Plasma Processing Of Nanomaterials

We are at a critical evolutionary juncture in the research and development of low-temperature plasmas, which have become essential to synthesizing and processing vital nanoscale materials. More and more industries are increasingly dependent on plasma technology to develop integrated small-scale devices, but physical limits to growth, and other challenges, threaten progress. Plasma Processing of Nanomaterials is an in-depth guide to the art and science of plasma-based chemical processes used to synthesize, process, and modify various classes of nanoscale materials such as nanoparticles, carbon nanotubes, and semiconductor nanowires. Plasma technology enables a wide range of academic and industrial applications in fields including electronics, textiles, automotives, aerospace, and biomedical. A prime example is the semiconductor industry, in which engineers revolutionized microelectronics by using plasmas to deposit and etch thin films and fabricate integrated circuits. An overview of progress and future potential in plasma processing, this reference illustrates key experimental and theoretical aspects by presenting practical examples of: Nanoscale etching/deposition of thin films Catalytic growth of carbon nanotubes and semiconductor nanowires Silicon nanoparticle synthesis Functionalization of carbon nanotubes Self-organized nanostructures Significant advances are expected in nanoelectronics, photovoltaics, and other emerging fields as plasma technology is further optimized to improve the implementation of nanomaterials with well-defined size, shape, and composition. Moving away from the usual focus on wet techniques embraced in chemistry and physics, the author sheds light on pivotal breakthroughs being made by the smaller plasma community. Written for a diverse audience working in fields ranging from nanoelectronics and energy sensors to catalysis and nanomedicine, this resource will help readers improve development and application of nanomaterials in their own work. About the Author: R. Mohan Sankaran received the American Vacuum Society’s 2011 Peter Mark Memorial Award for his outstanding contributions to tandem plasma synthesis.

The Special Issue “Plasma for Energy and Catalytic Nanomaterials” highlights the recent progress and advancements in the synthesis and applications of energy and catalytic nanomaterials by plasma. Compared with conventional preparation methods, plasma provides a fast, facile, and environmentally friendly method for synthesizing highly efficient nanomaterials. The synthesized nanomaterials generally show enhanced metal–support interactions, small-sized metal nanoparticles, specific metal structures, and abundant oxygen vacancies. The plasma method allows thermodynamically and dynamically difficult reactions to proceed at low temperatures due to the activation of energetic electrons. Despite the growing interest in plasma for energy and catalytic nanomaterials, the synthesis mechanisms of nanomaterials using plasma still remain obscure due to the complicated physical and chemical reactions that occur during plasma preparation. The Guest Editors and the MDPI staff are therefore pleased to offer this Special Issue to interested reader, including graduate and Ph.D. students, postdoctoral researchers, and the entire community interested in the field of nanomaterials. We share the conviction that the Issue can serve as a useful tool for updating the literature and to aid with the conception of new production and/or research programs. Further dedicated R&D advances are possible based on new instruments and materials under development.

Plasma technology can facilitate the fabrication of nanomaterials and nanoscale structures. On the other hand, nanotechnology could be possibly used in plasma science. Several advanced nanomaterials and nanodevices could be used to fabricate nanoplasma (nanoscale plasma), such as nanoelectrodes, nanoantennae, nanolasers, nanoreactors, nanomagnets, nanosensors, nanobatteries, nanogenerator and supercapacitors. This book provides information on fundamental design concepts and promising applications of nanoplasma. It explains how, for the next generation of electronic devices with high data rate communications, a high-speed operation of electronic switches could be attained using nanoplasma. Similarly, in the field of heath and aesthetics, nanoplasma can be used as a non-surgical localized treatments for the face and neck, such as eyelid correction. In addition, various kinds of advanced nanostructures can be fabricated using the plasma technology Outlines the main properties of nanotechnology-enhanced plasma Discusses major applications of plasma technology Assesses the major challenges of manufacturing nanoplasma on an industrial scale

We are at a critical evolutionary juncture in the research and development of low-temperature plasmas, which have become essential to synthesizing and processing vital nanoscale materials. More and more industries are increasingly dependent on plasma technology to develop integrated small-scale devices, but physical limits to growth, and other challenges, threaten progress. Plasma Processing of Nanomaterials is an in-depth guide to the art and science of plasma-based chemical processes used to synthesize, process, and modify various classes of nanoscale materials such as nanoparticles, carbon nanotubes, and semiconductor nanowires. Plasma technology enables a wide range of academic and industrial applications in fields including electronics, textiles, automotives, aerospace, and biomedical. A prime example is the semiconductor industry, in which engineers revolutionized microelectronics by using plasmas to deposit and etch thin films and fabricate integrated circuits. An overview of progress and future potential in plasma processing, this reference illustrates key experimental and theoretical aspects by presenting practical examples of: Nanoscale etching/deposition of thin films Catalytic growth of carbon nanotubes and semiconductor nanowires Silicon nanoparticle synthesis Functionalization of carbon nanotubes Self-organized nanostructures Significant advances are expected in nanoelectronics, photovoltaics, and other emerging fields as plasma technology is further optimized to improve the implementation of nanomaterials with well-defined size, shape, and composition. Moving away from the usual focus on wet techniques embraced in chemistry and physics, the author sheds light on pivotal breakthroughs being made by the smaller plasma community. Written for a diverse audience working in fields ranging from nanoelectronics and energy sensors to catalysis and nanomedicine, this resource will help readers improve development and application of nanomaterials in their own work. About the Author: R. Mohan Sankaran received the American Vacuum Society’s 2011 Peter Mark Memorial Award for his outstanding contributions to tandem plasma synthesis.

This book, entitled “Plasma-Based Synthesis and Modification of Nanomaterials” is a collection of nine original research articles devoted to the application of different atmospheric pressure (APPs) and low-pressure (LPPs) plasmas for the synthesis or modification of various nanomaterials (NMs) of exceptional properties. These articles also show the structural and morphological characterization of the synthesized NMs and their further interesting and unique applications in different areas of science and technology. The readers interested in the capabilities of plasma-based treatments will quickly be convinced that APPs and LPPs enable one to efficiently synthesize or modify differentiated NMs using a minimal number of operations. Indeed, the presented procedures are eco-friendly and usually involve single-step processes, thus considerably lowering labor investment and costs. As a result, the production of new NMs and their functionalization is more straightforward and can be carried out on a much larger scale compared to other methods and procedures involving complex chemical treatments and processes. The size and morphology, as well as the structural and optical properties of the resulting NMs are tunable and tailorable. In addition to the desirable and reproducible physical dimensions, crystallinity, functionality, and spectral properties of the resultant NMs, the NMs fabricated and/or modified with the aid of APPs are commonly ready-to-use prior to their specific applications, without any initial pre-treatments.

Nanomaterials are important tools for enabling technological progress as they can provide dramatically different properties as compared to the bulk counterparts. The field of nanoparticles is one of the most investigated within nanomaterials, thanks to the existing, relatively simple, means of manufacturing. In this thesis, high-power pulsed hollow cathode sputtering is used to nucleate and grow magnetic nanoparticles in a plasma. This sputtering technique provides a high degree of ionization of the sputtered material, which has previously been shown to aid in the growth of the nanoparticles. The magnetic properties of the particles are utilized and makes it possible for the grown particles to act as building blocks for self-assembly into more sophisticated nano structures, particularly when an external magnetic field is applied. These structures created are termed “nanowires” or “nanotrusses”, depending on the level of branching and inter-linking that occurs. Several different elements have been investigated in this thesis. In a novel approach, it is shown how nanoparticles with more advanced structures, and containing material from two hollow cathodes, can be fabricated using high-power pulses. The dual-element particles are achieved by using two distinct and individual elemental cathodes, and a pulse process that allows tuning of individual pulses separately to them. Nanoparticles grown and investigated are Fe, Ni, Pt, Fe-Ni and Ni-Pt. Alternatively, the addition of oxygen to the process allows the formation of oxide or hybrid metal oxide – metal particles. For all nanoparticles containing several elements, it is demonstrated that the stoichiometry can be easily varied, either by the amount of reactive gas let into the process or by tuning the amount of sputtered material through adjusting the electric power supplied to the different cathodes. One aim of the presented work is to find a suitable material for the use as a catalyst in the production of H2 gas through the process of water splitting. H2 is a good candidate to replace fossil fuels as an energy carrier. However, rare elements (such as Ir or Pt) needs to be used as the catalyst, otherwise a high overpotential is required for the splitting to occur, leading to a low efficiency. This work demonstrates a possible route to avoid this, by using nanomaterials to increase the surface-to-volume ratio, as well as optimizing the elemental ratio between different materials to lower the amount of noble elements required.

Plasma-processed biomimetic structures are an extremely focused and small subset of biomimetics. Although other methods can also be adopted, experimental synthesis of biomimetic structures mainly focuses on plasma processing. This book deals with the theoretical description of photonic structures available in nature, and the physics and applications of biomimetic structures prepared in the laboratory. It discusses anti-reflection properties of moth eye- or cicada wing-type nanostructured materials on semiconductor surfaces, with emphasis on plasma fabrication procedures. It also explains, with the help of related theories, the superhydrophobic or hydrophilic wetting properties demonstrated by most of these natural structures. It discusses biomedical applications, especially in implants, as one of the key applications of such materials. The book focuses mainly on plasma processing of biomimetic nanostructures and is, therefore, different from similar books that are more general in nature. It presents essential schematics, sufficient details, and advanced instrumentation techniques that would help readers understand why these structures are considered so important in materials science and physics.

Nanotechnology can profoundly benefit our health, environment and everyday life. In order to make this a reality, both technological and theoretical advancements of the nanomaterial synthesis methods are needed. A nanoparticle is one of the fundamental building blocks in nanotechnology and this thesis describes the control of the nucleation, growth and oxidation of titanium particles produced in a pulsed plasma. It will be shown that by controlling the process conditions both the composition (oxidationstate) and size of the particles can be varied. The experimental results are supported by theoretical modeling. If processing conditions are chosen which give a high temperature in the nanoparticle growth environment, oxygen was found to be necessary in order to nucleate the nanoparticles. The two reasons for this are 1: the lower vapor pressure of a titanium oxide cluster compared to a titanium cluster, meaning a lower probability of evaporation, and 2: the ability of a cluster to cool down by ejecting an oxygen atom when an oxygen molecule condenses on its surface. When the oxygen gas flow was slightly increased, the nanoparticle yield and oxidation state increased. A further increase caused a decrease in particle yield which is attributed to a slight oxidation ofthe cathode. By varying the oxygen flow, it was possible to control the oxidation state of the nanoparticles without fully oxidizing the cathode. Pure titanium nanoparticles could not be produced in a high vacuum system because oxygen containing gases such as residual water vapour have a profound influence on nanoparticle yield and composition. In an ultrahigh vacuum system titanium nanoparticles without significantoxygen contamination were produced by reducing the temperature of the growth environment and increasing the pressure of an argon-helium gas mixture within whichthe nanoparticles grew. The dimer formation rate necessary for this is only achievable at higher pressures. After a dimer has formed, it needs to grow by colliding with a titanium atom followed by cooling by collisions with multiple buffer gas atoms. The condensation event heats up the cluster to a temperature much higher than the gas temperature, where it is during a short time susceptible to evaporation. When the clusters’ internal energy has decreased by collisions with the gas to less than the energy required to evaporate a titanium atom, it is temporarily stable until the next condensation event occurs. The temperature difference by which the cluster has to cool down before it is temporarily stable is exactly as many kelvins as the gas temperature.The addition of helium was found to decrease the temperature of the gas, making it possible for nanoparticles of pure titanium to grow. The process window where this is possible was determined and the results presented opens up new possibilities to synthesize particles with a controlled contamination level and deposition rate.The size of the nanoparticles has been controlled by three means. The first is to change the electrical potential around the growth zone, which allows for size (diameter) control in the order of 25 to 75 nm without influencing the oxygen content of the particles. The second means is by increasing the pressure which decreases the ambipolar diffusion rate of the ions resulting in a higher growth material density. By doing this, the particle size can be increased from 50 to 250 nm, however the oxygen content also increases with increasing pressure when this is done in a high vacuum system. The last means of size control was by adding a helium flow to the process where higher flows resulted in smaller nanoparticle sizes. When changing the pressure in high vacuum, the morphology of the nanoparticles could be controlled. At low pressures, highly faceted near spherical particles were produced. Increasing the pressure caused the formation of cubic particles which appear to ‘fracture’ at higher pressures. At the highest pressure investigated, the particles became poly-crystalline with a cauliflower shape and this morphology was attributed to a lowad atom mobility. The ability to control the size, morphology and composition of the nanoparticles determines the success of applying the process to manufacture devices. In related work presented in this thesis it is shown that 150-200 nm molybdenum particles with cauliflower morphology were found to scatter light in which made them useful in photovoltaic applications, and the size of titanium dioxide nanoparticles were found to influence the selectivity of graphene based gas sensors.