The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Bharat Bhushan - One of the best experts on this subject based on the ideXlab platform.
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frontiers in nanotribology Magnetic Storage bio nanotechnology cosmetics and bioinspiration
Journal of Colloid and Interface Science, 2020Co-Authors: Bharat BhushanAbstract:Abstract The word “nanotribology” was introduced for the first time in the title of a paper and a book in 1995. This field encompasses fundamental studies of surface characterization, adhesion, friction, scratching, wear, and lubrication at the atomic scale. At most solid-solid interfaces of technological relevance, contact occurs at numerous asperities. It is of importance to investigate a single asperity contact in the fundamental tribological studies. A nanoprobe sliding on a surface in probe-based microscopies, including atomic force microscopy (AFM) at ultralow loads, simulates one such contact. AFMs and depth-sensing nanoindentation techniques are also used for nanomechanical characterization. The field is referred to as nanomechanics. AFMs can also be used for nanoelectrical characterization which includes electrical resistance, surface potential, and capacitance mapping. Research in the field of nanotribology and nanomechanics was initiated by or for the Magnetic Storage industry in the late 1980s. Later in the mid-1990s, nanotribology and nanomechanics research became important in bio/nanotechnology devices which involve relative motion, as well as ultrathin films. Adhesion, friction and wear issues in bio/nanotechnology devices led to the development of the field of bio/nanotribology. Research in ultrathin films used in the cosmetic industry, including hair, hair conditioner, skin, and skin cream, led to development of the field of nanotribology in cosmetics. Biologically inspired design, adaptation, or derivation from nature, referred to as biomimetics or bioinspiration, can guide us to initiate and produce nanomaterials, nanodevices, and processes in a sustainable and environmentally friendly manner. So called, green nanotribology research is important in this field. This perspective article presents an overview of fundamental understanding of nanotribology and nanomechanics and their applications in various fields ranging from Magnetic Storage, bio/nanotechnology, hair and hair conditioner, skin and skin cream, and bioinspiration (green nanotribology).
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Frontiers in nanotribology: Magnetic Storage, bio/nanotechnology, cosmetics, and bioinspiration.
Journal of colloid and interface science, 2020Co-Authors: Bharat BhushanAbstract:Abstract The word “nanotribology” was introduced for the first time in the title of a paper and a book in 1995. This field encompasses fundamental studies of surface characterization, adhesion, friction, scratching, wear, and lubrication at the atomic scale. At most solid-solid interfaces of technological relevance, contact occurs at numerous asperities. It is of importance to investigate a single asperity contact in the fundamental tribological studies. A nanoprobe sliding on a surface in probe-based microscopies, including atomic force microscopy (AFM) at ultralow loads, simulates one such contact. AFMs and depth-sensing nanoindentation techniques are also used for nanomechanical characterization. The field is referred to as nanomechanics. AFMs can also be used for nanoelectrical characterization which includes electrical resistance, surface potential, and capacitance mapping. Research in the field of nanotribology and nanomechanics was initiated by or for the Magnetic Storage industry in the late 1980s. Later in the mid-1990s, nanotribology and nanomechanics research became important in bio/nanotechnology devices which involve relative motion, as well as ultrathin films. Adhesion, friction and wear issues in bio/nanotechnology devices led to the development of the field of bio/nanotribology. Research in ultrathin films used in the cosmetic industry, including hair, hair conditioner, skin, and skin cream, led to development of the field of nanotribology in cosmetics. Biologically inspired design, adaptation, or derivation from nature, referred to as biomimetics or bioinspiration, can guide us to initiate and produce nanomaterials, nanodevices, and processes in a sustainable and environmentally friendly manner. So called, green nanotribology research is important in this field. This perspective article presents an overview of fundamental understanding of nanotribology and nanomechanics and their applications in various fields ranging from Magnetic Storage, bio/nanotechnology, hair and hair conditioner, skin and skin cream, and bioinspiration (green nanotribology).
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Micro/Nanotribology and Micro/Nanomechanics of Magnetic Storage Devices
Nanotribology and Nanomechanics II, 2011Co-Authors: Bharat BhushanAbstract:A Magnetic recording process involves relative motion between a Magnetic medium (tape or disk) against a stationary or rotating read/write Magnetic head. For ever-increasing, high areal recording density, the linear flux density (number of flux reversals per unit distance) and the track density (number of tracks per unit distance) should be as high as possible. The size of a single bit dimension for current devices is typically less than 1000 nm2. This dimension places stringent restrictions on the defect size present on the head and medium surfaces. Reproduced (read-back) Magnetic signal amplitude decreases with a decrease in the recording wavelength and/or the track width. The signal loss results from the Magnetic coating thickness, read gap length, and head-to-medium spacing (clearance or flying height). It is known that the signal loss as a result of spacing can be reduced exponentially by reducing the separation between the head and the medium. The need for increasingly higher recording densities requires that surfaces be as smooth as possible and the flying height (physical separation or clearance between a head and a medium) be as low as possible. The ultimate objective is to run two surfaces in contact (with practically zero physical separation) if the tribological issues can be resolved. Smooth surfaces in near contact lead to an increase in adhesion, friction, and interface temperatures, and closer flying heights lead to occasional rubbing of high asperities and increased wear. Friction and wear issues are resolved by appropriate selection of interface materials and lubricants, by controlling the dynamics of the head and medium, and the environment. A fundamental understanding of the tribology (friction, wear, and lubrication) of the Magnetic head/medium interface, both on macro- and micro/nanoscales, becomes crucial for the continued growth of this more than $ 60 billion a year Magnetic Storage industry. In this chapter, initially, the general operation of drives and the construction and materials used in Magnetic head and medium components are described. Then the micro/nanotribological and micro/nanomechanics studies including surface roughness, friction, adhesion, scratching, wear, indentation, and lubrication relevant to Magnetic Storage devices are presented.
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Introduction—Measurement Techniques and Applications
Nanotribology and Nanomechanics I, 2011Co-Authors: Bharat BhushanAbstract:In this introductory chapter, the definition and history of tribology and their industrial significance and origins and significance of an emerging field of micro/nanotribology are described. Next, various measurement techniques used in micro/nanotribological and micro/nanomechanical studies are described. The interest in micro/nanotribology field grew from Magnetic Storage devices and latter the applicability to emerging field micro/nanoelectromechanical systems (MEMS/NEMS) became clear. A few examples of Magnetic Storage devices and MEMS/NEMS are presented where micro/nanotribological and micro/nanomechanical tools and techniques are essential for interfacial studies. Finally, reasons why micro/nanotribological and micro/nanomechanical studies are important in Magnetic Storage devices and MEMS/NEMS are presented. In the last section, organization of the book is presented.
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micro nanotribology and micro nanomechanics of Magnetic Storage devices
2011Co-Authors: Bharat BhushanAbstract:A Magnetic recording process involves relative motion between a Magnetic medium (tape or disk) against a stationary or rotating read/write Magnetic head. For ever-increasing, high areal recording density, the linear flux density (number of flux reversals per unit distance) and the track density (number of tracks per unit distance) should be as high as possible. The size of a single bit dimension for current devices is typically less than 1000 nm2. This dimension places stringent restrictions on the defect size present on the head and medium surfaces. Reproduced (read-back) Magnetic signal amplitude decreases with a decrease in the recording wavelength and/or the track width. The signal loss results from the Magnetic coating thickness, read gap length, and head-to-medium spacing (clearance or flying height). It is known that the signal loss as a result of spacing can be reduced exponentially by reducing the separation between the head and the medium. The need for increasingly higher recording densities requires that surfaces be as smooth as possible and the flying height (physical separation or clearance between a head and a medium) be as low as possible. The ultimate objective is to run two surfaces in contact (with practically zero physical separation) if the tribological issues can be resolved. Smooth surfaces in near contact lead to an increase in adhesion, friction, and interface temperatures, and closer flying heights lead to occasional rubbing of high asperities and increased wear. Friction and wear issues are resolved by appropriate selection of interface materials and lubricants, by controlling the dynamics of the head and medium, and the environment. A fundamental understanding of the tribology (friction, wear, and lubrication) of the Magnetic head/medium interface, both on macro- and micro/nanoscales, becomes crucial for the continued growth of this more than $ 60 billion a year Magnetic Storage industry. In this chapter, initially, the general operation of drives and the construction and materials used in Magnetic head and medium components are described. Then the micro/nanotribological and micro/nanomechanics studies including surface roughness, friction, adhesion, scratching, wear, indentation, and lubrication relevant to Magnetic Storage devices are presented.
H. Hilgers - One of the best experts on this subject based on the ideXlab platform.
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Resonant Raman characterisation of ultra-thin nano-protective carbon layers for Magnetic Storage devices
Surface & Coatings Technology, 2003Co-Authors: M. V. Gradowski, B. Jacoby, R. Ohr, H. Hilgers, Andrea Ferrari, H.-h. Schneider, H. AdrianAbstract:Abstract Carbon thin films are very important as protective coatings for a wide range of applications such as Magnetic Storage devices. The key parameter of interest is the sp3 fraction, since it controls the mechanical properties of the film. Visible Raman spectroscopy is a very popular technique to determine the carbon bonding. However, the visible Raman spectra mainly depend on the configuration and clustering of the sp2 sites. This can result in the Raman spectra of different samples looking similar albeit having a different structure. Thus, visible Raman alone cannot be used to derive the sp3 content. Here we monitor the carbon bonding by using a combined study of Raman spectra taken at two wavelengths (514 and 244 nm). We show how the G peak dispersion is a very useful parameter to investigate the carbon samples and we endorse it as a production-line characterisation tool. The dispersion is proportional to the degree of disorder, thus making it possible to distinguish between graphitic and diamond-like carbon.
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Nanotribological properties of ultra-thin carbon coatings for Magnetic Storage devices
Surface & Coatings Technology, 2003Co-Authors: B. Jacoby, A. Wienss, R. Ohr, M. Von Gradowski, H. HilgersAbstract:In the Magnetic Storage industry ultra-thin amorphous carbon coatings are commonly used to protect read/write head and Magnetic media against corrosion and mechanical damage. In our work, the mechanical properties of different carbon coatings produced with magnetron-sputtering (MS) and filtered high-current pulsed arc (HCA) are compared by using an AFM-based scratching technique. The presented method allows the generation and analyzation of very shallow scratches with residual depths of only a few Angstroms and even below. This enables a determination of the scratch resistance of ultra-thin coatings even in the nanometer range widely independent from the hardness of the substrate. A comparison to X-ray reflectivity measurements exhibits a clear correlation between the scratch resistance and the mass density of the investigated coatings. It is shown that a variation of the film thicknesses from 5 to 2 nm has very different effects on their mechanical properties and strongly depends on the deposition technique and temperature. In tribological respect it turns out that the HCA films are superior to the MS films even if prepared at typical disk deposition temperatures of approximately 200 °C.
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Characterisation of amorphous carbon coatings for Magnetic Storage devices via AFM‐Nanoscratching devices. AFM‐Nanoscratching an amorphen Kohlenstoffschichten für die Speichertechnologie
Vakuum in Forschung und Praxis, 2003Co-Authors: B. Jacoby, A. Wienss, R. Ohr, M. V. Gradowski, B. Petereit, H. HilgersAbstract:The mechanical properties of ultra-thin amorphous carbon films used as protective coatings for Magnetic Storage devices were investigated by means of atomic force microscopy (AFM). Diamond-tipped cantilevers were used in order to generate scratches with residual scratch depths of only a few Angstroms and even below. The presented method simulates mechanical strains at the head-disk interface. A driftcompensating image subtracting technique allows the visualisation of these ultra-shallow scratches and enables the mechanical characterisation of only few Nanometer films widely independent from the hardness of the substrate. The scratch resistance as it is defined here correlates well with the mass density and the sp3 content of the investigated films.
Paul B Fischer - One of the best experts on this subject based on the ideXlab platform.
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single domain Magnetic pillar array of 35 nm diameter and 65 gbits in 2 density for ultrahigh density quantum Magnetic Storage
Journal of Applied Physics, 1994Co-Authors: Stephen Y Chou, Mark S Wei, Peter R Krauss, Paul B FischerAbstract:Using electron beam nanolithography and electroplating, arrays of Ni pillars on silicon that have a uniform diameter of 35 nm, a height of 120 nm, and a period of 100 nm were fabricated. The density of the pillar arrays is 65 Gbits/in.2—over two orders of magnitude greater than the state‐of‐the‐art Magnetic Storage density. Because of their nanoscale size, shape anisotropy, and separation from each other, each Ni pillar is single domain with only two quantized perpendicular magnetization states: up and down. Each pillar can be used to store one bit of information, therefore such nanoMagnetic pillar array Storage offers a rather different paradigm than the conventional Storage method. A quantum Magnetic disk scheme that is based on uniformly embedding single‐domain Magnetic structures in a nonMagnetic disk is proposed.
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Single‐domain Magnetic pillar array of 35 nm diameter and 65 Gbits/in.2 density for ultrahigh density quantum Magnetic Storage
Journal of Applied Physics, 1994Co-Authors: Stephen Y Chou, Mark S Wei, Peter R Krauss, Paul B FischerAbstract:Using electron beam nanolithography and electroplating, arrays of Ni pillars on silicon that have a uniform diameter of 35 nm, a height of 120 nm, and a period of 100 nm were fabricated. The density of the pillar arrays is 65 Gbits/in.2—over two orders of magnitude greater than the state‐of‐the‐art Magnetic Storage density. Because of their nanoscale size, shape anisotropy, and separation from each other, each Ni pillar is single domain with only two quantized perpendicular magnetization states: up and down. Each pillar can be used to store one bit of information, therefore such nanoMagnetic pillar array Storage offers a rather different paradigm than the conventional Storage method. A quantum Magnetic disk scheme that is based on uniformly embedding single‐domain Magnetic structures in a nonMagnetic disk is proposed.
A. Wienss - One of the best experts on this subject based on the ideXlab platform.
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Nanotribological properties of ultra-thin carbon coatings for Magnetic Storage devices
Surface & Coatings Technology, 2003Co-Authors: B. Jacoby, A. Wienss, R. Ohr, M. Von Gradowski, H. HilgersAbstract:In the Magnetic Storage industry ultra-thin amorphous carbon coatings are commonly used to protect read/write head and Magnetic media against corrosion and mechanical damage. In our work, the mechanical properties of different carbon coatings produced with magnetron-sputtering (MS) and filtered high-current pulsed arc (HCA) are compared by using an AFM-based scratching technique. The presented method allows the generation and analyzation of very shallow scratches with residual depths of only a few Angstroms and even below. This enables a determination of the scratch resistance of ultra-thin coatings even in the nanometer range widely independent from the hardness of the substrate. A comparison to X-ray reflectivity measurements exhibits a clear correlation between the scratch resistance and the mass density of the investigated coatings. It is shown that a variation of the film thicknesses from 5 to 2 nm has very different effects on their mechanical properties and strongly depends on the deposition technique and temperature. In tribological respect it turns out that the HCA films are superior to the MS films even if prepared at typical disk deposition temperatures of approximately 200 °C.
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Characterisation of amorphous carbon coatings for Magnetic Storage devices via AFM‐Nanoscratching devices. AFM‐Nanoscratching an amorphen Kohlenstoffschichten für die Speichertechnologie
Vakuum in Forschung und Praxis, 2003Co-Authors: B. Jacoby, A. Wienss, R. Ohr, M. V. Gradowski, B. Petereit, H. HilgersAbstract:The mechanical properties of ultra-thin amorphous carbon films used as protective coatings for Magnetic Storage devices were investigated by means of atomic force microscopy (AFM). Diamond-tipped cantilevers were used in order to generate scratches with residual scratch depths of only a few Angstroms and even below. The presented method simulates mechanical strains at the head-disk interface. A driftcompensating image subtracting technique allows the visualisation of these ultra-shallow scratches and enables the mechanical characterisation of only few Nanometer films widely independent from the hardness of the substrate. The scratch resistance as it is defined here correlates well with the mass density and the sp3 content of the investigated films.
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Applied surface analysis in Magnetic Storage technology
Applied Surface Science, 2001Co-Authors: Johannes Windeln, Christian Bram, Heinz-ludwig Eckes, Dirk Hammel, Johanna Huth, Jan Marien, Holger Röhl, Christoph Schug, Michael Wahl, A. WienssAbstract:Abstract This paper gives a synopsis of today’s challenges and requirements for a surface analysis and materials science laboratory with a special focus on Magnetic recording technology. The critical Magnetic recording components, i.e. the protective carbon overcoat (COC), the disk layer structure, the read/write head including the giant-magnetoresistive (GMR) sensor, are described and options for their characterization with specific surface and structure analysis techniques are given. For COC investigations, applications of Raman spectroscopy to the structural analysis and determination of thickness, hydrogen and nitrogen content are discussed. Hardness measurements by atomic force microscopy (AFM) scratching techniques are presented. Surface adsorption phenomena on disk substrates or finished disks are characterized by contact angle analysis or so-called piezo-electric mass adsorption systems (PEMAS), also known as quartz crystal microbalance (QCM). A quickly growing field of applications is listed for various X-ray analysis techniques, such as disk Magnetic layer texture analysis for X-ray diffraction, compositional characterization via X-ray fluorescence, compositional analysis with high lateral resolution via electron microprobe analysis. X-ray reflectometry (XRR) has become a standard method for the absolute measurement of individual layer thicknesses contained in multi-layer stacks and thus, is the successor of ellipsometry for this application. Due to the ongoing reduction of critical feature sizes, the analytical challenges in terms of lateral resolution, sensitivity limits and dedicated nano-preparation have been consistently growing and can only be met by state-of-the-art Auger electron spectrometers (AES), transmission electron microscopy (TEM) analysis, time-of-flight–secondary ion mass spectroscopy (ToF–SIMS) characterization, focused ion beam (FIB) sectioning and TEM lamella preparation via FIB. The depth profiling of GMR sensor full stacks was significantly improved by the ToF–SIMS Cs method.
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Subnanometer scale tribological properties of nitrogen containing carbon coatings used in Magnetic Storage devices
Journal of Vacuum Science & Technology A: Vacuum Surfaces and Films, 2000Co-Authors: A. Wienss, G. Persch-schuy, R. Hartmann, P. Joeris, U. HartmannAbstract:Ultrathin carbon coatings are used in the Magnetic Storage industry to protect sensitive sensor heads and Magnetic media against corrosion and mechanical damage. Such damage can be modeled by artificially generated scratches using scanning force microscope techniques. Loading forces in the μN range are applied, resulting in scratches with residual depths of only a few A. A special image subtraction technique is used which allows careful analysis of tiny grooves even on rough surfaces. The scratching resistance of various CNx films, magnetron sputtered on hard disks with a thickness of about 12 nm, was determined and found to improve with an increased nitrogen content (6–16 at.%). This behavior, together with a linear downward shift of the Raman G-peak position from 1569 to 1564 cm−1, supports the assumption that the incorporation of nitrogen increases the fraction of sp3 bonds.
B. Jacoby - One of the best experts on this subject based on the ideXlab platform.
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Resonant Raman characterisation of ultra-thin nano-protective carbon layers for Magnetic Storage devices
Surface & Coatings Technology, 2003Co-Authors: M. V. Gradowski, B. Jacoby, R. Ohr, H. Hilgers, Andrea Ferrari, H.-h. Schneider, H. AdrianAbstract:Abstract Carbon thin films are very important as protective coatings for a wide range of applications such as Magnetic Storage devices. The key parameter of interest is the sp3 fraction, since it controls the mechanical properties of the film. Visible Raman spectroscopy is a very popular technique to determine the carbon bonding. However, the visible Raman spectra mainly depend on the configuration and clustering of the sp2 sites. This can result in the Raman spectra of different samples looking similar albeit having a different structure. Thus, visible Raman alone cannot be used to derive the sp3 content. Here we monitor the carbon bonding by using a combined study of Raman spectra taken at two wavelengths (514 and 244 nm). We show how the G peak dispersion is a very useful parameter to investigate the carbon samples and we endorse it as a production-line characterisation tool. The dispersion is proportional to the degree of disorder, thus making it possible to distinguish between graphitic and diamond-like carbon.
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Nanotribological properties of ultra-thin carbon coatings for Magnetic Storage devices
Surface & Coatings Technology, 2003Co-Authors: B. Jacoby, A. Wienss, R. Ohr, M. Von Gradowski, H. HilgersAbstract:In the Magnetic Storage industry ultra-thin amorphous carbon coatings are commonly used to protect read/write head and Magnetic media against corrosion and mechanical damage. In our work, the mechanical properties of different carbon coatings produced with magnetron-sputtering (MS) and filtered high-current pulsed arc (HCA) are compared by using an AFM-based scratching technique. The presented method allows the generation and analyzation of very shallow scratches with residual depths of only a few Angstroms and even below. This enables a determination of the scratch resistance of ultra-thin coatings even in the nanometer range widely independent from the hardness of the substrate. A comparison to X-ray reflectivity measurements exhibits a clear correlation between the scratch resistance and the mass density of the investigated coatings. It is shown that a variation of the film thicknesses from 5 to 2 nm has very different effects on their mechanical properties and strongly depends on the deposition technique and temperature. In tribological respect it turns out that the HCA films are superior to the MS films even if prepared at typical disk deposition temperatures of approximately 200 °C.
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Characterisation of amorphous carbon coatings for Magnetic Storage devices via AFM‐Nanoscratching devices. AFM‐Nanoscratching an amorphen Kohlenstoffschichten für die Speichertechnologie
Vakuum in Forschung und Praxis, 2003Co-Authors: B. Jacoby, A. Wienss, R. Ohr, M. V. Gradowski, B. Petereit, H. HilgersAbstract:The mechanical properties of ultra-thin amorphous carbon films used as protective coatings for Magnetic Storage devices were investigated by means of atomic force microscopy (AFM). Diamond-tipped cantilevers were used in order to generate scratches with residual scratch depths of only a few Angstroms and even below. The presented method simulates mechanical strains at the head-disk interface. A driftcompensating image subtracting technique allows the visualisation of these ultra-shallow scratches and enables the mechanical characterisation of only few Nanometer films widely independent from the hardness of the substrate. The scratch resistance as it is defined here correlates well with the mass density and the sp3 content of the investigated films.