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arXiv2022

Simple coplanar waveguide resonator mask targeting metal-substrate interface

This white paper presents a single-layer mask, found at https://github.com/Boulder-Cryogenic-Quantum-Testbed/simple-resonator-mask. It is designed for fabrication of superconducting microwave resonators towards 1:1 comparisons of dielectric losses from the metal-substrate interface. Finite-element electromagnetic simulations are used to determine participation ratios of the four major regions of the on-chip devices, as well as to confirm lack of crosstalk between neighboring devices and demonstrate coupling tunability over three orders of magnitude. This mask is intended as an open-source community resource for facilitating precise and accurate comparisons of materials in the single-photon, millikelvin regime.

quant-ph↗

arXiv2022

Kinetic and chemorheological modeling of thermosetting polyurethanes obtained from an epoxidized soybean oil polyol crosslinked with glycerin

Thermosetting polyurethanes were obtained using an aromatic isocyanate and a hydrophobic polyol formulation obtained from epoxidized soybean oil (ESO) crosslinked with glycerin. A systematic DSC analysis of the effect of catalyst type, crosslinker concentration, isocyanate index and ESO crystallization on the cure kinetics was conducted. The combination of a stannic catalyst at 0.2 wt.\% and glycerin at 20 wt.\% produced a cure kinetics governed by autocatalytic heat flow where vitrification played a key role in the formation of chemical bonds. The evolution of Tg as a function of conversion, which followed Di-Benedetto{\'}s predictions, supported the hypothesis that vitrification was a preponderant phenomenon during cure. The ESO crystallization had a melting endotherm centered at 35°C, affecting substantially the availability of reactive hydroxide groups. Dynamic Mechanical Analysis (DMA) of a post-cured sample revealed a Tg centered at 220°C, whereas quasi-static flexural mechanical tests revealed a flexural modulus of 2.14 GPa and a flexural strength of 99.4 MPa. Rheological experiments using a rheometer at isothermal conditions supported the hypothesis that vitrification played a key role in the evolution of apparent viscosity. A master model using Kim-Macosko equations was obtained for the proposed formulation.

physics.app-ph↗

arXiv2022

Multiplication of freestanding semiconductor membranes from a single wafer by advanced remote epitaxy

Freestanding single-crystalline membranes are an important building block for functional electronics. Especially, compounds semiconductor membranes such as III-N and III-V offer great opportunities for optoelectronics, high-power electronics, and high-speed computing. Despite huge efforts to produce such membranes by detaching epitaxial layers from donor wafers, however, it is still challenging to harvest epitaxial layers using practical processes. Here, we demonstrate a method to grow and harvest multiple epitaxial membranes with extremely high throughput at the wafer scale. For this, 2D materials are directly formed on III-N and III-V substrates in epitaxy systems, which enables an advanced remote epitaxy scheme comprised of multiple alternating layers of 2D materials and epitaxial layers that can be formed by a single epitaxy run. Each epilayer in the multi-stack structure is then harvested by layer-by-layer peeling, producing multiple freestanding membranes with unprecedented throughput from a single wafer. Because 2D materials allow peeling at the interface without damaging the epilayer or the substrate, wafers can be reused for subsequent membrane production. Therefore, this work represents a meaningful step toward high-throughput and low-cost production of single-crystal membranes that can be heterointegrated.

physics.app-ph↗

arXiv2022

Efficient Circular Polarized Metamaterial RF Energy Harvester for Wi-Fi Applications

A new metamaterial based, circular polarized electromagnetic energy harvester is presented in this work. The structure, which is multilayer and utilises the well-known to the literature geometry of the spiral split ring resonator, operates at the Wi-Fi frequency band. Based on full electromagnetic analysis, the proposed harvester presents high efficiency (i.e., greater than 90%), adequate angle insensitivity (i.e., 44 deg.) and it is capable of absorbing circular polarised plane waves.

physics.app-ph↗

arXiv2022

Molecular beam homoepitaxy of N-polar AlN: enabling role of Al-assisted surface cleaning

N-polar aluminum nitride (AlN) is an important building block for next-generation high-power RF electronics. We report successful homoepitaxial growth of N-polar AlN by molecular beam epitaxy (MBE) on large-area cost-effective N-polar AlN templates. Direct growth without any in-situ surface cleaning leads to films with inverted Al-polarity. It is found that Al-assisted cleaning before growth enables the epitaxial film to maintain N-polarity. The grown N-polar AlN epilayer with its smooth, pit-free surface duplicates the structural quality of the substrate as evidenced by a clean and smooth growth interface with no noticeable extended defects generation. Near band-edge photoluminescence peaks are observed at room temperature on samples with MBE-grown layers but not on the bare AlN substrates, implying the suppression of non-radiative recombination centers in the epitaxial N-polar AlN. These results are pivotal steps towards future high-power RF electronics and deep ultraviolet photonics based on the N-polar AlN platform.

cond-mat.mtrl-sci↗

arXiv2022

Superconducting bimodal ionic photo-memristor

Memristive circuit elements constitute a cornerstone for novel electronic applications, such as neuromorphic computing, called to revolutionize information technologies. By definition, memristors are sensitive to the history of electrical stimuli, to which they respond by varying their electrical resistance across a continuum of nonvolatile states. Recently, much effort has been devoted to developing devices that present an analogous response to optical excitation. Here we realize a new class of device, a tunnelling photo-memristor, whose behaviour is bimodal: both electrical and optical stimuli can trigger the switching across resistance states in a way determined by the dual optical-electrical history. This unique behaviour is obtained in a device of ultimate simplicity: an interface between a high-temperature superconductor and a transparent semiconductor. The microscopic mechanism at play is a reversible nanoscale redox reaction between both materials, whose oxygen content determines the electron tunnelling rate across their interface. Oxygen exchange is controlled here via illumination by exploiting a competition between electrochemistry, photovoltaic effects and photo-assisted ion migration. In addition to their fundamental interest, the unveiled electro-optic memory effects have considerable technological potential. Especially in combination with high-temperature superconductivity which, beyond facilitating the high connectivity required in neuromorphic circuits, brings photo-memristive effects to the realm of superconducting electronics.

cond-mat.supr-con↗

arXiv2022

Design of Cryogenic Fully Differential Gain Boosting-OTA by the $g_{m}/I_{d}$ methodology used for a 14 bit Pipelined-SAR ADC

Quantum computing (QC) requires cryogenic electronic circuits as control and readout sub-systems of quantum chips to meet the qubit scale-up challenges.At this temperature,MOSFETs transistors exhibition many changes such as higher threshold voltage,higher mobility,and steeper substhreshold slope.We present a cryogenic fully differential gain boosting-OTA used for a 14 bit Pipelined-SAR ADC operating at 4.2K as the readout circuit for semiconductor-based quantum computing system.Using $g_{m}/I_{d}$ methodology to get pre-computed lookup tables based on the cryogenic 110nm BSIM4 model.The proposed OTA achieves very high unity-gain frequency@1.23GHz and open-loop low frequency gain@101dB.The total power consumption is 2.66mW at 4.2K,and a setting accuracy better than 0.01\% with $f_{-3dB}$ of 37MHz in a closed-loop application.

physics.app-ph↗

arXiv2022

Demonstration of Superconducting Optoelectronic Single-Photon Synapses

Superconducting optoelectronic hardware is being explored as a path towards artificial spiking neural networks with unprecedented scales of complexity and computational ability. Such hardware combines integrated-photonic components for few-photon, light-speed communication with superconducting circuits for fast, energy-efficient computation. Monolithic integration of superconducting and photonic devices is necessary for the scaling of this technology. In the present work, superconducting-nanowire single-photon detectors are monolithically integrated with Josephson junctions for the first time, enabling the realization of superconducting optoelectronic synapses. We present circuits that perform analog weighting and temporal leaky integration of single-photon presynaptic signals. Synaptic weighting is implemented in the electronic domain so that binary, single-photon communication can be maintained. Records of recent synaptic activity are locally stored as current in superconducting loops. Dendritic and neuronal nonlinearities are implemented with a second stage of Josephson circuitry. The hardware presents great design flexibility, with demonstrated synaptic time constants spanning four orders of magnitude (hundreds of nanoseconds to milliseconds). The synapses are responsive to presynaptic spike rates exceeding 10 MHz and consume approximately 33 aJ of dynamic power per synapse event before accounting for cooling. In addition to neuromorphic hardware, these circuits introduce new avenues towards realizing large-scale single-photon-detector arrays for diverse imaging, sensing, and quantum communication applications.

physics.app-ph↗

arXiv2022

Engineering bound states in the continuum at telecom wavelengths with non-Bravais lattices

Various optical phenomena can be induced in periodic arrays of nanoparticles by the radiative coupling of the local dipoles in each particle. Probably the most impressive example is bound states in the continuum (BICs), which are electromagnetic modes with a dispersion inside the light cone but infinite lifetime, i.e., modes that cannot leak to the continuum. Symmetry-protected BICs appear at highly symmetric points in the dispersion of periodic systems. Although the addition of nonequivalent lattice points in a unit cell is an easy and straightforward way of tuning the symmetry, BICs in such particle lattice, i.e., non-Bravais lattice, are less explored among periodic systems. Starting from a periodic square lattice of Si nanodisks, we have prepared three non-Bravais lattices by detuning size and position of the second disk in the unit cell. Diffraction-induced coupling excites magnetic/electric dipoles in each nanodisk, producing two surface lattice resonances at the $Γ$ point with a band gap in between. %of $\sim$ 41 meV. The high/low energy branch becomes a BIC for the size/position-detuned array, respectively, while both branches are bright (or leaky) when both size and position are detuned simultaneously. The role of magnetic and electric resonances in dielectric nanoparticles and the change of BIC to bright character of the modes is explained by the two different origins of BICs in the detuned arrays, which is further discussed with the aid of a coupled electric and magnetic dipole model. This study gives a simple way of tuning BICs at telecom wavelengths in non-Bravais lattices, including both plasmonic and dielectric systems, thus scalable to a wide range of frequencies.

physics.optics↗

arXiv2022

Nuclear spin self compensation system for moving MEG sensing with optical pumped atomic spin co-magnetometer

Recording the moving MEGs of a person in which a person's head could move freely as we record the brain's magnetic field is a hot topic in recent years. Traditionally, atomic magnetometers are utilized for moving MEGs recording and a large compensation coil system is utilized for background magnetic field compensation. Here we described a new potential candidate: an optically pumped atomic co-magnetometer(OPACM) for moving MEGs recording. In the OPACM, hyper-polarized nuclear spins could produce a magnetic field which will shield the background fluctuation low frequency magnetic field noise while the the fast changing MEGs signal could be recorded. The nuclear spins look like an automatic magnetic field shields and dynamically compensate the fluctuated background magnetic field noise. In this article, the magnetic field compensation is studied theoretically and we find that the compensation is closely related to several parameters such as the electron spin magnetic field, the nuclear spin magnetic field and the holding magnetic field. Based on the model, the magnetic field compensation could be optimized. We also experimentally studied the magnetic field compensation and the responses of the OPACM to different frequencies of magnetic field are measured. We show that the OPACM owns a clear suppression of low frequency magnetic field under 1Hz and response to magnetic field's frequencies around the band of the MEGs. Magnetic field sensitivity of $3fT/Hz^{1/2}$ has been achieved. Finally, we do a simulation for the OPACM as it is utilized for moving MEGs recording. For comparison, the traditional compensation system for moving MEGs recording is based on a coil which is around 2m in dimension while our compensation system is only 2mm in dimension. Moreover, our compensation system could work in situ and will not affect each other.

physics.app-ph↗

arXiv2022

In situ nonlinear Rayleigh wave technique to characterize the tensile plastic deformation of stainless steel 316L

The acoustic nonlinearity parameter(beta) is sensitive to dislocation parameters, which continuously change during plastic deformation. Dislocation-based damage in structures/components is the source of the failure; thus, beta has been studied as a metric for non-destructive evaluation. This work consists of two parts: the development of an in situ experimental setup for nonlinear Rayleigh wave measurements, and characterization of the dependence of beta on applied stress at different levels of initial plastic strain. First, we introduce an experimental setup and methods for repeatable in situ nonlinear ultrasonic measurements. Details on design considerations and measurement schemes are provided. In the second part, beta was measured in situ during an incremental monotonic tensile test. The measured βmonotonically decreases with plastic strain, but it is relatively insensitive to the applied stress during elastic deformation. This result highlights three aspects of the evolution of beta, which have not been sufficiently emphasized in prior work: the apparent insensitivity of beta to the applied stress during elastic deformation, decreasing beta with plastic deformation, and the saturation of beta. We attribute the trend of decreasing beta to a scaling of beta with monopole loop length during plastic deformation, which depends on initial microstructure. The saturation of beta at 1.8% coincides with a planar-to-wavy transition of dislocation structures. The in situ nonlinear ultrasonic experimental method presented in this work is significant as the in situ results can provide broader insights on beta and dislocation-based damage evolution than ex situ measurements alone.

cond-mat.mtrl-sci↗

arXiv2022

Fiber-optic multimode interference sensing: comprehensive characterization and its potential for strain-insensitive temperature sensing

A strain-insensitive temperature sensor based on multimode interference using standard multimode fibers (MMFs) is proposed according to the comprehensive study of the characteristics of the MMFs. The temperature and strain dependences on the core diameter, numerical aperture (NA), and the length of the MMF section in the single-mode--multimode--single-mode (SMS) fiber structure are investigated experimentally. The results indicate that the larger core diameter of the MMF leads to higher temperature sensitivity but lower strain sensitivity (absolute values); the higher NA does not influence the temperature sensitivity but results in higher absolute value of strain sensitivity; the longer MMF section brings lower temperature sensitivity but does not have an impact on strain sensitivity. These findings also contribute to the theoretical analysis of the length dependence in the SMS fiber sensors. Besides, the results of the characterization study show that the strain sensitivity is relatively low, which brings a possibility to develop a strain-insensitive temperature sensor. The proposed sensor is used for temperature sensing while the strain is constantly applied from 0 to 1100 $με$ with steps of 100 $με$. The measured results are consistent with the comprehensive study. The mean temperature sensitivity is 6.14 pm/$^{\circ}$C with a standard deviation of 0.39 pm/$^{\circ}$C, which proves that the proposed temperature sensor exhibits good stability and is insensitive to strain. We expect that these results will provide a profound guideline to fiber sensors based on multimode interference.

physics.optics↗

arXiv2022

Formation of bound states in the continuum in double trapezoidal grating

In the field of optics, bound state in the continuum (BIC) has been researched in many photonic crystals and periodic structures due to a strong resonance and an ultrahigh Q factor. Some designs of narrowband transmission filters, lasers, and sensors were proposed based on excellent optical properties of BIC. In this paper, we consider symmetrical rectangular grating structure firstly, then cut off the corner of one of the gratings, the Fano peak of quasi-BIC can be observed in the spectrum. After that, we further change the tilt parameter of the other grating, which minimizes the Fano line width. In the momentum space, the process of structural change corresponds to topological charges split from q=1 into two half charges q=1/2.We analyze guided mode resonance (GMR) excitation of the grating structure, and discuss the dispersion relations in the waveguide layer with the position of BIC in energy bands. In addition, the reflectance spectrum is found to exhibit asymmetric line-shapes with different values of the asymmetry parameters, M1 and M2. BIC is transformed into quasi-BIC as the symmetry of the structure is broken. This work demonstrates a double trapezoid structure with strong resonance properties, which has significant implications for exploring the phenomenon of BIC.

physics.optics↗

arXiv2022

Failure Mode Analysis in Microsecond UV Laser Annealing of Cu Thin Films

The need of surface-localized thermal processing is strongly increasing especially w.r.t three-dimensionally (3D) integrated electrical devices. UV laser annealing (UV-LA) technology well addresses this challenge. Particularly UV-LA can reduce resistivity by enlarging metallic grains in lines or thin films, irradiating only the interconnects for short timescales. However, the risk of failure in electrical performance must be correctly managed, and that of UV-LA has not been deeply studied yet. In this work microsecond-scale UV-LA is applied on a stack comparable to an interconnect structure (dielectric/Cu/Ta/SiO2/Si) in either melt or sub-melt regime for grain growth. The failure modes such as (i) Cu diffusion into SiO2, (ii) O incorporation into Cu, and (iii) intermixing between Cu and Ta are investigated.

physics.app-ph↗

arXiv2022

Rational design of carbon-based materials for purification and storage of energy carrier gases of methane and hydrogen

Today, fast-growing energy demands and fuel resource depletion are among the hottest concerning issues that treating our world. So, a huge need is felt to find efficient, affordable and eco-friendly energy storage and production systems. Much current research effort proved that gaseous energy carriers such as CH4 and H2 seem to be the right choice for alternative fuel resources. However, the most important challenge with this new-faced resource is the comparatively low volumetric energy storage density. Fortunately, the high-pressure gas storage technique inside the porous media of solid adsorbent is considered as one best way to tackle the energy density problem. Famous family of porous carbon materials, with a suitable pore size distribution centred in the micropore range and a large number of adsorption sites per volume of solid, open up a great scope for gas storing applications. This review article represents the state-of-the-art with a precise focus on what has and can be done to improve/enhance the gas/energy storage capacity of traditional and novel structures of low-cost carbon-based adsorbents. We review a wide variety of design strategies to synthesis carbonaceous adsorbents, with a strong focus on creating the connection between structural properties and gas adsorption performance. In this regard, various synthesis techniques have been studied with emphasis on the more interesting recent progress that allows better control and optimisation of porosity of porous carbons for maxing gas storage capacity. We will also show that carbon-based adsorbents, particularly activated carbons, have been extensively studied and remain a powerful candidate in the search for an energy carrier economy. In the end, a perspective is provided to forecast the future development of carbon-based materials.

cond-mat.mtrl-sci↗

arXiv2022

Performance of a MQXF Nb3Sn Quadrupole Magnet Under Different Stress Level

In a dipole or in a quadrupole accelerator magnet, the displacement of the coil turns induced by the electromagnetic forces can cause quenches limiting the magnet performance. For this reason, an azimuthal preload is applied to avoid azimuthal movements of the coil up to the required operational current. However, several tests showed that accelerator magnets can operate with a partial preload, i.e. that coil unloading during the ramp does not prevent reaching higher currents. This issue is particularly relevant for Nb3Sn magnets, where the loads applied to the Nb3Sn filaments can reach the degradation limits of critical current. In order to investigate the impact of coil preload on the quench performance, the MQXFS6 short model quadrupole for the High Luminosity Upgrade was tested under an azimuthal preload at 80% of the short sample current, reaching 93% of short sample current at 1.9 K. The preload was then released to 60%, still showing ability to operate in the range of 80-85% of short sample current as required by HL-LHC project. With this lower preload, the ability of going above 90% of short sample was lost, and a significant training appeared above 85%. When the preload was restored to the original 80% value, the magnet reached with few quenches 95% of short sample (13.4 T peak field). Magnetic measurements confirm the larger movement of the coil in the case with lower preload, and agree with finite element simulations.

physics.app-ph↗

arXiv2022

Thermally expanded graphite polyetherimide composite with superior electrical and thermal conductivity

Thermally expanded graphite (EG) polymer composite has high potential in modern thermoelectronic industry due to cost effectiveness, excellent electrical and thermal properties. In this study, we report that expanded graphite polyetherimide(EG/PEID) composite has been fabricated by simple solution mixing technique, reinforcing a low cost EG filler into host polymer matrix, polyetherimide (PEID). This technique enables the inclusion of 3D graphitic filler into polymer matrix retaining the worm structure of expanded graphite, thus developing continuous network throughout the composite. In result, ~19 orders of magnitude rise of the polymers electrical conductivity up to 969 S/m has been achieved upon the inclusion of the 10wt% of EG filler. Theoretical prediction using effective medium approach reveals the impact of an imperfectly conducting interface and interfacial tunneling on electrical conductivity of the composites. We also report that 10wt% EG filler composition composite exhibits the thermal conductivity (k) value of 7.3W/mK, implying significant enhancement of 3070% compared to pure PEID. Scanning Electron Microscopy (SEM) represents the morphology of fillers and composites, revealing the preserved structure of EG to develop the conductive pathway between polymer and filler. Investigation on the structural properties before and after the thermal expansion of EG fillers has been performed using Raman, X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) analysis. In summary, a simple fabrication route of solution mixing has been demonstrated to achieve an outstanding electrically and thermally conductive EG/PEID composite without compromising the efficiency of EG filler structure. The expanded graphite-based polymer composites can retain their outstanding properties in wide range of thermal and electronic industry.

cond-mat.mtrl-sci↗

arXiv2022

Hetero-interface of electrolyte/2D materials

Electrochemical gating has been demonstrated as a powerful tool to tune the physical properties of two-dimensional (2D) materials, leading to lots of fascinating quantum phenomena. However, the reported liquid-nature electrolytes (e.g, ionic liquid and ion-gel) cover the top surface of 2D materials, introduce the strain at the hetero-interface, and present sensitivity to humidity, which strongly limits the further exploration of the hetero-interface between electrolyte and 2D materials, and their wide applications for electronics and optoelectronics. Herein, by introducing a lithium-ion solid-state electrolyte, the character of the electric double layer (EDL) at hetero-interface and its effect on the optical property of transition metal chalcogenides (TMDs) have been revealed by Kelvin probe force microscopy (KPFM) and (time-resolved) photoluminescence measurements. The work function of TMDs can be strongly tailored by electrochemical gating, up to 0.7eV for WSe2 and 0.3 eV for MoS2, respectively. Besides, from the gate-dependent surface potential of TMDs with different thicknesses, the potential drop across the EDL has been quantitatively revealed. Furthermore, from the gate-dependent PL emission at room temperature, monolayer WS2 exhibits only neutral exciton emission in the whole range of gate voltage applied, which also exhibits exciton-exciton annihilation. Our results demonstrate that lithium-ion substrate is a promising alternative to explore the physics of 2D materials and the hetero-interface of electrolyte/2D materials by easily integrating both scanning probe and optical techniques.

physics.app-ph↗