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[ASME ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - San Francisco, California, USA (Monday 27 August 2018)] ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - Numerical Investigation of Shape Effect on Microdroplet Evaporation
摘要： As electronic devices continue to shrink in size and increase in functionality, effective thermal management has become a critical bottleneck that hinders continued advancement. Two-phase cooling technologies are of growing interest for electronics cooling due to their high heat removal capacity and small thermal resistance (< 0.3 K-cm2/W) [1]. One typical example of a two-phase cooling method is droplet evaporation, which can provide a high heat transfer coefficient with low superheat. While droplet evaporation has been studied extensively and used in many practical cooling applications (e.g., spray cooling), the relevant work has been confined to spherical droplets with axisymmetric geometries. A rationally designed evaporation platform that yields asymmetric meniscus droplets can potentially achieve larger meniscus curvatures, which give rise to higher vapor concentration gradients along the contact line region and therefore yield higher evaporation rates. In this study, we develop a numerical model to investigate the evaporation behavior of asymmetrical microdroplets suspended on a porous micropillar structure. The equilibrium profiles and mass transport characteristics of droplets with circular, triangular, and square contact shapes are explored using the Volume of Fluid (VOF) method. The evaporative mass transport at the liquid-vapor interface is modeled using a simplified Schrage model [2]. The results show highly non-uniform mass transport characteristics for asymmetrical microdroplets, where a higher local evaporation rate is observed near the locations where the meniscus has high curvature. This phenomenon is attributed to a higher local vapor concentration gradient that drives faster vapor diffusion at more curved regions, similar to a lightning rod exhibiting a strong electric field along a highly curved surface. By using contact line confinement to artificially tune the droplet into a more curved geometry, we find the total evaporation rate from a triangular-based droplet is enhanced by 13% compared to a spherical droplet with the same perimeter and liquid-vapor interfacial area. Such a finding can guide the design and optimization of geometric features to improve evaporation in high performance electronics cooling systems.
关键词： Schrage model,two-phase cooling,droplet evaporation,thermal management,VOF method,microdroplets
更新于2025-09-09 09:28:46
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Low-temperature synthesis of hydride semiconductor YH3?δ using Pt capped Y films and its chemical thermodynamics analysis
摘要： To decrease the temperature at which metallic yttrium (Y) reacts with H2 to form the semiconductor trihydride phase, we employed Pt capping layers as catalysts, and compared the result with those obtained when employing Pd, Ni, or their co-capping layers. It was found that Pt capping with 5 nm thickness makes trihydride phase majority when hydrogenated at 27°C, and allows us to obtain the trihydride phase with approximately 100% molar concentration when hydrogenated at 150 – 200°C. Chemical thermodynamics analysis of the experimental results reveals that both the enthalpy and entropy differences between pure states of trihydride phase and dyhydride phase with hydrogen vapor show monotonic hydrogenation temperature dependencies with their sign inversions at approximately the same temperature around 150°C, suggesting a particular thermodynamic mechanism specific to the hydrogen – yttrium system.
关键词： Platinum,Electron beam evaporation,Yttrium dihydride,Enthalpy,Yttrium trihydride,Yttrium,Entropy,Gibbs free energy
更新于2025-09-09 09:28:46
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Structural, morphological and optical properties of Cu2ZnxFe1-xSnS4 thin films grown by thermal evaporation
摘要： In this study, Cu2ZnxFe1-xSnS4 (CZFTS) (0≤x≤1) thin films were grown under vacuum evaporation on unheated glass substrates followed by sulfurization at 400 °C. The effects of sulfurization on the structural, morphological and optical properties were investigated for CZFTS material by varying Fe content. Crystal structure and phase of CZFTS thin films were analyzed by X-ray diffraction technique and Raman spectroscopy. In addition, the elemental composition and the stoichiometry of films were studied using energy dispersive spectroscopy. Surface morphology of samples was examined by scanning electron microscopy. Optical properties such as absorption coefficient, and gap energies were determined by the measurement of transmittance and reflectance in the spectral range 300-1800 nm. X-ray analysis indicates that all sulfurized CZFTS films present a polycrystalline nature and exhibit a preferential orientation along (112) plane. Cu2FeSnS4 (x=0) and Cu2ZnSnS4 (x=1) crystallize in stannite structure with I-42m and kesterite structure with I-4 space group, respectively. Raman analysis and elemental composition confirm that only the Cu2ZnSnS4 (x=1) and CZ0.75F0.25TS (x=0.75) phases are present with good crystallinity. Transmittance and reflectance spectra revealed that the films are homogenous mostly for x=0.75 and 1. Structural and optical parameters like crystallite size, absorption coefficient and band gaps were estimated for all the x values.
关键词： Sulfurization,Scanning electron microscopy,X-ray diffraction,Copper zinc iron tin sulfide,Evaporation,Thin films
更新于2025-09-09 09:28:46
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Production and Characterization of Vacuum Deposited Organic Light Emitting Diodes
摘要： A method for producing simple and efficient thermally-activated delayed fluorescence organic light-emitting diodes (OLEDs) based on guest-host or exciplex donor-acceptor emitters is presented. With a step-by-step procedure, readers will be able to repeat and produce OLED devices based on simple organic emitters. A patterning procedure allowing the creation of personalized indium tin oxide (ITO) shape is shown. This is followed by the evaporation of all layers, encapsulation and characterization of each individual device. The end goal is to present a procedure that will give the opportunity to repeat the information presented in cited publication but also using different compounds and structures in order to prepare efficient OLEDs.
关键词： ambipolar,Donor-Acceptor,Thermally Activated Delayed Fluorescence,exciplex,Organic Electronics,patterning,thermal evaporation,Issue 141,OLED,Engineering
更新于2025-09-09 09:28:46
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Optical characterisation of amorphous Se–Te–Sn thin films
摘要： Optical characterization of Sn doped Se–Te thin films has been carried out. The characterization has been carried out using transmission spectra in range 500–2500 nm. Bulk samples were prepared using melt quenching technique and thin films were deposited using thermal evaporation. XRD analysis was used to confirm the amorphous nature of prepared samples. Optical constants such as refractive index and extinction coefficient have been determined using Swanepoel’s method. Variation of refractive index with wavelength has been analysed using single effective oscillator model. Optical band gap of the deposited films was calculated using Tauc plots. The observed properties have been explained using the chemical bond approach.
关键词： Tauc plots,Swanepoel’s method,melt quenching technique,thermal evaporation,Se–Te–Sn thin films,Optical characterization
更新于2025-09-09 09:28:46
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Effect of BaO on the phase composition and properties of aluminates for Ba-W cathodes
摘要： In this study, we prepared (4.8+x)BaO·CaO·2Al2O3(0≤x≤1.6) aluminates by calcining the precursors under static air at 1500 °C for 120 min. The precursor powders were prepared using a liquid phase co-precipitation method. The effects of the molar content of BaO on the phase composition (before and after melting), melting properties, environmental stability, evaporation, and emission properties of the aluminates was investigated systematically The results showed that the phase of the aluminates completely transformed from Ba5CaAl4O12 to Ba3CaAl2O7 with an increase in the BaO content. After melting, the phase changed from Ba5CaAl4O12 to a mixed phase of Ba5CaAl4O12 and Ba3CaAl2O7. In the high-temperature molten state, the aluminates were in the ionic state, which generated a relatively low-energy Ba5CaAl4O12 phase during cooling crystallization. With every 0.4 mol increase in the BaO content, the initial melting temperature of the aluminates decreased by 10–20 ℃, while the environmental stability deteriorated gradually. When the aluminates reacted with H2O and CO2 in the air, the original phase still existed and the characteristic peaks gradually broadened, but with the formation of Ca(OH)2, CaCO3, and BaCO3. At 1050 °C, with an increase in the BaO content, the evaporation rate of the Ba-W cathodes increased and the emission current density first increased and then decreased. The main components of the Ba-W cathode evaporation were Ba and BaO. At n(BaO):n(CaO):n(Al2O3)=6:1:2, the Ba-W cathode showed the best emission performance, and its pulse emission current density at 1050 °C was as high as 35.31 A/cm2.
关键词： Ba-W cathode,Emission current,BaO content,Phase composition,Evaporation rate
更新于2025-09-09 09:28:46
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Fabrication of Ferromagnetic Co–MgF <sub/>2</sub> Granular Film With High Transmittance and Large Faraday Effect for Optical Magnetic Field Sensor
摘要： In the magneto-optical devices and sensors using the Faraday effect, maintaining the transmitted light intensity of a Faraday element is a key issue. A granular ?lm with ferromagnetic ?ne metals dispersed in an insulator matrix has been expected to have both high transmittance and large Faraday effect. In this paper, we fabricated the Co–MgF2 granular ?lm prepared by co-evaporation and investigated the effect of substrate heating temperature during co-evaporation and post-annealing on the transmittance and the Faraday rotation of the granular ?lm. The Co–MgF2 granular ?lm deposited at high substrate temperature was exhibited like a ferromagnetic behavior and high transmittance. Also, we found that the ?gure of merit [deg./dB], which was de?ned as a ratio of a Faraday rotation angle and decay of the transmitted light, was improved by post-annealing.
关键词： Faraday effect,Co-evaporation,granular ?lm,optical magnetic ?eld sensor
更新于2025-09-09 09:28:46
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Study of Annealing Influence on Basic Properties of Indium Tin Oxide Nanorod Films Deposited Using Glancing Angle Ion-Assisted Electron Beam Evaporation
摘要： Indium tin oxide (ITO) nanorod ?lms were deposited onto glass slides and Si wafers using ion-assisted electron beam evaporation with a glancing angle deposition technique. The annealing in?uence on the basic properties of the as-deposited ITO nanorod ?lms was studied in the range of 100–500 °C for two hours in air. The crystallinity of the ITO nanorod ?lms was enhanced with the increasing annealing temperature, and the average transmission of the as-deposited ITO nanorod ?lms in the visible range was 90%. This value did not change signi?cantly after the annealing process. The optical bandgap of the as-deposited ITO nanorod ?lms was 3.94 eV and increased slightly after annealing. The sheet resistance of the as-deposited ITO nanorod ?lms was 12.9 Ω/□ and increased to 57.8 Ω/□ at an annealing temperature of 500 °C. The as-deposited ITO nanorod ?lms showed nanorod structures with average diameters of 79 nm, which changed slightly with the annealing temperature. The root mean square roughness of the as-deposited ITO nanorod ?lms was 7.9 nm and changed slightly with annealing. The as-deposited ITO nanorod ?lms had an average contact angle of 110.9°, which decreased to 64.2° at an annealing temperature of 500 °C. The experimental results showed that varying the annealing temperature in?uenced the structural, electrical and wettability properties of the ITO nanorod ?lms while the optical properties and surface morphology were almost unaffected.
关键词： Physical Properties,Annealing Temperature,Glancing-Angle Ion-Assisted Electron-Beam Evaporation,ITO Nanorod Films
更新于2025-09-09 09:28:46
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Single electron transistors with e-beam evaporation of SiO <sub/>2</sub> tunnel barriers
摘要： Recent work on fabricating metal-insulator-metal (MIM) single electron transistors (SETs) using deposited dielectrics shows promise for becoming a manufacturable process due to compatibility with modern CMOS processes. This process, the “rib-SET” process [V. Joshi, A. O. Orlov, and G. L. Snider, J. Vac. Sci. Technol. B 26, 2587 (2008); G. Karbasian, A. O. Orlov, and G. L. Snider, J. Vac. Sci. Technol. B 33 (2015)], features a self-aligned island and should allow for scaling SETs below 10 nm. However, one of the biggest roadblocks in realizing a high-quality SET with this process has been dif?culties in developing high-quality, low-noise, MIM tunnel junctions. In this work, the authors report Pt-SiO2-Pt MIM SETs with tunnel barriers deposited by e-beam evaporation as an alternative to atomic layer deposition. There are some challenges in the formation of tunnel barriers via e-beam evaporation that are addressed. It is expected that platinum has a negligible native oxide; however, there is a substantial resistance in as-deposited Pt-SiO2-Pt structures that can be reduced by over 5 orders of magnitude by subjecting the ?nished devices to an anneal in a hydrogen plasma, suggesting the presence of an interfacial platinum oxide. It is shown that this treatment not only increases the conductance through the SET, but that it is necessary for forming high conductance tunnel barriers that are desired for making low-noise SETs.
关键词： single electron transistors,metal-insulator-metal,e-beam evaporation,SiO2 tunnel barriers,CMOS processes
更新于2025-09-09 09:28:46
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A Flexible Photothermal Cotton-CuS Nanocage-Agarose Aerogel towards Portable Solar Steam Generation
摘要： Solar-steam generation provides an economically efficient pathway to produce clean water by using solar light as an energy source. While this strategy is highly suitable for portable and small scale water purification for individuals, families and those living in remote areas, the development of highly efficient and flexible photothermal materials which can be easily transported for storage and deliver is required. In this study, a commercial degreasing cotton, photothermal CuS yolk-shell nanocages and agarose were combined to produce a highly flexible photothermal aerogel which delivered a high energy efficiency (94.9%) for solar-steam generation under 1.0 sun irradiation, corresponding to a water evaporation rate of 1.63 kg m-2 h-1. The preparation of the photothermal aerogel can be easily scaled up due to the simplicity of the applied casting method. The obtained aerogel showed excellent stability for solar steam generation with no degradation in performance after at least 15 cycles. The salinity of the clean water produced during solar-thermal desalination of seawater was only 0.54 ppm. The raw materials of cotton, agarose and CuS are all cost effective, thus this flexible photothermal aerogel has showed great potential for practical application in portable solar-thermal evaporators.
关键词： solar-thermal energy,nanocages,aerogel,water evaporation,Photothermal
更新于2025-09-09 09:28:46