Liquid Phase Epitaxial Growth Research Articles

MOF polycrystalline membrane on zinc metal anode through liquid-phase epitaxial growth

MOF polycrystalline membrane on zinc metal anode through liquid-phase epitaxial growth

Tunable magneto-transport properties in ultra-high Bi-doped Si prepared by liquid phase epitaxy

During the past decades, excavating the novel functional materials towards CMOS-compatible spin-transport devices has been treated as one of the most urgent tasks to revolutionize the current Si-based nonmagnetic spintronics. Among various strategies, triggering the exotic physics in Si via utilizing heavy-element hyperdoping is the most straightforward way to achieve the abovementioned expectation. In this work, by using liquid phase epitaxy growth, we have achieved the highest Bi doping level in Si up to 2.0 × 1021 cm−3. The resulting Bi-hyperdoped Si layers are confirmed to be single-crystalline and epitaxially regrown without extended defects or Bi agglomerates via various microstructural analysis. The Bi-hyperdoped Si layers exhibit a metallic-like behavior with the carrier densities up to 1.55 × 1015 cm−2 and a prominent electrical activation yield around 50 %. Negative magnetoresistance due to magnetic-field suppressed weak localization at both sides of the insulator-to-metal transition is observed. Tunable magneto-transport properties are realized in ultra-high Bi doped Si epilayers by controlling the donor concentration. This provides new possibilities for designing Si devices that integrate spin-charge conversion and spin transport. This work promises to enable heavy-element hyperdoped semiconductor epilayers as novel spin-based electronics material platform via a chip-technology compatible approach.

Liquid-phase epitaxy of neutron star crusts and white dwarf cores

ABSTRACT Near-equilibrium bottom-up crystallization of fully ionized neutron star crusts or white dwarf cores is considered. We argue that this process is similar to liquid-phase epitaxial (i.e. preserving order of previous layers) crystal growth or crystal pulling from melt in Earth laboratories whereby lateral positions of newly crystallizing ions are anchored by already solidified layers. Their vertical positions are set by charge neutrality. Consequently, interplane spacing of a growing crystal either gradually increases, tracing ne decrease, as the crystallization front moves away from the stellar centre, or decreases, tracing decrease of 〈Z〉, when the crystallization front crosses a boundary between layers of different compositions. This results in the formation of stretched Coulomb crystals, in contrast to the standard assumption of cubic crystal formation, which is based on energetics arguments but does not take into account growth kinetics. Overstretched crystals break, which limits the vertical sizes of growing crystallites. We study breaking shear strain and effective shear modulus of stretched matter and discuss possibility of macrocrystallite formation. The latter has interesting astrophysical implications, for instance, appearance of weak crustal layers, whose strength may increase by a few orders of magnitude upon breaking and refreezing at a late-time event. We also analyse interaction of adjacent Coulomb crystals, having different ion compositions, and estimate the strength of such interfaces.

Epitaxial graphene growth on cubic silicon carbide on silicon with high temperature neutron reflectometry: an operando study.

The growth of graphene on silicon carbide on silicon offers a very attractive route towards novel wafer-scale photonic and electronic devices that are easy to fabricate and can be integrated in silicon manufacturing. Using a Ni/Cu catalyst for the epitaxial growth of graphene has been successful in the mitigation of the very defective nature of the underlying silicon carbide on silicon, leading to a consistent graphene coverage over large scales. A more detailed understanding of this growth mechanism is warranted in order to further optimise the catalyst composition, preferably via the use of operando characterization measurements. Here, we report in situ neutron reflectometry measurements of (Ni, Cu)/SiC films on silicon wafers, annealed from room temperature to 1100 °C, which initiates graphene formation at the buried (Ni, Cu)/SiC interface. Detailed modelling of the high temperature neutron reflectometry and corresponding scattering length density profiles yield insights into the distinct physical mechanisms within the different temperature regimes. The initially smooth solid metallic layers undergo intermixing and roughening transitions at relatively low temperatures below 500 °C, and then metal silicides begin to form above 600 °C from interfacial reactions with the SiC, releasing atomic carbon. At the highest temperature range of 600-1100 °C, the low neutron scattering length density at high temperature is consistent with a silicon-rich, liquid surface phase corresponding to molten nickel silicides and copper. This liquid catalyst layer promotes the liquid-phase epitaxial growth of a graphene layer by precipitating the excess carbon available at the SiC/metal interface.

Transferable Force Field for Gallium Nitride Crystal Growth from the Melt Using On-The-Fly Active Learning.

Atomic-scale simulations of reactive processes have been stymied by two factors: the lack of a suitable semiempirical force field on one hand and the impractically large computational burden of using ab initio molecular dynamics on the other hand. In this paper, we use an "on-the-fly" active learning technique to develop a nonparameterized force field that, in essence, exhibits the accuracy of density functional theory and the speed of a classical molecular dynamics simulation. We developed a force field capable of capturing the crystallization of gallium nitride (GaN) during a novel additive manufacturing process featuring the reaction of liquid Ga and gaseous nitrogen precursors to grow crystalline GaN thin films. We show that this machine learning model is capable of producing a single force field that can model solid, liquid, and gas phases involved in the process. We verified our computational predictions against a range of experimental measurements relevant to each phase and against ab initio calculations, showing that this nonparametric force field produces properties with excellent accuracy as well as exhibits computationally tractable efficiency. The force field is capable of allowing us to simulate the solid-liquid coexistence interface and the crystallization of GaN from the melt. The development of this transferable force field opens the opportunity to simulate the liquid-phase epitaxial growth more accurately than before to analyze reaction and diffusion processes and ultimately to establish a growth model of the additive manufacturing process to create the gallium nitride thin films.

Anomalous and inverse spin Hall effects in Pt1-xBix/(YLuBiCa)3(FeGa)5O12 heterojunction

A garnet film with spatial magnetic moment distribution has been grown on gadolinium gallium garnet wafer (111) crystal plane, by regulating liquid phase epitaxial growth parameters and sub-lattice ions substitution, then 10 nm Pt1-xBix (x = 2% – 8%) alloy film was deposited on the surface of the garnet films. A new spin heterojunction Pt1-xBix/(YLuBiCa)3(FeGa)5O12 with both inverse spin Hall effect (ISHE) and anomalous spin Hall effect (ASHE) was designed and fabricated. The spatial magnetic moment distribution of the heterojunction has been found, which lays the foundation of the spin heterojunction for multiple spin injection with both spin electron reverse injection and anomalous injection. Because Bi ions doping and substitution increases the spin–orbit torque and the mixed conductance of the heterojunction, an oblique ASHE voltage curve and an enhanced ISHE voltage curve with double resonance peak were observed. It was confirmed that the injection of spinning electron into the heterojunction can be enhanced with both the ISHE and ASHE effect by adjusting the spatial magnetic moment distribution, which is a foundation for the future application of spin wave 3D antenna and other devices.

Preparation and dye separation performance of ZIF-67/mesoporous silica ceramic nanofiltration membrane by liquid phase epitaxy (LPE) growth method

Ceramic membrane plays an important role in separation process with advantages of high thermal and chemical resistances, but its applications on the nanofiltration are restricted because of the limitation of pore size. In this study, a commercial tubular ceramic membrane with pore diameter of 0.1 μm was firstly coated with mesoporous silica substrates, in which ZIF-67 nanocrystals were generated layer-by-layer inside the mesochannels via liquid phase epitaxy growth method. The open pore size of ceramic membrane can be precisely controlled by increasing the growth cycles of ZIF-67 nanocrystals. The influence of preparation conditions on the dye separation was investigated, including growth cycles, precursor concentration, and molar ratio of Co2+/2-methylimidazole (Co2+/Hmim). Under the optimized conditions, the rejection of methylene blue, methyl orange, chromium black T, rhodamine B, acid fuchsin, and Congo red were in the range of 92–99 % with membrane fluxes of 0.45–0.73 L m−2 h−1. Bovine serum albumin solution was used to evaluate the anti-fouling abilities of the ceramic membrane. The flux recovery ratio, which was calculated according to the ratio between the water permeance after washing and before filtration, was 52.3 % with the flux decline rate of 66.3 %.

In-situ X-ray diffraction analysis of SiGe liquid phase growth on Si using Al–Ge paste

We performed in-situ two-dimensional X-ray diffraction measurements during a silicon-germanium (SiGe) layer formation process to analyze the liquid-phase epitaxial growth of a SiGe layer on silicon (Si) substrate by a simple method of aluminum-germanium (Al–Ge) paste screen-printing and annealing. The aluminum (Al) and germanium (Ge) from the Al–Ge paste were found to be in the liquid phase starting around 540 °C for the Al–Ge paste containing Al and Ge powders, while it starts around 430 °C for the one containing Al–Ge alloy powder. During the cooling process from the peak temperature of 900 °C down to 430 °C, a SiGe layer was epitaxially grown in the same orientation as the Si substrate. Around 430 °C, the remaining material in the liquid phase formed during the temperature increase solidified and the reaction was terminated. The XRD results suggest that most of the Al in the liquid phase exists as liquid phase from the peak temperature down to 430 °C. The Al liquid phase mediates the melting of Si and Ge, and the Si substrate functions both as a Si source, and as a seed crystal for the growth of the SiGe layer. Both samples show that the Ge concentration is sharply increased in the SiGe layer to around 13 at% at the interface and retains a uniform concentration distribution up to the Al paste matrix/SiGe interface. The change in crystallinity during the liquid phase growth indicates that the properties of the SiGe layer formed by this method can be controlled by adjusting the composition of the Al–Ge paste and the annealing temperature profile.

Liquid-phase epitaxial growth of multiple MOF thin films with high lattice mismatch

We have prepared a series of multiple (bi-varietal and tri-varietal) pillar-layered MOF thin films [Cu2L2dabco]n (L = bdc, bpc and tpdc) with high lattice mismatch (up to 77.8%) using a liquid-phase epitaxial layer by layer method.

Research Progress and Applications of 2D Antimonene

Antimonene has attracted much attention due to its excellent properties such as high carrier mobility, excellent thermoelectric performance and high stability. In order to verify its theoretical advantages, a large number of experimental studies have been carried out and its applications explored. This paper mainly introduces the experimental preparation of antimonene by mechanical exfoliation, liquid phase exfoliation and epitaxial growth, summarizes the advantages and disadvantages of each method, and describes the applications of antimonene in sensor, battery, medicine and laser. Finally, prospects have been made to the future applications of antimonene in photoelectric field.

Development of the Composite Thermoluminescent Detectors Based on the Single Crystalline Films and Crystals of Perovskite Compounds.

This work is dedicated to the development of new types of composite thermoluminescent detectors based on the single crystalline films of Ce-doped GdAlO3 perovskite and Mn-doped YAlO3 and (Lu0.8Y0.2)AlO3:Mn perovskites as well as Ce and Pr-doped YAlO3 single crystal substrates. These detectors were obtained using the Liquid Phase Epitaxy growth method from the melt solution based on the PbO-B2O3 fluxes. Such composite detectors can by applied for the simultaneous registration of different components of mixed ionization fluxes using the differences between the thermoluminescent glow curves, recorded from the film and crystal parts of epitaxial structures. For creation of the new composite detectors, we considered using, for the film and crystal components of epitaxial structures (i) the different perovskite matrixes doped with the same type of activator or (ii) the same perovskite host with various types of activators. The thermoluminescent properties of the different types of epitaxial structures based on the abovementioned films and crystal substrates were examined in the conditions of β-particles and X-ray excitation with aim of determination of the optimal combination of perovskites for composite detectors. It was shown that, among the structures with all the studied compositions, the best properties for the simultaneous thermoluminescent detection of α- and X-rays were the GdAlO3:Ce film/YAlO3:Ce crystal epitaxial structure.

Liquid phase epitaxy growth and structural characterization of highly-doped Er3+:LiYF4 thin films

Single-crystalline layers of LiYF4, singly doped with Er3+ ions and codoped with Er3+,Gd3+ ions are grown on (001) oriented undoped bulk LiYF4 substrates by Liquid Phase Epitaxy using LiF as a solvent. For the starting composition 73 LiF – 27 REF3 mol% (RE = Y, Er, Gd), the onset of crystallization is about 746 °C. The effect of apparent supercooling on the growth behavior is studied indicating an optimum value of 0.5 °C. Layers of 30–90 μm in thickness are obtained corresponding to a growth rate of 0.8–1.6 ± 0.5 μm/min. The morphology, structure and composition of the layers are studied. The layers exhibit tetragonal structure (sp. gr. I41/a) and small lattice mismatch with respect to the substrate. The segregation coefficient for Er3+ ions is close to unity. Intense mid-infrared luminescence of Er3+ ions at ∼2.8 μm is observed from the layers, which, together with the waveguiding properties, indicates their suitability for waveguide lasers.

Numerical modeling of the crystallization process in liquid phase epitaxial growth of silicon

Numerical modeling is applied to investigate the liquid phase epitaxial growth of silicon from tin-silicon solutions in a “sandwich” cell system. The model is based on physical and numerical approaches which allow for transient computations of the solid-liquid interface shape during the crystallization process. Numerical simulations consider the thermo-solutal convection and the dependence of the solidification temperature on the liquid composition. Numerical results show that the top epitaxial layer grows faster and exhibits a wavier surface as compared to the bottom layer. The predicted layers thickness, solid-liquid interfaces shape and the growth rates are in agreement with the experimental observations. The influence of the cooling rate on the deposited layers thickness and smoothness was investigated at different liquid heights. It is found that the growth from wide liquid solutions (8 mm) at high cooling rates (2°C/min) is favorable for the deposition of thick Si layers of homogeneous thickness.

Nonlinear optical properties of graphdiyne/graphene van der Waals heterostructure for laser modulations

The construction of van der Waals heterostructures (vdWHs) is emerging as a promising approach for creating new materials with exotic functionalities and extraordinary optical properties in the field of laser modulations. However, the comprehensive research of vdWHs is still at an early stage that it needs further investigation of the corresponding optical properties and applications. In this paper, graphdiyne/graphene vdWH (GDY/G) is successfully fabricated through liquid-phase epitaxial growth method and its optical nonlinearities are investigated for both pulse laser generation and spatial self-phase modulation (SSPM). Using GDY/G as saturable absorber, the outputs of the passively Q-switched (PQS) Nd:Lu0.5Y0.5VO4 laser at 1343 nm under 878 nm direct pumping are investigated in detail, delivering a better performance than pristine graphdiyne or graphene. Moreover, as carrier for SSPM, GDY/G demonstrates a large nonlinear refractive index in the order of 10−5 cm2 W−1. These advantages can be attribute mainly to accelerated carrier relaxation and enhanced nonlinear optical properties due to synergistic effect of graphdiyne and graphene, which are stacked together to form the vdWH with interlayer coupling. The experimental results indicate that GDY/G possesses large potentials and bright prospects in laser modulations.

Novel Negative Capacitance Appeared in all Frequencies in Au/AlCu/SiO2/p-Si/Al Structure

AbstractTo the best of our knowledge. The current work shows that negative capacitance exists at all frequencies, contrary to what is claimed in the literature, which states that negative capacitance only exists at high or low frequencies. In this paper, Au/AlCu/SiO2/p-Si/Al structure was epitaxial grown by the liquid phase epitaxial growth technique. The structural characterization was studied using an X-ray diffraction pattern. The capacitance and conductance behavior was studied using I-V and C-V measurements at various temperatures, voltages, and frequencies. Negative capacitance appears at all frequencies ranging from low to high; moreover, capacitance has both positive and negative values at all frequencies, while the conductance has positive values only in all frequencies. The current-voltage characterization was used to investigation the ideality factor, barrier height, and series resistance. The barrier height and Richard constant were estimated, through investigating the current conduction mechanism of Au/AlCu/SiO2/p-Si/Al.

Metal-Organic Framework Assembled on Oriented Nanofiber Arrays for Field-Effect Transistor and Gas Sensor-Based Applications

Metal–organic framework (MOF) films are essential for numerous sensor and device applications. However, metal-organic framework materials have poor machinability due to their predominant powder-like nature, and their presence as the active layer in a device can seriously affect the performance and utility of the device. Herein, active layers of field-effect transistor (FETs) devices and chemiresistor gas sensors with high performance were constructed by loading Cu3(HITP)2 (HITP = 2,3,6,7,10,11-hexaiminotriphenylene) in situ-axial anchoring on oriented nanofiber arrays prepared via electrospinning. The strong interaction between polar groups on the polymer chains and metal ions promotes the nucleation of Cu3(HITP)2, steric hindrance makes particles of Cu3(HITP)2 with uniform size, morphology, and good crystallinity during nucleation by liquid phase epitaxial growth (LPE). Influences of differently-oriented Cu3(HITP)2 NFAs-based FETs on the electrical properties were studied, optimally oriented Cu3(HITP)2 NFAs-based FETs showed good mobility of 5.09 cm2/V·s and on/off ratio of 9.6 × 103. Moreover, excellent gas sensing response characteristics were exhibited in sensing volatile organic compounds (VOCs). Chemiresistor gas sensors with high response value, faster response and recovery are widely suited for VOCs. It brings new inspirations for the design and utilization of electrically conductive MOFs as an active layer for FETs and sensor units for chemiresistor gas sensors.

Composite Detectors Based on Single-Crystalline Films and Single Crystals of Garnet Compounds.

This manuscript summarizes recent results on the development of composite luminescent materials based on the single-crystalline films and single crystals of simple and mixed garnet compounds obtained by the liquid-phase epitaxy growth method. Such composite materials can be applied as scintillating and thermoluminescent (TL) detectors for radiation monitoring of mixed ionization fluxes, as well as scintillation screens in the microimaging techniques. The film and crystal parts of composite detectors were fabricated from efficient scintillation/TL materials based on Ce3+-, Pr3+-, and Sc3+-doped Lu3Al5O12 garnets, as well as Ce3+-doped Gd3−xAxAl5−yGayO12 mixed garnets, where A = Lu or Tb; x = 0–1; y = 2–3 with significantly different scintillation decay or positions of the main peaks in their TL glow curves. This work also summarizes the results of optical study of films, crystals, and epitaxial structures of these garnet compounds using absorption, cathodoluminescence, and photoluminescence. The scintillation and TL properties of the developed materials under α- and β-particles and γ-quanta excitations were studied as well. The most efficient variants of the composite scintillation and TL detectors for monitoring of composition of mixed beams of ionizing radiation were selected based on the results of this complex study.

Characteristics of spin-thermoelectric generators enhanced by incorporating liquid phase epitaxial Bi-substituted YIG films as a ferrimagnetic insulator

Liquid phase epitaxial (LPE) Bi-substituted YIG films exhibit a large growth-induced magnetic anisotropy (GIMA) perpendicular to the film surface. The GIMA depends on the melt composition and supercooling in the LPE growth. Our film shows a large Ku value of 0.1 × 104 J/m3 even at a Bi content, x, of 0. We assume that GIMA enhances the spin-orbital coupling (SOC) in the local d-electron spins of Fe3+, and that the SOC-enhanced thermal energy transfer from the phonon system to the spin system increases spin currents in spin-thermoelectric (STE) generation. We discuss the characteristics of STE generators on the basis of data obtained from ferromagnetic resonance measurements.

In situ observations of the dissolution of an AlN film into liquid Al using a high-temperature microscope

This report describes the implementation of an original liquid-phase epitaxy (LPE) technique using a Ga–Al solution. An N-polar AlN thin film prepared using a sapphire nitridation method was employed as the template for the LPE growth process. The growth behavior depended on attaining a competitive balance of the polarity inversion and the dissolution reaction of the AlN thin film. Therefore, to improve the overall LPE process, it was crucial to understand exactly when and how the AlN thin film dissolved in the solution. This study investigated the dissolution of the N-polar AlN thin film into liquid Al and the resulting AlN growth through in situ observation experiments. The AlN thin film dissolved at a lower temperature than the required temperature for AlN growth. On the basis of these findings, we designed an LPE growth process to obtain a homogeneous AlN layer without the dissolution of the N-polar AlN thin film. Ultimately, a homogeneous AlN layer was successfully formed on the nitrided sapphire substrate using Ga-60mol%Al at 1300 °C for 5 h.

Synthesis of Graphene and fabrication of Aluminium-Grp nanocomposites: A review

Graphene, a two-dimensional crystalline allotrope of carbon, has attracted the interest of a growing number of researchers due to its exceptional mechanical properties. Its higher optical transparency, superior thermal and electrical conductivity, and large specific area are all important characteristics that allow it to be used in a wide range of industries, including aircraft, electronics, newer materials, solar cells, and more. In this article, the various methods of graphene synthesis such as Mechanical Exfoliation, Chemical Vapor Deposition, Chemical Exfoliation, Liquid Phase Exfoliation and Epitaxial growth and the fabrication techniques of aluminium nanocomposites have been discussed. Even though graphene could be synthesized using various techniques, each one has its own set of advantages and disadvantages. This study examines and proposes one such approach to eliminate the problems with the traditional graphene production process. Further, the properties, structures, and Graphene-based aluminium Nanocomposites have been enumerated. Graphene could also be synthesized from agricultural waste to eradicate the problems in the conventional techniques and liquid metallurgy technique shall be used to produce aluminium-graphene nanocomposites.