Applications In Portable Devices Research Articles

Thickness dependence of the room-temperature ethanol sensor properties of Cu2O polycrystalline films

This study investigates the fabrication process of copper thin films via thermal evaporation, with precise control over film thickness achieved through Z-position adjustment. Analysis of the as-fabricated copper films reveals a discernible relationship between grain size (〈D〉) and Z-position, characterized by a phenomenological equation 〈D〉XRDn(Z)=〈D〉0n1+32rZ2+158rZ4 , which is further supported by a growth exponent (n) of 0.41 obtained from the analysis. This value aligns well with findings in the literature concerning the growth of copper films, thus underlining the validity and reliability of our experimental outcomes. The resulting crystallites, ranging in size from 20 to 26 nm, exhibit a resistivity within the range of 3.3–4.6 μΩ · cm. Upon thermal annealing at 200 °C, cuprite Cu2O thin films are produced, demonstrating crystallite sizes ranging from ∼9 to ∼24 nm with increasing film thickness. The observed monotonic reduction in Cu2O crystallites relative to film thickness is attributed to a recrystallization process, indicating amorphization when oxygen atoms are introduced, followed by the nucleation and growth of newly formed copper oxide phase. Changes in the optical bandgap of the Cu2O films, ranging from 2.31 to 2.07 eV, are attributed mainly to the quantum confinement effect, particularly important in Cu2O with size close than the Bohr exciton diameter (5 nm) of the Cu2O. Additionally, correlations between refractive index and extinction coefficient with film thickness are observed, notably a linear relationship between refractive index and charge carrier density. Electrical measurements confirm the presence of a p-type semiconductor with carrier concentrations of ∼1014 cm−3, showing a slight decrease with film thickness. This phenomenon is likely attributed to escalating film roughness, which introduces supplementary scattering mechanisms for charge carriers, leading to a resistivity increase, especially as the roughness approaches or surpasses the mean free path of charge carriers (8.61 nm). Moreover, ab-initio calculations on the Cu2O crystalline phase to investigate the impact of hydrostatic strain on its electronic and optical properties was conducted. We believe that our findings provide crucial insights that support the elucidation of the experimental results. Notably, thinner cuprite films exhibit heightened sensitivity to ethanol gas at room temperature, indicating potential for highly responsive gas sensors, particularly for ethanol breath testing, with significant implications for portable device applications.

Thermal management of Li-ion battery by using eutectic mixture of phase-change materials

Lithium-ion batteries have a wide range of applications in portable electronic devices, global positioning systems, and the automobile industry due to their remarkable attributes like high energy density, long life cycle, higher efficiency, low self-discharging, and worthier operational performance. Although under different vigilant operating parameters, lithium-ion batteries generate a significant amount of heat, which deteriorates their performance and can lead to thermal runaway. To mitigate this issue and to improve safety, battery life, capacity, and overall performance, a robust thermal management system is very necessary. This study scrutinizes the effect of a passive cooling method using phase-change materials and their eutectic mixture on a 2600 mAh lithium-ion battery pack during the charging and discharging at various C-rates (1C, 1.5C, and 2C). Phase-change materials used in the experimentation are salt hydrates namely calcium nitrate tetrahydrate and zinc nitrate hexahydrate and their eutectic mixture contains 55 % calcium nitrate tetrahydrate and 45 % zinc nitrate hexahydrate. Experimental results reveal that without the usage of any phase-change material, the highest temperature was recorded at a 2C rate due to high current, with cell 5 recording a temperature of 60.98 °C. Zinc nitrate hexahydrate reduced the temperature by 18.98 °C to maintain it at 42 °C, and calcium nitrate tetrahydrate led to a temperature drop of 14.48 °C, maintaining it at 46.50 °C. The eutectic mixture caused a temperature reduction of 21.97 °C, maintaining it at 39.01 °C. The results of this study illustrate that the implementation of eutectic mixture as a phase-change material diminishes both the maximum surface temperature and the temperature gradient. This implies its efficacy as a viable material for the cooling of battery packs.

Energy efficient artificial gustatory system for in-sensor computing

In this work, a novel bio-inspired artificial gustatory system is proposed for in-sensor neuromorphic computing. The system is demonstrated using a novel material-engineered compound-semiconductor double-gate ferroelectric tunnel FET. The behaviour of the device as a biosensor and as a spiking neuron is verified individually. Using extensive simulation in Atlas TCAD, the biosensor functionality is validated with ION sensitivity of 108. Likewise, the device shows excellent neuronal behaviour with energy consumption of 37 aJ/spike, without using any external circuitry. It also exhibits control over the spiking frequency through amplitude, frequency, and duty cycle of input synaptic current. By cascading the biosensor and neuron, a complete bio-mimicked gustatory system is designed to identify a separate pattern for different tastes. The proposed gustatory system integrates both the devices, and simultaneously performs sensing and spike encoding. The biosensor transduces the pH and dielectric constant of the target biomolecule, corresponding to gustatory neurons present in the taste buds of a biological gustatory system. The neuron performs spike encoding and acts as an input neuron in a classifying network, which corresponds to gustatory cortex of its biological counterpart. The system consumes an average power of 49.58 pW which is ∼1000 × lesser than the state-of-the-art artificial gustatory system, eliminating the need for complex hardware and exorbitant energy consumption. Therefore, the proposed gustatory system provides a highly efficient and compact solution for neuromorphic gustatory sensing and classification, with potential applications in portable, wearable, and implantable devices.

Home-made chemical vapor deposition-based synthesis of binder-free nanostructured magnesium-molybdenum-sulfide electrode materials for supercapacitor application

Molybdenum disulfides (MoS2) is considered as promising electrode materials (E-M) for high electrochemical performance (ECP) of lithium-ion batteries and supercapacitors due to their layered nanostructures. Herein, MoS2, MgS and hetrostructure MgS/MoS2 E-Ms comprising of nano-particles/sheets/needles like structures are synthesized on Nickel foam (Ni–F) by a simple home-made chemical vapor deposition (CVD) technique. The XRD analysis confirmed the formation of MoS2, MgS and MgS/MoS2 polycrystalline E-Ms growing along different directions. The FESEM analysis is confirmed that the addition of MgS layer over the surface of MoS2 change the surafce morphology from nano-particles to nano-needles. The change in structural and microstructural features is indicated the appearance of defects, micro-strain and dislocations density which are fruitful for excellent ECP. The cyclic voltammetry analysis is indicated the pseudocapacitive nature of the synthesized E-Ms. The maximum specific capacitance values for MoS2/Ni–F, MgS/Ni–F and MgS/MoS2/Ni–F E-Ms are 1273, 1688 and 3934 F/g at 1 A/g respectively. Moreover, the addition of MgS layer over MoS2/Ni–F is revealed the excellent cyclic stability of 98.76 % at current density of 10 A/g after 4000 cycles, energy density values are ranged from 79 to 136 W h/kg with homologous power density of 250–2500 W/kg and very small charge transfer resistance. The simulations of Power's Law and Dunn's model is confirmed that the excellent ECP is due to both capacitive and diffusive controlled contributions of heterostructured MgS/MoS2/Ni–F E-Ms. Additionally, MgS/MoS2/Ni–F E-Ms have both battery and pseudocapacitive nature due to unique nano-needles like morphology. The excellent electrochemical properties of MgS/MoS2/Ni–F E-Ms substantiate their potential applications in portable energy storage devices.

Bifunctional binder-free ZnCuSe2 nanostructures/carbon fabric-based triboelectric nanogenerator and supercapacitor for self-charging hybrid power system application

Herein, we report a simple self-charging hybrid power system (SCHPS) based on binder-free zinc copper selenide nanostructures (ZnCuSe2 NSs) deposited carbon fabric (CF), which is used as an active material in the fabrication of supercapacitor (SC) and triboelectric nanogenerator (TENG). At first, a binder-free ZnCuSe2/CF was synthesized via a simple and facial hydrothermal synthesis approach, and the electrochemical properties of the obtained ZnCuSe2/CF were evaluated by fabricating a symmetric quasi-solid-state SC (SQSSC). The ZCS-2 material on ZnCuSe2/CF-based SQSSC exhibited good electrochemical properties, and the obtained highest energy and power densities were 7.5 Wh kg−1 and 683.3 W kg−1, respectively with 97.6 % capacitance retention after 30000 cycles. Furthermore, the ZnCuSe2/CF was coated with silicone rubber elastomer using a doctor blade technique, which is used as a negative triboelectric material in the fabrication of the multiple TENG (M-TENG). The fabricated M-TENG exhibited excellent electrical output performance, and the robustness and mechanical stability of the device were studied systematically. The practicality and applicability of the proposed M-TENG and SQSSC were systematically investigated by powering various low-power portable electronic components. Finally, the SQSSC was combined with the M-TENG to construct a self-charging hybrid power system (SCHPS). The fabricated SCHPS provides a feasible solution for sustainable power supply, and it shows great potential in self-powered portable electronic device applications.

Application of portable sleep monitoring devices in pregnancy: a comprehensive review.

The physiological, hormonal and biomechanical changes during pregnancy may trigger sleep disorders breathing in pregnant women. Pregnancy-related sleep disorders may associate with adverse fetal and maternal outcomes including gestational diabetes, preeclampsia, preterm birth and gestational hypertension. Most of the screening and diagnostic studies that explore sleep disordered breathing during pregnancy were based on questionnaires which are inherently limited in providing definitive conclusions. The current gold standard for in diagnostics is overnight polysomnography involving the comprehensive measurements of physiological changes during sleep. However, applying the overnight laboratory PSG on pregnant women is not practical due to a number of challenges such patient inconvenience, unnatural sleep dynamics, and expenses due to highly trained personnel and technology. Parallel to the progress in wearable sensors and portable electronics, home sleep monitoring devices became indispensable tools to record the sleep signals of pregnant women at her own sleep environment.
This article reviews the application of portable sleep monitoring devices in pregnancy with particular emphasis on estimating the perinatal outcomes. The advantages and disadvantages of home based sleep monitoring systems compared to subjective sleep questionnaires and overnight polysomnography for pregnant women were evaluated. An overview on the efficiency of the application of home sleep monitoring in terms of accuracy and specificity were presented for particular fetal and maternal outcomes. Based on our review, more homogenous and comparable research is needed to produce conclusive results with home based sleep monitoring systems to study the epidemiology of SDB in pregnancy and its impact on maternal and neonatal health.&#xD.

Robust ultrahigh electromagnetic interference shielding effectiveness based on engineered structures of carbon nanotube films

High-performance electromagnetic interference (EMI) shielding materials with ultrathin, flexible, and pliable mechanical properties are highly desired for high-end equipments, yet there remain large challenges in the manufacture of these materials. Here, carbon nanotube film (CNTF)/copper (Cu) nanoparticle (NP) composite films are fabricated via a facile electrodeposition method to achieve high electromagnetic shielding efficiency. Notably, a CNTF/Cu NP composite film with 15μm thickness can achieve excellent EMI shielding efficiency of ∼248 dB and absolute EMI shielding effectiveness as high as 2.17×105 dB cm2 g-1, which are the best values for composite EMI shielding materials with similar or greater thicknesses. These engineered composite films exhibit excellent deformation tolerance, which ensures the robust reliability of EMI shielding efficiency after 20,000 cycles of repeated bending. Our results represent a critical breakthrough in the preparation of ultrathin, flexible, and pliable shielding films for applications in smart, portable and wearable electronic devices, and 5G communication.

СУЧАСНІ ТЕНДЕНЦІЇ РИНКУ ЛІТІЙ-ІОННИХ БАТАРЕЙ ДЛЯ ЕЛЕКТРОННИХ ПРИСТРОЇВ

A detailed review is presented in this work on the future perspectives of lithium-ion batteries with emphasis on potential of their application in portable electronic devices. As specific energy and power are key criteria in portable electronics applications, the Li-ion batteries have a clear advantage over other chemistries. The portable electronics sector requires miniaturization of batteries, while maintaining high capacity and power as well as complying with strict safety standards. Although LCO batteries still are dominant chemistry for portable electronics, it will gradually lose market share to NMC and NCA cells. These also have advantage of lower content of cobalt, which will become necessary within the overall strongly growing Li-ion battery market.

A hybrid cathode catalytic layer composed of M–N–C and Pt/C for direct methanol fuel cells with high methanol tolerance

Pt/C based direct methanol fuel cells (DMFCs) always suffer from a serious methanol crossover under a high concentration of methanol solution. In this paper, we report a novel hybrid cathode catalytic layer (CCL) consisting of a physical blend of Pt/C and Fe-N-C. DMFC based on the hybrid CCL with an optimized loadings (0.25 mg cm−2 Fe-N-C and 2 mgPt cm-2Pt/C) outputs a high power density of 28.87 mW cm−2 at 10 M methanol, and the single Pt/C based cell only shows a low power density of 12.04 mW cm−2 in comparison. Such a large improvement attributes to the increasing amount of reactive oxygen species (ROS), which is produced by Fe-N-C via an incomplete four-electron transfer process in oxygen reduction reaction (ORR). Inspired by this strategy, several M−N−C catalysts were synthesized, among which Cu-N-C shows the most brilliant performance to enhance the methanol tolerance of Pt/C. The peak power density of DMFC with Cu-N-C based hybrid CCL exceeds 31 mW cm−2 at 10 M methanol, which is superior to that of cells with Fe-N-C based hybrid CCL. This work provides a new approach for designing DMFCs with high energy density, which is practical for applications of portable power devices.

The Revival of Sorbents in Chronic Dialysis Treatment.

Interest in the use of sorbents in chronic dialysis treatment has undergone a revival in the last decades, for which two major factors are responsible. The first is the potential of sorbents as adjunct therapy for the removal of substances that are difficult to remove by conventional dialysis therapies. The second is their use in regeneration of dialysate, which is of pivotal importance in the design of portable or even wearable treatments, next to the potential for reducing water use during conventional dialysis treatment. Sorbent-enhanced dialysis with synthetic polymers was associated with a reduction in inflammatory parameters as compared to hemodialysis and even associated with improved survival in smaller studies, although this needs to be confirmed in large randomized trials. Incorporation of sorbents within a dialysis membrane (mixed matrix membrane) appears a promising way forward to reduce the complexity and costs of a dual therapy but needs to be tested invivo. For regeneration of dialysate, at present, a combination of urease, zirconium-based sorbents, and activated charcoal is used. Next to sodium release by the sorbent in exchange for ammonium and the CO2 release by the hydrolysis of urea has been a bottleneck in the design of wearable devices, although short-term trials have been performed. Still, for widespread and flexible application of sorbent-assisted portable or wearable devices, a direct urea sorbent would be a major asset. In the near future, it will likely become apparent whether sorbent-assisted dialysis techniques are feasible for routine implementation in clinical practice.

Gallium Ion Pre‐Insertion Protocol to (NH4)2V10O25·8H2O Cathode Materials for Reversible Aqueous Zn Battery

AbstractVanadate is one of the promising cathode materials for aqueous zinc ion batteries (AZIBs) due to its abundant resources and various valence states. However, the further development is restricted by their sluggish reaction kinetics between zinc ions and the host materials. In this work, several kinds of gallium ions pre‐intercalated vanadate electrode materials through a simple hydrothermal strategy are designed. Ga‐NHVO‐0.5 sample achieves a specific capacity of 438.23 mAh g−1 at current density of 0.2 A g−1. At the same time, it delivers an energy density of 250.34 Wh kg−1 at a power density of 55 W kg−1. The assembled button cells retain 83.84% of its initial capacity after 4000 times cycling, revealing their promising applications in portable power devices. Moreover, the devices still possess a favorable stability under different bending conditions.

Design and Simulation of an Ultra-Low-Power Hydrogen Sulfide Gas Sensor with a Cantilever Structure.

Metal oxide gas sensors usually require a few tens of milliwatts of power consumption to operate at high temperature, which limits their application in mobile and portable devices. Here, we proposed a cantilever structure to build an ultra-low power gas sensor for hydrogen sulfide gas detection. By employing a nano-film size effect to reduce the thermal conductivity of the material, and self-heated corrugation configuration, the power consumption of the gas sensor is significantly reduced. Through numerical analysis and finite element simulation, two different gas sensors were designed and the power consumption and stress distribution were analyzed and optimized. Under the operating temperature of 200 °C, only 0.27 mW power is consumed, the stress value is less than 250 MPa and the displacement is a few hundred of nanometers. The results serve as a guide and reference for ultra-low power MEMS device designs.

Methyl-Symmetrically Substituted Poly(3,4-Dimethylthiophene) as Cathode for Aluminum Ion Batteries.

The aggravation of energy problems and the scarcity of lithium resources have forced us to look for new energy storage systems. Aluminum ion batteries, as a promising energy storage system, have the advantages of environmental friendliness and abundant aluminum resources, and have the potential for application in large-scale energy storage and personal portable electronic devices. To solve the stability problem of aluminum ion batteries during cycling for large-scale energy storage needs, we report a polythiophene-based conductive polymer, poly(3,4-dimethylthiophene) (PDMT), as a high performance cathode material for aluminum ion batteries. By introducing two methyl groups on the thiophene ring, we successfully adjust the local charge density of the heterocyclic thiophene, thus changing the electron delocalization characteristics, and improving the electrochemical reaction activity of the polythiophene (PTH) material as a redox electrode material. This also maintains the symmetry and regularity of the polymer structure, giving the material better cycling stability. The discharge specific capacity reaches 110 mAh g-1 at a current density of 200 mA g-1, far exceeding conventional PTH cathodes (~70 mAh g-1), and the capacity retention rate is 92.7 % after 1000 cycles. It also shows excellent rate performance due to the flexible structure of the conductive polymer.

Multiple Redox‐Active Cyano‐Substituted Organic Compound Integrated with MXene Nanosheets for High‐Performance Flexible Aqueous Zn‐Ion Battery

AbstractAn eco‐friendly organic compound, with rich redox sites, considered a promising cathode material for aqueous zinc‐ion batteries (AZIBs). Despite its potential, limited specific capacity and cycle instability impede its practical application. Herein, an organic compound, hexaazatriphenylene hexacarbonitrile (6CN‐HAT), is designed with a π–π conjugated aromatic structure, and integrated with MXene nanosheets to construct a flexible self‐supporting electrode (6CN‐HAT@MXene). Ex‐situ characterizations and theoretical calculations verify that the charge storage mechanism predominantly involves coordination and non‐coordination reactions between reactive C═N and ─CN sites with cations. The introduction of MXene nanosheets not only bolster the stability and electronic conductivity of the 6CN‐HAT@MXene but also expose additional active sites for cation coordination. As a cathode material in AZIBs, 6CN‐HAT@MXene exhibits an outstanding discharge specific capacity of 413 mAh g−1 at 0.05 A g−1. Remarkably, even after 5000 cycles at 5 A g−1, the discharge capacity retained 91%. Furthermore, based on the 6CN‐HAT@MXene electrode, a flexible micro‐zinc‐ion batteries with high area capacity of 257.4 mF cm−2 is prepared using laser cutting technology, highlighting its potential for future applications in portable and wearable electronic devices.

Improving charge transfer via nickel–nickel oxide/molybdenum dioxide heterostructure for advanced supercapacitor electrode

Currently, asymmetric supercapacitors (ASCs), as significant energy storage devices, have gained tremendous attention for alleviating the ever-increasing demands of carbon-free energy. Herein, metallic nickel decorated nickel oxide/molybdenum dioxide nanorods are directly anchored on porous nickel foam (Ni-NiO/MoO2/NF) by a hydrothermal method and subsequent reduction engineering under H2/Ar aura. The H2-reduction induced oxygen vacancies, multi-phase configurations, and rich interfaces synergistically enchace the electrochemical energy storage capabilities of the Ni-NiO/MoO2/NF. Notably, the density functional theory (DFT) results indicate that the generated interfaces of both Ni/NiO and Ni/MoO2 facilitate the metallic characteristic and thus enhance the electrochemical redox activity. Consequently, the Ni-NiO/MoO2/NF shows a specific capacity of 256.8 C g–1 at 1 A g–1 and 159.9 C g–1 at 20 A g–1, as well as a good cycling durability (remains 90.7% capacity after 8000 cycles) in 2.0 M of KOH media. In addition, an ASC with a voltage window of 1.4 V is constructed by employing the Ni-NiO/MoO2/NF and activated carbon (AC) as positive electrode and negative electrode, respectively, which exhibits an energy density as 28.8 Wh kg−1 at 777.8 W kg−1 and 80.2% capacity retention after 8000 charge/discharge operation. Further, a home-made ASC is assembled and exhibits potential application to power an electric fan. This work provides an efficiently way to construct multi-component electrodes with abundant heterostructures for applications in portable devices.

Laser-Induced Breakdown Spectroscopy Applied to Elemental Analysis of Aqueous Solutions—A Comprehensive Review

Laser-induced breakdown spectroscopy (LIBS) has evolved considerably in recent years, particularly the application of portable devices for the elemental analysis of solids in the field. However, aqueous analysis using LIBS instruments, either in the laboratory or in the field, is rather rare, despite extensive research on the topic since 1984. Thus, our comprehensive review aims to provide a clear overview of this research to offer guidance to new users. To achieve this, we examined the literature published between 1984 and 2023, comparing various settings and parameters in a database. There are four different categories of LIBS instruments: laboratory-based, online, portable, and telescopic. Additionally, there are four main categories of sample preparation techniques: liquid bulk, liquid-to-solid conversion, liquid-to-aerosol conversion, and hydride generation. Various experimental setups are also in use, such as double-pulse. Moreover, different acquisition settings significantly influence the sensitivity and therefore the detection limits. Documentation of the different methods of sample preparation and experimental settings, along with their main advantages and disadvantages, can help new users make an informed choice for a particular desired application. In addition, the presentation of median detection limits per element in a periodic table of elements highlights possible research gaps and future research opportunities by showing which elements are rarely or not analysed and for which new approaches in sample preparation are required to lower the detection limits.

Synthesis and characterization of BxPU-Liy: A novel polyurethane-based solid electrolyte with disrupted crystallinity for enhanced ion transport

In response to the demand for high-performance and safe batteries in the field of energy storage, a novel polyurethane-based solid electrolyte system, BxPU-Liy, has been developed. Crystallinity had been effectively reduced by incorporating 1,1′-binaphthol with a special molecular structure leading enhanced ion migration. Among that, B5PU-Li20 demonstrates good mechanical properties and thermal stability, with an ionic conductivity of 3.28 × 10-5 S cm−1 at room temperature, increasing to 2.0 × 10-4 S cm−1 at 40 °C. Additionally, this material exhibits excellent electrochemical performance and battery cycling capabilities, offering a new direction for the development of high-performance battery technology, with potential applications in portable electronic devices, electric vehicles, and large-scale energy storage systems.

Hydrogen Fuel Cell Integration: Automotive, Residential Power Generation & Portable Devices

Hydrogen fuel has emerged as a promising element in the quest for sustainable energy solutions across diverse sectors. This abstract distils the findings and insights from extensive research into hydrogen fuel integration, focusing on its applications in the automotive industry, residential power generation, and portable devices. In the automotive sector, hydrogen fuel cell vehicles (FCVs) offer a zero-emission alternative with extended driving ranges and rapid refuelling times, addressing some of the limitations of battery electric vehicles (BEVs). However, the successful integration of hydrogen as a transportation fuel hinges on the development of a robust refuelling infrastructure, cost reductions in fuel cell technology, and the optimization of energy-intensive hydrogen production processes. In residential power generation, hydrogen shows promise as a versatile energy carrier, capable of powering homes through fuel cells or combined heat and power (CHP) systems. To ensure sustainable residential hydrogen power, research efforts should continue to focus on efficient hydrogen production methods, such as advanced electrolysis powered by renewable energy sources. Furthermore, the integration of hydrogen in portable devices, including backup power systems and mobile electronics, is being explored. Overcoming challenges related to safe hydrogen storage, efficient energy conversion, and addressing energy density limitations are critical for expanding the utility of hydrogen in this domain. To drive further advancements, key research directions include the development of lightweight and high-capacity hydrogen storage materials, improvements in energy conversion efficiency, and enhanced safety measures for hydrogen-powered portable devices. Moreover, cross-sector collaboration between automotive, residential, and portable device applications is vital to optimize hydrogen production and utilization. Regulatory support and incentives play a pivotal role in promoting the adoption of hydrogen technologies, along with comprehensive life-cycle assessments to quantify their environmental impact.

Microstructural effects of copper deposits on direct bonding for 3D IC integration

Cu-to-Cu direct bonding has been regarded as an important approach to achieve three-dimensional integrated circuit integration. This study aims to investigate the effects of microstructure and Xenon flash exposure on the direct bonding of copper deposits. Copper electrodeposits, along with a sputtered deposit, with various grain sizes, preferred orientations, as well as surface hardnesses, were prepared to clarify the influence of individual factors quantitatively. Experimental results show that joint strength and grain boundary density followed a positively linear relationship regardless of other microstructural differences, suggesting the dominating role of grain boundary diffusion. Grain refinement can effectively enhance bonding strength, even only one side of the directly bonded joints possessed fine grains. Considering the portable device applications which may suffer from drop shocks, drop testing of the packages comprising sputtered copper on Si chips joined with electroplated copper on Al2O3 substrates assembled by thermal compression bonding was performed for the first time. Noticeably, a proper flash irradiaiton prior to bonding brought about not only remarkable improvement in shear strength by up to 60 % but also drop resistance for direct-copper bonds. The resistance against drop shock for directly-bonded daisy chains subjected to an appropriate light exposure prior to bonding was superior than the joints bonded using impact-resistant solders.

The effect of temperature on absorbance of rubidium atoms in a vapor glass cell

Glass cells containing neutral atoms are commonly employed in spectroscopy experiments and have potential applications in metrology. The temperature of the vapor plays a vital role as it directly influences the absorption rate of rubidium atoms. In this research, we study the effect of vapor temperature on the absorption spectrum of rubidium atoms. We observed the broadening of the spectral line and increased absorption, enabling us to determine the absorbance of atoms within the cell. These results provide valuable insights for our future work to characterize absorbance of homemade vapor cells for portable quantum device applications.