Solid Phase Interface Research Articles

Nucleation and growth of Cu6Sn5 during the aging process of Cu/Sn interface in electronic packaging-by in-situ TEM

The rapid nucleation of Cu6Sn5 during the soldering process, as well as its growth at the solid-state interface system (Cu/Sn) during chip service, present significant challenges. To study this, we introduced a small amount of Co element into the Cu-Sn system in order to reduce the formation energy of Cu6Sn5. Through transmission electron microscopy, we performed in situ observations of the nucleation and growth of Cu6Sn5 at the Cu/Sn solid phase interface. Our experimental findings confirm that the diffusion of Cu element at the interface plays a dominant role in the nucleation and growth process of Cu6Sn5. During this diffusion process, once the local concentration of Cu surpasses a threshold, Cu6Sn5 begins to nucleate around the Cu-rich region. The driving force behind this phase transition arises from two factors: non-uniformity of atomic flux at grain boundaries leading to stress accumulation, and localized bonding between a pair of valence electrons on Cu and adjacent Sn atoms, resulting in the formation of a shared orbital. Based on the curvature of the nucleation solid interface, three distinct growth modes have been observed: spiral growth, layer-layer growth, and island growth. These variations stem from changes in the dynamic mechanism associated with the morphology coefficient linked to the interface arc length. The nucleation and growth of Cu6Sn5 are governed by anisotropic attachment kinetics, with the growth process transitioning to diffusion-controlled continuous growth.

Interfacial synergistic effect of Ru nanoparticles embedded onto amorphous/crystalline WO3 nanorods on boosting the pH-universal hydrogen evolution reaction

The development of high-efficiency pH-universal electrocatalyst is of great significance for hydrogen evolution reaction (HER). In this work, a rod-like Ru/WO3-VO electrocatalyst was constructed for HER via a solid-phase reaction strategy. Due to the restriction of atomic migration at solid phase interface, plenty of oxygen vacancies (VO) and structure distortions were generated in amorphous/crystalline WO3 phase (WO3-VO). The optimized Ru/WO3-VO annealed at 450 °C with 2.2 wt% Ru achieves outstanding intrinsic activity with low overpotential and Tafel slope in a 0–14 pH range. A turnover frequency value 7.2 higher than that of commercial Pt/C is abtaind on Ru/WO3-VO at overpotential of 100 mV. Density functional theory calculations reveal that H* adsorption and desorption balanced by tuning the interface electronic structure contributes synergistic effect to the pH-universal HER activity of Ru/WO3-VO. The crystalline/amorphous semiconductor-metal heterointerface is crucial to designing and synthesizing electrocatalysts for optimal HER activity.

New insights on nanostructure of ordered mesoporous Fe[sbnd]Mn bimetal oxides (OMFMs) by a novel inverse micelle method and their superior arsenic sequestration performance: Effect of calcination temperature and role of Fe/Mn oxides

A series of ordered mesoporous FeMn bimetal oxides (OMFMs) were fabricated by using a novel inverse micelle method, and the texture, nanostructure and interface chemistry properties of OMFMs were closely correlated to the calcination temperature. Due to the amorphous regular inner-connected nanostructure and bimetallic synergistic effect, the obtained OMFMs exhibited superior arsenic sequestration performance than pure mesoporous Fe oxides (PMF) and Mn oxides (PMM). The optimum ratio of Fe/Mn and calcination temperature for arsenic removal was 3/1 and 350 °C (OMFM-3), and the maximum As(III) and As(V) adsorption capacities of OMFM-3 were 174.59 and 134.58 mg/g, respectively. Solution pH value negligibly affected the uptake of arsenic (ranged from 3.0 to 7.0), while SiO32−/PO43− ions and humic acid (HA) displayed significant inhibitory effect on arsenic removal by OMFM-3. According to the mechanism of arsenic removal, which simultaneously analyzed the arsenic redox transformation in aqueous phase and on solid phase interface, it was concluded that manganese oxides in OMFM-3 mainly played the role as a remarkable As(III) oxidant in water, whereas iron oxides dominantly acted as an excellent arsenic species adsorbent. Finally, the prominent arsenic sequestration behavior and performance in surface water suggested that OMFM-3 could be a promising and hopeful candidate for arsenic-contaminated (especially As(III)) surface water and groundwater remediation and treatment.

General regularities of thermal decomposition of transition metal dihydrides in a medium with low hydrogen partial pressure

The results of the calorimetric studies of thermal dissociation of titanium, zirconium, magnesium, and palladium hydrides performed in recent years are presented. The multiplet character of thermal dissociation characteristic of all these hydrides is shown. A good correlation between the course of differential scanning calorimetry curves and the results of thermogravimetry has been demonstrated.The discrete nature of the decomposition processes is established. A sequence of mechanisms occurring during the heating of transition metal dihydrides in a medium with a low partial pressure of hydrogen has been proposed: rearrangement in the hydride phase; destruction of metal - hydrogen bonds to form a solid solution supersaturated with hydrogen; diffusion of hydrogen to the interface of solid phase - environment; molization of hydrogen at the exit from the solid phase.

Microwave-assisted three-liquid-phase salting-out extraction of docosahexaenoic acid (DHA)-rich oil from cultivation broths of Schizochytrium limacinium SR21

The extraction and separation of docosahexaenoic acid (DHA)-rich oils, proteins, and polysaccharides from microalgae is a challenge for industrial commercialization of DHA, such as drying and dewatering, cell wall disruption, laborious conventional extraction procedures and exploitation of large volumes of solvents. To address these concerns, a novel microwave-assisted three-liquid-phase salting-out extraction (MA-TLPSOE) was used to separate DHA-rich oils, proteins, and polysaccharides from wet cultivation broths of Schizochytrium limacinum SR21. The optimized MA-TLPSOE system was composed of 30% (w/w) n-hexane/13% (w/w) ethanol/9% (w/w) sodium carbonate and treated at high microwave power (650W) for 30s. Under optimized conditions, 100±0.59% oil and 100±0.64% DHA were partitioned in the top n-hexane phase while 93.75±0.25% of polysaccharides and 92.96±0.43% of proteins were distributed in the solid-phase interface. The effects of microwave power and duration, sodium carbonate, n-hexane, ethanol concentration and extraction time were studied. When the optimized system was enlarged from 20g to 60g, the yields of all effective components were almost the same. Thus, the MA-TLPSOE system is a promising and attractive technology, which could be used for the separation and extraction of various effective ingredients from complex natural products in a single step with significant recovery yield.

Antibacterial cotton fabrics based on hydrophilic amino-containing scaffolds.

A hydrophilic amino compound, 4,7,10-trioxatridecane-1,13-diamine, has been utilized in several chemical and biochemical studies. Among previous applications is its use as a flexible and economical spacer molecule to increase the length between two moieties of interest, one of which may be a solid-phase interface. In this study, we immobilized this molecule on cotton fabrics and showed that this modified surface (DA) exhibited significant antibacterial activities in both Gram-negative bacteria and a Gram-positive bacterium. Studies on the structure-activity relationship revealed that additional chemical modifications on DA usually led to lowered antibacterial activities, emphasizing an importance of having free amino groups. Further investigation by fluorescence microscope indicated that this modified surface likely interfered with the membrane integrity of bacteria, leading to cell lysis. In addition, this scaffold was also tested for its biocompatibility with mouse fibroblast cells, and exerted no detrimental effect to the cell growth, highlighting its potential as a practical antibacterial surface modifier.

A theoretical, numerical and experimental verification of the Reynolds thermal transpiration law

PurposeThe purpose of this paper is the theoretical presentation of tensorial formulation with surface mobility forces and numerical verification of Reynolds thermal transpiration law in a contemporary experiment with nanoflow.Design/methodology/approachThe velocity profiles in a single microchannel are calculated by solving the momentum equations and using thermal transpiration force as the boundary conditions. The mass flow rate and pressure of unstationary thermal transpiration modeling of the benchmark experiment has been achieved by the implementation of the thermal transpiration mobility force closure for the thermal momentum accommodation coefficient.FindingsAn original and easy-to-implement method has been developed to numerically prove that at the final equilibrium, i.e. zero-flow state, there is a connection between the Poiseuille flow in the center of channel and counter thermal transpiration flow on the surface. The numerical implementation of the Reynolds model of thermal transpiration has been performed, and its usefulness for the description of the benchmark experiment has been verified.Research limitations/implicationsThe simplified procedure requires the measurement or assumption of the helium-glass slip length.Practical implicationsThe procedure can be very useful in the design of micro-electro-mechanical systems and nano-electro-mechanical systems, especially for accommodation pumping.Originality/valueThe paper discussed possible constitutive equations in the transpiration shell-like layer. The new approach can be helpful for modeling phenomena occurring at a fluid–solid phase interface at the micro- and nanoscales.

Quantum melting of a two-dimensional Wigner crystal

The paper reviews theoretical predictions about the behavior of two-dimensional low-density electron systems at nearly absolute zero temperatures, including the formation of an electron (Wigner) crystal, crystal melting at a critical electron density, and transitions between crystal modifications in more complex (for example, two-layer) systems. The paper presents experimental results obtained from real two-dimensional systems in which the nonconducting (solid) state of the electronic system with indications of collective localization is actually realized. Experimental methods for detecting a quantum liquid–solid phase interface are discussed.

Effective As(III) and As(V) immobilization from aqueous solution by nascent ferrous hydroxide colloids (FHC)

Abstract In this study, the freshly prepared nascent ferrous hydroxide colloids (FHC) were used to eliminate two kinds of inorganic arsenic and simultaneously explore the arsenic speciation in aqueous phase and solid phase interface. The result indicated that when FHC maintained at a lower dosage (5–80 mg Fe/L), the As(III) removal efficiency was greater than that of As(V), which was consistent with the conclusion drawn from the maximum adsorption capacities by the Langmuir model (As(III) and As(V) were 122.63 mg/g Fe and 103.26 mg/g Fe, respectively). Furthermore, HPLC-ICP-MS and XPS analysis from liquid-solid two phase indicated that part of As(III) could be quickly oxidized into As(V) (approximately 5 min), while no As(V) was reduced to As(III) even under the longer reaction time (10 days). This redox transformation behavior of arsenic caused by the mineral transformation of nascent FHC, which formed secondary Fe(II)-Fe(III) (hydr)oxides minerals (newly formed Fe3O4 phase in situ). These results revealed that the nascent FHC have greatly potential practical application in arsenic contaminated groundwater, especially for As(III) removal directly without a pre-oxidation step.

Redox transformation of arsenic by magnetic thin-film MnO2 nanosheet-coated flowerlike Fe3O4 nanocomposites

Inorganic arsenic cycling in the natural environment is significantly controlled by manganese/iron oxides, and studying the redox transformation of arsenic in both aqueous and solid phase is therefore essential to understand its environmental toxicity and predict its environmental behavior. Herein, the synthesized magnetic thin-film MnO2 nanosheet-coated flowerlike Fe3O4 nanocomposites have been used to simultaneously investigate the potential redox transformation of arsenic in aqueous phase and arsenic speciation on the solid phase interface. The results showed the initial Mn/Fe ratio has serious influenced the morphologies, textural properties and uptake of arsenic in aqueous solution. The maximum adsorption capacities of As(III) and As(V) by MF2 were 76.73mg/g and 120.50mg/g, respectively. After 10h reaction, the total arsenic concentration in both As(III)-MF2 system and As(V)-MF2 system far below than that of 10μg/L, which was setted the maximum guideline concentration value in drinking water by World Health Organization (WHO). HPLC-ICP-MS revealed that in aqueous solution part of As(III) was oxidized into As(V), while As(V) was not reduced into As(III). X-ray absorption near edge structure (XANES) and XPS analysis from solid phase further confirmed that the MnO2 nanosheet mainly acted as an oxidant, while flowerlike Fe3O4 only played the role as an arsenic species adsorbent. Extended X-ray absorption fine structure (EXAFS) analysis indicated that both As(III) and As(V) formed inner-sphere bidentate binuclear corner-sharing (2C) complexes with an As-Fe interatomic distance of 3.32–3.34Å on the interface of As-MF2 solid phase.

Enhanced synthesis of Sn nanowires with aid of Se atom via physical vapor transport

We demonstrate tin (Sn) nanowires growth enhanced by Selenium (Se) atoms via physical vapor transport (PVT) method. The Raman spectroscopy, X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy show that Sn nanowires are synthesized with a large quantity, good quality and high purity of Sn. The growth of Sn nanowires is attributed to Solid–Vapor–Liquid mechanism. The effects of gold nanoparticles catalyst, Si substrate, and Se atoms on Sn nanowires growth are discussed in detail. We find that Se atom plays a key role in the growth of Sn nanowires. The gaseous Sn atoms are absorbed by the eutectic alloy droplets of Se–Au at first. Then Sn atoms precipitate at the liquid–solid phase interface due to a supersaturated solution and form a one-dimensional nanostructure. In all, this PVT method could provide a simple and quick way to synthesize monocrystalline Sn nanowires with an advantage in both quality and quantity. The optical transmittance of Sn nanowires thin film with 2μm2 density approaches 85–90% in visible wavelength. Therefore, the Sn nanowires thin film can be applied to transparent electrode along with their metallic property.

The strong influence of internal stresses on the nucleation of a nanosized, deeply undercooled melt at a solid-solid phase interface.

The effect of elastic energy on nucleation and disappearance of a nanometer size intermediate melt (IM) region at a solid-solid (S1S2) phase interface at temperatures 120 K below the melting temperature is studied using a phase-field approach. Results are obtained for broad range of the ratios of S1S2 to solid-melt interface energies, k(E), and widths, k(δ). It is found that internal stresses only slightly promote barrierless IM nucleation but qualitatively alter the system behavior, allowing for the appearance of the IM when k(E) < 2 (thermodynamically impossible without mechanics) and elimination of what we termed the IM-free gap. Remarkably, when mechanics is included within this framework, there is a drastic (16 times for HMX energetic crystals) reduction in the activation energy of IM critical nucleus. After this inclusion, a kinetic nucleation criterion is met, and thermally activated melting occurs under conditions consistent with experiments for HMX, elucidating what had been to date mysterious behavior. Similar effects are expected to occur for other material systems where S1S2 phase transformations via IM take place, including electronic, geological, pharmaceutical, ferroelectric, colloidal, and superhard materials.

Reactive Diffusion at the Contact of a Solid Phase with the Solder Melt

Problems of reactive diffusion at the solid phase and melt contact are studied theoretically. The rate constant is a fundamental parameter characterizing the dissolving rate at a certain configuration of experiment. Relationships between the solid phase dissolving rate, i.e. the solid phase interface boundary movement in the melt, and rates of growth of intermetallic phases in the metal (Cu) are observed. This procedure enables the creation of surface and subsurface layers of regulated thickness in metallic materials by means of reactive diffusion. The main intention was an experimental study of copper dissolving in melts of various solder alloys and the related reactive diffusion. We used Sn, SnCu, SnAgCu, SnZn and SnIn alloys as a solder material. The problems that need to be solved preferentially are emphasized. It concerns especially the determination of the rate constant of dissolving and verifying whether the proposed model equations can be used for this constant determination in cases of cylindrical and planar dissolving. Rapid growth of phases in the metal (Cu) and determination of the thickness of layers with these phases pose considerable time demands to X-ray microanalyses (WDX, EDX, BSE, SEM) of specimens after their long-time heating.

Study of the Reactive Diffusion in the Presence of Dissolution of Copper in the Solder Melts

In this work we give heed especially to the dominating process which is the solid metal A dissolving in the melt B. During the dissolving, the melt B saturates with the metal A and the process is influenced by convections which are characteristic for the given experimental configuration. A theoretical description of the kinetics of the solid phase dissolving in melt will be presented for the case of planar and cylindrical dissolving. The aim is to derive a relation for the interface boundary (t) movement in dependence on time and a time course of growth of the element A concentration in the melt B. There are problems with an accurate determination of the interface boundary movement after certain heating times of specimens, when it is observed experimentally, since intermetallic phases create in the original A metal at both the diffusion and cooling and some phases segregate at the solidifying melt cooling. The rate constant is a fundamental parameter characterizing the dissolving rate at a certain configuration. We present a theoretical description of dissolving of a long metallic cylinder submerged into a melt column and relations for the rate constant determination from the time of the whole metallic cylinder dissolution are derived. In our experiments were performed in which Cu was dissolving in the Sn melt for a Cu cylinder (wire) diameters 0.8÷2.5 mm and the rate constant K (T = 350°C) was determined. Relationships between the solid phase dissolving rate, i.e. the solid phase interface boundary movement (t) in the melt and rates of growth of intermetallic phases in the metal A will be observed. This procedure enables to create surface and subsurface layers of regulated thickness in metallic materials by means of reactive diffusion.

High Performance Gate-First pMISFET with TiN/HfSiON Gate Stacks Fabricated with PVD-Based In-Situ Method

We could obtain high performance gate-first pMISFET with TiN/HfSiON gate stacks fabricated with PVD-based in-situ method. High-quality Hf silicate gate dielectrics were formed by utilizing a solid phase interface reaction (SPIR) between a metal Hf layer and an SiO2 underlayer, and TiN electrodes were continuously grown on the gate dielectrics using a low-damage sputtering system without exposure to air.

Interface Engineering by PVD-Based In-Situ Fabrication Method for Advanced Metal/High-k Gate Stacks

We fabricated high-quality silicate gate dielectrics by utilizing a solid phase interface reaction (SPIR) between ultrathin metal layers and SiO2 underlayers. Metal diffusion to the SiO2 underlayer forms a high-quality silicate interlayer, and preserving the initial SiO2/Si bottom interface ensures good electrical properties. The Hf silicate dielectrics were fabricated by the SPIR method using Hf layers less than 0.5-nm-thick that were fully consumed by interface reactions, resulting in Hf silicate layers that remained amorphous after activation annealing. The superior electrical properties of the poly-Si/HfSixOy/SiO2/Si MOSFETs were demonstrated through low leakage current and high electron mobility. We also recently proposed a novel in-situ fabrication method that continuously fabricates high-k dielectrics using SPIR and metal electrodes with a low-damage sputtering system. We investigated structural and electrical properties of metal/high-k gate stacks and demonstrated the effectiveness of the in-situ method in improving electrical properties.

Impact of Physical Vapor Deposition-Based In situ Fabrication Method on Metal/High-k Gate Stacks

We proposed an in situ method for fabricating metal/high-k gate stacks. High-quality Hf silicate gate dielectrics were formed by utilizing a solid phase interface reaction (SPIR) between a metal Hf layer and an SiO2 underlayer, and TiN electrodes were continuously grown on the gate dielectrics using a low-damage sputtering system without exposure to air. We investigated the optimum SPIR conditions for TiN/HfSiO gate stacks, such as the thicknesses of the metal Hf and oxide underlayers, in situ annealing temperature, and oxygen pressure. The results indicate that the in situ method can be used to precisely control the SPIR to form silicate films and improve the electrical properties at metal/high-k interfaces. We demonstrated that the scaling of equivalent oxide thickness (EOT) was achieved and that the carbon impurity content at the gate stacks was successfully reduced by in situ silicate formation and continuous electrode deposition. As a consequence, we obtained excellent EOT versus gate leakage characteristics and succeeded in improving the hysteresis of capacitance–voltage curves for the TiN/HfSiO gate stacks.

Influence of wettability on petrophysical properties during imbibition in a random dense packing of equal spheres

Wettability, defined in terms of the value of contact angle of wetting–nonwetting–solid phase interface, is an important feature governing flow and transport processes in porous media. In this work we investigate the influence of wettability on the capillary pressure vs. saturation curve and on relative permeability during imbibition. To describe imbibition, we propose a new way of modeling it, based upon a physically consistent dynamic criterion for the imbibition of an individual pore, originally suggested by Melrose. We illustrate this approach in a simple but physically representative porous medium, the “ideal soil” (a dense random packing of equal spheres). Complete knowledge of the pore space geometry allows making a priori predictions of pore-level processes, without invoking adjustable parameters. This approach allows modeling imbibition for different values of contact angle and different initial conditions (as different drainage endpoints). The simulation yields the pore-level configuration of both fluid phases at each value of saturation. Relative permeabilities are calculated by simulating steady flow through the pore space occupied by each phase. The geometric and topological features of the flow network are directly connected to the geometry of the model rock and distribution of liquid phases in it. The simulated imbibition capillary pressure curves and relative permeability to the wetting phase are very sensitive to the value of contact angle in the whole range of wetting phase saturation. At the same time, relative permeability to the non-wetting phase is not much influenced by the wettability. Predicted capillary pressures and relative permeabilities compare favorably with experimental data for a range of wettabilities, providing strong support for the dynamic imbibition criterion.

High-quality HfSixOy gate dielectrics fabricated by solid phase interface reaction between physical-vapor-deposited metal–Hf and SiO2 underlayer

We fabricated high-quality Hf–silicate (HfSixOy) gate dielectrics by utilizing the solid phase interface reaction between physical-vapor-deposited metal–Hf (typically 0.5nm thick) and SiO2 underlayers. Metal diffusion to the SiO2 layer increases the permittivity of the underlayer, while preservation of the initial SiO2∕Si bottom interface ensures good electrical properties of the gate dielectrics. The Hf–silicate layer remains amorphous and the poly-Si∕HfSixOy gate stack endures activation annealing at 1000°C. The interface trap density was comparable to that of conventional SiO2 dielectrics and the hysteresis of capacitance–voltage curves was as low as 4mV for a bias swing between −2 and +2.5V. Moreover, high electron mobility, equal to 89% of the universal mobility, was obtained for the high-k gate transistor.

Role of the electric double layer in adhesion

1. Theoretical analysis has shown that the presence of electrostatic forces in the electric double layer formed at a solid phase interface is a significant factor in determining the strength of the adhesional bonding between the phases themselves. 2. Since these are long-range forces, they have a determining effect in fixing the work of adhesion in both planar contacts and elastic point-mass dielectric contacts. 3. The contributions of electrostatic and molecular forces to the strength of adhesional bonding have been compared at maximal charge density in the electric double layer, first for planar contacts and then for elastic point-mass contacts.