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Heat-Assisted Photoacidic Oxidation Method for Tailoring the Surface Chemistry of Polymer Dielectrics for Low-Power Organic Soft Electronics
摘要： The use in low-power soft electronics of the appropriate insulating polymer materials with a high dielectric constant (k) is considered a practical alternative to that of inorganic dielectric materials, which are brittle and have high processing temperatures. However, the polar surfaces of typical high-k polymer insulators are problematic. Further, it is a huge challenge to control their surface properties without damage because of their soft and chemically fragile nature. Here, a heat-assisted photoacidic oxidation method that can be used to effectively oxidize the outermost surfaces of high-k rubbery polymer films without degradation is presented. The oxidized surfaces prepared with the developed method contain large numbers of hydroxyl groups that enable the subsequent growth of dense and ordered self-assembled monolayers (SAMs) consisting of organosilanes. The whole process modifies the surface characteristics of polymer dielectrics effectively. The mechanisms of the oxidation of polymer surfaces and the subsequent SAM growth process are investigated. The resulting surface-tailored rubbery dielectrics exhibit superior electrical characteristics when used in organic transistors. These results demonstrate that this method can be used to realize practical soft organic electronics based on high-k polymer dielectrics.
关键词： self-assembled monolayers,organic semiconductors,polymer gate dielectric,polymer oxidation,surface chemistry
更新于2025-09-23 15:23:52
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Impact of oxide/barrier charge on threshold voltage instabilities in AlGaN/GaN metal-oxide-semiconductor heterostructures
摘要： Threshold voltage instabilities in AlGaN/GaN metal-oxide-semiconductor (MOS) heterostructures were investigated by means of capacitance-voltage (CV) hysteresis measurement and simulations. We focused on the impact of net charge at oxide/semiconductor interface (Qint) on the CV hysteresis. Our simulations suggest that due to different band bending at the interface, any positive or negative Qint with lower density (in the order of 1012 cm?2) results in a presence of relatively shallow unoccupied oxide/barrier interface states in equilibrium. On the other hand, high density of negative Qint (Qint/q ≈ ?1013 cm?2) results in very deep unoccupied interface states, which in turn leads to incomplete electron re-emission during backward CV sweep and thus increased CV hysteresis of the MOS heterostructures compared to previous case. Impact of Qint is illustrated experimentally on MOS heterostructures with Al2O3 gate dielectric grown by metal-organic chemical vapor deposition, showing Qint of ?1.2 × 1013 and +0.5 × 1012 cm?2 for structures with and without post-deposition annealing, respectively. Our results therefore suggest that normally-off AlGaN/GaN MOS heterostructure field-effect transistors featuring high density of negative Qint can be expected to be more susceptible for threshold voltage instabilities compared to normally-on counterparts.
关键词： MOS,Al2O3 gate dielectric,Heterostructure field-effect transistor,Interface traps,AlGaN/GaN
更新于2025-09-23 15:23:52
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Hybrid bilayer gate dielectric-based organic thin film transistors
摘要： Organic thin film transistors (OTFTs) are key building blocks for flexible, low cost electronics systems. They provide a viable alternative for silicon-based electronics with added advantages of low cost and flexibility. However, few issues like high-operating voltage, low-switching speed, high-leakage current and reliability are still a challenge. The overall performance of an OTFT depends on organic semiconductors and gate dielectric interface. In this paper, we review the current status and trends in the choice of dielectric layer for OTFTs. As a starting point, the performance parameters of an OTFT and their dependence on the dielectric layer are briefly discussed. A variety of dielectric materials which includes high-k inorganic, organic, surface coated inorganics and nanocomposites are also presented. The advantages and drawbacks of each of these materials are discussed in detail. We reviewed the latest developments in the dielectric materials especially, self-assembled monolayers (SAMs), hybrid bilayers and nanocomposites. SAM-based OTFTs offer several advantages but shift in the threshold voltage remains a concern. Nanocomposites are a latest addition to the dielectric materials, which offer advantages like solution processing and improved dielectric constant but have a rough surface. A hybrid bilayer that incorporates the inorganic dielectric as a base layer and a thin polymer layer over it to improve the surface properties offers several desirable characteristics over the other choices. Hence, we propose that hybrid bilayer gate dielectrics shall play a pivotal role in improving the OTFT performance.
关键词： low-k organic,high-k inorganic,Organic thin film transistor,self-assembled monolayer,gate dielectric,hybrid bilayer
更新于2025-09-23 15:23:52
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Recent progress on jet printing of oxide-based thin film transistors
摘要： Among the printing technologies for printed electronics, jet printing-based methods provide promising solutions to the fabrication of oxide-based thin film transistors (TFTs) for flexible and non-flexible electronics. Their direct patterning capability, non-vacuum and solution-based material formation process have attracted a significant amount of interests from both the academic and industry sectors. This topical review summarizes recent progress on the development of jet printed metal oxide TFTs with special attention given to the surface related effects, ink preparation and post-printing treatments, which are the critical aspects of obtaining high performance printed TFTs. Firstly, a brief introduction is made on the state of art jet printing technologies: the piezoelectric/thermal inkjet printing, the newly emerged electro-hydrodynamic jet printing and aerosol jet printing. Then, surface related issues of wettability and coffee-ring effect are discussed. At last, jet printing of oxide-based TFTs is reviewed according to the classification of printed material types: metal oxide semiconductors, gate dielectrics and conductive electrodes. The extensive review of low temperature annealing methods made this work particular interesting to the printing of oxide-based TFTs on flexible substrates.
关键词： gate dielectric,jet printing,oxide-based semiconductors,thin film transistors,electrode
更新于2025-09-23 15:22:29
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In Situ SiO <sub/>2</sub> Passivation of Epitaxial (100) and (110)InGaAs by Exploiting TaSiO <sub/><i>x</i> </sub> Atomic Layer Deposition Process
摘要： In this work, an in situ SiO2 passivation technique using atomic layer deposition (ALD) during the growth of gate dielectric TaSiOx on solid-source molecular beam epitaxy grown (100)InxGa1?xAs and (110)InxGa1?xAs on InP substrates is reported. X-ray reciprocal space mapping demonstrated quasi-lattice matched InxGa1?xAs epitaxy on crystallographically oriented InP substrates. Cross-sectional transmission electron microscopy revealed sharp heterointerfaces between ALD TaSiOx and (100) and (110)InxGa1?xAs epilayers, wherein the presence of a consistent growth of an ～0.8 nm intentionally formed SiO2 interfacial passivating layer (IPL) is also observed on each of (100) and (110)InxGa1?xAs. X-ray photoelectron spectroscopy (XPS) revealed the incorporation of SiO2 in the composite TaSiOx, and valence band offset (ΔEV) values for TaSiOx relative to (100) and (110)InxGa1?xAs orientations of 2.52 ± 0.05 and 2.65 ± 0.05 eV, respectively, were extracted. The conduction band offset (ΔEC) was calculated to be 1.3 ± 0.1 eV for (100)InxGa1?xAs and 1.43 ± 0.1 eV for (110)InxGa1?xAs, using TaSiOx band gap values of 4.60 and 4.82 eV, respectively, determined from the fitted O 1s XPS loss spectra, and the literature-reported composition-dependent InxGa1?xAs band gap. The in situ passivation of InxGa1?xAs using SiO2 IPL during ALD of TaSiOx and the relatively large ΔEV and ΔEC values reported in this work are expected to aid in the future development of thermodynamically stable high-κ gate dielectrics on InxGa1?xAs with reduced gate leakage, particularly under low-power device operation.
关键词： in situ SiO2 passivation,atomic layer deposition,InxGa1?xAs,band alignment,TaSiOx,gate dielectric
更新于2025-09-23 15:21:01
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Effect of post deposition annealing on the electrical properties of YSZ thin films deposited by pulsed laser technique
摘要： In this paper we report the detailed analysis of the effect of in-situ annealing on the electrical properties of yttrium stabilized zirconium oxide (YSZ) thin films grown by pulsed laser deposition on silicon substrates. The optimized metal/YSZ/Si devices showed low leakage current, good dielectric strength and a breakdown field strength of 4.13 MV/cm. The magnitudes of flat band voltage, and interfacial charge density have been extracted from the capacitance-voltage (C-V) characteristics of the MOS structure. The C-V characteristics show a small hysteresis which indicates the presence of traps. The observed shift in the flat band voltage and hysteresis are explained with the help of X-ray photoelectron spectroscopy. From the XPS depth profile analysis of the samples it was found that as we go from the surface to the interface, oxygen concentration in the deposited film decreases, i.e. the oxide becomes zirconium rich. This has been correlated with the observed electrical properties.
关键词： Thin films,Interface,Dielectric breakdown,Gate dielectric,Zirconium oxide (ZrO2),Pulsed laser deposition
更新于2025-09-16 10:30:52
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Low-frequency charge noise in Si/SiGe quantum dots
摘要： Electron spins in silicon have long coherence times and are a promising qubit platform. However, electric field noise in semiconductors poses a challenge for most single- and multiqubit operations in quantum-dot spin qubits. We investigate the dependence of low-frequency charge noise spectra on temperature and aluminum-oxide gate dielectric thickness in Si/SiGe quantum dots with overlapping gates. We find that charge noise increases with aluminum-oxide thickness. We also find strong dot-to-dot variations in the temperature dependence of the noise magnitude and spectrum. These findings suggest that each quantum dot experiences noise caused by a distinct ensemble of two-level systems, each of which has a nonuniform distribution of thermal activation energies. Taken together, our results suggest that charge noise in Si/SiGe quantum dots originates at least in part from a nonuniform distribution of two-level systems near the surface of the semiconductor.
关键词： temperature dependence,two-level systems,gate dielectric thickness,Si/SiGe quantum dots,charge noise
更新于2025-09-12 10:27:22
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Uniform Insulating Properties of Low-Temperature Curable Gate Dielectric for Organic Thin-Film Transistor Arrays on Plastic Substrate
摘要： Achieving a high-resolution display on a plastic substrate requires a to ensure dimensional stability during fabrication process, including the deposition of gate dielectrics. Evaluation platform to confirm the uniform insulating properties of organic dielectric material prior to actual application to organic thin-film transistor (OTFT) arrays was proposed. This test method enabled verification of the suitability of the low-temperature curable dielectric and chemical resistance during fabrication process. A cross-linked poly(hydroxy imide) (PHI) that can be cured at a low temperature of 130°C exhibited stable insulating properties in a large area that sudden breakdown was not observed in an electric field up to 4 MV/cm. Thiophene-thiazole-based copolymer semiconductor was used as an active layer and inkjet-printed. In all the processes, the temperature of the substrate was kept below 130°C, and 4.8-inch electrophoretic display panels on a polyethylene naphthalate (PEN) substrate with a resolution of 98 dpi was demonstrated.
关键词： Organic thin-film transistors,Organic gate dielectric,Plastic substrates,Low-temperature process,Polymer semiconductor,Flexible displays,Inkjet printing
更新于2025-09-10 09:29:36
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Modulating chain conformations of polyvinyl alcohol through low cost and nontoxic glyoxal crosslinker: Application in high performance organic transistors
摘要： High leakage current and presence of numerous polar hydroxyl groups have often appeared as severe performance obstacles for polyvinyl alcohol (PVA) on its application in organic ?eld e?ect transistor devices. Herein, we report a facile, yet e?cient functionalization and chain structure modi?cation technique to enhance its e?cacy as a gate insulating layer. In this work, we have used glyoxal as a cross-linking agent of PVA to modulate its chain conformation and performed a detailed analysis to explore the role of glyoxal crosslinking on the electrical and structural properties of PVA. Applying various amount of glyoxal solution we have properly optimized the dose of the crosslinker to be used in the crosslinking reaction so that minimum amount of leakage can be achieved. Substantial improvement in the insulation properties as well as surface characteristics was observed after the structural modi?cation of the polymer. Correspondingly, organic FETs were fabricated using crosslinked PVA to gauge the e?ect of crosslinking on the device performance of the transistors. Post-crosslinking improvements in the polymer bulk and surface characteristics were clearly emulated in the device performance parameters. Field-e?ect mobility as high as 5.4 cm2/V-s and 1.7 cm2/V-s were achieved employing crosslinked PVA as gate dielectric layer in Dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) and pentacene based devices, respectively. Thus, our study illustrates the viability of crosslinking PVA using glyoxal and hence, can catalyze the limited use of PVA in electronic applications.
关键词： Crosslinking,Organic ?eld e?ect transistor,Gate dielectric,Polyvinyl alcohol,Glyoxal
更新于2025-09-10 09:29:36
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Towards epitaxial graphene p-n junctions as electrically programmable quantum resistance standards
摘要： We report the fabrication and measurement of top gated epitaxial graphene p-n junctions where exfoliated hexagonal boron nitride (h-BN) is used as the gate dielectric. The four-terminal longitudinal resistance across a single junction is well quantized at the von Klitzing constant RK with a relative uncertainty of 10?7. After the exploration of numerous parameter spaces, we summarize the conditions upon which these devices could function as potential resistance standards. Furthermore, we offer designs of programmable electrical resistance standards over six orders of magnitude by using external gating.
关键词： p-n junctions,quantum resistance standards,gate dielectric,hexagonal boron nitride,epitaxial graphene
更新于2025-09-09 09:28:46