Showing papers on "Atomic layer deposition published in 2019"
TL;DR: In this paper, the double buffer layer of Cd-free Cu(In,Ga)(Se,S)2 (CIGSSe) solar cells with Zn(O,S,OH) x /Zn0.8Mg0.2O double buffer layers, deposited by a combination of chemical bath deposition and atomic layer deposition techniques, is presented.
Abstract: In this article, the excellent properties of state-of-the-art Cd-free Cu(In,Ga)(Se,S)2 (CIGSSe) solar cells with Zn(O,S,OH) x /Zn0.8Mg0.2O double buffer layers, deposited by a combination of chemical bath deposition and atomic layer deposition techniques, are presented. By the replacement of conventional CdS buffer layers with this double buffer layer, the open-circuit voltage ( V oc) deficit of the devices could be significantly reduced, and V oc increased by approximately 15 mV. In addition, the fill factor and short-circuit current were also improved, increasing the device efficiency by approximately 0.5 absolute percent compared with devices with CdS buffers. The Cd-free double buffer layer improved the device efficiency regardless of the bandgap of the CIGSSe absorber. The minority carrier lifetime ( τ ) measured via time-resolved photoluminescence became longer, indicating that carrier recombination is mitigated using the double buffer layer. Based on the device parameters extracted by fitting the Suns– V oc characteristics to the double-diode model, the longer τ could be attributed to the decreased recombination rate in the space-charge region, rather than in the bulk and at the interface. The best performing cell was evaluated by a reliable third party, the National Institute of Advanced Industrial Science and Technology; this cell achieved a new world record efficiency of 23.35% for 1-cm2-sized thin-film polycrystalline solar cells. The device parameters of this cell are also discussed in this article.
765 citations
TL;DR: Pt-Ru bimetallic dimer structures are prepared through atomic layer deposition process and the roles of Pt and Ru in hydrogen evolution reaction are identified.
Abstract: Single atom catalysts exhibit particularly high catalytic activities in contrast to regular nanomaterial-based catalysts. Until recently, research has been mostly focused on single atom catalysts, and it remains a great challenge to synthesize bimetallic dimer structures. Herein, we successfully prepare high-quality one-to-one A-B bimetallic dimer structures (Pt-Ru dimers) through an atomic layer deposition (ALD) process. The Pt-Ru dimers show much higher hydrogen evolution activity (more than 50 times) and excellent stability compared to commercial Pt/C catalysts. X-ray absorption spectroscopy indicates that the Pt-Ru dimers structure model contains one Pt-Ru bonding configuration. First principle calculations reveal that the Pt-Ru dimer generates a synergy effect by modulating the electronic structure, which results in the enhanced hydrogen evolution activity. This work paves the way for the rational design of bimetallic dimers with good activity and stability, which have a great potential to be applied in various catalytic reactions. Atomically precise control over elemental distributions presents a challenge in the preparation of catalytic nanomaterials. Here the authors report Pt-Ru bimetallic dimer structures through atomic layer deposition process and identify the roles of Pt and Ru in hydrogen evolution reaction.
307 citations
TL;DR: In this paper, a nucleation layer consisting of an ultra-thin polymer with nucleophilic hydroxyl and amine functional groups was used to nucleate a conformal, low-conductivity aluminum zinc oxide layer by atomic layer deposition (ALD).
294 citations
01 Dec 2019
TL;DR: In this paper, a two-dimensional indium selenide (α-In2Se3) channel material was used as the channel material in the device, and a passivation method based on the atomic layer deposition of aluminium oxide (Al2O3) was developed.
Abstract: Ferroelectric field-effect transistors employ a ferroelectric material as a gate insulator, the polarization state of which can be detected using the channel conductance of the device. As a result, the devices are potentially of use in non-volatile memory technology, but they suffer from short retention times, which limits their wider application. Here, we report a ferroelectric semiconductor field-effect transistor in which a two-dimensional ferroelectric semiconductor, indium selenide (α-In2Se3), is used as the channel material in the device. α-In2Se3 was chosen due to its appropriate bandgap, room-temperature ferroelectricity, ability to maintain ferroelectricity down to a few atomic layers and its potential for large-area growth. A passivation method based on the atomic layer deposition of aluminium oxide (Al2O3) was developed to protect and enhance the performance of the transistors. With 15-nm-thick hafnium oxide (HfO2) as a scaled gate dielectric, the resulting devices offer high performance with a large memory window, a high on/off ratio of over 108, a maximum on current of 862 μA μm−1 and a low supply voltage. A ferroelectric semiconductor field-effect transistor, which uses the two-dimensional ferroelectric semiconductor α-In2Se3 as a channel material, could offer enhanced capabilities compared with conventional ferroelectric field-effect transistors in non-volatile memory applications.
250 citations
TL;DR: This review introduces the progress made in ALD, both for computational and experimental methodologies, and provides an outlook of this emerging technology in comparison with other film deposition methods.
245 citations
TL;DR: In this paper, the authors present a review of the current status of knowledge about the conformality of ALD processes, including an overview of relevant gas transport regimes, definitions of exposure and sticking probability, and a distinction between different ALD growth types observed in high aspect ratio structures.
Abstract: Atomic layer deposition (ALD) relies on alternated, self-limiting reactions between gaseous reactants and an exposed solid surface to deposit highly conformal coatings with a thickness controlled at the submonolayer level. These advantages have rendered ALD a mainstream technique in microelectronics and have triggered growing interest in ALD for a variety of nanotechnology applications, including energy technologies. Often, the choice for ALD is related to the need for a conformal coating on a 3D nanostructured surface, making the conformality of ALD processes a key factor in actual applications. In this work, we aim to review the current status of knowledge about the conformality of ALD processes. We describe the basic concepts related to the conformality of ALD, including an overview of relevant gas transport regimes, definitions of exposure and sticking probability, and a distinction between different ALD growth types observed in high aspect ratio structures. In addition, aiming for a more standardized and direct comparison of reported results concerning the conformality of ALD processes, we propose a new concept, Equivalent Aspect Ratio (EAR), to describe 3D substrates and introduce standard ways to express thin film conformality. Other than the conventional aspect ratio, the EAR provides a measure for the ease of coatability by referring to a cylindrical hole as the reference structure. The different types of high aspect ratio structures and characterization approaches that have been used for quantifying the conformality of ALD processes are reviewed. The published experimental data on the conformality of thermal, plasma-enhanced, and ozone-based ALD processes are tabulated and discussed. Besides discussing the experimental results of conformality of ALD, we will also give an overview of the reported models for simulating the conformality of ALD. The different classes of models are discussed with special attention for the key assumptions typically used in the different modelling approaches. The influence of certain assumptions on simulated deposition thickness profiles is illustrated and discussed with the aim of shedding light on how deposition thickness profiles can provide insights into factors governing the surface chemistry of ALD processes. We hope that this review can serve as a starting point and reference work for new and expert researchers interested in the conformality of ALD and, at the same time, will trigger new research to further improve our understanding of this famous characteristic of ALD processes.
228 citations
TL;DR: This Perspective provides an overview of the current developments in the field of area-selective ALD, discusses the challenge of achieving a high selectivity, and provides a vision for how area- selective ALD processes can be improved.
Abstract: Bottom-up nanofabrication by area-selective atomic layer deposition (ALD) is currently gaining momentum in semiconductor processing, because of the increasing need for eliminating the edge placement errors of top-down processing. Moreover, area-selective ALD offers new opportunities in many other areas such as the synthesis of catalysts with atomic-level control. This Perspective provides an overview of the current developments in the field of area-selective ALD, discusses the challenge of achieving a high selectivity, and provides a vision for how area-selective ALD processes can be improved. A general cause for the loss of selectivity during deposition is that the character of surfaces on which no deposition should take place changes when it is exposed to the ALD chemistry. A solution is to implement correction steps during ALD involving for example surface functionalization or selective etching. This leads to the development of advanced ALD cycles by combining conventional two-step ALD cycles with correction steps in multistep cycle and/or supercycle recipes.
200 citations
01 Dec 2019
TL;DR: In this paper, the atomic layer deposition of high-κ gate dielectrics on two-dimensional semiconductors using a monolayer molecular crystal as a seeding layer was reported.
Abstract: Two-dimensional semiconductors could be used as a channel material in low-power transistors, but the deposition of high-quality, ultrathin high-κ dielectrics on such materials has proved challenging. In particular, atomic layer deposition typically leads to non-uniform nucleation and island formation, creating a porous dielectric layer that suffers from current leakage, particularly when the equivalent oxide thickness is small. Here, we report the atomic layer deposition of high-κ gate dielectrics on two-dimensional semiconductors using a monolayer molecular crystal as a seeding layer. The approach can be used to grow dielectrics with an equivalent oxide thickness of 1 nm on graphene, molybdenum disulfide (MoS2) and tungsten diselenide (WSe2). Compared with dielectrics created using established methods, our dielectrics exhibit a reduced roughness, density of interface states and leakage current, as well as an improved breakdown field. With the technique, we fabricate graphene radio-frequency transistors that operate at 60 GHz, and MoS2 and WSe2 complementary metal–oxide–semiconductor transistors with a supply voltage of 0.8 V and subthreshold swing down to 60 mV dec−1. We also create MoS2 transistors with a channel length of 20 nm, which exhibit an on/off ratio of over 107. Using a monolayer molecular crystal as a seeding layer, hafnium oxide dielectrics with an equivalent oxide thickness of only 1 nm can be deposited on graphene, molybdenum disulfide and tungsten diselenide.
160 citations
TL;DR: In the past decade, atomic layer deposition (ALD) has become an important thin film deposition technique for applications in nanoelectronics, catalysis, and other areas due to its high conformality as discussed by the authors.
Abstract: In the past decade, atomic layer deposition (ALD) has become an important thin film deposition technique for applications in nanoelectronics, catalysis, and other areas due to its high conformality...
149 citations
TL;DR: In this article, an excellent photoanode of black BiVO4@amorphous TiO2−x to tackle the problem of wide bandgap and poor photostability is reported.
Abstract: Recent advances in solar water splitting by using BiVO4 as a photoanode have greatly optimized charge carrier and reaction dynamics, but relatively wide bandgap and poor photostability are still bottlenecks. Here, an excellent photoanode of black BiVO4@amorphous TiO2−x to tackle both problems is reported. Its applied bias photon‐to‐current efficiency for solar water splitting is up to 2.5%, which is a new record for a single oxide photon absorber. This unique core–shell structure is fabricated by coating amorphous TiO2 on nanoporous BiVO4 with the aid of atomic layer deposition and further hydrogen plasma treatment at room temperature. The black BiVO4 with moderate oxygen vacancies reveals a bandgap reduction of ≈0.3 eV and significantly enhances solar utilization, charge transport and separation simultaneously, compared with conventional BiVO4. The amorphous layer of TiO2−x acts as both oxygen‐evolution catalyst and protection layer, which suppresses anodic photocorrosion to stabilize black BiVO4. This configuration of black BiVO4@amorphous TiO2−x may provide an effective strategy to prompt solar water splitting toward practical applications.
141 citations
TL;DR: Recently, cuprous oxide (Cu2O) based photocathodes have gained research attention for hydrogen (H2) production through photoelectrochemical (PEC) water splitting reactions due to marginally lower synthesis cost and low energy intensity fabrication processes as mentioned in this paper.
TL;DR: In this article, the authors describe the fabrication of a heterojunction photoelectrode by combining the wet chemical synthesis of Bi2WO6 with the formation of Fe2O3 layer by atomic layer deposition (ALD) technique.
Abstract: The present paper describes the fabrication of a heterojunction photoelectrode by combining the wet chemical synthesis of Bi2WO6 with the formation of Fe2O3 layer by atomic layer deposition (ALD) technique. Fe2O3 with different atomic thicknesses was layered onto spin-coated Bi2WO6 nanoflakes by controlling the number of deposition cycles. The influence of the thickness of the Fe2O3 layers on photoelectrocatalytic detection and remediation was also studied. The deposition of a 15-nm layer of Fe2O3 on Bi2WO6 led to the best photoelectrochemical response under visible light activation. The performance of 15-nm Fe2O3–Bi2WO6 (4.3 μA/cm2) was 3.6 times higher than that of pristine Bi2WO6 (1.2 μA/cm2) at an external bias of 0.6 V. The enhanced performance was due to the increased spectral breadth of light absorption and efficient transfer of photogenerated charge carriers by the suppression of electron–hole pairs. The optimized photoelectrode detected tetracycline antibiotic in aqueous solution with a 0.3 μM limit of detection and photoelectrocatalytically degraded around 95% tetracycline. The heterojunction photoelectrode structure prepared using ALD enables inexpensive, non-enzymatic, amperometric determination and degradation of tetracycline in a stable and reproducible manner via a deduced mechanism. Our strategy can be used to fabricate photoelectrodes for a wide range of applications.
TL;DR: A review of the status and prospects of plasma-assisted ALD with a focus on the developments since the publication of the review by Profijt et al. as mentioned in this paper is provided.
Abstract: Processing at the atomic scale is becoming increasingly critical for state-of-the-art electronic devices for computing and data storage, but also for emerging technologies such as related to the internet-of-things, artificial intelligence, and quantum computing. To this end, strong interest in improving nanoscale fabrication techniques such as atomic layer deposition (ALD) has been present. New ALD processes are being sought continuously and particularly plasma-assisted processes are considered an enabler for a wide range of applications because of their enhanced reactivity. This review provides an update on the status and prospects of plasma-assisted ALD with a focus on the developments since the publication of the review by Profijt et al. [J. Vac. Sci. Technol. A 29, 050801 (2011)]. In the past few years, plasma ALD has obtained a prominent position in the field of ALD with (i) a strong application base as demonstrated by the breakthrough in high-volume manufacturing; (ii) a large number of established processes, out of which several are being enabled by the plasma step; and (iii) a wide range of plasma ALD reactor designs, demonstrating many methods by which plasma species can be applied in ALD processes. In addition, new fundamental insights have been obtained, for instance, with respect to plasma damage, on the effect of ions on the material properties and on the so-called redeposition effect. Regarding new and emerging developments, plasma ALD is expected to take a prominent position in the atomic-scale processing toolbox and will contribute to ongoing developments in area-selective deposition, controlled growth of 2D materials, and atomic layer etching.
TL;DR: In this paper, a novel type of sensor device, based on ZnO nanowires (NWs) coated with a thin layer of boron nitride (BN) decorated with palladium nanoparticles (NPs) was proposed.
Abstract: High selectivity and sensitivity were measured using a novel type of sensor device, based on ZnO nanowires (NWs) coated with a thin layer of boron nitride (BN) decorated with palladium nanoparticles (NPs). Vapor–Liquid–Solid (VLS) growth and Atomic Layer Deposition (ALD) routes, two scalable technologies, have been used for the synthesis of the sensing device nanomaterials. X-Ray Photoelectron Spectroscopy (XPS), Electron Energy Loss Spectroscopy (EELS), Energy-dispersive X-ray (EDX) spectroscopy and Transmission Electron Microscopy (TEM) studies revealed the presence of both the 5 nm layer of BN and metallic Pd NPs around the ZnO NWs. The nanomaterials were then integrated within a miniaturized sensor device in order to measure their performance for H2 detection at different concentrations and temperatures, in the presence of various gases such as C6H6, C7H8, C2H5OH, and CH3COCH3. High hydrogen response signals of 12.28 (±0.61) have been measured, even for H2 concentrations as low as 10 ppm, confirming the efficiency of the novel designed Pd/BN/ZnO NW sensor. Due to the beneficial synergistic effect of ZnO, BN and Pd nanomaterials, the new sensing device clearly outperformed other sensors based on ZnO NWs. In addition, the sensor was resistant to humidity, and hydrogen gas could be detected for concentrations as low as 0.5 ppm. The high performance obtained with the novel Pd/BN/ZnO NW based sensor along with its easy gas phase processing opens new perspectives and opportunities for the sensing community and will hopefully promote the hydrogen economy.
TL;DR: In this paper, a full-color display based on micro light-emitting diodes (μLEDs) can be fabricated on monolithic epitaxial wafers.
Abstract: Full-color displays based on micro light-emitting diodes (μLEDs) can be fabricated on monolithic epitaxial wafers. Nanoring (NR) structures were fabricated on a green LED epitaxial wafer; the color of NR-μLEDs was tuned from green to blue through strain relaxation. An Al2O3 layer was deposited on the sidewall of NR-μLEDs, which improved the photoluminescence intensity by 143.7%. Coupling with the exposed multiple quantum wells through nonradiative resonant energy transfer, red quantum dots were printed to NR-μLEDs for a full-color display. To further improve the color purity of the red light, a distributed Bragg reflector is developed to reuse the excitation light.
TL;DR: In this article, area-selective atomic layer deposition (ALD) is proposed as a bottom-up alternative to current nanopatterning techniques, and self-assembled monolayers have been successfully employed as deactors.
Abstract: Area-selective atomic layer deposition (AS-ALD) is a promising “bottom-up” alternative to current nanopatterning techniques. Self-assembled monolayers (SAM) have been successfully employed as deact...
TL;DR: Results reveal the unique structural characteristic of Al2O3 overlayers on metal surfaces coated by ALD method and provide a practical strategy to explore stable and efficient supported Pd catalysts for methane combustion.
Abstract: Supported Pd catalysts are active in catalyzing the highly exothermic methane combustion reaction but tend to be deactivated owing to local hyperthermal environments. Herein we report an effective approach to stabilize Pd/SiO2 catalysts with porous Al2 O3 overlayers coated by atomic layer deposition (ALD). 27 Al magic angle spinning NMR analysis showed that Al2 O3 overlayers on Pd particles coated by the ALD method are rich in pentacoordinated Al3+ sites capable of strongly interacting with adjacent surface PdOx phases on supported Pd particles. Consequently, Al2 O3 -decorated Pd/SiO2 catalysts exhibit active and stable PdOx and Pd-PdOx structures to efficiently catalyze methane combustion between 200 and 850 °C. These results reveal the unique structural characteristics of Al2 O3 overlayers on metal surfaces coated by the ALD method and provide a practical strategy to explore stable and efficient supported Pd catalysts for methane combustion.
TL;DR: In this article, an oxide-based surface modification with precise thickness control at an atomic level for enhanced electrochemical performance of Ni-rich cathode materials at extended voltage ranges was proposed.
Abstract: Ni-rich LiNi0.8Co0.1Mn0.1O2 oxide has been modified by ultrathin Al2O3 coatings via atomic layer deposition (ALD) at a growth rate of 1.12 A/cycle. All characterizations results including TEM, SEM, XRD and XPS together confirm high conformality and uniformity of the resultant Al2O3 layer on the surface of LiNi0.8Co0.1Mn0.1O2 particles. Coating thickness of the Al2O3 layer is optimized at ~2 nm, corresponding to 20 ALD cycles to enhance the electrochemical performance of Ni-rich cathode materials at extended voltage ranges. As a result, 20 Al2O3 ALD-coated LiNi0.8Co0.1Mn0.1O2 cathode material can deliver an initial discharge capacity of 212.8 mAh/g, and an associated coulombic efficiency of 84.0% at 0.1 C in a broad voltage range of 2.7–4.6 V vs. Li+/Li in the first cycle, which were both higher than 198.2 mAh/g and 76.1% of the pristine LiNi0.8Co0.1Mn0.1O2 without the Al2O3 protection. Comparative differential capacity (dQ/dV) profiles and electrochemical impedance spectra (EIS) recorded in the first and 100th cycles indicated significant Al2O3 ALD coating effects on suppressing phase transitions and electrochemical polarity of the Ni-rich LiNi0.8Co0.1Mn0.1O2 core during reversible lithiation/delithiation. This work offers oxide-based surface modifications with precise thickness control at an atomic level for enhanced electrochemical performance of Ni-rich cathode materials at extended voltage ranges.
TL;DR: In this paper, a Cd-free Cu2ZnSnS4 (CZTS) solar cell with an aluminum oxide (Al2O3) passivation layer prepared by atomic layer deposition (ALD) is reported.
Abstract: Environmentally friendly earth-abundant Cd-free Cu2ZnSnS4 (CZTS) solar cells have recently achieved increasing power conversion efficiency by using ZnSnO as the buffer layer. However, the large open circuit voltage (Voc) deficit remains the key concern. Here, we report a Cd-free CZTS solar cell that exhibits an energy conversion efficiency of 10.2% resulting from the application of an aluminium oxide (Al2O3) passivation layer prepared by atomic layer deposition (ALD). We found that the application of full ALD cycles as well as trimethylaluminum (TMA) exposures resulted in a significant increase in Voc and relate this to the properties of the CZTS interface. Both processes facilitate the formation of a thicker Cu-deficient nanolayer with a higher concentration of Na and O, forming a homogeneous passivation layer across the CZTS surface. This nanolayer reduces the local potential fluctuation of band edges and leads to the widened electrical band gap and suppressed defects recombination at the heterojunction interface, thus improvement in Voc and device performance. The ability of nanolayers to alter the atomic composition in the near surface region of compound semiconductors might be beneficial for a wider range of semiconductor devices.
TL;DR: In this article, a surface modification method was proposed to enhance the interface stability of hard carbon anodes for high-performance sodium-ion batteries by using an artificial solid electrolyte interface (SEI).
TL;DR: By assistance of an atomic layer deposition (ALD) technique, CsPbBr3 perovskite thin films with preferred orientation and enlarged grain size are obtained on predeposited interfacial modification layers and are integrated into a visible light communication system as a light receiver on transmitting texts.
Abstract: Self-powered photodetectors (PDs) based on inorganic metal halide perovskites are regarded as promising alternatives for the next generation of photodetectors. However, uncontrollable film growth and sluggish charge extraction at interfaces directly limit the sensitivity and response speed of perovskite-based photodetectors. Herein, by assistance of an atomic layer deposition (ALD) technique, CsPbBr3 perovskite thin films with preferred orientation and enlarged grain size are obtained on predeposited interfacial modification layers. Thanks to improved film quality and double side interfacial engineering, the optimized CsPbBr3 (Al2 O3 /CsPbBr3 /TiO2 , ACT) perovskite PDs exhibit outstanding performance with ultralow dark current of 10-11 A, high detectivity of 1.88 × 1013 Jones and broad linear dynamic range (LDR) of 172.7 dB. Significantly, excellent long-term environmental stability (ambient conditions >100 d) and flexibility stability (>3000 cycles) are also achieved. The remarkable performance is credited to the synergistic effects of high carrier conductivity and collection efficiency, which is assisted by ALD modification layers. Finally, the ACT PDs are successfully integrated into a visible light communication system as a light receiver on transmitting texts, showing a bit rate as high as 100 kbps. These results open the window of high performance all-inorganic halide perovskite photodetectors and extends to rational applications for optical communication.
TL;DR: Low-temperature atomic layer deposition of Al2O3 on practical, ready-to-use composite cathodes of NCM622 (60% Ni), a technologically important material for lithium-ion battery applications, shows significantly improved retention and performance and the surface of the latter is found to be corroded to a much greater extent.
Abstract: Conformal coating of nm-thick Al2O3 layers on electrode material is an effective strategy for improving the longevity of rechargeable batteries. However, solid understanding of how and why surface coatings work the way they do has yet to be established. In this article, we report on low-temperature atomic layer deposition (ALD) of Al2O3 on practical, ready-to-use composite cathodes of NCM622 (60% Ni), a technologically important material for lithium-ion battery applications. Capacity retention and performance of Al2O3-coated cathodes (≤10 ALD growth cycles) are significantly improved over uncoated NCM622 reference cathodes, even under moderate cycling conditions. Notably, the Al2O3 surface shell is preserved after cycling in full-cell configuration for 1400 cycles as revealed by advanced electron microscopy and elemental mapping. While there are no significant differences in terms of bulk lattice structure and transition-metal leaching among the coated and uncoated NCM622 materials, the surface of the latter is found to be corroded to a much greater extent. In particular, detachment of active material from the secondary particles and side reactions with the electrolyte appear to lower the electrochemical activity, thereby leading to accelerated capacity degradation.
TL;DR: This strategy offers a new avenue for developing a new-generation high-energy, ultrahigh stable supercapacitor for real-life applications through atomic layer deposition (ALD) and nitrogen plasma.
Abstract: The large-scale application of supercapacitors (SCs) for portable electronics is restricted by low energy density and cycling stability. To alleviate the limitations, a unique interface engineering strategy is suggested through atomic layer deposition (ALD) and nitrogen plasma. First, commercial carbon cloth (CC) is treated with nitrogen plasma and later inorganic NiCo2 O4 (NCO)/NiO core-shell nanowire arrays are deposited on nitrogen plasma-treated CC (NCC) to fabricate the ultrahigh stable SC. An ultrathin layer of NiO deposited on the NCO nanowire arrays via conformal ALD plays a vital role in stabilizing the NCO nanowires for thousands of electrochemical cycles. The optimized NCC/NCO/NiO core-shell electrode exhibits a high specific capacitance of 2439 F g-1 with a remarkable cycling stability (94.2% over 20 000 cycles). Benefiting from these integrated merits, the foldable solid-state SCs are fabricated with excellent NCC/NCO/NiO core-shell nanowire array electrodes. The fabricated SC device delivers a high energy density of 72.32 Wh kg-1 at a specific capacitance of 578 F g-1 , with ultrasmall capacitance decline rate of 0.0003% per cycle over 10 000 charge-discharge cycles. Overall, this strategy offers a new avenue for developing a new-generation high-energy, ultrahigh stable supercapacitor for real-life applications.
Posted Content•
TL;DR: In this article, transparent Al 2 O 3 films with different thicknesses, deposited by using atomic layer deposition (ALD), were utilized as buffer layers between the front electrode transparent conductive oxide (TCO) and CdS layers to solve this problem.
Abstract: The application of thinner cadmium sulfide (CdS) window layer is a feasible approach to improve the performance of cadmium telluride (CdTe) thin film solar cells. However, the reduction of compactness and continuity of thinner CdS always deteriorates the device performance. In this work, transparent Al 2 O 3 films with different thicknesses, deposited by using atomic layer deposition (ALD), were utilized as buffer layers between the front electrode transparent conductive oxide (TCO) and CdS layers to solve this problem, and then, thin-film solar cells with a structure of TCO/Al 2 O 3 /CdS/CdTe/BC/Ni were fabricated. The characteristics of the ALD-Al 2 O 3 films were studied by UV–visible transmittance spectrum, Raman spectroscopy, and atomic force microscopy (AFM). The light and dark J–V performances of solar cells were also measured by specific instrumentations. The transmittance measurement conducted on the TCO/Al 2 O 3 films verified that the transmittance of TCO/Al 2 O 3 were comparable to that of single TCO layer, meaning that no extra absorption loss occurred when Al 2 O 3 buffer layers were introduced into cells. Furthermore, due to the advantages of the ALD method, the ALD-Al 2 O 3 buffer layers formed an extremely continuous and uniform coverage on the substrates to effectively fill and block the tiny leakage channels in CdS/CdTe polycrystalline films and improve the characteristics of the interface between TCO and CdS. However, as the thickness of alumina increased, the negative effects of cells were gradually exposed, especially the increase of the series resistance (R s ) and the more serious “roll-over” phenomenon. Finally, the cell conversion efficiency (η) of more than 13.0% accompanied by optimized uniformity performances was successfully achieved corresponding to the 10 nm thick ALD-Al 2 O 3 thin film.
TL;DR: Si photocathodes integrated with Ag-supported dendritic Cu catalysts are used to perform light-driven reduction of CO2 to C2 and C3 products in aqueous solution.
Abstract: Si photocathodes integrated with Ag-supported dendritic Cu catalysts are used to perform light-driven reduction of CO2 to C2 and C3 products in aqueous solution. A back illumination geometry with an n-type Si absorber was used to permit the use of absorbing metallic catalysts. Selective carrier collection was accomplished by a p+ implantation on the illumination side and an n+ implantation followed by atomic layer deposition of TiO2 on the electrolyte site. The Ag-supported dendritic Cu CO2 reduction catalyst was formed by evaporation of Ag followed by high-rate electrodeposition of Cu to form a high surface area structure. Under simulated 1 sun illumination in 0.1 M CsHCO3 saturated with CO2, the photovoltage generated by the Si (∼600 mV) enables C2 and C3 products to be produced at −0.4 vs. RHE. Texturing of both sides of the Si increases the light-limited current density, due to reduced reflection on the illumination side, and also deceases the onset potential. Under simulated diurnal illumination conditions photocathodes maintain over 60% faradaic efficiency to hydrocarbon and oxygenate products (mainly ethylene, ethanol, propanol) for several days. After 10 days of testing, contamination from the counter electrode is observed, which causes an increase in hydrogen production. This effect is mitigated by a regeneration procedure which restores the original catalyst selectivity. A tandem, self-powered CO2 reduction device was formed by coupling a Si photocathode with two series-connected semitransparent CH3NH3PbI3 perovskite solar cells, achieving an efficiency for the conversion of sunlight to hydrocarbons and oxygenates of 1.5% (3.5% for all products).
TL;DR: In this article, the utilization of ALD for the functionalization of anodic anodic TiO2 nanotube (TNT) layers by secondary materials to advance their physicochemical and photoelectrochemical properties is reviewed.
TL;DR: This work introduces a general colloidal atomic layer deposition (c-ALD) synthesis to grow an alumina shell with tunable thickness around nanocrystalline cores of various compositions spanning from ionic semiconductors to metal oxides and metals.
Abstract: The ability to tune thin oxide coatings by wet-chemistry is desirable for many applications, yet it remains a key synthetic challenge. In this work, we introduce a general colloidal atomic layer deposition (c-ALD) synthesis to grow an alumina shell with tunable thickness around nanocrystalline cores of various compositions spanning from ionic semiconductors (i.e., CsPbX3, with X = Br, I, Cl) to metal oxides and metals (i.e., CeO2 and Ag). The distinctive characteristics of each core (i.e., emission, facile surface functionalization, stability) allowed us to optimize and to elucidate the chemistry of the c-ALD process. Compared to gas-phase ALD, this newly developed synthesis has the advantage of preserving the colloidal stability of the nanocrystalline core while controlling the shell thickness from 1 to 6 nm. As one example of the opportunities offered by the growth of a thin oxide shell, we study the anion exchange reaction in the CsPbX3 perovskites nanocrystals by in situ X-ray diffraction, which had been impeded so far by the instability of this class of materials and by the fast exchange kinetics.
TL;DR: A number of applications are presented, a path forward, including likely near-term commercial products, is given, and a short early history of particle ALD is given.
Abstract: The functionalization of fine primary particles by atomic layer deposition (particle ALD) provides for nearly perfect nanothick films to be deposited conformally on both external and internal particle surfaces, including nanoparticle surfaces. Film thickness is easily controlled from several angstroms to nanometers by the number of self-limiting surface reactions that are carried out sequentially. Films can be continuous or semi-continuous. This review starts with a short early history of particle ALD. The discussion includes agitated reactor processing, both atomic and molecular layer deposition (MLD), coating of both inorganic and polymer particles, nanoparticles, and nanotubes. A number of applications are presented, and a path forward, including likely near-term commercial products, is given.
TL;DR: In this paper, hollow p-CuO/n-ZnO nanofibers with controllable compositions were successfully synthesized by combining the electrospinning and atomic layer deposition (ALD) method, and the effect of compositions on the gas-sensing performance were systematically studied.
Abstract: In virtue of their fantastic sensing performance, heterojunction-based gas sensors has gained ascending attention and gradually become a new generation of high-performance gas sensors. However, due to the poor control on the element composition and distribution of heterostructure, it remains a great challenge to optimize and repeat the gas-sensing performance. In this paper, hollow p-CuO/n-ZnO nanofibers with controllable compositions were successfully synthesized by combining the electrospinning and atomic layer deposition (ALD) method, and the effect of compositions on the gas-sensing performance were systematically studied. The ratios of Zn to Cu (RZn/Cu) were well controlled by adjusting the amounts of raw materials and the deposition cycles of ALD in orthogonal experiments, which offers a good opportunity to optimize the gas sensing performances. Interestingly, with the increase of RZn/Cu, the gas responses to 100 ppm H2S at 250 °C first increased to 60.5 (RZn/Cu = 15.6) and then decreased gradually. The optimum response of these materials was improved about 6-fold versus the pure ZnO and 45-fold versus pure CuO. Meanwhile, the selectivity and stability of these H2S sensors were also got much optimized. The enhanced sensing performance is believed to be mainly attributed to the optimal ratio of p-CuO/n-ZnO and the mixed heterojunction with radial concentration gradient.