52 research outputs found
Sputter Deposited Magnetostrictive Layers for SAW Magnetic Field Sensors
For the best possible limit of detection of any thin film-based magnetic field sensor, the functional magnetic film properties are an essential parameter. For sensors based on magnetostrictive layers, the chemical composition, morphology and intrinsic stresses of the layer have to be controlled during film deposition to further control magnetic influences such as crystallographic effects, pinning effects and stress anisotropies. For the application in magnetic surface acoustic wave sensors, the magnetostrictive layers are deposited on rotated piezoelectric single crystal substrates. The thermomechanical properties of quartz can lead to undesirable layer stresses and associated magnetic anisotropies if the temperature increases during deposition. With this in mind, we compare amorphous, magnetostrictive FeCoSiB films prepared by RF and DC magnetron sputter deposition. The chemical, structural and magnetic properties determined by elastic recoil detection, X-ray diffraction, and magneto-optical magnetometry and magnetic domain analysis are correlated with the resulting surface acoustic wave sensor properties such as phase noise level and limit of detection. To confirm the material properties, SAW sensors with magnetostrictive layers deposited with RF and DC deposition have been prepared and characterized, showing comparable detection limits below 200 pT/Hz1/2 at 10 Hz. The main benefit of the DC deposition is achieving higher deposition rates while maintaining similar low substrate temperatures
How to solve problems in micro- and nanofabrication caused by the emission of electrons and charged metal atoms during e-beam evaporation
We discuss how the emission of electrons and ions during
electron-beam-induced physical vapor deposition can cause problems in micro-
and nanofabrication processes. After giving a short overview of different types
of radiation emitted from an electron-beam (e-beam) evaporator and how the
amount of radiation depends on different deposition parameters and conditions,
we highlight two phenomena in more detail: First, we discuss an unintentional
shadow evaporation beneath the undercut of a resist layer caused by the one
part of the metal vapor which got ionized by electron-impact ionization. These
ions first lead to an unintentional build-up of charges on the sample, which in
turn results in an electrostatic deflection of subsequently incoming ionized
metal atoms towards the undercut of the resist. Second, we show how low-energy
secondary electrons during the metallization process can cause cross-linking,
blisters, and bubbles in the respective resist layer used for defining micro-
and nanostructures in an e-beam lithography process. After the metal
deposition, the cross-linked resist may lead to significant problems in the
lift-off process and causes leftover residues on the device. We provide a
troubleshooting guide on how to minimize these effects, which e.g. includes the
correct alignment of the e-beam, the avoidance of contaminations in the
crucible and, most importantly, the installation of deflector electrodes within
the evaporation chamber.Comment: 13 pages, 7 figure
Si/SiGe QuBus for single electron information-processing devices with memory and micron-scale connectivity function
The connectivity within single carrier information-processing devices
requires transport and storage of single charge quanta. Our all-electrical
Si/SiGe shuttle device, called quantum bus (QuBus), spans a length of 10
m and is operated by only six simply-tunable voltage pulses. It
operates in conveyor-mode, i.e. the electron is adiabatically transported while
confined to a moving QD. We introduce a characterization method, called
shuttle-tomography, to benchmark the potential imperfections and local
shuttle-fidelity of the QuBus. The fidelity of the single-electron shuttle
across the full device and back (a total distance of 19 m) is
. Using the QuBus, we position and detect up to 34
electrons and initialize a register of 34 quantum dots with arbitrarily chosen
patterns of zero and single-electrons. The simple operation signals,
compatibility with industry fabrication and low spin-environment-interaction in
Si/SiGe, promises spin-conserving transport of spin qubits for quantum
connectivity in quantum computing architectures.Comment: 11 pages, 6 figure
Effects of mild hypothermia on hemodynamics in cardiac arrest survivors and isolated failing human myocardium
Post-cardiac arrest myocardial dysfunction is a common phenomenon after return of spontaneous circulation (ROSC) and contributes to hemodynamic instability and low survival rates after cardiac arrest. Mild hypothermia for 24 h after ROSC has been shown to significantly improve neurologic recovery and survival rates. In the present study we investigate the influence of therapeutic hypothermia on hemodynamic parameters in resuscitated patients and on contractility in failing human myocardium. We analyzed hemodynamic data from 200 cardiac arrest survivors during the hypothermia period. The initial LVEF was 32.6 ± 1.2% indicating a significantly impaired LV function. During hypothermia induction, the infusion rate of epinephrine could be significantly reduced from 9.1 ± 1.3 μg/min [arrival intensive care unit (ICU) 35.4°C] to 4.6 ± 1.0 μg/min (34°C) and 2.8 ± 0.5 μg/min (33°C). The dobutamine and norepinephrine application rates were not changed significantly. The mean arterial blood pressure remained stable. The mean heart rate significantly decreased from 91.8 ± 1.7 bpm (arrival ICU) to 77.3 ± 1.5 bpm (34°C) and 70.3 ± 1.4 bpm (33°C). In vitro we investigated the effect of hypothermia on isolated ventricular muscle strips from explanted failing human hearts. With decreasing temperature, the contractility increased to a maximum of 168 ± 23% at 27°C (n = 16, P < 0.05). Positive inotropic response to hypothermia was accompanied by moderately increased rapid cooling contractures as a measure of sarcoplasmic reticulum (SR) Ca2+ content, but can be elicited even when the SR Ca2+ release is blocked in the presence of ryanodine. Contraction and relaxation kinetics are prolonged with hypothermia, indicating increased Ca2+ sensitivity as the main mechanism responsible for inotropy. In conclusion, mild hypothermia stabilizes hemodynamics in cardiac arrest survivors which might contribute to improved survival rates in these patients. Mechanistically, we demonstrate that hypothermia improves contractility in failing human myocardium most likely by increasing Ca2+-sensitivity
Sensing dot with high output swing for scalable baseband readout of spin qubits
A key requirement for quantum computing, in particular for a scalable quantum
computing architecture, is a fast and high-fidelity qubit readout. For
semiconductor based qubits, one limiting factor is the output swing of the
charge sensor. We demonstrate GaAs and Si/SiGe asymmetric sensing dots (ASDs),
which exceed the response of a conventional charge sensing dot by more than ten
times, resulting in a boosted output swing of . This
substantially improved output signal is due to a device design with a strongly
decoupled drain reservoir from the sensor dot, mitigating negative feedback
effects of conventional sensors. The large output signal eases the use of very
low-power readout amplifiers in close proximity to the qubit and will thus
render true scalable qubit architectures with semiconductor based qubits
possible in the future.Comment: 8 pages, 7 figure
Tailoring potentials by simulation-aided design of gate layouts for spin qubit applications
Gate-layouts of spin qubit devices are commonly adapted from previous
successful devices. As qubit numbers and the device complexity increase,
modelling new device layouts and optimizing for yield and performance becomes
necessary. Simulation tools from advanced semiconductor industry need to be
adapted for smaller structure sizes and electron numbers. Here, we present a
general approach for electrostatically modelling new spin qubit device layouts,
considering gate voltages, heterostructures, reservoirs and an applied
source-drain bias. Exemplified by a specific potential, we study the influence
of each parameter. We verify our model by indirectly probing the potential
landscape of two design implementations through transport measurements. We use
the simulations to identify critical design areas and optimize for robustness
with regard to influence and resolution limits of the fabrication process.Comment: 10 pages, 6 figure
The SpinBus Architecture: Scaling Spin Qubits with Electron Shuttling
Quantum processor architectures must enable scaling to large qubit numbers
while providing two-dimensional qubit connectivity and exquisite operation
fidelities. For microwave-controlled semiconductor spin qubits, dense arrays
have made considerable progress, but are still limited in size by wiring
fan-out and exhibit significant crosstalk between qubits. To overcome these
limitations, we introduce the SpinBus architecture, which uses electron
shuttling to connect qubits and features low operating frequencies and enhanced
qubit coherence. Device simulations for all relevant operations in the Si/SiGe
platform validate the feasibility with established semiconductor patterning
technology and operation fidelities exceeding 99.9 %. Control using room
temperature instruments can plausibly support at least 144 qubits, but much
larger numbers are conceivable with cryogenic control circuits. Building on the
theoretical feasibility of high-fidelity spin-coherent electron shuttling as
key enabling factor, the SpinBus architecture may be the basis for a spin-based
quantum processor that meets the scalability requirements for practical quantum
computing.Comment: 15 pages, 9 figure
An interdisciplinary approach to the study of kiln firing: a case study from the Campus Galli open-air museum (southern Germany)
Pottery kilns are a common feature in the archaeological record of different periods. However, these pyrotechnological installations are still seldom the target of interdisciplinary investigations. To fill this gap in our knowledge, an updraft kiln firing experiment was run at the Campus Galli open-air museum (southern Germany) by a team consisting of experimental archaeologists, material scientists, geoarchaeologists, and palaeobotanists. The entire process from the preparation of the raw materials to the firing and opening of the kiln was carefully recorded with a particular focus on the study of the raw materials used for pottery making, as well as on fuel usage. The temperatures were monitored by thermocouples placed at different positions in the combustion and firing chambers. In addition, thermocouples were installed within the kiln wall to measure the temperature distribution inside the structure itself. Unfired raw materials as well as controlled and experimentally thermally altered ceramic samples were then characterised with an integrated analysis including ceramic petrography, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and portable X-ray fluorescence (pXRF). Our work provides data about mineralogical and microstructural developments in both pottery kiln structures and the ceramics produced in this type of installations. This is helpful to discuss the limits and potential of various scientific analyses commonly used in ancient ceramic pyrotechnological studies. Overall, our work contributes to a better understanding of updraft kiln technology and offers guidelines on how to address the study of this type of pyrotechnological installations using interdisciplinary research strategies
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