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Impact of Post-Lithography Polymer Residue on the Electrical Characteristics of MoS <sub/>2</sub> and WSe <sub/>2</sub> Field Effect Transistors
摘要： The residue of common photo- and electron-beam resists, such as poly(methyl methacrylate) (PMMA), is often present on the surface of 2D crystals after device fabrication. The residue degrades device properties by decreasing carrier mobility and creating unwanted doping. Here, MoS2 and WSe2 field effect transistors (FETs) with residue are cleaned by contact mode atomic force microscopy (AFM) and the impact of the residue on: 1) the intrinsic electrical properties, and 2) the effectiveness of electric double layer (EDL) gating are measured. After cleaning, AFM measurements confirm that the surface roughness decreases to its intrinsic state (i.e., ≈0.23 nm for exfoliated MoS2 and WSe2) and Raman spectroscopy shows that the characteristic peak intensities (E2g and A1g) increase. PMMA residue causes p-type doping corresponding to a charge density of ≈7 × 1011 cm?2 on back-gated MoS2 and WSe2 FETs. For FETs gated with polyethylene oxide (PEO)76:CsClO4, removing the residue increases the charge density by 4.5 × 1012 cm?2, and the maximum drain current by 247% (statistically significant, p < 0.05). Removing the residue likely allows the ions to be positioned closer to the channel surface, which is essential for achieving the best possible electrostatic gate control in ion-gated devices.
关键词： MoS2,ionic gating,WSe2,field effect transistor,polymer residue
更新于2025-09-10 09:29:36
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Detection of Alpha-Fetoprotein in Hepatocellular Carcinoma Patient Plasma with Graphene Field-Effect Transistor
摘要： The detection of alpha-fetoprotein (AFP) in plasma is important in the diagnosis of hepatocellular carcinoma (HCC) in humans. We developed a biosensor to detect AFP in HCC patient plasma and in a phosphate buffer saline (PBS) solution using a graphene field-effect transistor (G-FET). The G-FET was functionalized with 1-pyrenebutyric acid N-hydroxysuccinimide ester (PBASE) for immobilization of an anti-AFP antibody. AFP was detected by assessing the shift in the voltage of the Dirac point (?VDirac) after binding of AFP to the anti-AFP-immobilized G-FET channel surface. This anti-AFP-immobilized G-FET biosensor was able to detect AFP at a concentration of 0.1 ng mL?1 in PBS, and the detection sensitivity was 16.91 mV. In HCC patient plasma, the biosensor was able to detect AFP at a concentration of 12.9 ng mL?1, with a detection sensitivity of 5.68 mV. The sensitivity (?VDirac) depended on the concentration of AFP in either PBS or HCC patient plasma. These data suggest that G-FET biosensors could have practical applications in diagnostics.
关键词： alpha-fetoprotein,biosensor,graphene,hepatocellular carcinoma,field-effect transistor
更新于2025-09-10 09:29:36
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Proposal and Demonstration of GaN-Based Normally-Off Vertical Field-Effect Transistor with a Design of Back Current Block Layer
摘要： Vertical field-effect transistor (VFET) structure has the advantage in improving both the breakdown voltage (BV) and on-resistance (RON) of semiconductor power devices when compared with the lateral devices. GaN-based normally-off VFET device is designed and demonstrated in this work and an additional back current block layer (B-CBL) is proposed and employed to further improve the device performances. By introducing the B-CBL design, the electric field distribution along the gate aperture is more uniform which leads to an obvious increase (~30%) of BV in the proposed device while the RON is kept nearly constant. Therefore, the figure of merit (FOM) value of the proposed VFET is improved apparently in comparison with that of the conventional GaN-based VFET devices.
关键词： back current block layer (B-CBL),normally-off devices,Vertical field-effect transistor (VFET)
更新于2025-09-10 09:29:36
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Double carrier transport in electron-doped region in black phosphorus FET
摘要： Double carrier transport has been observed in thin film black phosphorus (BP) field effect transistor devices in the highly electron-doped region. BP thin films with a typical thickness of 15 nm were encapsulated by hexagonal boron nitride thin films to avoid degradation by air exposure. Their Hall mobility reached 5300 cm2/V s and 5400 cm2/V s at 4.2 K in the hole- and electron-doped regions, respectively. The gate voltage dependence of conductivity exhibits an anomalous shoulder structure in the electron-doped region. In addition, at gate voltages above the shoulder, the magnetoresistance changes to positive, and there appears an additional slow Shubnikov-de Haas oscillation. These results strongly suggest the appearance of second carriers, which originate from the second subband with a localized band edge.
关键词： black phosphorus,Shubnikov-de Haas oscillation,double carrier transport,electron-doped region,field effect transistor
更新于2025-09-10 09:29:36
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Improved pH Sensitivity and Reliability for Extended Gate Field-Effect Transistor Sensors Using High- <i>k</i> Sensing Membranes
摘要： In this study, we fabricated extended-gate (EG) ?eld-effect transistor (FET) pH sensors with dual-gate (DG) structures, using a range of dielectric sensing membranes (SiO2, Si3N4, HfO2 and Ta2O5) to vary their sensitivity. The fabricated EGFETs consisted of a silicon-on-insulator (SOI)-based metal-oxide semiconductor ?eld-effect transistor (MOSFET) transducer and an EG sensor. We ampli?ed the sensitivity of the device far beyond the Nernst limit (59 mV/pH), which is the theoretical maximum of conventional ion-selective FET (ISFET) sensing, by applying capacitive coupling. Among the evaluated dielectric sensing membranes, we obtained the highest sensitivity (478 mV/pH), low hysteresis (100.2 mV) and drift rate (24.6 mV/h) from the pH sensor with a Ta2O5 membrane. Hence, we expect DG FET con?gurations using Ta2O5 ?lms as EG sensing membranes to be useful for high performance biosensor applications, as they satisfy the requirements for sensitivity, stability and reliability.
关键词： Ion-Sensitive Field-Effect Transistor,Sensitivity,High-k Sensing Membrane,Dual-Gate Field-Effect Transistor,pH Sensor,Capacitive Coupling
更新于2025-09-09 09:28:46
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Influence of charge accumulation at the grain boundary on the electrical behavior of a ferroelectric field-effect transistor
摘要： A phase field method was used to investigate the influence of charge accumulation at the grain boundary on the electrical behavior of a ferroelectric field-effect transistor containing a polycrystalline gate. Both the domain structure and the electrical behavior of the ferroelectric field-effect transistor were found to depend on the coefficient χ, which represents the charge accumulation at the grain boundary. With increasing χ, both the width of the memory window of the capacitance–voltage curves and the on-state source–drain current decreased, while the off-state source–drain current increased. This can be explained in terms of the weakening polarization effect in the grain interior owing to the presence of a built-in electric field caused by the accumulated charge at the grain boundary.
关键词： electrical behavior,charge accumulation,phase field method,grain boundary,ferroelectric field-effect transistor
更新于2025-09-09 09:28:46
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Scanning probe microscopy and potentiometry using a junction field effect transistor based sensor
摘要： Scanning tunneling microscopy in its conventional form relies on a steady state tunneling current of 10?12–10?6 A. However, for various applications, it is desirable to reduce the current load to a minimum. Here, we present first experiments using a cooled junction field effect transistor in open gate operation, thereby reducing the DC-current to less than 10?19 A. This enables almost ideal measurements of the local electrochemical potential on a surface. Various methods applying dynamic modes can be used to maintain a constant distance between the scanning probe and the sample surface. Here, we use an AC-bias applied to the sample and a lock-in amplifier connected to the preamplifier to evaluate the conductance of the tunneling gap.
关键词： potentiometry,scanning probe microscopy,junction field effect transistor,sensor
更新于2025-09-09 09:28:46
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[Nanostructure Science and Technology] Nanowire Electronics || Properties Engineering of III–V Nanowires for Electronic Application
摘要： Semiconductors have been the core materials of many technological advances in recent years. Silicon, the most studied and used semiconducting material, has been the center of semiconductor industry for decades because it is available abundantly and easy to dope, and silicon dioxide is a superior dielectric material in microelectronic industry. This material can be used to make computer chips, optoelectronics devices, and solar cell. Silicon reshapes the way we live and is unarguably one of the most important materials in modern society. Through its dominant role in the semiconductor industry for now, the search for alternatives is fueled by the unstoppable demand for high-performance and low-power electronics. Among different kinds of semiconductors, III–V semiconductor holds promising properties for replacing silicon, and in particular, the NW structure of III–V semiconductor has been studied extensively.
关键词： nanowire field-effect transistor,semiconductors,contact engineering,crystal engineering,III–V nanowires,surface modification,electronic application
更新于2025-09-09 09:28:46
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Preparation and application of polystyrene-grafted alumina core-shell nanoparticles for dielectric surface passivation in solution-processed polymer thin film transistors
摘要： Polystyrene-grafted alumina nanoparticles were synthesized by silane coupling between dimethylchlorosilane-terminated polystyrene (PS) and gamma-type alumina nanoparticles and characterized. The surface grafting density of the polystyrene chains on the nanoparticles was estimated to be 0.13 molecules per square nanometer. The Al2O3-PS nanoparticles are solution processable in organic solvents, including ethyl acetate, butyl acetate, and toluene, which enabled preparation of blends with polystyrene or poly(methyl methacrylate). The dielectric constant of the Al2O3-PS nanoparticle/polymer blend films is composition tunable from 2.59 to 7.79. The alumina-PS nanoparticles and their blends with polymers were found to form efficient surface passivation films on the oxide dielectric layer in organic field-effect transistors (OFETs).
关键词： core-shell nanoparticle,alumina-polymer gate insulator,organic field-effect transistor,surface modification
更新于2025-09-09 09:28:46
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Catalyst-free synthesis of few-layer graphene films on silicon dioxide/Si substrates using ethylene glycol by chemical vapor deposition
摘要： Catalyst-free growth of graphene directly on dielectric substrates is a challenging work for graphene-based electronics. In this paper, a simple method to synthesize large area few layer graphene films on silicon dioxide/Si substrates by chemical vapor deposition is reported. A novel liquid carbon source (ethylene glycol) is used, without any catalysts. The obtained graphene films are characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy. The field effect transistor with graphene film as channel material is fabricated, and the carrier mobility is 707 cm2/V.S. This work offers a new strategy to directly grow graphene on silicon dioxide/Si substrates, and the as-synthesized graphene films may have potential applications in sensors, conductive films, electronic devices, etc.
关键词： Field effect transistor,Synthesis,Catalyst-free,Graphene,Ethylene glycol
更新于2025-09-09 09:28:46