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Choi, Byeonghoon, Dongwoo Shin, Hee-Seung Lee et Hyunjoon Song. « Nanoparticle design and assembly for p-type metal oxide gas sensors ». Nanoscale 14, no 9 (2022) : 3387–97. http://dx.doi.org/10.1039/d1nr07561f.
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Sang, Xianhe, Yongfu Wang, Qinglin Wang, Liangrui Zou, Shunhao Ge, Yu Yao, Xueting Wang, Jianchao Fan et Dandan Sang. « A Review on Optoelectronical Properties of Non-Metal Oxide/Diamond-Based p-n Heterojunction ». Molecules 28, no 3 (30 janvier 2023) : 1334. http://dx.doi.org/10.3390/molecules28031334.
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Diamond holds promise for optoelectronic devices working in high-frequency, high-power and high-temperature environments, for example in some aspect of nuclear energetics industry processing and aerospace due to its wide bandgap (5.5 eV), ultimate thermal conductivity, high-pressure resistance, high radio frequency and high chemical stability. In the last several years, p-type B-doped diamond (BDD) has been fabricated to heterojunctions with all kinds of non-metal oxide (AlN, GaN, Si and carbon-based semiconductors) to form heterojunctions, which may be widely utilized in various optoelectronic device technology. This article discusses the application of diamond-based heterostructures and mainly writes about optoelectronic device fabrication, optoelectronic performance research, LEDs, photodetectors, and high-electron mobility transistor (HEMT) device applications based on diamond non-metal oxide (AlN, GaN, Si and carbon-based semiconductor) heterojunction. The discussion in this paper will provide a new scheme for the improvement of high-temperature diamond-based optoelectronics.
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Sulas-Kern, Dana B., Elisa M. Miller et Jeffrey L. Blackburn. « Photoinduced charge transfer in transition metal dichalcogenide heterojunctions – towards next generation energy technologies ». Energy & ; Environmental Science 13, no 9 (2020) : 2684–740. http://dx.doi.org/10.1039/d0ee01370f.
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We review recent strides in understanding and manipulating photoinduced charge transfer in heterojunctions between 2D transition metal dichalcogenides and other semiconductors, with implications for a broad array of energy applications.
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Ma, Liang, Shuang Chen, Yun Shao, You-Long Chen, Mo-Xi Liu, Hai-Xia Li, Yi-Ling Mao et Si-Jing Ding. « Recent Progress in Constructing Plasmonic Metal/Semiconductor Hetero-Nanostructures for Improved Photocatalysis ». Catalysts 8, no 12 (7 décembre 2018) : 634. http://dx.doi.org/10.3390/catal8120634.
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Hetero-nanomaterials constructed by plasmonic metals and functional semiconductors show enormous potential in photocatalytic applications, such as in hydrogen production, CO2 reduction, and treatment of pollutants. Their photocatalytic performances can be better regulated through adjusting structure, composition, and components’ arrangement. Therefore, the reasonable design and synthesis of metal/semiconductor hetero-nanostructures is of vital significance. In this mini-review, we laconically summarize the recent progress in efficiently establishing metal/semiconductor nanomaterials for improved photocatalysis. The defined photocatalysts mainly include traditional binary hybrids, ternary multi-metals/semiconductor, and metal/multi-semiconductors heterojunctions. The underlying physical mechanism for the enhanced photocatalysis of the established photocatalysts is highlighted. In the end, a brief summary and possible future perspectives for further development in this field are demonstrated.
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Mun, Seong Jun, et Soo-Jin Park. « Graphitic Carbon Nitride Materials for Photocatalytic Hydrogen Production via Water Splitting : A Short Review ». Catalysts 9, no 10 (25 septembre 2019) : 805. http://dx.doi.org/10.3390/catal9100805.
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The generation of photocatalytic hydrogen via water splitting under light irradiation is attracting much attention as an alternative to solve such problems as global warming and to increase interest in clean energy. However, due to the low efficiency and selectivity of photocatalytic hydrogen production under solar energy, a major challenge persists to improve the performance of photocatalytic hydrogen production through water splitting. In recent years, graphitic carbon nitride (g-C3N4), a non-metal photocatalyst, has emerged as an attractive material for photocatalytic hydrogen production. However, the fast recombination of photoexcited electron–hole pairs limits the rate of hydrogen evolution and various methods such as modification, heterojunctions with semiconductors, and metal and non-metal doping have been applied to solve this problem. In this review, we cover the rational design of g-C3N4-based photocatalysts achieved using methods such as modification, metal and non-metal doping, and heterojunctions, and we summarize recent achievements in their application as hydrogen production photocatalysts. In addition, future research and prospects of hydrogen-producing photocatalysts are also reviewed.
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Liu, Yuanyue, Paul Stradins et Su-Huai Wei. « Van der Waals metal-semiconductor junction : Weak Fermi level pinning enables effective tuning of Schottky barrier ». Science Advances 2, no 4 (avril 2016) : e1600069. http://dx.doi.org/10.1126/sciadv.1600069.
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Two-dimensional (2D) semiconductors have shown great potential for electronic and optoelectronic applications. However, their development is limited by a large Schottky barrier (SB) at the metal-semiconductor junction (MSJ), which is difficult to tune by using conventional metals because of the effect of strong Fermi level pinning (FLP). We show that this problem can be overcome by using 2D metals, which are bounded with 2D semiconductors through van der Waals (vdW) interactions. This success relies on a weak FLP at the vdW MSJ, which is attributed to the suppression of metal-induced gap states. Consequently, the SB becomes tunable and can vanish with proper 2D metals (for example, H-NbS2). This work not only offers new insights into the fundamental properties of heterojunctions but also uncovers the great potential of 2D metals for device applications.
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Bertho, Sabine, Wibren D. Oosterbaan, Veerle Vrindts, Jean Christophe Bolsée, Fortunato Piersimoni, Donato Spoltore, Jan D'Haen, Laurence Lutsen, Dirk Vanderzande et Jean V. Manca. « Poly(3-alkylthiophene) Nanofibers for Photovoltaic Energy Conversion ». Advanced Materials Research 324 (août 2011) : 32–37. http://dx.doi.org/10.4028/www.scientific.net/amr.324.32.
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The use of nanostructured non-conventional semiconductors such as conjugated polymers and metal oxides (e.g. TiO2), opens promising perspectives towards a new generation of solar cells based on the concept of donor:acceptor bulk heterojunctions. In this concept donor material and acceptor material form interpenetrating networks allowing light absorption, charge transfer and charge transport throughout the entire bulk of the thin film. Since nanomorphology is of crucial importance for this type of solar cells, in this contribution the use of nanofibers in bulk heterojunction solar cells is explored in order to obtain highways for charge transport. We investigate in particular the use of P3AT (poly(3-alkylthiophene)) nanofibers and show that the polymer fraction aggregated into fibers can be easily controlled by temperature. We find an optimal efficiency at intermediate fiber fraction and show that it can be linked to the morphology of the active layer.
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Janavicius, Lukas L., Julian A. Michaels, Clarence Chan, Dane J. Sievers et Xiuling Li. « Programmable vapor-phase metal-assisted chemical etching for versatile high-aspect ratio silicon nanomanufacturing ». Applied Physics Reviews 10, no 1 (mars 2023) : 011409. http://dx.doi.org/10.1063/5.0132116.
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Defying the isotropic nature of traditional chemical etch, metal-assisted chemical etching (MacEtch) has allowed spatially defined anisotropic etching by using patterned metal catalyst films to locally enhance the etch rate of various semiconductors. Significant progress has been made on achieving unprecedented aspect ratio nanostructures using this facile approach, mostly in solution. However, the path to manufacturing scalability remains challenging because of the difficulties in controlling etch morphology (e.g., porosity and aggregation) and etch rate uniformity over a large area. Here, we report the first programmable vapor-phase MacEtch (VP-MacEtch) approach, with independent control of the etchant flow rates, injection and pulse time, and chamber pressure. In addition, another degree of freedom, light irradiation is integrated to allow photo-enhanced VP-MacEtch. Various silicon nanostructures are demonstrated with each of these parameters systematically varied synchronously or asynchronously, positioning MacEtch as a manufacturing technique for versatile arrays of three-dimensional silicon nanostructures. This work represents a critical step or a major milestone in the development of silicon MacEtch technology and also establishes the foundation for VP-MacEtch of compound semiconductors and related heterojunctions, for lasting impact on damage-free 3D electronic, photonic, quantum, and biomedical devices.
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Cao, Zhen, Moussab Harb, Sergey M. Kozlov et Luigi Cavallo. « Structural and Electronic Effects at the Interface between Transition Metal Dichalcogenide Monolayers (MoS2, WSe2, and Their Lateral Heterojunctions) and Liquid Water ». International Journal of Molecular Sciences 23, no 19 (7 octobre 2022) : 11926. http://dx.doi.org/10.3390/ijms231911926.
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Transition metal dichalcogenides (TMDCs) can be used as optical energy conversion materials to catalyze the water splitting reaction. A good catalytical performance requires: (i) well-matched semiconductor bandgaps and water redox potential for fluent energy transfer; and (ii) optimal orientation of the water molecules at the interface for kinetically fast chemical reactions. Interactions at the solid–liquid interface can have an important impact on these two factors; most theoretical studies have employed semiconductor-in-vacuum models. In this work, we explored the interface formed by liquid water and different types of TMDCs monolayers (MoS2, WSe2, and their lateral heterojunctions), using a combined molecular dynamics (MD) and density functional theory (DFT) approach. The strong interactions between water and these semiconductors confined the adsorbed water layer presenting structural patterns, with the water molecules well connected to the bulk water through the hydrogen bonding network. Structural fluctuations in the metal chalcogenide bonds during the MD simulations resulted in a 0.2 eV reduction of the band gap of the TMDCs. The results suggest that when designing new TMDC semiconductors, both the surface hydrophobicity and the variation of the bandgaps originating from the water-semiconductor interface, need to be considered.
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Song, Ze, Binbin Wei, Qilong Wang, Wenhui Wang, Zhangyu Cao, Li Zhang, Qingge Mu et al. « High-performance metal electrode-enhanced double parallel p–n heterojunctions photodetector ». Journal of Applied Physics 133, no 12 (28 mars 2023) : 124502. http://dx.doi.org/10.1063/5.0141523.
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Highly sensitive uncooled mid-wave infrared (MWIR) photodetectors have a very wide range of applications ranging from the sensor and image to communications. Traditional MWIR detection semiconductors require liquid nitrogen cooling to depress dark current, which impeded the wide applications of devices. Here, we report a metal electrode-enhanced double parallel BP/InSe/BP van der Waals heterostructure uncooled MWIR photodetector. The device exhibits ultrahigh light on/off ratio of 108 and a very low dark current of 0.16 pA. The competitive performance includes high photoresponsivity ( R) of 27.8 A W−1, excellent specific detectivity ( D*) of 3.8 × 1012 cm Hz1/2 W−1, very low noise equivalent power (NEP) of 3.7 × 10−16 W Hz−1/2, and fast response speed of τr = 3.5 μs and τd = 2.4 μs in the visible range. Notably, in the MWIR range, the light on/off ratio of ∼104, NEP of 3.0 × 10−13 W Hz−1/2, and D* of 4.8 × 109 cm Hz1/2 W−1 was realized. The work sheds light on developing a high-performance uncooled MWIR photodetector by designed band alignment.
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Macaluso, Roberto, Giuseppe Lullo, Isodiana Crupi, Daniele Sciré, Fulvio Caruso, Eric Feltin et Mauro Mosca. « Progress in Violet Light-Emitting Diodes Based on ZnO/GaN Heterojunction ». Electronics 9, no 6 (13 juin 2020) : 991. http://dx.doi.org/10.3390/electronics9060991.
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Progress in light-emitting diodes (LEDs) based on ZnO/GaN heterojunctions has run into several obstacles during the last twenty years. While both the energy bandgap and lattice parameter of the two semiconductors are favorable to the development of such devices, other features related to the electrical and structural properties of the GaN layer prevent an efficient radiative recombination. This work illustrates some advances made on ZnO/GaN-based LEDs, by using high-thickness GaN layers for the p-region of the device and an ad hoc device topology. Heterojunction LEDs consist of a quasicoalesced non-intentionally doped ZnO nanorod layer deposited by chemical bath deposition onto a metal–organic vapor-phase epitaxy -grown epitaxial layer of p-doped GaN. Circular 200 μm-sized violet-emitting LEDs with a p-n contact distance as low as 3 μm exhibit a turn-on voltage of 3 V, and an emitting optical power at 395 nm of a few microwatts. Electroluminescence spectrum investigation shows that the emissive process can be ascribed to four different recombination transitions, dominated by the electron-hole recombinations on the ZnO side.
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Hu, Chuqiao, Zhijian Du, Zhongming Wei, La Li et Guozhen Shen. « Functionalized Ti3C2Tx MXene with layer-dependent band gap for flexible NIR photodetectors ». Applied Physics Reviews 10, no 2 (juin 2023) : 021402. http://dx.doi.org/10.1063/5.0140861.
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Ti3C2T x MXene as a representative material in the emerging two-dimensional (2D) MXene family with high conductivity, abundant functional surface terminals, and large layer spacing is supposed to show specific semiconducting properties like other 2D graphene or transition metal dichalcogenides, thus extending Moore's law beyond silicon. However, despite extensive efforts, the design of Ti3C2T x MXene based semiconductor materials often depends on the availability of traditional semiconductors to form heterojunctions, where Ti3C2T x MXene is still in metallic characters and is not in dominant status in the heterojunctions. Here, we demonstrate semiconducting Ti3C2T x MXene modified with dodecyl (−C12H26) groups, as functionalized Ti3C2T x MXene possesses opened and typical layer-dependent bandgap. The new arising characteristics, red-shift of characteristic peaks, and intensity ratio of the A1g(C)/A1g(Ti, C, T x) in Raman spectroscopy suggested the successful grafting of the −C12H26 groups on the Ti3C2T x MXenes. In addition, the theoretical calculations by density functional theory, photoluminescence spectrum, together with photoelectric measurements of Ti3C2T x-C12H26 MXene on different layers, show a tunable bandgap of 0.49–2.15 eV and superior photoresponse properties in fabricating near infrared photodetectors.
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Garcia-Peiro, Jose I., Javier Bonet-Aleta, Carlos J. Bueno-Alejo et Jose L. Hueso. « Recent Advances in the Design and Photocatalytic Enhanced Performance of Gold Plasmonic Nanostructures Decorated with Non-Titania Based Semiconductor Hetero-Nanoarchitectures ». Catalysts 10, no 12 (14 décembre 2020) : 1459. http://dx.doi.org/10.3390/catal10121459.
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Plasmonic photocatalysts combining metallic nanoparticles and semiconductors have been aimed as versatile alternatives to drive light-assisted catalytic chemical reactions beyond the ultraviolet (UV) regions, and overcome one of the major drawbacks of the most exploited photocatalysts (TiO2 or ZnO). The strong size and morphology dependence of metallic nanostructures to tune their visible to near-infrared (vis-NIR) light harvesting capabilities has been combined with the design of a wide variety of architectures for the semiconductor supports to promote the selective activity of specific crystallographic facets. The search for efficient heterojunctions has been subjected to numerous studies, especially those involving gold nanostructures and titania semiconductors. In the present review, we paid special attention to the most recent advances in the design of gold-semiconductor hetero-nanostructures including emerging metal oxides such as cerium oxide or copper oxide (CeO2 or Cu2O) or metal chalcogenides such as copper sulfide or cadmium sulfides (CuS or CdS). These alternative hybrid materials were thoroughly built in past years to target research fields of strong impact, such as solar energy conversion, water splitting, environmental chemistry, or nanomedicine. Herein, we evaluate the influence of tuning the morphologies of the plasmonic gold nanostructures or the semiconductor interacting structures, and how these variations in geometry, either individual or combined, have a significant influence on the final photocatalytic performance.
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Pizzio, Luis, Manuela Manrique-Holguín, Julián Andrés Rengifo-Herrera et John Jairo Alvear-Daza. « G-C3N4/TIO2 NANOCOMPOSITES AND THEIR APPLICATION IN PHOTOCATALYTIC CO2 REDUCTION : A MINIREVIEW ». Latin American Applied Research - An international journal 53, no 1 (1 janvier 2023) : 71–76. http://dx.doi.org/10.52292/j.laar.2023.1158.
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g-C3N4/TiO2 nanocomposites seem to be promising materials for photocatalytic reductive applications such as water splitting and CO2 reduction. The g-C3N4 is known as a metal-free semiconductor exhibiting a high reductive conduction band (CB) (-1.3 V vs. NHE) and visible light absorption (Eg =2.7 eV), while TiO2 is the most popular photocatalyst. However, both semiconductors show high electron/hole recombination, and in the case of TiO2, lack of visible light absorption. Both problems could be overcome by designing type II heterojunctions or a direct Z-scheme between g-C3N4 and TiO2. These strategies make these composites suitable for CO2 photocatalytic reduction and solar fuel production. Herein, the main aspects related to photocatalytic CO2 reduction in aqueous media to obtain solar fuels such as methane and methanol, synthesis of g-C3N4/TiO2 nanocomposites, and their reactivity will be addressed and reviewed.
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Pargoletti, Eleonora, et Giuseppe Cappelletti. « Breakthroughs in the Design of Novel Carbon-Based Metal Oxides Nanocomposites for VOCs Gas Sensing ». Nanomaterials 10, no 8 (29 juillet 2020) : 1485. http://dx.doi.org/10.3390/nano10081485.
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Nowadays, the detection of volatile organic compounds (VOCs) at trace levels (down to ppb) is feasible by exploiting ultra-sensitive and highly selective chemoresistors, especially in the field of medical diagnosis. By coupling metal oxide semiconductors (MOS e.g., SnO2, ZnO, WO3, CuO, TiO2 and Fe2O3) with innovative carbon-based materials (graphene, graphene oxide, reduced graphene oxide, single-wall and multi-wall carbon nanotubes), outstanding performances in terms of sensitivity, selectivity, limits of detection, response and recovery times towards specific gaseous targets (such as ethanol, acetone, formaldehyde and aromatic compounds) can be easily achieved. Notably, carbonaceous species, highly interconnected to MOS nanoparticles, enhance the sensor responses by (i) increasing the surface area and the pore content, (ii) favoring the electron migration, the transfer efficiency (spillover effect) and gas diffusion rate, (iii) promoting the active sites concomitantly limiting the nanopowders agglomeration; and (iv) forming nano-heterojunctions. Herein, the aim of the present review is to highlight the above-mentioned hybrid features in order to engineer novel flexible, miniaturized and low working temperature sensors, able to detect specific VOC biomarkers of a human’s disease.
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Shur, Michael. « (Invited) Ultrawide Bandgap Transistors for High Temperature and Radiation Hard Applications ». ECS Meeting Abstracts MA2022-02, no 37 (9 octobre 2022) : 1348. http://dx.doi.org/10.1149/ma2022-02371348mtgabs.
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Some of the best high-temperature commercial devices are now GaN field-effect transistors (FETs) on silicon substrates. However, these devices cannot meet requirements for space applications requiring high radiation hardness and for operations at temperatures as high as 600 oC. High temperature and radiation hard applications stimulated interest in developing transistors using ultrawideband gap materials including AlN, AlGaN with a high molecular fraction of aluminum, gallium oxide, diamond, boron nitride, and their heterojunctions. A wider bandgap and, therefore, larger energy required to produce an electron-hole pair and larger energy gap discontinuities in heterostructures formed by these materials make them both more tolerant to radiation and more capable of operating at higher temperatures. Insulated gate (Metal Insulator Heterostructure FET (MISHFET) structures with high K-materials implemented in the AlGaN materials system, the power FINFET configurations implemented in GaN and diamond, and gate edge and channel engineering approaches are key technologies for ultra-wide bandgap semiconductor applications. Using all AlGaN materials is now a proven approach to compete with GaN. Measured and predicted materials properties of BN and diamond promise an even better performance but the power device applications of these materials and their heterojunctions have not yet been sufficiently explored. I will review the material parameters of ultra-wideband gap semiconductors and specific device designs linking them to the expected radiation hardness and high-temperature performance and to improving the reliability and lifetime of ultra-wideband gap transistors.
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Giannazzo, Filippo, Emanuela Schilirò, Giuseppe Greco et Fabrizio Roccaforte. « Conductive Atomic Force Microscopy of Semiconducting Transition Metal Dichalcogenides and Heterostructures ». Nanomaterials 10, no 4 (22 avril 2020) : 803. http://dx.doi.org/10.3390/nano10040803.
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Semiconducting transition metal dichalcogenides (TMDs) are promising materials for future electronic and optoelectronic applications. However, their electronic properties are strongly affected by peculiar nanoscale defects/inhomogeneities (point or complex defects, thickness fluctuations, grain boundaries, etc.), which are intrinsic of these materials or introduced during device fabrication processes. This paper reviews recent applications of conductive atomic force microscopy (C-AFM) to the investigation of nanoscale transport properties in TMDs, discussing the implications of the local phenomena in the overall behavior of TMD-based devices. Nanoscale resolution current spectroscopy and mapping by C-AFM provided information on the Schottky barrier uniformity and shed light on the mechanisms responsible for the Fermi level pinning commonly observed at metal/TMD interfaces. Methods for nanoscale tailoring of the Schottky barrier in MoS2 for the realization of ambipolar transistors are also illustrated. Experiments on local conductivity mapping in monolayer MoS2 grown by chemical vapor deposition (CVD) on SiO2 substrates are discussed, providing a direct evidence of the resistance associated to the grain boundaries (GBs) between MoS2 domains. Finally, C-AFM provided an insight into the current transport phenomena in TMD-based heterostructures, including lateral heterojunctions observed within MoxW1–xSe2 alloys, and vertical heterostructures made by van der Waals stacking of different TMDs (e.g., MoS2/WSe2) or by CVD growth of TMDs on bulk semiconductors.
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Vecchi, Pierpaolo, Alberto Piccioni, Irene Carrai, Raffaello Mazzaro, Michele Mazzanti, Vito Cristino, Stefano Caramori et Luca Pasquini. « Understanding the Carrier Dynamics of Complex Heterojunctions for Water Splitting through Wavelength-Dependent Intensity Modulated Photocurrent Spectroscopy ». ECS Meeting Abstracts MA2022-02, no 48 (9 octobre 2022) : 1871. http://dx.doi.org/10.1149/ma2022-02481871mtgabs.
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Metal oxide semiconductors are promising materials to be employed as photoanodes in photoelectrochemical (PEC) devices to drive the oxygen evolution reaction (OER) for the conversion of solar energy into chemical fuels. These materials need to efficiently absorb light, have good bulk transport properties to separate the photogenerated charges, and induce fast charge transfer from the electrode inside the solution. To this aim, the best selected materials are usually combined to form efficient heterojunction structures, often with the help of surface catalysts. The understanding of charge carrier dynamics in complex heterojunctions is of the utmost importance for the performance optimization of photoelectrochemical cells and “ operando” techniques are most valuable, because they provide information about the charge separation, bulk transport, charge transfer at each junction, and at the semiconductor-electrolyte interface of the system upon external stimuli, such as illumination, applied bias and chemical environment. In the presence of multiple competing processes and complex interfaces, which are often found in photoelectrodes for water splitting, the construction of an electrical model that describe the carrier dynamics under a light stimulus can be difficult, since the frequency response of the PEC system may depend on several interlaced resistive and capacitive contributions, which are sometimes difficult to separate or to interpret in an unambiguous fashion. The characterization of the relevant kinetic processes occurring at junctions and semiconductor/electrolyte interfaces can be effectively carried out by implementing wavelength-dependent Intensity Modulated Photocurrent Spectroscopy (WD-IMPS). This innovative approach allows to selectively probe different layer of the heterojunction and identify the electron transport properties in the bulk and at the interface. We employed this straightforward technique to study the carrier dynamics of a WO3/BiVO4/CoFe-Prussian blue heterojunction in a conventional three electrode cell for water splitting, and we identified interfacial recombination processes affecting the semiconductor heterojunction, as well as the positive contribution of the inorganic catalyst on the charge separation efficiency of the BiVO4 layer.[1] Herein, the proposed methodology is used to separate and address the role of each active component within complex interfaces coupled with different catalysts and in different electrolytic environments and represents a valuable tool for improving the understanding of dynamic processes relevant to PEC water splitting. References [1] Vecchi, P., Piccioni, A., Mazzaro, R., Mazzanti, M., Cristino, V., Caramori, S. and Pasquini, L. (2022), Charge Separation Efficiency in WO3/BiVO4 Photoanodes with CoFe Prussian Blue Catalyst Studied by Wavelength-Dependent Intensity Modulated Photocurrent Spectroscopy. Sol. RRL. Accepted Author Manuscript. https://doi.org/10.1002/solr.202200108
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Chaulagain, Narendra, Harshitha Rajashekhar, Navneet Kumar, Ehsan Vahidzadeh, Kazi Alam et Karthik Shankar. « Hot Hole Utilization in Au-TiO2 and Au-C3N4-TiO2 Core-Shell Heterojunctions for High Performance Photoelectrochemical Water Splitting ». ECS Meeting Abstracts MA2022-01, no 51 (7 juillet 2022) : 2383. http://dx.doi.org/10.1149/ma2022-01512383mtgabs.
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Gold nanoparticles (Au NPs) coated with TiO2 shells exhibit strong localized surface plasmon resonance (LSPR) peaks at ~550-600 nm. The Au plasmons decay in femtoseconds through both interband and intraband damping processes to produce hot electron-hole pairs. These hot carriers have excess energy at room temperature which can be utilized to generate electricity or drive a chemical reaction. However, the hot carriers experience ultrafast recombination and thermal relaxation in hundreds of femtoseconds to a few picoseconds due to electron-electron scattering and collisions with phonons. A Schottky barrier heterojunction between Au and a n-type semiconductor such as TiO2 is an ideal method to separate the hot carrier pairs. In Au-TiO2 Schottky junctions, hot electrons are injected into TiO2 through thermionic emission and/or field emission before recombination and thermal equilibration, at timescales of roughly 250 fs. However the harvesting of residual hot holes in Au remains problematic partly because of the difficulty in forming Schottky junctions between Au and p-type semiconductors. The harvesting of hot holes is particularly important considering that hot holes in Au are on average, more energetic than hot electrons. In this work, we use an innovative photoanode architecture to harvest hot holes. Our photoanode architecture consists of Au NPs coated with a thin layer of amorphous TiO2 and deposited on transparent conductive oxide (TCO)-coated glass substrates. Hot electrons are extracted from the Au into the TCO contact through the TiO2 shell. Hot holes tunnel through the TiO2 to reach the alkaline electrolyte whether they oxidize hydroxyl ions and dissolved oxygen species to generate oxygen. Another novelty is the use of a layer of graphitic carbon nitride (g-C3N4) quantum dots to pump the plasmon through exciton-to-plasmon energy transfer and increase the production of hot carriers. g-C3N4 works to enhance the plasmonic light harvesting due to the excellent overlap between the emission of g-C3N4 and the LSPR absorption band of Au. Photocurrent densities as high as 3.7 mA/cm2 were achieved under AM1.5G one sun illumination with concomitant high Faradaic efficiencies. Photoelectrochemical action spectra collected using filtered AM1.5G illumination and monochromatic LEDs revealed the prominent role of visible photons in water-splitting performed using Au-C3N4-TiO2 core-shell ternary heterojunctions. A key goal moving forward is to replace the noble metal (Au) with transition metal nitride plasmonic absorbers while sustaining the high level of photoelectrochemical performance.
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Gautam, Ujjal K., Yoshio Bando, Pedro M. F. J. Costa, Xiaosheng Fang, Benjamin Dierre, Takashi Sekiguchi et Dmitri Golberg. « Inorganically filled carbon nanotubes : Synthesis and properties ». Pure and Applied Chemistry 82, no 11 (6 août 2010) : 2097–109. http://dx.doi.org/10.1351/pac-con-09-12-08.
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Since the discovery of carbon nanotubes (CNTs) in 1991, widespread research has been carried out to understand their useful physical and electronic properties and also to explore their use in devices. CNTs have many unique properties such as tunable electrical resistance, mechanical robustness, and high thermal conductivity, which when combined with other inorganic materials such as phosphors or superconductors could lead to hetero-structures with diverse functionality. We have been able to obtain mass production of such materials wherein CNTs form core-shell heterostructures with metals, semiconductors, insulators, and even metal-semiconductor heterojunctions. The emerging strategy employs a high-temperature chemical vapor deposition (CVD) technique and high heating rates. Interestingly, due to their high temperature stability, CNTs can act as a nanoreactor for production of exotic materials inside it. In this article, we take ZnS-filled CNTs as an example to explain our synthesis strategy. We explore the optical behavior of these complex materials, analyzing both their luminescence and degradation upon exposure to an electron beam. In addition, the mechanical response of filled CNTs has been evaluated individually inside a transmission electron microscope fitted with an atomic force microscopy–transmission electron microscopy (AFM–TEM) sample holder. Many applications can be envisioned for these nanostructures ranging from nanothermometers to photo-protective storage and delivery devices.
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Turkdogan, Sunay, et Bayram Kilic. « Synthesis and characterization of metal oxide semiconductors by a facile co-electroplating-annealing method and formation of ZnO/CuO pn heterojunctions with rectifying behavior ». Materials Research Express 5, no 1 (3 janvier 2018) : 015902. http://dx.doi.org/10.1088/2053-1591/aaa1c3.
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Li, Yanwei, Chun Zhao, Deliang Zhu, Peijiang Cao, Shun Han, Youming Lu, Ming Fang, Wenjun Liu et Wangying Xu. « Recent Advances of Solution-Processed Heterojunction Oxide Thin-Film Transistors ». Nanomaterials 10, no 5 (18 mai 2020) : 965. http://dx.doi.org/10.3390/nano10050965.
Texte intégralRésumé :
Thin-film transistors (TFTs) made of metal oxide semiconductors are now increasingly used in flat-panel displays. Metal oxides are mainly fabricated via vacuum-based technologies, but solution approaches are of great interest due to the advantages of low-cost and high-throughput manufacturing. Unfortunately, solution-processed oxide TFTs suffer from relatively poor electrical performance, hindering further development. Recent studies suggest that this issue could be solved by introducing a novel heterojunction strategy. This article reviews the recent advances in solution-processed heterojunction oxide TFTs, with a specific focus on the latest developments over the past five years. Two of the most prominent advantages of heterostructure oxide TFTs are discussed, namely electrical-property modulation and mobility enhancement by forming 2D electron gas. It is expected that this review will manifest the strong potential of solution-based heterojunction oxide TFTs towards high performance and large-scale electronics.
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Langer, Jerzy M., C. Delerue, M. Lannoo et Helmut Heinrich. « Transition-metal impurities in semiconductors and heterojunction band lineups ». Physical Review B 38, no 11 (15 octobre 1988) : 7723–39. http://dx.doi.org/10.1103/physrevb.38.7723.
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Delerue, C., M. Lannoo et Jerzy M. Langer. « Transition-Metal Impurities in Semiconductors and Heterojunction Band Lineups ». Physical Review Letters 61, no 2 (11 juillet 1988) : 199–202. http://dx.doi.org/10.1103/physrevlett.61.199.
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Hiragond, Chaitanya B., Niket S. Powar et Su-Il In. « Recent Developments in Lead and Lead-Free Halide Perovskite Nanostructures towards Photocatalytic CO2 Reduction ». Nanomaterials 10, no 12 (21 décembre 2020) : 2569. http://dx.doi.org/10.3390/nano10122569.
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Perovskite materials have been widely considered as emerging photocatalysts for CO2 reduction due to their extraordinary physicochemical and optical properties. Perovskites offer a wide range of benefits compared to conventional semiconductors, including tunable bandgap, high surface energy, high charge carrier lifetime, and flexible crystal structure, making them ideal for high-performance photocatalytic CO2 reduction. Notably, defect-induced perovskites, for example, crystallographic defects in perovskites, have given excellent opportunities to tune perovskites’ catalytic properties. Recently, lead (Pb) halide perovskite and their composites or heterojunction with other semiconductors, metal nanoparticles (NPs), metal complexes, graphene, and metal-organic frameworks (MOFs) have been well established for CO2 conversion. Besides, various halide perovskites have come under focus to avoid the toxicity of lead-based materials. Therefore, we reviewed the recent progress made by Pb and Pb-free halide perovskites in photo-assisted CO2 reduction into useful chemicals. We also discussed the importance of various factors like change in solvent, structure defects, and compositions in the fabrication of halide perovskites to efficiently convert CO2 into value-added products.
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Lei, Yong, Xiaozhan Yang et Wenlin Feng. « Synthesis of vertically-aligned large-area MoS2 nanofilm and its application in MoS2/Si heterostructure photodetector ». Nanotechnology 33, no 10 (17 décembre 2021) : 105709. http://dx.doi.org/10.1088/1361-6528/ac3c7e.
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Abstract Van der Waals heterostructures based on the combination of 2D transition metal dichalcogenides and conventional semiconductors offer new opportunities for the next generation of optoelectronics. In this work, the sulfurization of Mo film is used to synthesize vertically-aligned MoS2 nanofilm (V-MoS2) with wafer-size and layer controllability. The V-MoS2/n-Si heterojunction was fabricated by using a 20 nm thickness V-MoS2, and the self-powered broadband photodetectors covering from deep ultraviolet to near infrared is achieved. The device shows superior responsivity (5.06 mA W−1), good photodetectivity (5.36 × 1011 Jones) and high on/off ratio I on/I off (8.31 × 103 at 254 nm). Furthermore, the V-MoS2/n-Si heterojunction device presents a fast response speed with the rise time and fall time being 54.53 ms and 97.83 ms, respectively. The high photoelectric performances could be attributed to the high-quality heterojunction between the V-MoS2 and n-Si. These findings suggest that the V-MoS2/n-Si heterojunction has great potential applications in the deep ultraviolet-near infrared detection field, and might be used as a part of the construction of integrated optoelectronic systems.
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Hsu, Julia W. P., et Matthew T. Lloyd. « Organic/Inorganic Hybrids for Solar Energy Generation ». MRS Bulletin 35, no 6 (juin 2010) : 422–28. http://dx.doi.org/10.1557/mrs2010.579.
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AbstractOrganic and hybrid (organic/inorganic) solar cells are an attractive alternative to traditional silicon-based photovoltaics due to low-temperature, solution-based processing and the potential for rapid, easily scalable manufacturing. Using oxide semiconductors, instead of fullerenes, as the electron acceptor and transporter in hybrid solar cells has the added advantages of better environmental stability, higher electron mobility, and the ability to engineer interfacial band offsets and hence the photovoltage. Further improvements to this structure can be made by using metal oxide nanostructures to increase heterojunction areas, similar to bulk heterojunction organic photovoltaics. However, compared to all-organic solar cells, these hybrid devices produce far lower photocurrent, making improvement of the photocurrent the highest priority. This points to a less than optimized polymer/metal oxide interface for carrier separation. In this article, we summarize recent work on examining the polymer structure, electron transfer, and recombination at the polythiophene-ZnO interface in hybrid solar cells. Additionally, the impact of chemical modification at the donor-acceptor interface on the device characteristics is reviewed.
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Ni, Junhao, Quangui Fu, Kostya (Ken) Ostrikov, Xiaofeng Gu, Haiyan Nan et Shaoqing Xiao. « Status and prospects of Ohmic contacts on two-dimensional semiconductors ». Nanotechnology 33, no 6 (18 novembre 2021) : 062005. http://dx.doi.org/10.1088/1361-6528/ac2fe1.
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Abstract In recent years, two-dimensional materials have received more and more attention in the development of semiconductor devices, and their practical applications in optoelectronic devices have also developed rapidly. However, there are still some factors that limit the performance of two-dimensional semiconductor material devices, and one of the most important is Ohmic contact. Here, we elaborate on a variety of approaches to achieve Ohmic contacts on two-dimensional materials and reveal their physical mechanisms. For the work function mismatch problem, we summarize the comparison of barrier heights between different metals and 2D semiconductors. We also examine different methods to solve the problem of Fermi level pinning. For the novel 2D metal-semiconductor contact methods, we analyse their effects on reducing contact resistance from two different perspectives: homojunction and heterojunction. Finally, the challenges of 2D semiconductors in achieving Ohmic contacts are outlined.
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Lee, Jongchan, Hee-Ok Kim, Jae-Eun Pi, Sooji Nam, Seung-Youl Kang, Kwang-Ho Kwon et Sung Haeng Cho. « Transparent phototransistor with high responsivity, sensitivity, and detectivity from heterojunction metal oxide semiconductors ». Applied Physics Letters 117, no 11 (14 septembre 2020) : 111103. http://dx.doi.org/10.1063/5.0014562.
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Meng, Fan-Jian, Rui-Feng Xin et Shan-Xin Li. « Metal Oxide Heterostructures for Improving Gas Sensing Properties : A Review ». Materials 16, no 1 (27 décembre 2022) : 263. http://dx.doi.org/10.3390/ma16010263.
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Metal oxide semiconductor gas sensors are widely used to detect toxic and inflammable gases in industrial production and daily life. The main research hotspot in this field is the synthesis of gas sensing materials. Previous studies have shown that incorporating two or more metal oxides to form a heterojunction interface can exhibit superior gas sensing performance in response and selectivity compared with single phase. This review focuses on mainly the synthesis methods and gas sensing mechanisms of metal oxide heterostructures. A significant number of heterostructures with different morphologies and shapes have been fabricated, which exhibit specific sensing performance toward a specific target gas. Among these synthesis methods, the hydrothermal method is noteworthy due to the fabrication of diverse structures, such as nanorod-like, nanoflower-like, and hollow sphere structures with enhanced sensing properties. In addition, it should be noted that the combination of different synthesis methods is also an efficient way to obtain metal oxide heterostructures with novel morphologies. Despite advanced methods in the metal oxide semiconductors and nanotechnology field, there are still some new issues which deserve further investigation, such as long-term chemical stability of sensing materials, reproducibility of the fabrication process, and selectivity toward homogeneous gases. Moreover, the gas sensing mechanism of metal oxide heterostructures is controversial. It should be clarified so as to further integrate laboratory theory research with practical exploitation.
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Lv, Chuying, Su Qin, Yang Lei, Xinao Li, Jianfeng Huang et Junmin Liu. « Direct Z-Scheme Heterojunction Catalysts Constructed by Graphitic-C3N4 and Photosensitive Metal-Organic Cages for Efficient Photocatalytic Hydrogen Evolution ». Nanomaterials 12, no 5 (7 mars 2022) : 890. http://dx.doi.org/10.3390/nano12050890.
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The demand for improving the activity, durability, and recyclability of metal-organic cages (MOCs) that work as photocatalytic molecular devices in a homogeneous system has promoted research to combine them with other solid materials. An M2L4 type photosensitive metal-organic cage MOC-Q2 with light-harvesting ligands and catalytic Pd2+ centers has been synthesized and further heterogenized with graphitic carbon nitride to prepare a robust direct Z-scheme heterojunction photocatalyst for visible-light-driven hydrogen generation. The optimized g-C3N4/MOC-Q2 (0.7 wt%) sample exhibits a high H2 evolution activity of 6423 μmol g−1 h−1 in 5 h, and a total turnover number of 39,695 after 10 h, significantly superior to the bare MOC-Q2 used in the homogeneous solution and the comparison sample Pd/g-C3N4/L-4. The enhanced performances of g-C3N4/MOC-Q2 can be ascribed to its direct Z-scheme heterostructure, which effectively improves the charge separation and transfer efficiency. This work presents a rational approach of designing a binary photocatalytic system through combing micromolecular MOCs with heterogeneous semiconductors for water splitting.
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Verma, Chandra Shekhar, Neelam Shukla et Purna Bose. « A Review On Chemical Bath Deposition Mediated Synthesis Of Binary/Ternary Photoconductive Metal Sulfide Thin Films ». ECS Transactions 107, no 1 (24 avril 2022) : 19647–54. http://dx.doi.org/10.1149/10701.19647ecst.
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Photoconductors are normally composed of semiconductors, which show an enhancement in the electrical conductivity due to the absorption of photons. Among the binary compounds PbS, ZnS, and CdS are the most typical inorganic semiconductor materials owing to their band structure. The properties of Zn1-xCdxS thin films lie in between the properties of ZnS and CdS, widely used as a wide band gap window material in heterojunction photovoltaic solar cells and in photoconductive device. Some ternary compounds based on CdS and PbS has been formed such as PbS with some percentage of Cd(CdxPb1-XS), and it has been observed by optical measurement that that the band gap value of this ternary compounds varies with x. In this review paper, we will emphasis the fabrication of thin film of binary and ternary metal-sulphide compounds by chemical bath deposition method.
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Zhang, Zhihao, et Jiaying Ye. « Free-Standing Multilayer MoS2-BP Heterostructures for High Performance Self-Powered Photodetector ». Journal of Physics : Conference Series 2440, no 1 (1 janvier 2023) : 012011. http://dx.doi.org/10.1088/1742-6596/2440/1/012011.
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Abstract Phototransistors based on two-dimensional materials such as graphene, transition metal sulfides, and black phosphorus are widely used in in recent years. However, these materials have weak optical absorption, low carrier mobility or poor air stability, which restrict their application in the field of high-sensitivity detection. The inter-stacking of two-dimensional semiconductors can achieve excellent performance, and has promising applications in the field of optoelectronics. The stacking of two-dimensional semiconductors can form van der Waals heterostructures with low defect states and spatial homogeneity, which is an effective way to improve the performance of 2D photodetectors. Based on this, this paper constructs a free-standing multilayer MoS2-BP heterostructure by mechanical exfoliation for high performance self-powered photodetector. The strong space charge region can effectively separate the photogenerated carriers, so it has a good photodetection capability in the self-driven state. Moreover, we analyse and summarize the working mechanism of photodetectors based on 2D materials, and review high sensitivity detectors of recent years based on 2D material heterojunction. Finally, the challenges to further improve the detection sensitivity are pointed out. Thus, our free-standing multilayer MoS2-BP heterostructure propose a useful experience and reference for the future development of self-power photodetectors.
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Andleeb, Shaista, Xiaoyu Wang, Haiyun Dong, Sreeramulu Valligatla, Christian Niclaas Saggau, Libo Ma, Oliver G. Schmidt et Feng Zhu. « Fast-Response Micro-Phototransistor Based on MoS2/Organic Molecule Heterojunction ». Nanomaterials 13, no 9 (27 avril 2023) : 1491. http://dx.doi.org/10.3390/nano13091491.
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Over the past years, molybdenum disulfide (MoS2) has been the most extensively studied two-dimensional (2D) semiconductormaterial. With unique electrical and optical properties, 2DMoS2 is considered to be a promising candidate for future nanoscale electronic and optoelectronic devices. However, charge trapping leads to a persistent photoconductance (PPC), hindering its use for optoelectronic applications. To overcome these drawbacks and improve the optoelectronic performance, organic semiconductors (OSCs) are selected to passivate surface defects, tune the optical characteristics, and modify the doping polarity of 2D MoS2. Here, we demonstrate a fast photoresponse in multilayer (ML) MoS2 by addressing a heterojunction interface with vanadylphthalocyanine (VOPc) molecules. The MoS2/VOPc van der Waals interaction that has been established encourages the PPC effect in MoS2 by rapidly segregating photo-generated holes, which move away from the traps of MoS2 toward the VOPc molecules. The MoS2/VOPc phototransistor exhibits a fast photo response of less than 15 ms for decay and rise, which is enhanced by 3ordersof magnitude in comparison to that of a pristine MoS2-based phototransistor (seconds to tens of seconds). This work offers a means to realize high-performance transition metal dichalcogenide (TMD)-based photodetection with a fast response speed.
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Li, Xian’e, Qilun Zhang, Xianjie Liu et Mats Fahlman. « Pinning energies of organic semiconductors in high-efficiency organic solar cells ». Journal of Semiconductors 44, no 3 (1 mars 2023) : 032201. http://dx.doi.org/10.1088/1674-4926/44/3/032201.
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Abstract With the emergence of new materials for high-efficiency organic solar cells (OSCs), understanding and finetuning the interface energetics become increasingly important. Precise determination of the so-called pinning energies, one of the critical characteristics of the material to predict the energy level alignment (ELA) at either electrode/organic or organic/organic interfaces, are urgently needed for the new materials. Here, pinning energies of a wide variety of newly developed donors and non-fullerene acceptors (NFAs) are measured through ultraviolet photoelectron spectroscopy. The positive pinning energies of the studied donors and the negative pinning energies of NFAs are in the same energy range of 4.3−4.6 eV, which follows the design rules developed for fullerene-based OSCs. The ELA for metal/organic and inorganic/organic interfaces follows the predicted behavior for all of the materials studied. For organic–organic heterojunctions where both the donor and the NFA feature strong intramolecular charge transfer, the pinning energies often underestimate the experimentally obtained interface vacuum level shift, which has consequences for OSC device performance.
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Kitaura, Ryo. « (Invited, Digital Presentation) Ultrathin Lateral Heterostructures Based on Two-Dimensional Semiconductors ». ECS Meeting Abstracts MA2022-01, no 10 (7 juillet 2022) : 784. http://dx.doi.org/10.1149/ma2022-0110784mtgabs.
Texte intégralRésumé :
Low-dimensional (2D) materials, including carbon nanotubes, graphene, boron nitrides, and transition metal dichalcogenides (TMDs), have provided a platform to explore novel physics at the nano-scale. In addition to the fascinating properties of low-dimensional materials themselves, they allow exploring novel superstructures, such as heterojunctions, heterostacks, and superlattices, which give even broader possibilities. We are working on low-dimensional superstructures fabricated by (1) crystal growth with metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE), and (2) stacking each component with the full-dry-transfer-based manipulation technique[1]-[6]. This presentation will focus on our recent works on low-dimensional superstructures, such as 2D ultrathin lateral superlattices. For example, we have successfully realized MoS2/WS2 2D lateral superlattices with a periodicity of down to one-atom-thick by MOCVD with an automatic valve control system. Also, we have observed characteristic PL arising probably from 1D junction structures. More details on the fabrication and optical properties of these superstructures will be addressed in this talk. [1] Y. Murai, et. al., ACS Nano 2021, doi.org/10.1021/ascnano.1c04584 [2] T. Hotta, et. al., ACS Nano 2021, 51:1370-1377. [3] T. Hotta, et al., Phys. Rev. B 2020, 102:115424. [4] S. Zhao et al., Phys. Rev. Lett. 2020, 124:106101. [5] Y. Uchiyama et. al., npj 2D Mater. App. 2019, 3:26. [6] M. Okada, et. al., ACS Nano 2018, 12:2498-2505.
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Lee, Sunghwan, Donghun Lee, Fei Qin, Yuxuan Zhang, Molly Rothschild, Han Wook Song et Kwangsoo No. « (Invited) Oxide Electronics and Recent Progress in Bipolar Applications ». ECS Meeting Abstracts MA2022-01, no 19 (7 juillet 2022) : 1071. http://dx.doi.org/10.1149/ma2022-01191071mtgabs.
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The discovery of oxide electronics is of increasing importance today as one of the most promising new technologies and manufacturing processes for a variety of electronic and optoelectronic applications such as next-generation displays, batteries, solar cells, memory devices, and photodetectors[1]. The high potential use seen in oxide electronics is due primarily to their high carrier mobilities and their ability to be fabricated at low temperatures[2]. However, since the majority of oxide semiconductors are n-type oxides, current applications are limited to unipolar devices, eventually developing oxide-based bipolar devices such as p-n diodes and complementary metal-oxide semiconductors. We have contributed to a wide range of oxide semiconductors and their electronics and optoelectronic device applications. Particularly, we have demonstrated n-type oxide-based thin film transistors (TFT), integrating In2O3-based n-type oxide semiconductors from binary cation materials to ternary cation species including InZnO, InGaZnO (IGZO), and InAlZnO. We have suggested channel/metallization contact strategies to achieve stable and high TFT performance[3, 4], identified vacancy-based native defect doping mechanisms[5], suggested interfacial buffer layers to promote charge injection capability[6], and established the role of third cation species on the carrier generation and carrier transport[7]. More recently, we have reported facile manufacturing of p-type SnOx through reactive magnetron sputtering from a Sn metal target[8]. The fabricated p-SnOx was found to be devoid of metallic phase of Sn from x-ray photoelectron spectroscopy and demonstrated stable performance in a fully oxide-based p-n heterojunction together with n-InGaZnO. The oxide-based p-n junctions exhibited a high rectification ratio greater than 103 at ±3 V, a low saturation current of ~2x10-10, and a small turn-on voltage of -0.5 V. In this presentation, we review recent achievements and still remaining issues in transition metal oxide semiconductors and their device applications, in particular, bipolar applications including p-n heterostructures and complementary metal-oxide-semiconductor devices as well as single polarity devices such as TFTs and memristors. In addition, the fundamental mechanisms of carrier transport behaviors and doping mechanisms that govern the performance of these oxide-based devices will also be discussed. ACKNOWLEDGMENT This work was supported by the U.S. National Science Foundation (NSF) Award No. ECCS-1931088. S.L. and H.W.S. acknowledge the support from the Improvement of Measurement Standards and Technology for Mechanical Metrology (Grant No. 20011028) by KRISS. K.N. was supported by Basic Science Research Program (NRF-2021R11A1A01051246) through the NRF Korea funded by the Ministry of Education. REFERENCES [1] K. Nomura et al., Nature, vol. 432, no. 7016, pp. 488-492, Nov 25 2004. [2] D. C. Paine et al., Thin Solid Films, vol. 516, no. 17, pp. 5894-5898, Jul 1 2008. [3] S. Lee et al., Journal of Applied Physics, vol. 109, no. 6, p. 063702, Mar 15 2011, Art. no. 063702. [4] S. Lee et al., Applied Physics Letters, vol. 104, no. 25, p. 252103, 2014. [5] S. Lee et al., Applied Physics Letters, vol. 102, no. 5, p. 052101, Feb 4 2013, Art. no. 052101. [6] M. Liu et al., ACS Applied Electronic Materials, vol. 3, no. 6, pp. 2703-2711, 2021/06/22 2021. [7] A. Reed et al., Journal of Materials Chemistry C, 10.1039/D0TC02655G vol. 8, no. 39, pp. 13798-13810, 2020. [8] D. H. Lee et al., ACS Applied Materials & Interfaces, vol. 13, no. 46, pp. 55676-55686, 2021/11/24 2021.
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Soref, Richard. « Applications of Silicon-Based Optoelectronics ». MRS Bulletin 23, no 4 (avril 1998) : 20–24. http://dx.doi.org/10.1557/s0883769400030220.
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Silicon-based optoelectronics is a diversified technology that has grown steadily but not exponentially over the past decade. Some applications—such as smart-pixel signal processing and chip-to-chip optical interconnects—have enjoyed impressive growth, whereas other applications have remained quiescent. A few important applications such as optical diagnosis of leaky metal-oxide-semiconductor-field-effect-transistor circuits, have appeared suddenly. Over the years, research and development has unveiled some unique and significant aspects of Si-based optoelectronics. The main limitation of this technology is the lack of practical silicon light sources—Si lasers and efficient Si light-emitting devices (LEDs)—though investigators are “getting close” to the LED.Silicon-based optoelectronics refers to the integration of photonic and electronic components on a Si chip or wafer. The photonics adds value to the electronics, and the electronics offers low-cost mass-production benefits. The electronics includes complementary-metal-oxide semiconductors (CMOS), very large-scale integration (VLSI), bipolar CMOS, SiGe/Si heterojunction bipolar transistors, and heterostructure field-effect transistors. In this discussion, we will use a loose definition of optoelectronics that includes photonic and optoelectronic integrated circuits (PICs and OEICs), Si optical benches, and micro-optoelectromechanical (MOEM) platforms. Optoelectronic chips and platforms are subsystems of computer systems, communication networks, etc. Silicon substrates feature a superior native oxide, in addition to excellent thermal, mechanical, and economic properties. Silicon wafers “shine” as substrates for PICs and OEICs.
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Janipour, Mohsen, I. Burc Misirlioglu et Kursat Sendur. « A Theoretical Treatment of THz Resonances in Semiconductor GaAs p–n Junctions ». Materials 12, no 15 (29 juillet 2019) : 2412. http://dx.doi.org/10.3390/ma12152412.
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Semiconductor heterostructures are suitable for the design and fabrication of terahertz (THz) plasmonic devices, due to their matching carrier densities. The classical dispersion relations in the current literature are derived for metal plasmonic materials, such as gold and silver, for which a homogeneous dielectric function is valid. Penetration of the electric fields into semiconductors induces locally varying charge densities and a spatially varying dielectric function is expected. While such an occurrence renders tunable THz plasmonics a possibility, it is crucial to understand the conditions under which propagating resonant conditions for the carriers occur, upon incidence of an electromagnetic radiation. In this manuscript, we derive a dispersion relation for a p–n heterojunction and apply the methodology to a GaAs p–n junction, a material of interest for optoelectronic devices. Considering symmetrically doped p- and n-type regions with equal width, the effect of certain parameters (such as doping and voltage bias) on the dispersion curve of the p–n heterojunction were investigated. Keeping in sight the different effective masses and mobilities of the carriers, we were able to obtain the conditions that yield identical dielectric functions for the p- and n-regions. Our results indicated that the p–n GaAs system can sustain propagating resonances and can be used as a layered plasmonic waveguide. The conditions under which this is feasible fall in the frequency region between the transverse optical phonon resonance of GaAs and the traditional cut-off frequency of the diode waveguide. In addition, our results indicated when the excitation was slightly above the phonon resonance frequency, the plasmon propagation attained low-loss characteristics. We also showed that the existence or nonexistence of the depletion zone between the p- and n- interfaces allowed certain plasmon modes to propagate, while others decayed rapidly, pointing out the possibility for a design of selective filters.
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Zhang, Linzhu, Lu Chen, Yuzhou Xia, Zhiyu Liang, Renkun Huang, Ruowen Liang et Guiyang Yan. « Modification of Polymeric Carbon Nitride with Au–CeO2 Hybrids to Improve Photocatalytic Activity for Hydrogen Evolution ». Molecules 27, no 21 (3 novembre 2022) : 7489. http://dx.doi.org/10.3390/molecules27217489.
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The construction of a multi-component heterostructure for promoting the exciton splitting and charge separation of conjugated polymer semiconductors has attracted increasing attention in view of improving their photocatalytic activity. Here, we integrated Au nanoparticles (NPs) decorated CeO2 (Au–CeO2) with polymeric carbon nitride (PCN) via a modified thermal polymerization method. The combination of the interfacial interaction between PCN and CeO2 via N-O or C-O bonds, with the interior electronic transmission channel built by the decoration of Au NPs at the interface between CeO2 and PCN, endows CeAu–CN with excellent efficiency in the transfer and separation of photo-induced carriers, leading to the enhancement of photochemical activity. The amount-optimized CeAu–CN nanocomposites are capable of producing ca. 80 μmol· H2 per hour under visible light irradiation, which is higher than that of pristine CN, Ce–CN and physical mixed CeAu and PCN systems. In addition, the photocatalytic activity of CeAu–CN remains unchanged for four runs in 4 h. The present work not only provides a sample and feasible strategy to synthesize highly efficient organic polymer composites containing metal-assisted heterojunction photocatalysts, but also opens up a new avenue for the rational design and synthesis of potentially efficient PCN-based materials for efficient hydrogen evolution.
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Prokes, S. M., et Kang L. Wang. « Novel Methods of Nanoscale Wire Formation ». MRS Bulletin 24, no 8 (août 1999) : 13–19. http://dx.doi.org/10.1557/s0883769400052842.
Texte intégralRésumé :
In recent years, tremendous interest has been generated in the fabrication and characterization of nanoscale structures such as quantum dots and wires. For example, there is interest in the electronic, magnetic, mechanical, and chemical properties of materials with reduced dimensions. In the case of nanoscale semiconductors, quantum effects are expected to play an increasingly prominent role in the physics of nanostructures, and a new class of electronic and optoelectronic devices may be possible. In addition to new and interesting physics, the formation and characterization of nanoscale magnetic structures could result in higher-density storage capacity in hard disks and optical-recording media. Likewise, phonon confinement leads to a drastic reduction of thermal conductivity and can be used to improve the performance of thermoelectric devices.In 1980, H. Sakaki predicted theoretically that quantum wires may have applications in high-performance transport devices, due to their sawtoothlike density of states (E1/2), where E is the electron energy. Since then, most quantum wires have been made by fabricating a gratinglike gate on top of a two-dimensional (2D) electron gas contained in a semiconductor heterojunction or in metal-oxide-semiconductor structures. By applying a negative gate voltage to the system, its structure can be changed from a 2D to a one-dimensional (1D) regime, where electron confinement is achieved by an electrostatic confining potential. It was not until recently that “physical” semiconductor quantum wires with the demonstrated 1D confinement by physical boundaries began to be fabricated.
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Jariwala, Deep. « (Invited) 2D Dimensional Quantum Materials for CMOS and Beyond CMOS Devices ». ECS Meeting Abstracts MA2022-01, no 29 (7 juillet 2022) : 1292. http://dx.doi.org/10.1149/ma2022-01291292mtgabs.
Texte intégralRésumé :
The isolation of a growing number of two-dimensional (2D) materials has inspired worldwide efforts to integrate distinct 2D materials into van der Waals (vdW) heterostructures. While a tremendous amount of research activity has occurred in assembling disparate 2D materials into “all-2D” van der Waals heterostructures and making outstanding progress on fundamental studies, practical applications of 2D materials will require a broader integration strategy. I will present our ongoing and recent work on integration of 2D materials with 3D electronic materials to realize logic switches and memory devices with novel functionality that can potentially augment the performance and functionality of Silicon technology. First, I will present our recent work on gate-tunable diode1 and tunnel junction devices2 based on integration of 2D chalcogenides with Si and GaN. Following this I will present our recent work on non-volatile memories based on Ferroelectric Field Effect Transistors (FE-FETs) made using a heterostructure of MoS2/AlScN3 and I also will present our work on Ferroelectric Diode (ferrodiode) devices4 also based on thin AlScN. If time permits, I will also cover our ongoing efforts in scaling FE-FETs based on MoS2 and AlScN to < 100 nm channel lengths over large areas and also discuss in-memory computing using ferrodiode devices and also touch upon our efforts in photonics and light trapping using 2D semiconductors. I will end by giving a broad perspective on future opportunities of 2D semiconductors in micro and nanoelectronics. References: Miao, J.; Liu, X.; Jo, K.; He, K.; Saxena, R.; Song, B.; Zhang, H.; He, J.; Han, M.-G.; Hu, W.; Jariwala, D. Nano Letters 2020, 20, (4), 2907-2915. Miao, J.; Leblanc, C.; Liu, X.; Song, B.; Zhang, H.; Krylyuk, S.; Davydov, A. V.; Back, T.; Glavin, N. R.; Jariwala, D.,2D Metal Selenide-Silicon Steep Sub-Threshold Heterojunction Triodes with High On-Current Density arXiv:2111.06396 Liu, X.; Wang, D.; Zheng, J.; Musavigharavi, P.; Miao, J.; Stach, E. A.; Olsson III, R. H.; Jariwala, D. Nano Letters 2021, 21, 3753–3761. Liu, X.; Zheng, J.; Wang, D.; Musavigharavi, P.; Stach, E. A.; Olsson III, R.; Jariwala, D. Applied Physics Letters 2021, 118, 202901
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RAO, M. C. « SCIENTIFIC APPROACH TO RENEWABLE ENERGY THROUGH SOLAR CELLS ». International Journal of Modern Physics : Conference Series 22 (janvier 2013) : 11–17. http://dx.doi.org/10.1142/s2010194513009860.
Texte intégralRésumé :
Renewable energy is increasingly viewed as critically important globally. Solar cells convert the energy of the sun into electricity. The method of converting solar energy to electricity is pollution free, and appears a good practical solution to the global energy problems. Energy policies have pushed for different technologies to decrease pollutant emissions and reduce global climate change. Photovoltaic technology, which utilizes sunlight to generate energy, is an attractive alternate energy source because it is renewable, harmless and domestically secure. Transparent conducting metal oxides, being n-type were used extensively in the production of heterojunction cells using p-type Cu 2 O . The long held consensus is that the best approach to improve cell efficiency in Cu 2 O -based photovoltaic devices is to achieve both p- and n-type Cu 2 O and thus p-n homojunction of Cu 2 O solar cells. Silicon, which, next to oxygen, is the most represented element in the earth's crust, is used for the production of monocrystalline silicon solar cells. Silicon is easily obtained and processed and it is not toxic and does not form compounds that would be environmentally harmful. In contemporary electronic industry silicon is the main semiconducting element. Thin-film cadmium telluride (CdTe) solar cells are the basis of a significant technology with major commercial impact on solar energy production. Polycrystalline thin-film solar cells such as CuInSe 2 (CIS), Cu (In, Ga) Se 2 (CIGS) and CdTe compound semiconductors are important for terrestrial applications because of their high efficiency, long-term stable performance and potential for low-cost production. Highest record efficiencies of 19.2% for CIGS and 16.5% for CdTe have been achieved.
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Murzin, Serguei P. « Formation of ZnO/CuO Heterostructures Based on Quasi-One-Dimensional Nanomaterials ». Applied Sciences 13, no 1 (30 décembre 2022) : 488. http://dx.doi.org/10.3390/app13010488.
Texte intégralRésumé :
Nanostructured metal oxides are of great interest both for advanced research and for a wide range of applications that contribute to the increasing demands of electronics, photonics, catalysis, sensorics, and other high-tech industries and are being actively researched and developed. One-dimensional nanocrystal arrays of copper and zinc oxides have become prominent in optoelectronic devices and energy conversion systems. However, although desirable improved properties have been demonstrated, the morphology of materials containing copper and zinc oxide nanowires is extremely sensitive to synthesis conditions and difficult to control. Studies focused on the morphology control of such quasi-one-dimensional materials are not numerous, so the consideration of this issue is still relevant. The characteristics of devices based on such oxide materials can be improved by taking advantage of nanoheterojunctions. A special feature is the possibility of forming a polycrystalline heterojunction in a system of semiconductors belonging to different crystalline syngonies. Currently, much attention is devoted to developing reliable methods of obtaining such nanomaterials, including those, based on processes exploiting novel physical effects. Possibilities of synthesis by pulse-periodic laser irradiation of arrays of quasi-one-dimensional ZnO nanostructures with varying micromorphology on metallic substrates, as well as the creation of ZnO/CuO heterostructures based on ZnO nanowires, were considered. The main distinguishing feature of this approach was the use of laser-induced vibrations to intensify diffusion processes in the solid phase of metallic materials as compared to the simple effects of laser beam heating. Expanding the area of application of the advanced method of creating oxide heterostructures requires a detailed and comprehensive study of new possibilities used to form structures with improved physical properties.
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Rahman, Md Wahidur, Chandan Joishi, Nidhin Kurian Kalarickal, Hyunsoo Lee et Siddharth Rajan. « High-Permittivity Dielectric for High-Performance Wide Bandgap Electronic Devices ». ECS Meeting Abstracts MA2022-02, no 32 (9 octobre 2022) : 1210. http://dx.doi.org/10.1149/ma2022-02321210mtgabs.
Texte intégralRésumé :
In this presentation, we will review recent work on the integration of high permittivity dielectrics with wide and and ultra-wide bandgap semiconductor devices to obtain improved high power and high frequency applications. We will first discuss the use of such structures for vertical power devices. The high permittivity dielectrics help to reduce surface fields and therefore prevent tunnel leakage from Schottky barriers [1]. Insertion of high permittivity dielectrics can also enable better field termination in high voltage vertical devices [2]. We will discuss recent results using such high permittivity dielectrics in vertical device structures based on Gallium Oxide, leading to high vertical electric fields up to 5.7 MV/cm being sustained in the structure. We will discuss the application of these high permittivity dielectrics for three-terminal high frequency [3] and high voltage [4,5] wide bandgap transistor applications. In lateral transistors built from wide and ultra-wide bandgap semiconductors, gate breakdown and non-uniform electric fields lead to average device breakdown fields that are significantly lower than material limits. We will show how high permittivity dielectrics inserted between the gate and drain can prevent gate breakdown, and also create much more uniform electric field profiles. An analytical model to explain this will be presented and compared with 2-dimensional device simulations. Finally, we will show experimental results for lateral devices from the high Al-composition AlGaN [6], -Ga2O3[7], and AlGaN/GaN [8] material systems, where in each case, we are able to achieve state-of-art breakdown performance for devices such as lateral Schottky diodes and transistors. For example, we have achieved up to 8.3 MV/cm field in high Al-content AlGaN devices, >5.5 MV/cm in -Ga2O3-based transistors, and >3 MV/cm lateral electric field in AlGaN/GaN HEMTs. The high breakdown fields also enable us to achieve state-of-art switching figures of merit in these devices. The authors acknowledge funding from NNSA ETI Consortium, AFOSR GAME MURI Program (Program Manager Dr. Ali Sayir), AFOSR (Program Manager Dr. Kenneth Goretta) NSF ECCS- and the DARPA DREAM program (Program Manger Dr. YK Chen), managed by ONR (Program Manager Dr. Paul Maki) for support of the work. References [1] Xia, Zhanbo, et al. "Metal/BaTiO3/β-Ga2O3 dielectric heterojunction diode with 5.7 MV/cm breakdown field." Applied Physics Letters 115.25 (2019): 252104. [2] Lee, Hyun-Soo, et al. "High-permittivity dielectric edge termination for vertical high voltage devices." Journal of Computational Electronics 19.4 (2020): 1538-1545. [3] Xia, Zhanbo, et al. "Design of transistors using high-permittivity materials." IEEE Transactions on Electron Devices 66.2 (2019): 896-900. [4] Kalarickal, Nidhin Kurian, et al. "Electrostatic engineering using extreme permittivity materials for ultra-wide bandgap semiconductor transistors." IEEE Transactions on Electron Devices 68.1 (2020): 29-35. [5] Hanawa, Hideyuki, et al. "Numerical Analysis of Breakdown Voltage Enhancement in AlGaN/GaN HEMTs With a High-k Passivation Layer." IEEE Transactions on Electron Devices 61.3 (2014): 769-775. [6] Razzak, Towhidur, et al. "BaTiO3/Al0. 58Ga0. 42N lateral heterojunction diodes with breakdown field exceeding 8 MV/cm." Applied Physics Letters 116.2 (2020): 023507. [7] Kalarickal, Nidhin Kurian, et al. "β-(Al0.18Ga0.82)2O3/Ga2O3 Double Heterojunction Transistor With Average Field of 5.5 MV/cm." IEEE Electron Device Letters 42.6 (2021): 899-902. [8] Rahman, Mohammad Wahidur, et al. "Hybrid BaTiO3/SiNx/AlGaN/GaN lateral Schottky barrier diodes with low turn-on and high breakdown performance." Applied Physics Letters 119.1 (2021): 013504.
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Swain, Gayatri, Sabiha Sultana, John Moma et Kulamani Parida. « Fabrication of Hierarchical Two-Dimensional MoS2 Nanoflowers Decorated upon Cubic CaIn2S4 Microflowers : Facile Approach To Construct Novel Metal-Free p–n Heterojunction Semiconductors with Superior Charge Separation Efficiency ». Inorganic Chemistry 57, no 16 (3 août 2018) : 10059–71. http://dx.doi.org/10.1021/acs.inorgchem.8b01221.
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Mizuno, Tomohisa, Naoki Mizoguchi, Kotaro Tanimoto, Tomoaki Yamauchi, Mitsuo Hasegawa, Toshiyuki Sameshima et Tsutomu Tezuka. « New Source Heterojunction Structures with Relaxed/Strained Semiconductors for Quasi-Ballistic Complementary Metal–Oxide–Semiconductor Transistors : Relaxation Technique of Strained Substrates and Design of Sub-10 nm Devices ». Japanese Journal of Applied Physics 49, no 4 (20 avril 2010) : 04DC13. http://dx.doi.org/10.1143/jjap.49.04dc13.
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Debasis Mukherjee, Rajkumar Mandal,. « Design and Performance Assessment of Split Gate Dielectric Modulated Junction less TFET Variation of Hfo2 by the Divided Gate Insulator for High Sensitivity Using Tcad Simulation ». Mathematical Statistician and Engineering Applications 71, no 4 (31 décembre 2022) : 9068–81. http://dx.doi.org/10.17762/msea.v71i4.1672.
Texte intégralRésumé :
A number of more recent discoveries in microbiology have made reliable identification of nano-biomolecules and extensive analyses of them necessary. A variety of proteins, including DNA, biotin-streptavidin, amino acids, as well as many types of bacteria and viruses, must be found and analyzed in order to fully comprehend any odd behavior occurring inside of live cells. Rapid testing and detection are essential steps in preventing undiscovered biohazards from eradicating the human race and other terrestrial living things. Since many decades ago, developing an accurate, affordable biosensor has been a struggle for scientists [1]. When compared to pricey laboratory-based sensors and detection methods, FET-based lab-on-chip nano biosensors appear to be a promising substitute. It is significantly more dependable than conventional bulk sensors because of its size, affordability, low power consumption, resilience, faster response time, and better sensitivity [1]. Due to their precision, adaptability, and compatibility with embedded systems, dielectrically modulated FET biosensors with Nano cavities are emerging as a promising research area that can yield useful data on bio-analyses. As an alternative to conventionally doped TFET devices, using a charge plasma SiGe-heterojunction double gate TFET, a label-free biosensor can be produced, bypassing the need for conventional semiconductors, which require a large thermal budget and are susceptible to random dopant fluctuations (RDFs). The effect of changing the dielectric constant (k), the positive and negative charge density, the gate work function, and the cavity size has been investigated to better understand how these factors affect the performance of the proposed biosensor. These parameters modify the biosensor's electric characteristics, improving detection [2]. There is also discussion of how these factors influence the device's drain current, electric field, surface potential, sub-threshold swing (SS), insulator-to-metal film (ION/IOFF) ratio, and electron tunneling rate (ETR). The sensitivity of the drain current in the proposed biosensor is also investigated. There is no restriction on whether or whether the proposed structure is used for charged or neutral molecules.Under lower supply voltages, it is discovered that the SG-DM current JLFET's sensitivity is high, measuring 1.2 *10^3, with a potential sensitivity of 1.4 V. A result, the SG-DM [2] JLFET exhibits good application potential while consuming little power and having ahigh sensitivity.
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Kuschev, Sergei B., Liana Yu Leonova, Anatoly N. Latyshev, Oleg V. Ovchinnikov et Elena V. Popova. « APPLICATION OF LUMINESCENCE AND ABSORPTION SPECTRA TO CONTROL THE FORMATION OF A HETEROJUNCTION IN NANOSTRUCTURED RUTILE FILMS SENSITIZED BY CDS QUANTUM DOTS ». Kondensirovannye sredy i mezhfaznye granitsy = Condensed Matter and Interphases 21, no 3 (26 septembre 2019) : 399–405. http://dx.doi.org/10.17308/kcmf.2019.21/1147.
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The effect of photon processing (FO) on the formation of a heterojunction in the TiO2/QD’sCdS interface obtained by applying separately synthesized CdS quantum dots to the TiO2 film in the rutile phase has been studied. The changes of luminescence spectra and absorption of the investigated samples after this treatment discovered. It is shown that the separation of charge carriers occurs only after irradiation of samples with a powerful light pulse of a xenon lamp.
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Yang, Li, Jian-Ping Zhou, Qi-Wen Chen et Hong-Dan Yang. « Direct observation of carrier migration in heterojunctions to discuss the p-n and direct Z-scheme heterojunctions ». Nanotechnology, 11 juillet 2022. http://dx.doi.org/10.1088/1361-6528/ac800e.
Texte intégralRésumé :
Abstract Type II p-n heterojunction and direct Z-scheme heterojunction are identical staggered band alignments, but were reported ambiguously in many composite photocatalysts because their carriers migrate in opposite directions. In this research, metal oxides CuO, NiO and Co3O4-based heterojunctions with Na0.9Mg0.45Ti3.55O8 (NMTO) were synthesized via a simple hydrothermal method. The CuO/NMTO heterojunction was demonstrated as a direct Z-scheme heterojunction, whereas the NiO/NMTO and Co3O4/NMTO heterojunctions showed type II p-n band alignment, distinguished by the direct observation of carrier migration under light illumination, and confirmed by the X-ray photoelectron spectroscopy, Mott-Schottky measurements, ultraviolet photoelectron spectra and capture experiments. These all heterojunctions enjoyed better photocatalytic performance to degrade methylene blue and antibiotics (Enrofloxacin, Metronidazole and tetracycline) than the pure NMTO, attributed to their effective separation of the photoinduced electron-hole pairs owing to the staggered band alignment. Prominently, the NiO/NMTO and Co3O4/NMTO p-n heterojunctions exhibited superior degradation ability to the CuO/NMTO Z-scheme heterojunction. The initial relative Fermi position of two semiconductors is the prerequisite to determine whether the p-n heterojunction or direct Z-scheme heterojunction is built because the electrons diffuse from one semiconductor with a higher Fermi level to another with a lower Fermi level while the holes diffuse reversely until a united Fermi level when they combine. The built-in electric field at the heterojunction interface is determined by the difference in the initial Fermi levels or work functions of two semiconductors, regulating the separation ability of photogenerated electrons and holes to affect the photocatalytic performance. Thus, the high difference in the initial Fermi levels of semiconductors is crucial in the development of heterojunctions with staggered band alignment to obtain high performance in photocatalytic reactions.