Atomic layer deposition: an overview.
About: This article is published in Chemical Reviews.The article was published on 2010-01-01. It has received 4756 citations till now. The article focuses on the topics: Atomic layer epitaxy & Atomic layer deposition.
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TL;DR: A highly active photocathode for solar H(2) production is presented, consisting of electrodeposited cuprous oxide, which was protected against photocathodic decomposition in water by nanolayers of Al-doped zinc oxide and titanium oxide and activated for hydrogen evolution with electroDeposited Pt nanoparticles.
Abstract: A clean and efficient way to overcome the limited supply of fossil fuels and the greenhouse effect is the production of hydrogen fuel from sunlight and water through the semiconductor/water junction of a photoelectrochemical cell, where energy collection and water electrolysis are combined into a single semiconductor electrode. We present a highly active photocathode for solar H(2) production, consisting of electrodeposited cuprous oxide, which was protected against photocathodic decomposition in water by nanolayers of Al-doped zinc oxide and titanium oxide and activated for hydrogen evolution with electrodeposited Pt nanoparticles. The roles of the different surface protection components were investigated, and in the best case electrodes showed photocurrents of up to -7.6 mA cm(-2) at a potential of 0 V versus the reversible hydrogen electrode at mild pH. The electrodes remained active after 1 h of testing, cuprous oxide was found to be stable during the water reduction reaction and the Faradaic efficiency was estimated to be close to 100%.
1,856 citations
Cites background from "Atomic layer deposition: an overvie..."
...Here, the issue of Cu 2 O instability in water under illumination is addressed by depositing protective layers on the electrode surface by atomic layer depositio...
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TL;DR: A practical synthesis method to produce isolated single platinum atoms and clusters using the atomic layer deposition technique and indicates that the partially unoccupied density of states of the platinum atoms' 5d orbitals on the nitrogen-doped graphene are responsible for the excellent performance.
Abstract: Platinum-based catalysts have been considered the most effective electrocatalysts for the hydrogen evolution reaction in water splitting. However, platinum utilization in these electrocatalysts is extremely low, as the active sites are only located on the surface of the catalyst particles. Downsizing catalyst nanoparticles to single atoms is highly desirable to maximize their efficiency by utilizing nearly all platinum atoms. Here we report on a practical synthesis method to produce isolated single platinum atoms and clusters using the atomic layer deposition technique. The single platinum atom catalysts are investigated for the hydrogen evolution reaction, where they exhibit significantly enhanced catalytic activity (up to 37 times) and high stability in comparison with the state-of-the-art commercial platinum/carbon catalysts. The X-ray absorption fine structure and density functional theory analyses indicate that the partially unoccupied density of states of the platinum atoms’ 5d orbitals on the nitrogen-doped graphene are responsible for the excellent performance. Downsizing platinum based nanocatalysts has the twin advantages of lower platinum usage and increased activity per platinum atom. Here, the authors report an atomic layer deposition technique for single platinum atom catalyst fabrication and assess their hydrogen evolution activity.
1,374 citations
TL;DR: This article reviews the use of nanopore technology in DNA sequencing, genetics and medical diagnostics and suggests that nanopore-based sensors could be competitive with other third-generation DNA sequencing technologies.
Abstract: Nanopore analysis is an emerging technique that involves using a voltage to drive molecules through a nanoscale pore in a membrane between two electrolytes, and monitoring how the ionic current through the nanopore changes as single molecules pass through it. This approach allows charged polymers (including single-stranded DNA, double-stranded DNA and RNA) to be analysed with subnanometre resolution and without the need for labels or amplification. Recent advances suggest that nanopore-based sensors could be competitive with other third-generation DNA sequencing technologies, and may be able to rapidly and reliably sequence the human genome for under $1,000. In this article we review the use of nanopore technology in DNA sequencing, genetics and medical diagnostics.
1,299 citations
TL;DR: Atomic layer deposition (ALD) is a vapor phase technique capable of producing thin films of a variety of materials as discussed by the authors, including metal oxides such as Zn1−xSnxOy, ZrO2, Y2O3, and Pt.
1,280 citations
04 Mar 2016
TL;DR: The reactive force field (ReaxFF) interatomic potential is a powerful computational tool for exploring, developing and optimizing material properties as mentioned in this paper, but it is often too computationally intense for simulations that consider the full dynamic evolution of a system.
Abstract: The reactive force-field (ReaxFF) interatomic potential is a powerful computational tool for exploring, developing and optimizing material properties. Methods based on the principles of quantum mechanics (QM), while offering valuable theoretical guidance at the electronic level, are often too computationally intense for simulations that consider the full dynamic evolution of a system. Alternatively, empirical interatomic potentials that are based on classical principles require significantly fewer computational resources, which enables simulations to better describe dynamic processes over longer timeframes and on larger scales. Such methods, however, typically require a predefined connectivity between atoms, precluding simulations that involve reactive events. The ReaxFF method was developed to help bridge this gap. Approaching the gap from the classical side, ReaxFF casts the empirical interatomic potential within a bond-order formalism, thus implicitly describing chemical bonding without expensive QM calculations. This article provides an overview of the development, application, and future directions of the ReaxFF method.
1,239 citations
Cites methods from "Atomic layer deposition: an overvie..."
...Recent studies have focused on ALD of Al2O3 using trimethylaluminum (TMA) and H2O cycles as a route for developing Ge-based metal oxide semiconductors (CMOS).(89,93,94) To demonstrate the temperature dependence of TMA nucleation on a bare Ge(100) surface, which has been previously reported in the literature,(95) MD simulations were performed at 23 °C, 227 °C, and 427 °C....
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References
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3,206 citations
TL;DR: Some of the observed new chemical, optical, and thermal properties of metallic nanocrystals when their size is confined to the nanometer length scale and their dynamical processes are observed on the femto- to picosecond time scale are described.
Abstract: The properties of a material depend on the type of motion its electrons can execute, which depends on the space available for them (i.e., on the degree of their spatial confinement). Thus, the properties of each material are characterized by a specific length scale, usually on the nanometer dimension. If the physical size of the material is reduced below this length scale, its properties change and become sensitive to its size and shape. In this Account we describe some of the observed new chemical, optical, and thermal properties of metallic nanocrystals when their size is confined to the nanometer length scale and their dynamical processes are observed on the femto- to picosecond time scale.
2,655 citations
TL;DR: In this article, the thermal boundary resistance at interfaces between helium and solids (Kapitza resistance) and thermal boundary resistances at interfaces interfaces between two solids are discussed for temperatures above 0.1 K. The apparent qualitative differences in the behavior of the boundary resistance in these two types of interfaces can be understood within the context of two limiting models of boundary resistance, the acoustic mismatch model, which assumes no scattering, and the diffuse mismatch model that all phonons incident on the interface will scatter.
Abstract: The thermal boundary resistance present at interfaces between helium and solids (Kapitza resistance) and the thermal boundary resistance at interfaces between two solids are discussed for temperatures above 0.1 K. The apparent qualitative differences in the behavior of the boundary resistance at these two types of interfaces can be understood within the context of two limiting models of the boundary resistance, the acoustic mismatch model, which assumes no scattering, and the diffuse mismatch model, which assumes that all phonons incident on the interface will scatter. If the acoustic impedances of the two media in contact are very different, as is the case for helium (liquid or solid) in contact with a solid, then phonon scattering at the interface will reduce the boundary resistance. In the limiting case of diffuse mismatch, this reduction is typically over 2 orders of magnitude. Phonons are very sensitive to surface defects, and therefore the Kapitza resistance is very sensitive to the condition of the interface. For typical solid-solid interfaces, at which the acoustic impedances are less different, the influence of diffuse scattering is relatively small; even for the two limiting cases of acoustic mismatch and diffuse mismatch the predicted boundary resistances differ by very little (\ensuremath{\lesssim} 30%). Consequently, the experimentally determined values are expected to be rather insensitive to the condition of the interface, in agreement with recent observations. Subsurface (bulk) disorder and imperfect physical contact between the solids play far more important roles and led to the irreproducibilities observed in the early measurements of the solid-solid thermal boundary resistance.
2,485 citations
TL;DR: In this paper, the surface chemistry of the trimethylaluminum/water ALD process is reviewed, with an aim to combine the information obtained in different types of investigations, such as growth experiments on flat substrates and reaction chemistry investigation on high-surface-area materials.
Abstract: Atomic layer deposition(ALD), a chemical vapor deposition technique based on sequential self-terminating gas–solid reactions, has for about four decades been applied for manufacturing conformal inorganic material layers with thickness down to the nanometer range. Despite the numerous successful applications of material growth by ALD, many physicochemical processes that control ALD growth are not yet sufficiently understood. To increase understanding of ALD processes, overviews are needed not only of the existing ALD processes and their applications, but also of the knowledge of the surface chemistry of specific ALD processes. This work aims to start the overviews on specific ALD processes by reviewing the experimental information available on the surface chemistry of the trimethylaluminum/water process. This process is generally known as a rather ideal ALD process, and plenty of information is available on its surface chemistry. This in-depth summary of the surface chemistry of one representative ALD process aims also to provide a view on the current status of understanding the surface chemistry of ALD, in general. The review starts by describing the basic characteristics of ALD, discussing the history of ALD—including the question who made the first ALD experiments—and giving an overview of the two-reactant ALD processes investigated to date. Second, the basic concepts related to the surface chemistry of ALD are described from a generic viewpoint applicable to all ALD processes based on compound reactants. This description includes physicochemical requirements for self-terminating reactions,reaction kinetics, typical chemisorption mechanisms, factors causing saturation, reasons for growth of less than a monolayer per cycle, effect of the temperature and number of cycles on the growth per cycle (GPC), and the growth mode. A comparison is made of three models available for estimating the sterically allowed value of GPC in ALD. Third, the experimental information on the surface chemistry in the trimethylaluminum/water ALD process are reviewed using the concepts developed in the second part of this review. The results are reviewed critically, with an aim to combine the information obtained in different types of investigations, such as growth experiments on flat substrates and reaction chemistry investigation on high-surface-area materials. Although the surface chemistry of the trimethylaluminum/water ALD process is rather well understood, systematic investigations of the reaction kinetics and the growth mode on different substrates are still missing. The last part of the review is devoted to discussing issues which may hamper surface chemistry investigations of ALD, such as problematic historical assumptions, nonstandard terminology, and the effect of experimental conditions on the surface chemistry of ALD. I hope that this review can help the newcomer get acquainted with the exciting and challenging field of surface chemistry of ALD and can serve as a useful guide for the specialist towards the fifth decade of ALD research.
2,212 citations
Book•
01 Jan 1949
TL;DR: In this paper, the scientific foundations of the vacuum technique were discussed and the following papers were published: Scientific foundations of vacuum technique, Scientific foundations for vacuum technique and its application in computer vision.
Abstract: Scientific foundations of vacuum technique , Scientific foundations of vacuum technique , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
1,727 citations