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Absence of Evidence for Fixed Charge in Metal-Aluminum Oxide-Silicon Tunnel Diodes
摘要： Here, a controlled variation in the fixed charge density (NF) and thickness of aluminum oxide tunnel insulators is reported, and the impact on Schottky barrier height ΦB in metal–insulator–semiconductor (MIS) diodes is studied. Analysis of metal–aluminum oxide–silicon capacitor structures indicates a change in NF from t1 × 1012 cm?2 in as-deposited films to ?1 × 1012 cm?2 in annealed films. An analytical model and numerical device physics simulations are used to predict changes in ΦB based on these changes in NF and alumina thickness. Surprisingly, Mott–Schottky derived ΦB values did not follow the trends predicted by these electrostatic models. In fact, there seems to be no discernable effect of NF in diodes with alumina thicknesses below 2 nm, contrary to contactless measurements of the fixed charge of films of similar thickness. The ΦB trends are better explained by a dipole model. It is further shown that in as-deposited MIS diodes, the dipole is a function of alumina layer thickness, whereas in annealed MIS diodes, the dipole and ΦB were roughly constant independent of alumina thickness. These data suggest a strategy by which the ΦB of MIS tunnel contacts can be controlled and which has implication for the design of electrical contacts.
关键词： atomic layer deposition,fixed charges,silicon,barrier height,Schottky diodes
更新于2025-09-23 15:21:01
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Photonic materials for high-temperature applications: Synthesis and characterization by X-ray ptychographic tomography
摘要： Photonic materials for high-temperature applications need to withstand temperatures usually higher than 1000 ?C, whilst keeping their function. When exposed to high temperatures, such nanostructured materials are prone to detrimental morphological changes, however the structure evolution pathway of photonic materials and its correlation with the loss of material’s function is not yet fully understood. Here we use high-resolution ptychographic X-ray computed tomography (PXCT) and scanning electron microscopy (SEM) to investigate the structural changes in mullite inverse opal photonic crystals produced by a very-low-temperature (95 ?C) atomic layer deposition (ALD) super-cycle process. The 3D structural changes caused by the high-temperature exposure were quantified and associated with the distinct structural features of the ceramic photonic crystals. Other than observed in photonic crystals produced via powder colloidal suspensions or sol-gel infiltration, at high temperatures of 1400 ?C we detected a mass transport direction from the nano pores to the shells. We relate these different structure evolution pathways to the presence of hollow vertexes in our ALD-based inverse opal photonic crystals. Although the periodically ordered structure is distorted after sintering, the mullite inverse opal photonic crystal presents a photonic stopgap even after heat treatment at 1400 ?C for 100 h.
关键词： Ptychography X-ray computed tomography,High-temperature applications,3D image analysis,Photonic materials,Low-temperature atomic layer deposition
更新于2025-09-23 15:21:01
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Graphene films decorated with TiO2 grown by atomic layer deposition: characterization and photocatalytic activity study under UV-visible light
摘要： The great potential of graphene can be enhanced thanks to the functionalization of its surface. For this aim, different thicknesses of TiO2 were grown on graphene films by atomic layer deposition (ALD) at 200 °C using H2O and TiCl4 as precursors. The changes in electronic structure of graphene after the deposition of TiO2 and the influence of graphene in TiO2 photocatalytic activity under UV-Visible irradiation were studied. Results indicated the presence of inhomogeneity and intrinsic strain effects within the same sample. Undecorated graphene showed pre-existent strain due to the mismatch between graphene film and the underlying substrate, while non-intentional self-doping is caused by the presence of charged impurities. The deposition of TiO2 films with thickness ≤10 nm led graphene to be p-doped, while strain became the dominant effect increasing film thickness. Oxygen vacancies in the film decreased exponentially by increasing the film thickness leading to a stoichiometric O/Ti atomic ratio of TiO2 above 10 nm thickness. The combination of TiO2 and graphene enhanced the efficiency of electron-hole separation of TiO2 under UV-Visible light, leading to a higher photocatalytic activity tested for methyl red molecule degradation, making TiO2/Graphene hybrid material a promising candidate for the photodegradation of pollutants and water purification.
关键词： Atomic Layer Deposition,Graphene,Photocatalytic Activity,TiO2,UV-Visible Light
更新于2025-09-23 15:21:01
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Memristive Behavior Enabled by Amorphousa??Crystalline 2D Oxide Heterostructure
摘要： The emergence of memristive behavior in amorphous–crystalline 2D oxide heterostructures, which are synthesized by atomic layer deposition (ALD) of a few-nanometer amorphous Al2O3 layers onto atomically thin single-crystalline ZnO nanosheets, is demonstrated. The conduction mechanism is identified based on classic oxygen vacancy conductive channels. ZnO nanosheets provide a 2D host for oxygen vacancies, while the amorphous Al2O3 facilitates the generation and stabilization of the oxygen vacancies. The conduction mechanism in the high-resistance state follows Poole–Frenkel emission, and in the low-resistance state is fitted by the Mott–Gurney law. From the slope of the fitting curve, the mobility in the low-resistance state is estimated to be ≈2400 cm2 V?1 s?1, which is the highest value reported in semiconductor oxides. When annealed at high temperature to eliminate oxygen vacancies, Al is doped into the ZnO nanosheet, and the memristive behavior disappears, further confirming the oxygen vacancies as being responsible for the memristive behavior. The 2D heterointerface offers opportunities for new design of high-performance memristor devices.
关键词： zinc oxide,2D heterostructures,memristors,atomic layer deposition,oxygen vacancies
更新于2025-09-23 15:19:57
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Layered Nonstoichiometric V <sub/>7</sub> O <sub/>16</sub> Thin Films with Controlled Oxygen-Deficient Multivalent States and Crystalline Phases
摘要： Layered nonstoichiometric vanadium oxides have aroused strong interest in energy conversion, storage, chemical catalysis, sensors and optoelectronic devices. It is still a critical challenge to control unique atomic-layer constructions and oxygen-dependent multivalent states in layered metal oxides. Here, we demonstrated the layered nonstoichiometric V7O16 thin films with controlled multivalent states and crystalline phases obtained by the combination of atomic layer deposition (ALD) and oxygen-dependent crystallization. The nonstoichiometric composition and crystalline microstructures are dominated by the oxidation states of vanadium and the thicknesses of the pristine films during the formation of layered V7O16 thin films. Variable-temperature optical and electrical behaviors suggest that no abrupt electronic and structural transitions are observed in the layered V7O16 thin films at a temperature ranging from 78 to 475 K. We expect that the oxygen-dependent multivalent states and crystalline phases in layered V7O16 will provide more opportunities to fabricate layered oxides and electrochemical devices based on nonstoichiometric vanadium oxides.
关键词： atomic layer deposition,vanadium oxide,layered oxide,V7O16,oxygen-dependent crystallization
更新于2025-09-23 15:19:57
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Novel benzodithiophene type low band gap polymer solar cell application and device stability study with atomic layer deposition encapsulation technique
摘要： Novel benzodithiophene type copolymer was synthesized through a solvent evaporation technique. Poly(5-(5-(4, 8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4, 5-b’]dithiophen-2-yl)thiophen-2-yl)-2, 3-bis(3, 4-bis(decyloxy)phenyl)-8-(thiophen-2-yl) quinoxaline) (P-TQTBDT) solar cells were encapsulated with conventional and Atomic Layer Deposition (ALD) techniques. Characterizations of the samples were carried out via nuclear magnetic resonance (NMR), gel permeation chromotagraphy (GPC) and cyclic voltammetry (CV) techniques. Stability studies were carried out both P3HT and P-TQTBDT solar cells for comparison of commercial P3HT and our novel polymer solar cell. Our results con?rm that ALD is a promising technique for encapsulation of polymer solar cell since stability of P-TQTBDT improved to 72% durability from 38% durability with ALD encapsulation technique during 300 h under AM1.5 G solar irradiation. P-TQTBDT solar cell showed higher stability (about 10%) than P3HT solar cell for both encapsulation methods. We focused on the stability of polymer solar cell can be improved with ALD encapsulation technique. Our aim was to compare P-TQTBDT polymer solar cell with P3HT solar cell. The stability results of P-TQTBDT showed that P-TQTBDT copolymer could be promising polymer to obtain very high stability of polymer solar cells.
关键词： atomic layer deposition,solar cell,stability tests,ISOS stability tests,benzodithiophene,organic solar cell
更新于2025-09-23 15:19:57
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Atomic Layer Deposition Assisted Encapsulation of Quantum Dot Luminescent Microspheres toward Display Applications
摘要： Quantum dots (QDs) are promising for being used in advanced displays due to their outstanding emission properties. Herein, a novel encapsulation method for QDs is reported and ultra-stable QDs@SiO2@Al2O3 luminescent microspheres (QLuMiS) are obtained by combining a sol–gel method for the intermediate SiO2 layer with a fluidized powder atomic layer deposition (ALD) for the outer Al2O3 layer. The rich hydroxyl coverage on the QDs@SiO2 surface provides abundant chemisorption sites, which are beneficial for the deposition of Al2O3 in the ALD process. Simultaneously, the water-oxygen channels in the SiO2 layer are blocked by the Al2O3 layer, which protects the QDs against deterioration. Consequently, the QLuMiS exhibit an excellent stability with 86% of the initial light conversion efficiency after 1000 h of blue light aging under a light power density of 2000 mW cm?2. Such stability is significantly better than that of QDs@Al2O3 and QDs@SiO2 samples. Moreover, under this strong irradiation aging condition with blue light, the extrapolated lifetime (L50) of QLuMiS is 4969 h, which is ten times longer than that of QDs@SiO2 and is the best record as far as is known. Finally, a prototype of a QLuMiS-based cell-phone screen with a wide color gamut of 115% NTSC is demonstrated.
关键词： luminescent microspheres,quantum dots,atomic layer deposition,encapsulation
更新于2025-09-23 15:19:57
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Plasmonic titanium nitride via atomic layer deposition: A low-temperature route
摘要： To integrate plasmonic devices into industry, it is essential to develop scalable and CMOS compatible plasmonic materials. In this work, we report high plasmonic quality titanium nitride (TiN) on c-plane sapphire grown by plasma-enhanced atomic layer deposition. TiN with low losses, high metallicity, and a plasma frequency below 500 nm was achieved at temperatures less than 500 °C by exploring the effects of chemisorption time, substrate temperature, and plasma exposure time on the material properties. A reduction in chemisorption time mitigates premature precursor decomposition at TS > 375 °C, and a trade-off between reduced impurity concentration and structural degradation caused by plasma bombardment is achieved for 25 s plasma exposure. 85 nm thick TiN films grown at a substrate temperature of 450 °C, compatible with CMOS processes, with 0.5 s chemisorption time and 25 s plasma exposure exhibited a high plasmonic figure of merit (jε0/ε00j) of 2.8 and resistivity of 31 μΩ cm. As a result of the improved quality, subwavelength apertures were fabricated in the TiN thin films and are shown to exhibit extraordinary transmission.
关键词： plasmonic figure of merit,CMOS compatible,low-temperature route,atomic layer deposition,plasmonic titanium nitride
更新于2025-09-23 15:19:57
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Controlled growth of MoS2 by atomic layer deposition on patterned gold pads
摘要： Approaches to synthesize large-area MoS2 thin films have been extensively investigated in recent years towards system-level micro-/nanoelectronics applications. Methods including chemical vapor deposition (CVD) and atomic layer deposition (ALD) can enable uniform and wafer-scale MoS2 films on insulating substrates, but without selective control on the growth location. Herein, we report a controlled growth of ultra-thin MoS2 films on Au pads patterned on insulating substrates by using ALD-based techniques. Clear difference in the incubation period duration of the ALD process among different substrate surfaces have been observed. Selective growth of MoS2 can be achieved on patterned Au on SiO2/Si substrate while the incubation period is shorter on sapphire substrate as compared with that on SiO2/Si. In addition, the influence of deposition temperature on the film growth dynamics on difference surfaces has been studied. Such controlled growth of MoS2 by ALD can be very attractive in future optoelectronics applications and the synthesis on patterned Au is promising in fulfilling its application potentials such as electrocatalyst in hydrogen evolution reaction.
关键词： B2. Semiconducting materials,A3. Atomic layer deposition,B1. Sulfides
更新于2025-09-23 15:19:57
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Achieving a superior electrocatalytic activity of carbon cloth via atomic layer deposition as a flexible counter electrode for efficient dye-sensitized solar cells
摘要： Dye-sensitized solar cell (DSSC) is appealing to renewable energy communities because of its attractive features of low cost, facile assembly and short energy payback time. Nevertheless, the commonly used platinum as the counter electrode (CE) encounters great difficulties in its scarcity and noble nature. Herein, we demonstrate a promising and facile route to attain an earth-abundant, high-conductivity Pt-free flexible CE with the controllable catalytic activity via the atomic layer deposition (ALD) of ZnO as the nanoscale sacrificial template. Our result reveals the electrocatalytic activity of carbon cloth as a function of surface morphology can be successfully tailored by the ALD cycle. It can be ascribed to the interplay of ZnO and carbon during carbothermic reduction, offering the synergetic effects of the defects and oxygen doping on the carbon cloth surface as the enhanced catalytic sites for the regeneration of triiodide into iodide. As a proof of concept, the DSSC using the activated carbon cloth via ALD is enabled to deliver a boosted conversion efficiency by 79%, as compared with that using pristine carbon cloth. Such a promising route can open up a perspective for reaching an earth-abundant, high-conductivity carbon-based flexible CE with the superior catalytic activity for the photoelectrochemical cells.
关键词： Pt-free counter electrode,Dye-sensitized solar cell,Carbon cloth,Atomic layer deposition,ZnO
更新于2025-09-23 15:19:57