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"Huth, Michael"
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A concise dictionary of the avant-gardes
\"For a concise edition of his legendary arts dictionary of information and opinion, the distinguished critic and arts historian Richard Kostelanetz selects entries from the 2018 third edition. Typically he provides intelligence unavailable anywhere else, no less in print than online, about a wealth of subjects and individuals. Focused upon what is truly innovative and excellent, Kostelanetz also ranges widely with insight and surprise, including appreciations of artistic athletes such as Muhammad Ali and the Harlem Globetrotters and such collective creations as Las Vegas and his native New York City. Continuing the traditions of cheeky high-style Dictionarysts, honoring Ambrose Bierce and Samuel Johnson (both with individual entries), Kostelanetz offers a \"reference book\" to be enjoyed, not only in bits and chunks but continuously as one of the ten books someone would take if he or she planned to be stranded on a desert isle.\"--Page i.
Book
Precursor sticking coefficient determination from indented deposits fabricated by electron beam induced deposition
A fast simulation approach for focused electron beam induced deposition (FEBID) numerically solves the diffusion–reaction equation (continuum model) of the precursor surface on the growing nanostructure in conjunction with a Monte Carlo simulation for electron transport in the growing deposit. An important requirement in this regard is to have access to a methodology that can be used to systematically determine the values for the set of precursor parameters needed for this model. In this work we introduce such a method to derive the precursor sticking coefficient as one member of the precursor parameter set. The method is based on the analysis of the different growth regimes in FEBID, in particular the diffusion-enhanced growth regime in the center region of an intentionally defocused electron beam. We employ the method to determine the precursor sticking coefficient for bis(benzene)chromium, Cr(C 6 H 6 ) 2 , and trimethyl(methylcyclopentadienyl)platinum(IV), Me 3 CpPtMe, and find a value of about 10 −2 for both precursors, which is substantially smaller than the sticking coefficients previously assumed for Me 3 CpPtMe (1.0). Furthermore, depositions performed at different substrate temperatures indicate a temperature dependence of the sticking coefficient.
Journal Article
Pattern generation for direct-write three-dimensional nanoscale structures via focused electron beam induced deposition
Fabrication of three-dimensional (3D) nanoarchitectures by focused electron beam induced deposition (FEBID) has matured to a level that highly complex and functional deposits are becoming available for nanomagnetics and plasmonics. However, the generation of suitable pattern files that control the electron beam’s movement, and thereby reliably map the desired target 3D structure from a purely geometrical description to a shape-conforming 3D deposit, is nontrivial. To address this issue we developed several writing strategies and associated algorithms implemented in C++. Our pattern file generator handles different proximity effects and corrects for height-dependent precursor coverage. Several examples of successful 3D nanoarchitectures using different precursors are presented that validate the effectiveness of the implementation.
Journal Article
Writing 3D Nanomagnets Using Focused Electron Beams
Focused electron beam induced deposition (FEBID) is a direct-write nanofabrication technique able to pattern three-dimensional magnetic nanostructures at resolutions comparable to the characteristic magnetic length scales. FEBID is thus a powerful tool for 3D nanomagnetism which enables unique fundamental studies involving complex 3D geometries, as well as nano-prototyping and specialized applications compatible with low throughputs. In this focused review, we discuss recent developments of this technique for applications in 3D nanomagnetism, namely the substantial progress on FEBID computational methods, and new routes followed to tune the magnetic properties of ferromagnetic FEBID materials. We also review a selection of recent works involving FEBID 3D nanostructures in areas such as scanning probe microscopy sensing, magnetic frustration phenomena, curvilinear magnetism, magnonics and fluxonics, offering a wide perspective of the important role FEBID is likely to have in the coming years in the study of new phenomena involving 3D magnetic nanostructures.
Journal Article
AC conductivity and correlation effects in nano-granular Pt/C
Nano-granular metals are materials that fall into the general class of granular electronic systems in which the interplay of electronic correlations, disorder and finite size effects can be studied. The charge transport in nano-granular metals is dominated by thermally-assisted, sequential and correlated tunneling over a temperature-dependent number of metallic grains. Here we study the frequency-dependent conductivity (AC conductivity) of nano-granular Platinum with Pt nano-grains embedded into amorphous carbon (C). We focus on the transport regime on the insulating side of the insulator metal transition reflected by a set of samples covering a range of tunnel-coupling strengths. In this transport regime polarization contributions to the AC conductivity are small and correlation effects in the transport of free charges are expected to be particularly pronounced. We find a universal behavior in the frequency dependence that can be traced back to the temperature-dependent zero-frequency conductivity (DC conductivity) of Pt/C within a simple lumped-circuit analysis. Our results are in contradistinction to previous work on nano-granular Pd/
ZrO
2
in the very weak coupling regime where polarization contributions to the AC conductivity dominated. We describe possible future applications of nano-granular metals in proximity impedance spectroscopy of dielectric materials.
Journal Article
Three-dimensional magnetic nanotextures with high-order vorticity in soft magnetic wireframes
Additive nanotechnology enable curvilinear and three-dimensional (3D) magnetic architectures with tunable topology and functionalities surpassing their planar counterparts. Here, we experimentally reveal that 3D soft magnetic wireframe structures resemble compact manifolds and accommodate magnetic textures of high order vorticity determined by the Euler characteristic,
χ
. We demonstrate that self-standing magnetic tetrapods (homeomorphic to a sphere;
χ
= + 2) support six surface topological solitons, namely four vortices and two antivortices, with a total vorticity of + 2 equal to its Euler characteristic. Alternatively, wireframe structures with one loop (homeomorphic to a torus;
χ
= 0) possess equal number of vortices and antivortices, which is relevant for spin-wave splitters and 3D magnonics. Subsequent introduction of
n
holes into the wireframe geometry (homeomorphic to an
n
-torus;
χ
< 0) enables the accommodation of a virtually unlimited number of antivortices, which suggests their usefulness for non-conventional (e.g., reservoir) computation. Furthermore, complex stray-field topologies around these objects are of interest for superconducting electronics, particle trapping and biomedical applications.
The spin texture of a magnetic system can host a variety of topological spin textures, the most famous of these being skyrmions. Here, Volkov et al demonstrate higher order vorticity in magnetic wireframe nanostructures and introduce a general protocol for the creation of arbitrary numbers of vortices and antivortices in such wireframe structures.
Journal Article
Direct-write of free-form building blocks for artificial magnetic 3D lattices
By the fabrication of periodically arranged nanomagnetic systems it is possible to engineer novel physical properties by realizing artificial lattice geometries that are not accessible via natural crystallization or chemical synthesis. This has been accomplished with great success in two dimensions in the fields of artificial spin ice and magnetic logic devices, to name just two. Although first proposals have been made to advance into three dimensions (3D), established nanofabrication pathways based on electron beam lithography have not been adapted to obtain free-form 3D nanostructures. Here we demonstrate the direct-write fabrication of freestanding ferromagnetic 3D nano-architectures. By employing micro-Hall sensing, we have determined the magnetic stray field generated by our free-form structures in an externally applied magnetic field and we have performed micromagnetic and macro-spin simulations to deduce the spatial magnetization profiles in the structures and analyze their switching behavior. Furthermore we show that the magnetic 3D elements can be combined with other 3D elements of different chemical composition and intrinsic material properties.
Journal Article
Fast and Efficient Simulation of the FEBID Process with Thermal Effects
Focused electron-beam-induced deposition (FEBID) is a highly versatile direct-write approach with particular strengths in the 3D nanofabrication of functional materials. Despite its apparent similarity to other 3D printing approaches, non-local effects related to precursor depletion, electron scattering and sample heating during the 3D growth process complicate the shape-true transfer from a target 3D model to the actual deposit. Here, we describe an efficient and fast numerical approach to simulate the growth process, which allows for a systematic study of the influence of the most important growth parameters on the resulting shape of the 3D structures. The precursor parameter set derived in this work for the precursor Me3PtCpMe enables a detailed replication of the experimentally fabricated nanostructure, taking beam-induced heating into account. The modular character of the simulation approach allows for additional future performance increases using parallelization or drawing on the use of graphics cards. Ultimately, beam-control pattern generation for 3D FEBID will profit from being routinely combined with this fast simulation approach for optimized shape transfer.
Journal Article
Mobile fluxons as coherent probes of periodic pinning in superconductors
The interaction of (quasi)particles with a periodic potential arises in various domains of science and engineering, such as solid-state physics, chemical physics, and communication theory. An attractive test ground to investigate this interaction is represented by superconductors with artificial pinning sites, where magnetic flux quanta (Abrikosov vortices) interact with the pinning potential
U
(
r
) =
U
(
r
+
R
) induced by a nanostructure. At a combination of microwave and dc currents, fluxons act as mobile probes of
U
(
r
): The ac component shakes the fluxons in the vicinity of their equilibrium points which are unequivocally determined by the local pinning force counterbalanced by the Lorentz force induced by the dc current, linked to the curvature of
U
(
r
) which can then be used for a successful fitting of the voltage responses. A good correlation of the deduced dependences
U
(
r
) with the cross sections of the nanostructures points to that pinning is primarily caused by vortex length reduction. Our findings pave a new route to a non-destructive evaluation of periodic pinning in superconductor thin films. The approach should also apply to a broad class of systems whose evolution in time can be described by the coherent motion of (quasi)particles in a periodic potential.
Journal Article
Focused Electron Beam-Based 3D Nanoprinting for Scanning Probe Microscopy: A Review
Scanning probe microscopy (SPM) has become an essential surface characterization technique in research and development. By concept, SPM performance crucially depends on the quality of the nano-probe element, in particular, the apex radius. Now, with the development of advanced SPM modes beyond morphology mapping, new challenges have emerged regarding the design, morphology, function, and reliability of nano-probes. To tackle these challenges, versatile fabrication methods for precise nano-fabrication are needed. Aside from well-established technologies for SPM nano-probe fabrication, focused electron beam-induced deposition (FEBID) has become increasingly relevant in recent years, with the demonstration of controlled 3D nanoscale deposition and tailored deposit chemistry. Moreover, FEBID is compatible with practically any given surface morphology. In this review article, we introduce the technology, with a focus on the most relevant demands (shapes, feature size, materials and functionalities, substrate demands, and scalability), discuss the opportunities and challenges, and rationalize how those can be useful for advanced SPM applications. As will be shown, FEBID is an ideal tool for fabrication/modification and rapid prototyping of SPM-tipswith the potential to scale up industrially relevant manufacturing.
Journal Article