Liquid Indium Research Articles

Tailoring indium oxide film characteristics through oxygen reactants in atomic layer deposition with highly reactive liquid precursor

Indium oxide (InOx) films were deposited via atomic layer deposition (ALD) using a novel liquid indium precursor, dimethyl[N1-(tert-butyl)–N2,N2-dimethylethane-1,2-diamine]indium (DMITN). In this process, the reactant (H2O, O3, or O2 plasma) and substrate temperature (100–250 ℃) were varied. The DMITN precursor showed excellent reactivity with all three reactants. The growth characteristics (ALD window, growth per cycle, and step coverage) and film properties (impurities, stoichiometry, oxygen bonding state, crystallinity, film density, and electrical properties) differed based on the ALD process employed, ascribed to the distinct thermal energies and inherent reactivities of the chosen oxidants. As the oxidation energy of the reactants increased (H2O < O3 < O2 plasma), the growth per cycle (GPC) and the oxygen–indium bond ratio of InOx increased. Crystallinity analysis also revealed significant differences depending on the reactants, where the Hall mobility was predominantly influenced by the crystal alignment. The step coverage at an aspect ratio of 40:1 was markedly superior with the use of H2O and O3 reactants (approximately 95 %) compared to that with O2 plasma (approximately 74 %). These findings highlight the capability of controlling the growth and properties of InOx films by judiciously selecting the reactant, emphasizing the versatility of the DMITN precursor in ALD processes.

“Two-in-one” high stretchable healable WPU based conductive hydrogel for intelligent wearable sensing

In recent years, conductive hydrogel based sensors have been widely used because of their flexibility and convenience, especially in strain sensing, handwriting recognition, object shape recognition and so on. In this research, the conductive hydrogel with “two-in-one” structure was well designed to avoid the agglomeration and leakage of liquid metal by using polyvinylpyrrolidone modified liquid gallium indium alloy/polydopamine composite hydrogel as the top layer and hydrogen bonding crosslinked waterborne polyurethane/poly(vinyl alcohol) composite hydrogel as the bottom layer, respectively. Finally, a hydrogel based sensor with excellent stretchability and sensitivity was successfully obtained. The tensile strength of the prepared composite hydrogel exceeded 2 MPa. The elongation at break could be greater than 500 %. The toughness was greatly improved due to the introduction of waterborne polyurethane, which was greater than 7.5 MJ/m3. The GF value of the sensors reached 4.54. More interestingly, the mechanical self-healing ability of composite hydrogel prepared by adding polydopamine, reached about 70 % of the original. The hydrogel based sensor was able to use for gesture recognition and controlling the manipulator in human-computer interaction. This research can provide a practical idea to achieve advanced intelligent wearable sensing.

A novel annular slit-type emitter developed for multi-jet electrospray propulsion

Electrospray thrusters employ ionization in the liquid phase to produce and propel streams of molecular ions or highly charged droplets at significant velocities. In this study, we developed a novel annular slit-type emitter for electrospray and investigated its operational modes under varying applied potentials in both open atmosphere and vacuum conditions. To assess the performance of the annular slit-type emitter in comparison to the conventional capillary-type emitter, benchtop electrospray experiments were conducted using water and glycerin as working fluids for both emitter types. The study examined the formation of the Taylor cone, cone-to-jet transition, stable jet, whipping jet, and multi-jet, along with their dependence on fluid viscosity and electric potential for both emitter designs. Clear distinctions in hydrodynamic mode, drop-to-cone mode, and cone-to-jet transition mode were observed between the two emitters. As the electric potential increased, the capillary-type emitter exhibited a whipping and pulsating water jet, while glycerin displayed a steady tilted jet. In contrast, the annular slit-type emitter demonstrated a pulsating water jet followed by a distinctive dripping mode at higher electric potentials, while glycerin formed multiple steady jets around the annular slit. Notably, the annular slit-type emitter, when subjected to an 18.5 kV potential, produced seven electrospray jets for glycerin, a phenomenon attributed to the novel design of the emitter and the viscosity of glycerin enabling the generation of multiple cone-jets at a specific electrostatic potential around the slit peripheral meniscus. Vacuum chamber tests of the annular-type emitter using liquid indium as an ion source at 1 × 10−5 Torr revealed an ion-current density of 0.3 mA/mm, resulting in a thrust of 290 μN.

Temperature-induced gradual polymorphic structural crossover in liquid indium, tin, and antimony

Temperature-induced gradual polymorphic structural crossover in liquid indium, tin, and antimony

Beam commissioning of the SARAF Injector and MEBT (protons)

The SARAF Phase II cryogenic linear accelerator (linac) is currently under construction and will be commissioned through collaborative efforts between SNRC and CEA. The linac will accelerate a 5 mA pulsed/continuous wave (CW) proton and deuteron beam, reaching energies of up to 35 MeV and 40 MeV, respectively. The linac injector consists of Phase I components, including an ECR ion source, a Low-Energy Beam Transport (LEBT) line, and a 4-rod Radio Frequency Quadruple (RFQ). Additionally, a new Medium Energy Beam Transport (MEBT) line has been installed and integrated into the injector infrastructure. The MEBT includes three rebuncher resonators, magneto-optical elements, and beam diagnostics. The MEBT beam diagnostics, as well as the Phase I D-plate installed downstream, were used for beam characterization. The downstream-installed Temporary Beam Line (TBL) and a prototype of the Gallium Indium Liquid Target (GALIT) were used for commissioning, operating at high beam duty cycles, including CW mode. The report describes the proton beam commissioning process of the injector prior to the delivery of the cryomodules, scheduled for the second half of 2023.

Thickness-Dependent Room-Temperature Optoelectronic Gas Sensing Performances of 2D Nonlayered Indium Oxide Crystals from a Liquid Metal Printing Process.

Due to excellent gas sensing performances, such as high responsivity, good selectivity, and long-term stability, two-dimensional (2D) nonlayered metal oxide semiconductors have attracted wide attention. However, their thickness-dependent gas sensing behaviors are rarely investigated, which is critical in the development of practical 2D sensors. In this work, 2D In2O3 crystals with a range of thicknesses are realized by extracting the self-limited oxide layer from the liquid indium droplets in a controlled environment. A strong thickness-dependent optoelectronic NO2 sensing behavior at room temperature is observed. While full reversibility and excellent selectivity toward NO2 are shown despite the thicknesses of 2D In2O3, the 1.9 nm thick In2O3 exhibits a maximum response amplitude (ΔI/Ig = 1300) for 10 ppm of NO2 at room temperature with 365 nm light irradiation, which is about 18, 58, and 810 times larger than those of its 3.1 nm thick, 4.5 nm thick, and 6.2 nm thick counterparts, respectively. The shortest response and recovery times (i.e., 40 s/48 s) are demonstrated for the 1.88 nm thick In2O3 as well. We correlate such a phenomenon with the change in the In2O3 band structure, which is influenced by the thickness of 2D crystals. This work provides in-depth knowledge of the thickness-dependent gas-sensing performances of emerging 2D nonlayered metal oxide crystals, as well as the opportunities to develop next-generation high-performing room-temperature gas sensors.

Gas sensors based on the oxide skin of liquid indium.

Various non-stratified two-dimensional (2D) materials can be obtained from liquid metal surfaces that are not naturally accessible. Homogenous nucleation on atomically flat interfaces of liquid metals with air produces unprecedented high-quality oxide layers that can be transferred onto desired substrates. The atomically flat and large areas provide large surface-to-volume ratios ideal for sensing applications. Versatile crucial applications of the liquid metal-derived 2D oxides have been realized; however, their gas-sensing properties remain largely underexplored. The cubic In2O3 structure, which is nonlayered, can be formed as an ultrathin layer on the surface of liquid indium during the self-limiting Cabrera-Mott oxidation process in the air. The morphology, crystal structure, and band structure of the harvested 2D In2O3 nanosheets from liquid indium are characterized. Sensing capability toward several gases, both inorganic and organic, entailing NO2, O2, NH3, H2, H2S, CO, and Methyl ethyl ketone (MEK) are explored. A high ohmic resistance change of 1974% at 10 ppm, fast response, and recovery times are observed for NO2 at an optimum temperature of 200 °C. The sensing fundamentals are investigated for NO2, and its performances and cross-selectivity to different gases are analyzed. The NO2 sensing response from room temperature to 300 °C has been measured and discussed, and stability after 24 hours of continuous operation is presented. The results demonstrate liquid metal-derived 2D oxides as promising materials for gas sensing applications.

Thermodynamic measurements and ab initio calculations of the indium-lithium system

The limiting enthalpy of the solution of liquid indium in liquid tin was measured at 723 K. The calorimetric method was applied to determine the standard enthalpy of the formation of intermetallic phases and alloys from the In-Li system. The measurements were done at 747 K and 756 K. The structures of prepared alloys were confirmed by the X-ray diffraction measurements. Besides that, the ab initio calculations allowed the modeling of the formation energies, the volume thermal expansion, the heat capacity under constant pressure, and the elastic properties of the intermetallic phases. The theoretical formation energies show good agreement with the experimental findings. The analysis of the phonon dispersion indicates an instability of the InLi phase in the Fd-3m space group. A further investigation on the atomic arrangement in the case of the equiatomic ratio is suggested.

A Promising Crystalline KCl: Electrolyte Material for Studying the Electrochemical Properties of Cerium on Liquid Indium Electrodes

Potassium chloride crystals are good conductors in the UV to mid-infrared broadband and can be widely used as materials for high-power CO2 lasers. However, the most important use of potassium chloride crystals has been overlooked; their stable chemistry and wide electrochemical window allow them to form molten eutectic salts with other chlorides for the dry reprocessing of spent fuel. The aim of this work is to investigate the electrochemical properties of the actinide substitute cerium metal on liquid indium media in order to provide basic data for further realization of lanthanides (Ln)/actinides (An) separation. In this paper, we investigated the electrochemical behavior of 3LiCl-2KCl-CeCl3 melt at liquid metal media indium (In) electrode using various transient electrochemical analysis methods, such as cyclic voltammetry, square wave voltammetry and open circuit potential technique. The quasi-equilibrium potentials of Ce3+ at different temperatures on the liquid metal In electrode were determined. On the redox process, the reaction kinetics of the oxidation–reduction process in the 3LiCl-2KCl-CeCl3 system is studied. It was determined that the reduction of Ce3+ at the liquid metal In electrode is an irreversible single-step process with three electron transfers. The relationship between the diffusion coefficient and the reduction process of Ce3+ ions on liquid metal indium electrodes at different temperatures was determined. The expression for the diffusion coefficient and temperature of Ce3+ at the liquid metal indium electrode is: lnD = 1.43 − 7974.69/T.

Determination of indium melting curve at high pressure by picosecond acoustics

Picosecond acoustics combined with a diamond anvil cell is used to study liquid indium and to determine with high accuracy both the sound velocity and the melting curve over an extended pressure and temperature range. The sound velocities, determined by phonon surface imaging, complement previous inelastic x-ray scattering determinations and are in good agreement with estimations according to a thermodynamic model. Based on exact thermodynamic relations, the equation of state of the liquid phase is obtained using the isothermal bulk modulus ${B}_{T,0}$ and its first pressure derivative ${B}_{T}^{\ensuremath{'}}$. These quantities are derived from the precise experimental determination of the variation of the sound velocity as a function of pressure. Melting is determined via the detection of abrupt changes in the elastic properties between solid and liquid phases and through the monitoring of the solid-liquid coexistence. The melting curve constrained up to 6 GPa and 673 K is shown to be well described by the Simon-Glatzel equation in the full $(p,T)$ range explored.

Plasma-enhanced atomic-layer-deposited indium oxide thin film using a DMION precursor within a wide process window

In this study, we developed a new liquid indium precursor, dimethyl[N-(tert-butyl)-2-methoxy-2-methylpropan-1-amine] indium (DMION), to deposit indium oxide films using the plasma-enhanced atomic layer deposition (PEALD) method. The indium oxide films were deposited using DMION and Ar/O2 plasma as the precursor and reactant, respectively, with relatively high growth per cycle (GPC, ∼1.2 Å/cycle) within a wide atomic layer deposition (ALD) window (35–300 °C). Impurities such as carbon and nitrogen were not detected regardless of the deposition temperature. The crystallinity of the films had a bixbyite cubic structure within the ALD window and facets could be controlled by deposition temperature modulation; (400) facets were dominant at low deposition temperatures (35 and 100 °C), whereas (222) facets were dominant at high deposition temperatures (200 and 300 °C). The dominant facets and orientations of the indium oxide crystal were maintained until 400 °C in the post-annealing process. The thin-film transistors (TFTs) using indium oxide deposited at 200 °C exhibited high field-effect (∼32.1 cm2/Vs) mobility with a reasonable threshold voltage (∼1.8 V) and subthreshold voltage swing (∼0.48 V/decade).

Thermophysical Characteristics of Liquid Metal In-Bi-Sn Eutectic (Field's Metal) as a Similarity Coolant

Abstract This work investigated the thermophysical characteristics of liquid indium–bismuth–tin eutectic alloy also known as Field's Metal for the purposes of use as a similar fluid for liquid metal reactors. The density, specific heat capacity, viscosity, thermal conductivity, and the coefficient of thermal expansion were determined for liquid Field's Metal for temperature ranges from its melting point 333 K to 423 K. The work captured the effect of temperature on these properties and each property's magnitude. The findings were used to create mathematical correlations to predict the value of the thermophysical property at a specified temperature for use in natural circulation studies. Notably, the work also observed non-Newtonian shear thinning behavior of the alloy near the melting point and that the non-Newtonian behavior relaxes as the material obtains more energy. The results are consistent with the behavior of other liquid metals including variances that occur close to the melting point.

Liquid Metal Fiber Mat as a Highly Stable Solid-State Junction for Inkjet-Printed Flexible Reference Electrodes.

An all-solid liquid-metal-fiber-mat-based membrane flexible reference electrode (LMFM-FRE) was developed by combining liquid metal eutectic gallium indium (EGaIn) and poly(styrene-block-butadiene-block-styrene) (SBS) as a liquid junction layer. Ag ink was printed and chlorinated by electroplating to form the AgCl layer. Then, agarose containing KCl was coated as the electrolyte layer, and LMFM was added as the liquid junction layer. The liquid junction layer can increase the hydrophobicity of the electrode surface, limit the loss of internal Cl-, and significantly improve the stability of the electrode. The potential fluctuation of LMFM-FRE does not exceed 1 mV within 1 h, and it is still the same after 1 month. In addition, its potential changes in ion species and concentration, pH value, and ambient light are small, and its cyclic voltammetry characteristics are consistent with the standard reference electrode. Even in the case of temperature change and mechanical deformation, the potential change of LMFM-FRE is minimal. In general, the materials used and fabrication by inkjet printing make it possible to manufacture the reference electrode on a large scale, which is particularly important in many electrochemical sensing fields.

Morphogenesis of Liquid Indium Microdroplets on Solid Molybdenum Surfaces during Solidification at Normal Pressure and under Vacuum Conditions.

Electrical and optical applications based on micro- and nanoparticles have specific demands on their interfacial properties. These properties are strongly related to atmospheric conditions to which the particles were exposed during their formation. In this study, metallic In microparticles are synthesized by solidification of In droplets on an amorphous Mo substrate at normal pressure and under vacuum conditions. The influence of ambient pressure on the interface and surface shape is investigated. While solidification at atmospheric pressure leads to collapsed particles with undisturbed contact to the substrate, low pressures result in smooth spherical particles but with cavities inside. Numerical simulations with COMSOL Multiphysics reveal different temperature profiles and heat flux in particles during solidification for both cases. This indicates different starting conditions of the solidification, which leads to the described phenomenon eventually. The investigation of the varying process conditions on the particle shape in combination with the calculated and measured temperature curves over time gives valuable insights into new approaches to synthesize micro- and nanoparticles with defined interfacial properties. Both ambient pressure and cooling rate provide well-controllable and reliable parameters for the realization of different interfacial shapes.

Hard Copper Wetting with Liquid Indium in Ultrahigh Vacuum and Gaseous Medium and Interfacial Energy Calculation at Different Temperature

Hard Copper Wetting with Liquid Indium in Ultrahigh Vacuum and Gaseous Medium and Interfacial Energy Calculation at Different Temperature

Hybrid‐type stretchable interconnects with double‐layered liquid metal‐on‐polyimide serpentine structure

We demonstrate a new double-layer structure for stretchable interconnects, where the top surface of a serpentine polyimide support is coated with a thin eutectic gallium–indium liquid metal layer. Because the liquid metal layer is constantly fixed on the solid serpentine body in this liquid-on-solid structure, the overall stretching is accomplished by widening the solid frame itself, with little variation in the total length and cross-sectional area of the current path. Therefore, we can achieve both invariant resistance and infinite fatigue life by combining the stretchable configuration of the underlying body with the freely deformable nature of the top liquid conductor. Further, we fabricated various types of double-layer interconnects as narrow as 10 μm using the roll-painting and lift-off patterning technique based on conventional photolithography and quantitatively validated their beneficial properties. The new interconnecting structure is expected to be widely used in applications requiring high-performance and high-density stretchable circuits owing to its superior reliability and capability to be monolithically integrated with thin-film devices.

An UHF Reconfigurable Liquid-Metal Monopole Antenna Based on a 2-D Surface

This article demonstrates an ultrahigh frequency (UHF) liquid-metal monopole antenna qualified for reconfiguring its resonant frequency by stretching or shortening its length on a 2-D surface. The proposed antenna consists of liquid eutectic gallium and indium (EGaIn) and NaOH solution. A power supply generates a direct current (DC) potential between the EGaIn and NaOH solution. Depending on the electrically-driven method to push or withdraw the EGaIn, the antenna is capable of forming different lengths to redistribute the current of the radiating element. Compared with the microchannel liquid-metal antenna, the proposed antenna can be tuned on a 2-D surface, rather than relying on the microchannel for shaping. By varying the length of EGaIn on a 2-D surface, the proposed antenna can provide continuously tunable frequency range and repeatability. For EGaIn monopole antenna with lengths from 50 to 10 mm, the measured resonant frequency operates from 0.78 to 2.42 GHz for a tuning ratio 3.1:1. The application of the design, operation of tuning liquid-metal antenna at several frequencies, and measurement process are explained in this article.

Atmospheric Pressure Catalytic Vapor Deposition of Graphene on Liquid In and Cu-In Alloy Substrates

Liquid substrates are great candidates for the growth of high-quality graphene using chemical vapour deposition (CVD) due to their atomically flat and defect free surfaces. A detailed study of graphene growth using atmospheric pressure CVD (APCVD) on liquid indium (In) was conducted. It was found that the effect of the growth parameters on the quality of the graphene produced is highly dependent on the properties of the substrate used. A short residence time of 6.8 sec for the reactive gases led to a high graphene quality, indicating the good catalytic behaviour of In. The role of hydrogen partial pressure was found to be crucial, with monolayer and bilayer graphene films with a low defect density obtained at low PH2 (38.6 mbar), whilst more defective, thicker graphene films with a partial coverage being obtained at high PH2 (74.3 mbar). The graphene deposition was insensitive to growth time as the graphene growth on liquid In was found to self-limit to bilayer. For further investigation, five compositions of Cu-In alloys were made by arc-melting. Graphene was then grown using the optimum conditions for In and the quality of the graphene was found to degrade with increasing Cu wt.%. This work will aid the future optimisation of the growth conditions based upon the substrate’s properties.

Electrodeposition of Gallium and Indium from Non-aqueous Electrolytes

In this work, we studied the electrodeposition of gallium and indium from 1,2-dimethoxyethane (DME)-based and dimethyl sulfoxide (DMSO)-based electrolytes, respectively.1,2 Cyclic voltammetry in combination with rotating (ring) disk electrode and electrochemical quartz-crystal microbalance were used to identify the redox chemistry and electrodeposition behavior of both metals. Scanning electron microscopy (SEM) was used to investigate the structural morphology of the deposited materials.Gallium electrodeposition was studied from a bath composed of gallium(III) chloride, an inert background salt and DME. The electroreduction process occurred in two steps: (1) from gallium(III) to gallium(I), and (2) from gallium(I) to gallium(0). Metallic gallium was deposited as spheres with diameters of several hundreds of nanometers that were stacked on top of each other. X-ray photoelectron spectroscopy revealed that each gallium sphere was covered by a thin gallium oxide shell. These shells prevent individual gallium spheres from agglomerating to larger entities. Electrochemical experiments indicated that these oxide layers were electrically conductive. It was demonstrated that electrodeposition proceeded via a droplet-on-droplet electrodeposition mechanism. A growth mechanism for an individual growing gallium sphere was also postulated.Indium electrodeposition was studied from a bath composed of indium(III) methanesulfonate, a background salt and DMSO. indium(III) methanesulfonate was synthesized from methanesulfonic acid and indium(III) oxide. The latter is an intermediate formed during the purification of indium from primary and secondary resources. Conversion of indium(III) oxide into metallic indium could therefore lower the energetic cost of its production. Analogously to gallium, Indium(III) is reduced to indium(I), and then to indium(0). It was demonstrated that indium(I) disproportionates to indium(III) and indium(0), leading to the formation of micron-sized metallic indium particles in the electrolyte. At 26 °C, indium deposited as smooth, flat films whereas at 160 °C, it deposited as liquid indium droplets. Electrodeposition of indium above its melting point enables the process to be performed in a continuous manner; indium droplets accumulate and grow, and will ultimately glide off the electrode, and drop to the bottom of the cell, forming a liquid pool from which the metal can be tapped off.In the attached figure, SEM images of (1) gallium deposited at 26 °C and (2) indium, deposited at 26 °C and 160 °C are shown. Figure 1

Dependence of the effective surface tension of liquid phase eutectic gallium indium on wrinkles of the surface oxide

We investigated the effective surface tension of liquid eutectic gallium indium (EGaIn) with oxide skin. Our visualization of the EGaIn interface during extension and compression indicated the compression causes the wrinkles on the oxide skin, which is then partially smoothed out by extension. We found that the creation of the interface was the combined result of tearing of the oxide skin and the unfolding of oxide wrinkles. Our experiments revealed that the effective surface tension depends on oxide wrinkle, and the value is 0.7 N/m in the absence of wrinkles, but can be as small as ∼0.5 N/m in the presence of surface wrinkles.