {FE}}$ </tex-math></inline-formula> ) and ON/ OFF current ratio ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\scriptstyle{\text{ON/OFF}}}$ </tex-math></inline-formula> ) at low voltages (< 2 V). For instance, the S-TC TFTs gave <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{\text {FE}}$ </tex-math></inline-formula> of 19.67 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\scriptstyle{\text{ON/OFF}}}$ </tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5.48\times 10^{{8}}$ </tex-math></inline-formula> . Furthermore, the A-TC TFTs with tandem structure yielded <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{\text {FE}}$ </tex-math></inline-formula> of 30.15 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs, a small threshold voltage of −1.25, a low subthreshold swing of 89 mV/decade, and a high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\scriptstyle{\text{ON/OFF}}}$ </tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.70\times 10^{{9}}$ </tex-math></inline-formula> . It was found that the TC TFTs demonstrated better electrical performance than the sum of individual TG and BG TFTs. Under bias stress tests, the TC TFTs experience less <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {th}}$ </tex-math></inline-formula> shift ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {V}_{\text {th}}$ </tex-math></inline-formula> ) than the TG and BG TFTs.

Effects of high voltage electric field on storage life and antioxidant capacity of whole pomegranate fruit

The objective of this study was to investigate the effects of high voltage electric field (HVEF) on the antioxidant system in stored pomegranate fruit. The experiments were conducted at cold storage for two months under three selected electric field levels (0, 1.5 and 3 kV/cm). Results showed that non-enzymatic antioxidant contents including phenols and ascorbic acid were better preserved by 1.5 kV/cm treatment than control after 60 days of storage. While the activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) in pomegranate fruit were significantly enhanced with 1.5 kV/cm treatment compared to control, Guaiacol peroxidase (G-POX) levels in the control group increased steadily and were highest at the end of the storage. Although the results obtained from 3 kV/cm treatment were acceptable till the end of the first month, due to oxidative damage of reactive oxygen species (ROS) produced in response to HVEF stress, their results come close to the control group at the end of the second month. These data suggest that the optimum electric field intensity for enhancing antioxidant contents in stored pomegranate fruits was 1.5 kV/cm.

Laser-induced graphene electrode based flexible heterojunction photovoltaic cells

Graphene based nanomaterials have attracted significant research interest due to their unique optoelectronic properties which can be tuned to tailor the functionalization in various photovoltaic (PV) applications. These PVs are capable of powering various wearable and flexible electronic devices such as touch-panels, light-emitting diodes (LEDs), sensors, high speed field effect transistors (FETs), etc., which can be a low-cost alternative to traditionally employed silicon solar cells. However, in terms of processing performance and electrical properties, current methods of manufacturing graphene-based PVs have numerous drawbacks. Therefore, there is a need for more effective fabrication methods with commercial feasibility and roll-to-roll processing of graphene-based PVs. This article is the first to present a laser-based patterning technique for fabricating graphene electrodes from polyimide that are compatible with flexible and thermally sensitive substrates for solar cell applications. A heterojunction PV, with ferroelectric Cr-doped BiFeO3 (BFCrO), was deposited on the flexible graphene as the energy harvesting layer sandwiched between p-NiO and n-WS2 window layers. Subsequently, its PV performance was compared with the similar multi-junction PV built on the Indium‑tin Oxide (ITO) one. The LIG electrode outperformed the ITO with its excellent stability, flexibility, and conductivity. The maximum power conversion efficiency (PCE) culminated was 5.20% which is around 5 folds enhancement when compared to the ITO based PV. Furthermore, after bending graphene electrode to 130°, the sheet resistance returned to its original value, while the resistance of ITO increased due to the cracking effect. With these unique properties, LIG electrodes can be promising for the development of flexible ferroelectric BFO based heterojunction PV devices.

USING PERCOLATIVE CRYSTALLINE 0.3 CUO/PVDF NANOCOMPOSITE GATE DIELECTRIC FOR FABRICATING HIGH-EFFECT MOBILITY THIN FILM TRANSISTOR OPERATING AT LOW VOLTAGE

Thin-film transistor (TFT) with various layers of crystalline Poly-vinylidene fluoride (PVDF)/CuO percolative nanocomposites based on Anthracene as a gate dielectric insulator have been fabricated. A device with excellent electrical characteristics at low operating voltages (&lt;1V) has been designed. Different layers (L) of the film were also prepared to achieve the best optimization of ideal gate insulator with various static dielectric constants (εr). Capacitance density, leakage current at 1V gate voltage and electrical characteristics of OFETs with a single and multi layer films have been investigated. This device was showed highest field effect mobility of 2.27 cm2/Vs, a threshold voltage of -1.6V, an exceptionally low sub threshold slope of 380 mV/decade and an on/off ratio of 106. Such a High-ε three layered (3L) PVDF/CuO gate dielectric appears to be highly promising candidates for organic non-volatile memory, sensor and field-effect transistors (FETs).

Effects of High Magnetic Field on Partial Discharge and Flashover Behavior of Epoxy Resin

High-field magnets use epoxy resin as the insulation for superconducting coil terminals. Surface flashover on the interface between the gas and solid insulation will cause insulation failure. In this paper, effects of high magnetic field on surface partial discharge and surface flashover of the epoxy resin are investigated. Experimental results show that high magnetic field causes the decrease of relative permittivity and further changes the electric field distribution along the surface of epoxy resin. Surface partial discharge behavior is directed by both the decrease of surface electric field at the interface and the decrease of breakdown voltage of air gap in high magnetic field. Lorentz force begins to play a role during the extension of electron avalanche by changing the migration of charge carriers and weakening the equivalent effect of the normal electric field near the triple junction. Opposite trends are observed with the increase of magnetic flux density when the direction of Lorentz force is parallel or perpendicular to the surface of epoxy resin.