Ion Beam Modification Of Phase Change Materials For Optical Applications

Active optical metasurfaces with dynamic switchable, tunable, and reconfigurable optical functionalities are an emerging field in photonics and optoelectronics. Especially, chalcogenide-based phase-change materials, such as Ge2Sb2Te5 (GST), can be fast and repeatedly switched by external stimuli between crystalline and amorphous states, typically accompanied by a tremendous difference of its electrical and optical properties. This thesis introduces ion irradiation of GST thin films in order to design purely GST-based metasurfaces in different ways: First, ion irradiation can directly be utilized to generate lattice defects, structural disorder, and ultimately amorphize GST to trigger the phase-change from crystalline to amorphous. Several structural and electronic transitions were observed during the ion bombardment of initially crystalline (rock-salt or hexagonal) GST films. As the amount of damage can be precisely controlled by adjusting the ion fluence, ion irradiated GST posseses gradually tailorable optical properties. Furthermore, a focused ion beam system was utilized to locally tailor disorder within crystalline GST films in sub-wavelength dimensions in order to design reconfigurable metasurfaces. Second, the phase-change behavior of GST itself can be manipulated by ion beam impurity doping. The incorporation of e.g. group V elements shifts the crystallization temperature. By controlling the doping level in highly confined regions, switchable active metasurfaces can be fabricated that are either triggered thermally or by applying various intense laser pulses. Both approaches show that ion irradiation is a powerful tool to transform phase-change materials in active, inherently planar, non-volatile, and reconfigurable optical devices.

"Phase Change Materials: Science and Applications" provides a unique introduction of this rapidly developing field. Clearly written and well-structured, this volume describes the material science of these fascinating materials from a theoretical and experimental perspective. Readers will find an in-depth description of their existing and potential applications in optical and solid state storage devices as well as reconfigurable logic applications. Researchers, graduate students and scientists with an interest in this field will find "Phase Change Materials" to be a valuable reference.

This conference consisted of 15 oral sessions, including three plenary papers covering areas of general interest, 22 specialist invited papers and 51 contributed presentations as well as three poster sessions. There were several scientific highlights covering a diverse spectrum of materials and ion beam processing methods. These included a wide range of conventional and novel applications such as: optical displays and opto-electronics, motor vehicle and tooling parts, coatings tailored for desired properties, studies of fundamental defect properties, the production of novel (often buried) compounds, and treating biomedical materials. The study of nanocrystals produced by ion implantation in a range of host matrices, particularly for opto-electronics applications, was one especially new and exciting development. Despite several decades of study, major progress was reported at the conference in understanding defect evolution in semiconductors and the role of defects in transient impurity diffusion. The use of implantation to tune or isolate optical devices and in forming optically active centres and waveguides in semiconductors, polymers and oxide ceramics was a major focus of several presentations at the conference. The formation of hard coatings by ion assisted deposition or direct implantation was also an area which showed much recent progress. Ion beam techniques had also developed apace, particularly those based on plasma immersion ion implantation or alternative techniques for large area surface treatment. Finally, the use of ion beams for the direct treatment of cancerous tissue was a particularly novel and interesting application of ion beams.

While ion-beam techniques have been used to create thin films in the semiconductor industry for several decades, these methods have been too costly for other surface treatment applications. However, as manufacturing devices become increasingly smaller, the use of a directed-energy ion beam is finding novel industrial applications that require the custom tailoring of new materials and devices, including magnetic storage devices, photonics, opto-electronics, and molecular transport. Engineering Thin Films and Nanostructures with Ion Beams offers a thorough narrative of the recent advances that make this technology relevant to current and future applications. Featuring internationally recognized researchers, the book compiles their expertise in a multidimensional source that: Highlights the mechanisms and visual evidence of the effects of single-ion impacts on metallic surfaces Considers how ion-beam techniques can help achieve higher disk-drive densities Introduces gas-cluster ion-beam technology and reviews its precedents Explains how ion beams are used to aggregate metals and semiconductors into nanoclusters with nonlinear optical properties Addresses current challenges in building equipment needed to produce nanostructures in an industrial setting Examines the combination of ion-beam techniques, particularly with physical vapor deposition Delineates the fabrication of nanopillars, nanoflowers, and interconnected nanochannels in three dimensions by using atomic shadowing techniques Illustrates the production of nanopores of varying dimensions in polymer films, alloys, and superconductors using ion-beam irradiation Shows how fingerprints can be made more reliable as forensic evidence by recoil-mixing them into the substrate using ion beams From the basics of the ion-beam modification of materials to state-of-the-art applications, Engineering Th

Today, the application of phase change materials (PCMs) has developed in different industries, including the solar cooling and solar power plants, photovoltaic electricity systems, the space industry, waste heat recovery systems, preservation of food and pharmaceutical products, and domestic hot water. PCMs use the principle of latent heat thermal storage to absorb energy in large quantities when there is a surplus and release it when there is a deficit. This promising technology has already been successfully implemented in many construction projects. The aim of this book is to assist the scientists and to provide the reader with a comprehensive overview of the properties that characterize the phase change materials from theoretical and experimental perspectives with a focus on their technological applications. The present status and future perspectives of phase change material are discussed.

This book presents the method of ion beam modification of solids in realization, theory and applications in a comprehensive way. It provides a review of the physical basics of ion-solid interaction and on ion-beam induced structural modifications of solids. Ion beams are widely used to modify the physical properties of materials. A complete theory of ion stopping in matter and the calculation of the energy loss due to nuclear and electronic interactions are presented including the effect of ion channeling. To explain structural modifications due to high electronic excitations, different concepts are presented with special emphasis on the thermal spike model. Furthermore, general concepts of damage evolution as a function of ion mass, ion fluence, ion flux and temperature are described in detail and their limits and applicability are discussed. The effect of nuclear and electronic energy loss on structural modifications of solids such as damage formation, phase transitions and amorphization is reviewed for insulators and semiconductors. Finally some selected applications of ion beams are given.

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Ion implantation presents a continuously evolving technology. While the benefits of ion implantation are well recognized for many commercial endeavors, there have been recent developments in this field. Improvements in equipment, understanding of beam-solid interactions, applications to new materials, improved characterization techniques, and more recent developments to use implantation for nanostructure formation point to new directions for ion implantation and are presented in this book.

"Phase Change Materials: Science and Applications" provides a unique introduction of this rapidly developing field. Clearly written and well-structured, this volume describes the material science of these fascinating materials from a theoretical and experimental perspective. Readers will find an in-depth description of their existing and potential applications in optical and solid state storage devices as well as reconfigurable logic applications. Researchers, graduate students and scientists with an interest in this field will find "Phase Change Materials" to be a valuable reference.