Download or read book Reaction Mechanisms and Dynamics in the Early Stage of High Oxide Atomic Layer Deposition written by Giulio D'Acunto and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomic layer deposition (ALD) is an outstanding deposition technique to deposit highly conformal and uniform thin films with atomic precision. In particular, ALD of transition metal oxide layers from metal amido complexes and water finds its way in several technological fields, including green energy devices and in the semiconductor industry. These ALD reactions are believed to follow a reaction scheme based on the ligand exchange mechanism, in which the surface on which deposition takes place plays a largely static role and the ligands of the used precursor are chemically unchanged during the reaction. To address the correctness of the model, time-resolved in situ and operando ambient pressure x-ray photoelectron spectroscopy (APXPS) technique was employed during the ALD of HfO2 on InAs covered by a thermal or native oxide, TiO2(101) and oxidised as well as clean Si(111).The classic ligand exchange reaction mechanism does not adequately describe the reaction path in any of the investigated sample systems. In particular, ALD of HfO2 on SiO2 follows a bimolecular reaction mechanism based on the insertion of an hydrogen atom of one of the ligands in an amido complex dimer. As a result of its bimolecular nature, this reaction can take place only on a SiO2 surface of a sufficiently high coverage of physisorbed complexes. Similarly, on TiO2 the early stage of the reaction is based on dissociative adsorption, followed by an intra- and inter- molecular reaction path, leading to the formation of new sets of surface species never before identified in any of the previous ALD models.For easily reducible surfaces, such as InAs oxide and TiO2, evidence is found for HfOx formation already during the first ALD half-cycle, due to the transfer of O atoms from the surface to the metal complex. Clearly, this contradicts the static role of the surface in standard ALD models. Interestingly, in the case of InAs covered by a thermal or native oxide, this phenomenon, which lies behind the so-called self cleaning effect, guarantees a sharp interface between the III-V material and HfO2, which is a prerequisite for next generation MOSFETs.These results open new doors for improving devices based on ALD. Time-resolved in situ and operando APXPS allows to follow the kinetics and mechanisms involved in ALD, in real time at second time resolution with significant benefit for the further improvement of general understanding of ALD reactions.

Download or read book In Situ Infrared Spectroscopy Study of Atomic Layer Deposition of High kappa Metal Oxide and Metal on Passivated Silicon Surfaces written by and published by . This book was released on 2008 with total page 199 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomic layer deposition (ALD) is a novel and promising film deposition method for microelectronics and many other areas with documented commercial success. Notable advantages include accurate thickness control and high conformality, all of which are particularly important for deep trenches, porous materials and nanoparticles. The key elements of ALD including starting surfaces and precursors are investigated with in situ Fourier transform infrared spectroscopy, using a variety of starting surfaces: hydrogen-terminated Si (H/Si), oxidized Si, nitrided Si, and self-assembled monolayers (SAMs) grafted on H/Si surfaces. In particular, the formation of nitrided surfaces using thermal NH3 reaction with flat and vicinal H/Si(111) is studied and a mechanistic understanding is achieved with the aid of density functional theory calculation. An unexpected NH incorporated bridging structure is found at the dihydride step edge. The properties and stability of methyl and carboxylic groups terminated alkene-based SAMs grafted to H/Si(111) surface via direct Si-C bonds are also addressed. The carboxylic groups terminated SAM can be grafted without formation of interfacial SiO2. Moreover, the use of SiNx and SAM successfully minimizes the interfacial SiO2 during ALD process. With a thorough understanding of the starting surfaces, the nature of ALD grown high-kappa metal oxides and metal is studied. Water- and ozone-based ALD of HfO2 and Al2O3 are investigated mechanistically. Unexpected intermediate species and reaction pathways are found to depend on ozone partial pressure, such as formate intermediate for Al2O3 deposition. La2O3 and Cu deposited by novel precursors, La(iPr-MeAMD)3/D2O and [Cu(sBu-amd)]2/H2 respectively, are explored in many aspects such as the nature of precursor gas phase, the ALD temperature window, the film properties, and so on. In all cases, a mechanistic picture of the surface interaction and film growth is unraveled using infrared spectroscopy and other complementary techniques, such as Rutherford back scattering spectroscopy and X-ray photoelectron spectroscopy. Gas phase studies show that the two precursors are both readily hydrolyzed and highly reactive. ALD-deposited La2O3 films are of poor quality due to the hygroscopic nature of La2O3, and Cu diffusion and agglomeration are inferred from the evolution of IR vibrational modes.

Download or read book Surface and Subsurface Reaction Mechanisms in Atomic Layer Deposition of Metals and Metal Oxides written by Joel Richard Schneider and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanotechnology has shown remarkable versatility and strength in response to large-scale challenges facing society today, despite many of its technical applications being on the atomic scale. From renewable energy devices to medical and sequencing technologies, to three-dimensional transistor architectures, advanced water purification, and novel organic-inorganic hybrid materials, nanotechnology has enabled powerful advances through precisely creating materials with specific chemistries and nanostructures. Thin films are particularly robust in their applications, and atomic layer deposition (ALD) is a thin film deposition technique with demonstrated strengths in precision, tunability, and structural control. The core principles of ALD that allow it to achieve these powerful results rely on self-limiting surface chemical reactions; however, despite the prevalence of ALD reports in the literature there are still many surface mechanisms that are poorly understood. ALD material properties can be highly sensitive to process conditions, impurities introduced from surface reactions, subtle changes in reaction rates, and many more phenomena, so it is critical to fully understand the surface reaction mechanisms at play in ALD to effectively implement processes and design chemistries for new materials. Especially as ALD is often idealized to behave in a simple self-limiting manner, the presence of more complex surface reactions that deviate from this behavior necessitates deeper study. As a result, this dissertation presents work to find, characterize, and model new reaction mechanisms in ALD that cause deviations from ideal behavior, then generalize that understanding and apply it to new chemical systems. The first half of the work focuses on activating surface species in the ALD of metal oxides. ALD of iron oxide using ozone is investigated as a case study, and we find that during the process ozone generates reactive oxygen species that migrate below the surface of the growing film where they are stored. The expansion of the ALD reactions beyond the surface of the film to a reservoir of active species in the subsurface region has a host of implications on the ALD process and the resulting material. The storage of reactive species results in high growth rates, and the physical movement of species through the film causes preferential crystalline rearrangement and film roughening. Further studies of nickel oxide ALD found related behaviors, indicating it grows by a similar mechanism of subsurface active species storage. In both cases, the oxygen species are reactive enough to activate surface combustion reactions, including in ALD of other materials grown on top of the reactive reservoirs. These mechanisms are consistent with reports of some other oxides, suggesting oxygen mobility and oxidizability of the metal center may be important factors in facilitating this reservoir mechanism. The second half of this thesis focuses instead on surface passivating species in metal ALD. As ALD hinges on self-limiting reactions resulting from the surface being passivated toward further reaction, the persistence of passivation is key to consistent and precise process function. A promising precursor for ruthenium ALD, Ru(DMBD)(CO)3, is studied due to its unique passivation mechanism of L-type ligands bonded to a zero-oxidation state metal center. Some reports have hypothesized this bonding results in excellent nucleation and growth properties, while others that it results in poor deposition control with better applications in continuous-deposition processes. By studying this ALD process, we can then gain insight into both surface passivation mechanisms and broader principles for process design of metals and zero-oxidation state compounds. We find the precursor undergoes a spontaneous decarbonylation reaction mechanism whereby the surface is initially passivated with carbonyl species that are lost with increasing temperature or time. Comparison of in situ characterization data and first principles kinetic modeling support these findings. Our results help explain inconsistencies in previous reports as well as observations of other zero-oxidation state precursors. Together, characterizing new surface mechanisms in ALD of both activating and passivating species gives a more complete picture of how a range of ALD processes can deviate from idealized and simplified self-limiting surface reactions. These findings span the breadth of both metal and metal oxide ALD, and we apply the insights to new ALD systems involving multicomponent and catalytically activated ALD processes. These grow the chemical toolbox of ALD and illustrate how a proper fundamental chemical understanding of ALD is important not only for effective implementation and control of existing processes but also for generalizing, expanding, and designing tools for ALD to further widen its horizons.

Download or read book Chemistry of Atomic Layer Deposition written by Seán Thomas Barry and published by Walter de Gruyter GmbH & Co KG. This book was released on 2021-11-08 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book will help chemists and non-chemists alike understand the fundamentals of surface chemistry and precursor design, and how these precursors drive the processes of atomic layer deposition, and how the surface-precursor interaction governs atomic layer deposition processes. The underlying principles in atomic layer deposition rely on the chemistry of a precursor with a surface.

Download or read book Atomic Layer Deposition ALD written by Callisto Joan MacIsaac and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern society demands smaller, more precise devices for both microelectronic and energy technologies. The development of methods and processes that can deposit reliably uniform, conformal thin films on the nanoscale is essential to fields as diverse as catalysts and solar cells. Therefore, atomic layer deposition (ALD), a thin-film deposition technique that accomplishes these goals by using self-limiting sequential reactions between alternating precursors to achieve atomic precision over the product film, is an important tool for the modern era. Combining ALD with molecular layer deposition (MLD), which follows the same principles as ALD but deposits entire organic molecules to build films, results in a powerful system that enables the deposition of inorganic, organic, and hybrid inorganic-organic materials. Understanding the nucleation mechanisms, surface reaction chemistry, and applications of these materials and ALD/MLD processes is essential to commercialization and wider use. Through in situ Fourier transform infrared (FTIR) spectroscopy, we studied the zinc-tin-oxide (ZTO) system, a ternary ALD process that is a combination of the zinc oxide and tin oxide binary ALD processes. Previous research had indicated that the ternary system is characterized by non-idealities in the ALD growth, and we identify as a potential cause of these effects incomplete removal of the ligands from the tetrakis(dimethylamino)tin precursor, which leads to a nucleation delay when depositing ZnO on SnO2. A significant fraction of the ligands remain on the surface during the ALD of SnO2 and endure when the process is switched to ZnO ALD. This result suggests that the occupation of surface reactive sites by these persisting ligands may be the cause of the observed nucleation delay with potential ramifications for many other binary and ternary systems where persisting ligands may be present. In addition, we studied the mechanism of ALD-grown MoS2 thin films. It was observed by atomic force microscopy (AFM), grazing incidence small angle X-ray scattering (GISAXS), and X-ray reflectivity (XRR) that nucleation proceeds by the formation of small islands that coalesce into a complete film in under 100 cycles, with further film growth failing to occur after coalescence. This inertness is attributed to the chemical inactivity of the basal planes of MoS2. It was found that the final thickness of the as-grown film is not determined by the number of ALD cycles as per the normal regime, but by the temperature that the film is deposited at. This self-limiting layer synthesis (SLS) has been reported in the literature for higher temperature depositions of MoS2, but this is the first report of the effect in a low temperature, amorphous MoS2 ALD system. The thickness of films growth by ALD with the precursors Mo(CO)6 and H2S was found to saturate at around 7 nm on both native oxide-covered silicon and bulk crystalline MoS2 substrates, which may indicate that the SLS behavior is inherent to the ALD process and not substantially a product of the substrate surface potential. Finally, we demonstrated a new ALD/MLD hybrid process that used the MoS2 ALD precursor Mo(CO)6 and the counter reagent 1,2-ethanedithiol to create a MoS2-like material with organic domains. This Mo-thiolate possesses many properties that link it to MoS2, such as activity towards the hydrogen evolution reaction (HER) and similar Raman modes, but has a significantly lower density, optical transparency, and higher geometric surface area. It was found that the process has a 1.3 Å growth per cycle and can catalyze the HER reaction at an overpotential of 294 mV at -10 mA/cm2 , which is superior to planar MoS2 and ranks the as-deposited catalyst with the best nanostructured MoS2-based catalysts. We propose that this activity comes from the higher surface area induced by the incorporation of organic chains into the films. In summary, we explored the mechanisms and nucleation behavior of several ALD systems of interest to energy applications using both in situ and ex situ analysis techniques. These studies demonstrated the importance of understanding ALD surface chemistry to the overall chemical composition of the resultant films, the ramifications of different nucleation regimes in determining morphologies, and the power of ALD/MLD in creating analogues to previously known species with improved physical properties.

Download or read book VUV and Soft X Ray Photoionization written by Uwe Becker and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 678 pages. Available in PDF, EPUB and Kindle. Book excerpt: Leading investigators offer the first comprehensive study of gas phase photoionization research in the VUV and soft X-ray regime since the massive employment of synchrotron radiation as a spectroscopic tool. Chapters cover all aspects of photoionization phenomena from total cross sections to highly differentiated measurements such as coincidence experiments and spin-resolved electron spectroscopy. This work is abundant with illustrations.

Download or read book Hard X ray Photoelectron Spectroscopy HAXPES written by Joseph Woicik and published by Springer. This book was released on 2015-12-26 with total page 576 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides the first complete and up-to-date summary of the state of the art in HAXPES and motivates readers to harness its powerful capabilities in their own research. The chapters are written by experts. They include historical work, modern instrumentation, theory and applications. This book spans from physics to chemistry and materials science and engineering. In consideration of the rapid development of the technique, several chapters include highlights illustrating future opportunities as well.

Download or read book Additive Manufacturing of Titanium Alloys written by Bhaskar Dutta and published by Butterworth-Heinemann. This book was released on 2016-06-17 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: Additive Manufacturing of Titanium Alloys: State of the Art, Challenges and Opportunities provides alternative methods to the conventional approach for the fabrication of the majority of titanium components produced via the cast and wrought technique, a process which involves a considerable amount of expensive machining. In contrast, the Additive Manufacturing (AM) approach allows very close to final part configuration to be directly fabricated minimizing machining cost, while achieving mechanical properties at least at cast and wrought levels. In addition, the book offers the benefit of significant savings through better material utilization for parts with high buy-to-fly ratios (ratio of initial stock mass to final part mass before and after manufacturing). As titanium additive manufacturing has attracted considerable attention from both academicians and technologists, and has already led to many applications in aerospace and terrestrial systems, as well as in the medical industry, this book explores the unique shape making capabilities and attractive mechanical properties which make titanium an ideal material for the additive manufacturing industry. Includes coverage of the fundamentals of microstructural evolution in titanium alloys Introduces readers to the various Additive Manufacturing Technologies, such as Powder Bed Fusion (PBF) and Directed Energy Deposition (DED) Looks at the future of Titanium Additive Manufacturing Provides a complete review of the science, technology, and applications of Titanium Additive Manufacturing (AM)

Download or read book Atomic Layer Deposition of Oxide Films written by Raija Matero and published by . This book was released on 2004 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Study of the Initial Surface Reactions in Atomic Layer Deposition of Oxides Silicides and Nitrides Thin Films on Silicon Substrates written by Karla Maria Bernal Ramos and published by . This book was released on 2014 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, key aspects of the surface chemistry associated with atomic layer deposition (ALD) are discussed. ALD is a novel and promising film deposition technique that can deliver precise thickness control at the angstrom or monolayer level; the self-limiting aspect of ALD makes it a unique method that can lead to excellent step coverage and conformal deposition on high aspect ratio structures. In spite of its central role in efficient film deposition processes, little is known about the mechanisms of the chemical reactions involved. Even the most basic information, such as the initial surface reactions, is in many instances unknown. There is a limited knowledge on the surface chemistry (e.g., substrate, precursor's reactivity) effects for the growth of the films. Reactivity in ALD is controlled by the nature of the substrate, where specific nucleation sites are often responsible for the initial deposition and where a change in chemistry may take place as the first layer of the growing film is formed. The precursor's reactivity towards the surface being used and its properties are fundamental aspects in an ALD process. The majority of the experiments discussed in this dissertation are devoted to the elucidation of the reaction mechanisms of the thin films. The experiments are carried out using in-situ Fourier transform infrared spectroscopy (FTIR) in order to examine the chemical composition of surface adsorbates. The use of in-situ characterization techniques is crucial for better control and understanding of thin film deposition. Knowledge of the surface chemistry underpinning the ALD processes is essential in order to design precursors in a rational way that will lead to successful film growth.

Download or read book Design and Implementation of an Atomic Layer Deposition System with a Coupled In situ X ray Photoelectron Spectroscopy Tool written by Kyle Shiel and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomic layer deposition (ALD) is an important tool for the research and fabrication of thin-films, used across a wide variety of applications, including the creation of thin metal-oxides, used in the fabrication of high-k semiconductor devices. This scope of this study was to design and build a 'home-made' ALD chamber, with a coupled in-situ X-ray Photoelectron Spectroscopy (XPS) tool, in order to be able to characterise the chemical components of thermally grown ALD films before exposing them to atmospheric contamination. Thermally grown films of aluminium oxide were grown using trimethylaluminium (TMA) as a precursor and H2O as a co-reactant. These films were grown at differing temperatures and initial surface conditions, in order to test which conditions led to the most ideal films. Titanium oxide films were also grown using a similar method, (employing titanium isopropoxide (TTIP) as the precursor and H2O as the co-reactant) to ensure the chamber was compatible with a variety of different ALD techniques. While some degree of aluminosilicate growth was observed for all aluminium oxide samples, the growth rates and film compositions for both the TMA and TTIP films were similar to those observed in other studies. These findings show that the system designed works as intended and shows its potential to be used as a process characterisation tool for ALD thin-film processes.

Download or read book Classical And Quantum Dynamics In Condensed Phase Simulations Proceedings Of The International School Of Physics written by Bruce J Berne and published by World Scientific. This book was released on 1998-06-17 with total page 881 pages. Available in PDF, EPUB and Kindle. Book excerpt: The school held at Villa Marigola, Lerici, Italy, in July 1997 was very much an educational experiment aimed not just at teaching a new generation of students the latest developments in computer simulation methods and theory, but also at bringing together researchers from the condensed matter computer simulation community, the biophysical chemistry community and the quantum dynamics community to confront the shared problem: the development of methods to treat the dynamics of quantum condensed phase systems.This volume collects the lectures delivered there. Due to the focus of the school, the contributions divide along natural lines into two broad groups: (1) the most sophisticated forms of the art of computer simulation, including biased phase space sampling schemes, methods which address the multiplicity of time scales in condensed phase problems, and static equilibrium methods for treating quantum systems; (2) the contributions on quantum dynamics, including methods for mixing quantum and classical dynamics in condensed phase simulations and methods capable of treating all degrees of freedom quantum-mechanically.

Download or read book Spectroscopy of Complex Oxide Interfaces written by Claudia Cancellieri and published by Springer. This book was released on 2018-04-09 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book summarizes the most recent and compelling experimental results for complex oxide interfaces. The results of this book were obtained with the cutting-edge photoemission technique at highest energy resolution. Due to their fascinating properties for new-generation electronic devices and the challenge of investigating buried regions, the book chiefly focuses on complex oxide interfaces. The crucial feature of exploring buried interfaces is the use of soft X-ray angle-resolved photoemission spectroscopy (ARPES) operating on the energy range of a few hundred eV to increase the photoelectron mean free path, enabling the photons to penetrate through the top layers – in contrast to conventional ultraviolet (UV)-ARPES techniques. The results presented here, achieved by different research groups around the world, are summarized in a clearly structured way and discussed in comparison with other photoemission spectroscopy techniques and other oxide materials. They are complemented and supported by the most recent theoretical calculations as well as results of complementary experimental techniques including electron transport and inelastic resonant X-ray scattering.

Download or read book Plasma Catalysis written by Annemie Bogaerts and published by MDPI. This book was released on 2019-04-02 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, N2 fixation for the synthesis of NH3 or NOx, methane conversion into higher hydrocarbons or oxygenates. It is also widely used for air pollution control (e.g., VOC remediation). Plasma catalysis allows thermodynamically difficult reactions to proceed at ambient pressure and temperature, due to activation of the gas molecules by energetic electrons created in the plasma. However, plasma is very reactive but not selective, and thus a catalyst is needed to improve the selectivity. In spite of the growing interest in plasma catalysis, the underlying mechanisms of the (possible) synergy between plasma and catalyst are not yet fully understood. Indeed, plasma catalysis is quite complicated, as the plasma will affect the catalyst and vice versa. Moreover, due to the reactive plasma environment, the most suitable catalysts will probably be different from thermal catalysts. More research is needed to better understand the plasma–catalyst interactions, in order to further improve the applications.

Download or read book Metal Nanoparticles for Catalysis written by Franklin Tao and published by Royal Society of Chemistry. This book was released on 2014-06-12 with total page 285 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalysis is a central topic in chemical transformation and energy conversion. Thanks to the spectacular achievements of colloidal chemistry and the synthesis of nanomaterials over the last two decades, there have also been significant advances in nanoparticle catalysis. Catalysis on different metal nanostructures with well-defined structures and composition has been extensively studied. Metal nanocrystals synthesized with colloidal chemistry exhibit different catalytic performances in contrast to metal nanoparticles prepared with impregnation or deposition precipitation. Additionally, theoretical approaches in predicting catalysis performance and understanding catalytic mechanism on these metal nanocatalysts have made significant progress. Metal Nanoparticles for Catalysis is a comprehensive text on catalysis on Nanoparticles, looking at both their synthesis and applications. Chapter topics include nanoreactor catalysis; Pd nanoparticles in C-C coupling reactions; metal salt-based gold nanocatalysts; theoretical insights into metal nanocatalysts; and nanoparticle mediated clock reaction. This book bridges the gap between nanomaterials synthesis and characterization, and catalysis. As such, this text will be a valuable resource for postgraduate students and researchers in these exciting fields.

Download or read book Atomic Layer Deposition ALD written by Jeannie Valdez and published by . This book was released on 2015 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomic layer deposition (ALD) is a thin film deposition technique used in the mass production of microelectronics. In this book, novel nonvolatile memory devices are discussed. The chapters examine the low-temperature fabrication process of single-crystal platinum non-thin films using plasma-enhanced atomic layer deposition (PEALD). A comprehensive review of ALD surface coatings for battery systems is provided, as well as a theoretical calculation on the mechanism of thermal and plasma-enhanced atomic layer deposition of SiO2; and fluorine doping behavior in Zn-based conducting oxide film grown by ALD.

Download or read book Transmission Electron Microscopy written by C. Barry Carter and published by Springer. This book was released on 2016-08-24 with total page 543 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text is a companion volume to Transmission Electron Microscopy: A Textbook for Materials Science by Williams and Carter. The aim is to extend the discussion of certain topics that are either rapidly changing at this time or that would benefit from more detailed discussion than space allowed in the primary text. World-renowned researchers have contributed chapters in their area of expertise, and the editors have carefully prepared these chapters to provide a uniform tone and treatment for this exciting material. The book features an unparalleled collection of color figures showcasing the quality and variety of chemical data that can be obtained from today’s instruments, as well as key pitfalls to avoid. As with the previous TEM text, each chapter contains two sets of questions, one for self assessment and a second more suitable for homework assignments. Throughout the book, the style follows that of Williams & Carter even when the subject matter becomes challenging—the aim is always to make the topic understandable by first-year graduate students and others who are working in the field of Materials Science Topics covered include sources, in-situ experiments, electron diffraction, Digital Micrograph, waves and holography, focal-series reconstruction and direct methods, STEM and tomography, energy-filtered TEM (EFTEM) imaging, and spectrum imaging. The range and depth of material makes this companion volume essential reading for the budding microscopist and a key reference for practicing researchers using these and related techniques.