A novel copper precursor for electron beam induced deposition

A fluorine free copper precursor, Cu(tbaoac)2 with the chemical sum formula CuC16O6H26 is introduced for focused electron beam induced deposition (FEBID). FEBID with 15 keV and 7 nA results in deposits with an atomic composition of Cu:O:C of approximately 1:1:2. Transmission electron microscopy proved that pure copper nanocrystals with sizes of up to around 15 nm were dispersed inside the carbonaceous matrix. Raman investigations revealed a high degree of amorphization of the carbonaceous matrix and showed hints for partial copper oxidation taking place selectively on the surfaces of the deposits. Optical transmission/reflection measurements of deposited pads showed a dielectric behavior of the material in the optical spectral range. The general behavior of the permittivity could be described by applying the Maxwell–Garnett mixing model to amorphous carbon and copper. The dielectric function measured from deposited pads was used to simulate the optical response of tip arrays fabricated out of the same precursor and showed good agreement with measurements. This paves the way for future plasmonic applications with copper-FEBID

Microcompression high cycle fatigue tests up to 10 million cycles

Nanomechanical tests are moving beyond hardness and modulus to encompass host of different mechanical properties like strain rate sensitivity [1, 2], stress relaxation [3], creep, and fracture toughness [4] by taking advantage of focused ion beam milled geometries. Adding high cycle fatigue to this list will be useful to extend the gamut of properties studied at the micro/nanoscale. However, this presents inherent challenges like low oscillation frequencies, long duration of tests and large thermal drift when attempted with standard indenters. This presentation will report, for the first time, the development of micropillar compression-compression high cycle fatigue tests going up to 10 million cycles. This has been made possible by the development of a novel piezo-based nanoindentation technique that allows accessing extremely high strain rates (\u3e104 s-1) and high oscillation frequencies (up to 10 kHz). The associated instrumentation and technique development, design of the fatigue tests at the micron scale, data analysis methodology, experimental protocol and challenges will be discussed. Validation data on single crystal silicon, a reference material, will be presented to demonstrate the reliability of the designed high cycle fatigue tests. Finally, case studies of compression-compression high cycle micropillar fatigue on nanostructured materials will be presented and their results will be discussed in light of existing literature data, particularly the operative deformation mechanism(s). The convolution of time dependent plasticity in such tests will also be addressed. It is hoped that this study will pave way for routine high cycle fatigue tests of metals at the micron scale and provide clues for designing a similar indentation fatigue test. [1] Mohanty G, Wheeler JM, Raghavan R, Wehrs J, Hasegawa M, Mischler S, et al. Elevated temperature, strain rate jump microcompression of nanocrystalline nickel. Philosophical Magazine 2015;95:1878-95. [2] Wehrs J, Mohanty G, Guillonneau G, Taylor AA, Maeder X, Frey D, et al. Comparison of In Situ Micromechanical Strain-Rate Sensitivity Measurement Techniques. Jom 2015;67:1684-93. [3] Mohanty G, Wehrs J, Boyce BL, Taylor AA, Hasegawa M, Philippe L, et al. Room temperature stress relaxation in nanocrystalline Ni measured by micropillar compression and miniature tension. Journal of Materials Research 2016;In press. [4] Sebastiani M, Johanns K, Herbert EG, Carassiti F, Pharr G. A novel pillar indentation splitting test for measuring fracture toughness of thin ceramic coatings. Philosophical Magazine 2015;95:1928-44

Pulsed current-voltage electrodeposition of stoichiometric Bi2Te3 nanowires and their crystallographic characterization by transmission electron backscatter diffraction

Bi2Te3 nanowires with diameters ranging from 25 to 270 nm, ultra-high aspect ratio, and uniform growth front were fabricated by electrodeposition, pulsing between zero current density during the off time and constant potential during the on time (pulsed-current-voltage method, p-IV). The use of zero current density during the off time is to ensure no electrodeposition is carried out and the system is totally relaxed. By this procedure, stoichiometric nanowires oriented perpendicular to the c-axis is obtained for the different diameters of porous alumina templates. In addition, the samples show a uniform growth front with ultra-high aspect ratio single crystal nanowires. The high degree of crystallinity was verified by transmission electron backscatter diffraction. This characterization revealed that the nanowires present both large single crystalline areas and areas with alternating twin configurations

Interfacial adhesion of compositional gradient ternary FCC alloy films

Combinatorial materials design of thin films allows for the investigation of fundamental mechanic relationships and optimization of thin films for engineering applications. By depositing a wide range of compositions on a single sample, a systematic study of the full alloy composition of particular material system can be investigated for a number of different properties in a relatively short amount of time. Using an integrated shutter controller, specifically designed and manufactured to allow for precise control over coating design, ternary alloys with the full compositional range can be deposited on a single wafer. By specifically programming the shutters it was possible to create multilayered thickness gradients of three elements, which were then annealed to create thin films with a large compositional gradient across the wafer. The adhesion strength of an Al2O3­ ALD coating on two such compositional gradient FCC alloy adhesion layers, AlCuAu and AuAgPd, was investigated as a function of the changing composition. The AlCuAu alloy sample consists of multiple phases and intermetallics across the wafer which are dependent on composition; whereas the AuAgPd alloy is a solid-solution across the compositional gradient. For this investigation, instrumented indentation with a conical diamond tip was used to locally measure the adhesion of the ALD coating with different adhesion layer compositions. By performing small arrays of indents over the surface of the coating, it was possible to test the adhesion-promoting properties of a broad spectrum of interface compositions in a single sample. Please click Additional Files below to see the full abstract

More on Supersymmetric Domain Walls, N Counting and Glued Potentials

Various features of domain walls in supersymmetric gluodynamics are discussed. We give a simple field-theoretic interpretation of the phenomenon of strings ending on the walls recently conjectured by Witten. An explanation of this phenomenon in the framework of gauge field theory is outlined. The phenomenon is argued to be particularly natural in supersymmetric theories which support degenerate vacuum states with distinct physical properties. The issue of existence (or non-existence) of the BPS saturated walls in the theories with glued (super)potentials is addressed. The amended Veneziano-Yankielowicz effective Lagrangian belongs to this class. The physical origin of the cusp structure of the effective Lagrangian is revealed, and the limitation it imposes on the calculability of the wall tension is explained. Related problems are considered. In particular, it is shown that the so called discrete anomaly matching, when properly implemented, does not rule out the chirally symmetric phase of supersymmetric gluodynamics, contrary to recent claims.Comment: 40 pages, Latex, 5 figures. Several references added, final version to be published in Physical Review

Existence of spinning solitons in gauge field theory

We study the existence of classical soliton solutions with intrinsic angular momentum in Yang-Mills-Higgs theory with a compact gauge group $\mathcal{G}$ in (3+1)-dimensional Minkowski space. We show that for \textit{symmetric} gauge fields the Noether charges corresponding to \textit{rigid} spatial symmetries, as the angular momentum, can be expressed in terms of \textit{surface} integrals. Using this result, we demonstrate in the case of $\mathcal{G}=SU(2)$ the nonexistence of stationary and axially symmetric spinning excitations for all known topological solitons in the one-soliton sector, that is, for 't Hooft--Polyakov monopoles, Julia-Zee dyons, sphalerons, and also vortices.Comment: 21 pages, to appear in Phys.Rev.

Calogero-Sutherland Approach to Defect Blocks

Extended objects such as line or surface operators, interfaces or boundaries play an important role in conformal field theory. Here we propose a systematic approach to the relevant conformal blocks which are argued to coincide with the wave functions of an integrable multi-particle Calogero-Sutherland problem. This generalizes a recent observation in 1602.01858 and makes extensive mathematical results from the modern theory of multi-variable hypergeometric functions available for studies of conformal defects. Applications range from several new relations with scalar four-point blocks to a Euclidean inversion formula for defect correlators.Comment: v2: changes for clarit

Localizing gravity on a 't Hooft-Polyakov monopole in seven dimensions

We present regular solutions for a brane world scenario in the form of a 't Hooft-Polyakov monopole living in the three-dimensional spherical symmetric transverse space of a seven-dimensional spacetime. In contrast to the cases of a domain-wall in five dimensions and a string in six dimensions, there exist gravity-localizing solutions for both signs of the bulk cosmological constant. A detailed discussion of the parameter space that leads to localization of gravity is given. A point-like monopole limit is discussed.Comment: 29 pages, 17 figure

Counting Domain Walls in N=1 Super Yang-Mills Theory

We study the multiplicity of BPS domain walls in N=1 super Yang-Mills theory, by passing to a weakly coupled Higgs phase through the addition of fundamental matter. The number of domain walls connecting two specified vacuum states is then determined via the Witten index of the induced worldvolume theory, which is invariant under the deformation to the Higgs phase. The worldvolume theory is a sigma model with a Grassmanian target space which arises as the coset associated with the global symmetries broken by the wall solution. Imposing a suitable infrared regulator, the result is found to agree with recent work of Acharya and Vafa in which the walls were realized as wrapped D4-branes in IIA string theory.Comment: 28 pages, RevTeX, 3 figures; v2: discussion of the index slightly expanded, using an alternative regulator, and references added; v3: typos corrected, to appear in Phys. Rev.

Intraoperative electroencephalogram patterns as predictors of postoperative delirium in older patients: a systematic review and meta-analysis

BackgroundPostoperative delirium (POD) significantly affects patient outcomes after surgery, leading to increased morbidity, extended hospital stays, and potential long-term cognitive decline. This study assessed the predictive value of intraoperative electroencephalography (EEG) patterns for POD in adults.MethodsThis systematic review and meta-analysis followed the PRISMA and Cochrane Handbook guidelines. A thorough literature search was conducted using PubMed, Medline, and CENTRAL databases focusing on intraoperative native EEG signal analysis in adult patients. The primary outcome was the relationship between the burst suppression EEG pattern and POD development.ResultsFrom the initial 435 articles identified, 19 studies with a total of 7,229 patients were included in the systematic review, with 10 included in the meta-analysis (3,705 patients). In patients exhibiting burst suppression, the POD incidence was 22.1% vs. 13.4% in those without this EEG pattern (p=0.015). Furthermore, an extended burst suppression duration associated with a higher likelihood of POD occurrence (p = 0.016). Interestingly, the burst suppression ratio showed no significant association with POD.ConclusionsThis study revealed a 41% increase in the relative risk of developing POD in cases where a burst suppression pattern was present. These results underscore the clinical relevance of intraoperative EEG monitoring in predicting POD in older patients, suggesting its potential role in preventive strategies.Systematic Review RegistrationThis study was registered on International Platform for Registered Protocols for Systematic Reviews and Meta-Analyses: INPLASY202420001, https://doi.org/10.37766/inplasy2024.2.0001