Ultrafast Growth Research Articles

Ultrafast growth of high-quality large-sized GaSe crystals by liquid metal promoter

Ultrafast growth of high-quality large-sized GaSe crystals by liquid metal promoter

Ultra-Fast Growth of ZnO Nanorods on Cotton Fabrics and Their Self-Cleaning and Physiological Comfort Properties

The main aim of the present study was to investigate the effect of microwave irradiation time on the photocatalytic and physiological comfort characteristics of zinc-oxide-nanorod-coated cotton fabrics. An ultra-fast technique was employed to grow the zinc oxide nanorods on cotton fabrics using a microwave-assisted hydrothermal method. The axial (length) and lateral (diameter) growth of the zinc oxide nanorods was observed to increase with microwave irradiation time. The ZnO nanorods uniformly and entirely covered the cotton fibers. The surface morphology, topography and chemical characteristics of the ZnO nanorods were investigated by scanning electron microscopy (SEM), EDS analysis, X-ray diffraction (XRD), atomic force microscopy (AFM) and inductively coupled plasma-optical emission spectrometry (ICP-OES). The degradation of orange II dye under UV light irradiation was observed to assess photocatalytic self-cleaning and solution discoloration ability. The ZnO-nanorod-coated cotton fabrics exhibited excellent photocatalytic activity, as the stains of orange II dye disappeared predominantly within 4 h and the coated fabrics became almost white after 6 h. Analyses of thermal properties, water vapor permeability (WVP), air permeability and stiffness were also performed to investigate the physiological comfort of the ZnO-nanorod-coated fabrics. The thermal conductivity and thermal absorptivity were observed to increase with an increase in the size and density of the ZnO nanorods. Moreover, non-significant reductions in water vapor permeability and air permeability were observed with application of the ZnO nanorods. The stiffness of the ZnO-nanorod-coated cotton fabric increased due to the complete coverage of fibers by the uniform growth of the ZnO nanorods. The ZnO-nanorod-coated cotton fabrics also showed good washing durability and reusability.

Femtosecond Laser Regulated Ultrafast Growth of Mushroom-Like Architecture for Oil Repellency and Manipulation.

Natural organisms can create various microstructures via a spontaneous growth mode. In contrast, artificial protruding microstructures are constructed by subtractive methods that waste materials and time or by additive methods that require additional materials. Here, we report a facile and straightforward strategy for a laser-induced self-growing mushroom-like microstructure on a flat surface. By simply controlling the localized femtosecond laser heating and ablation on the poly(ethylene terephthalate) tape/heat-shrinkable polystyrene bilayer surface, it is discovered that a mushroom-like architecture can spontaneously and rapidly grow out from the original surface within 0.36 s. The dimension of the re-entrant micropillar array (cap diameter, pillar spacing, and height) can be accurately controlled through the intentional control of laser scanning. Followed by a fluorination and spray coating, the obtained surface can realize the repellency and manipulation of oil droplets. This work provides new opportunities in the fields of microfabrication, microfluidics, microreactor engineering, and wearable antifouling electronics.

Surface chemistry models for GaAs epitaxial growth and hydride cracking using reacting flow simulations

Hydride vapor phase epitaxy (HVPE) is a promising technology that can aid in the cost reduction of III-V materials and devices manufacturing, particularly high-efficiency solar cells for space and terrestrial applications. However, recent demonstrations of ultrafast growth rates (∼500 μm/h) via uncracked hydrides are not well described by present models for the growth. Therefore, it is necessary to understand the kinetics of the growth process and its coupling with transport phenomena, so as to enable fast and uniform epitaxial growth. In this work, we derive a kinetic model using experimental data and integrate it into a computational fluid dynamics simulation of an HVPE growth reactor. We also modify an existing hydride cracking model that we validate against numerical simulations and experimental data. We show that the developed growth model and the improved cracking model are able to reproduce experimental growth measurements of GaAs in an existing HVPE system.

Ultrafast Growth of Large Area Graphene on Si Wafer by a Single Pulse Current.

Graphene has many excellent optical, electrical and mechanical properties due to its unique two-dimensional structure. High-efficiency preparation of large area graphene film is the key to achieve its industrial applications. In this paper, an ultrafast quenching method was firstly carried out to flow a single pulse current through the surface of a Si wafer with a size of 10 mm × 10 mm for growing fully covered graphene film. The wafer surface was firstly coated with a 5-nm-thick carbon layer and then a 25-nm-thick nickel layer by magnetron sputtering. The optimum quenching conditions are a pulse current of 10 A and a pulse width of 2 s. The thus-prepared few-layered graphene film was proved to cover the substrate fully, showing a high conductivity. Our method is simple and highly efficient and does not need any high-power equipment. It is not limited by the size of the heating facility due to its self-heating feature, providing the potential to scale up the size of the substrates easily. Furthermore, this method can be applied to a variety of dielectric substrates, such as glass and quartz.

Industrial pulsed laser deposition for ultra-fast growth of high-temperature superconducting thin films with nanostructured pinning centers

Industrial pulsed laser deposition for ultra-fast growth of high-temperature superconducting thin films with nanostructured pinning centers

Large‐Size Monolayer MoSe2 Single Crystals: Ultrafast Growth of Large‐Area Uniform, Millimeter‐Size MoSe2 Single Crystals on Low‐Cost Soda‐Lime Glass (Adv. Mater. Interfaces 12/2021)

Soda-lime glass presents a smooth “liquid-phase” surface at high temperature (≈900 °C), which is helpful for the fast growth of large-size monolaye MoSe2 single crystals. The unique “beam-bridge” assisted metal-precursor feeding strategy contributes to sufficient, homogeneous release of Mo-based precursor, thereby leading to the ultrafast growth (≈50 μm s−1) of monolayer MoSe2 single crystals of millimeter-size, as presented in article number 2100415 by Xiaolong Zou, Fenghua Chen, Yanfeng Zhang, and co-workers.

Ultrafast Growth of Large‐Area Uniform, Millimeter‐Size MoSe2 Single Crystals on Low‐Cost Soda‐Lime Glass

Abstract2D semiconducting transition metal dichalcogenides (TMDCs) have emerged as essential building blocks for engineering next‐generation integrated electronics. To achieve this, the controllable synthesis of monolayer TMDCs with high crystal quality, low cost, and high yield is crucial, while it remains challenging. Herein, the direct synthesis of large‐area uniform, millimeter‐size monolayer MoSe2 single crystals on a 6‐centimeter‐long soda‐lime glass template, by using a designed “beam‐bridge” assisted metal oxide precursor feeding strategy via chemical vapor deposition (CVD), is reported. Notably, several tenths of millimeter‐scale, triangular‐shaped monolayer MoSe2 single crystals are obtained in one batch within 25 s’ growth, affording so far the fastest growth rate (≈50 µm s−1). This ultrafast growth behavior is proposed to be mediated by the sufficient, homogeneous release of Mo‐based precursor, the catalytic property of sodium atoms on soda‐lime glass substrate, as well as the improved surface kinetics on the molten glass surface. Moreover, the thickness‐controlled growth from monolayer to bilayers is also realized. This work provides brand new insights for the batch production of large single‐crystal TMDCs, which should propel its practical applications in versatile fields.

Ultra-fast growth of cuprate superconducting films: Dual-phase liquid assisted epitaxy and strong flux pinning

Cuprate superconductors are key candidate materials toward high energy-efficient devices. Improving their growth rate and performance under magnetic fields are indispensable for achieving even higher efficiency. For the first time, we demonstrated the ultra-high rate up to 100 nm/s in the growth of dual-phase cuprate superconducting film (EuBa2Cu3O7-BaHfO3). The growth rate achieved is two orders of magnitude higher than that at lab-scale and was also the highest on record to our best knowledge. Epitaxial growth mechanism assisted by the transient liquid phase is proposed, as evidenced by formation of Eu2BaCuO5 and Ba–Cu–O metastable phases under high supersaturation conditions. The high growth rate results in formation of mixed defective landscape, consisting of short nanorods, nanoparticles and naturally formed defects (e.g., staking faults). Due to such unique microstructure, we confirm that weak Jc anisotropy is dominated by random pinning mechanism. Contribution of isotropic and anisotropic Jc to Jctotal also varies with temperatures and magnetic field strength, which is a consequence of evolution of dominant pinning in film. As a result, the in-field current carrying capacity is significantly enhanced (exceeding 430 A/4 mm-width at 4.2 K, 18 T, B//c), being among the top tier of commercialized superconductor materials. This study establishes the correlation between ultra-high growth rate and flux pinning behaviors, which provides feasibility of dramatically improvement of production efficiency with the low price-performance ratio of future high temperature superconductor.

Ultra-fast growth (up to 100 nm s−1) of heavily doped EuBa2Cu3O7 film with highly aligned BaHfO3 nanocolumn structure

Ultra-fast growth (up to 100 nm s−1) of high temperature superconducting film was demonstrated by using an advanced pulsed laser deposition technique. Highly textured EuBa2Cu3O7−δ (EuBCO) film with 8 mol.% of BaHfO3 (BHO) was deposited on the IBAD-based Hastelloy substrates. Structure characterizations reveal formation of high density of BHO nanocolumns with diameter of ∼5 nm in the film, which is well beyond the expectation. Comparison study on different amount of BHO in EBCO film confirmed that nanocolumn formation strongly depends on the dopant level. The epitaxial growth process of BHO is dominated by ultra-fast self-assembly associated with enhanced diffusion of high flux element and liquid phase. Due to the correlated pinning landscape, a pronounced broad peak appears at B//c in the J c(θ) curves at 30 K 5 T, while a strong pinning force of about 900 GN m−3 at 4.2 K, 10 T (B//c) are achieved.

Ultrafast Growth of h-MoO3 Microrods and Its Acetone Sensing Performance

Hexagonal molybdenum trioxide (h-MoO3) was synthesized by microwave-assisted hydrothermal method, allowing an ultrafast growth of unidimensional microrods with well-faceted morphology. The crystalline structure of this metastable phase was confirmed by X-ray diffraction (XRD) and Raman spectroscopy. Scanning electron microscopy (SEM) showed that hexagonal microrods can be obtained in one minute with well-defined exposed facets and the fine control of morphology. Sensing tests of the acetone biomarker revealed that the h-MoO3 microrods exhibit, at low ppm level, good sensor signal, fast response/recovery times, selectivity to different interferent gases, and a lower detection limit of 400 ppb.

Dandelion‐Like Microswarms: Ultrafast Growth and Locomotion of Dandelion‐Like Microswarms with Tubular Micromotors (Small 38/2020)

In article number 2003678, Xiaolong Lu, Wenjuan Liu, and co‐workers report dandelion‐like microswarms assembled from tubular micromotors, which are capable of performing ultrafast growth and locomotion. With the ultrasound oscillation of self‐generated bubbles, such microswarms could move at an average speed of up to 50 mm s−1 and exhibit an instant and wireless response to ultrasound stimuli.

Ultrafast Growth and Locomotion of Dandelion-Like Microswarms with Tubular Micromotors.

Dynamic assembly and cooperation represent future frontiers for next generations of advanced micro/nano robots, but the required local interaction and communication cannot be directly translated from macroscale robots through the minimization because of tremendous technological challenges. Here, an ultrafast growth and locomotion methodology is presented for dandelion-like microswarms assembled from catalytic tubular micromotors. With ultrasound oscillation of self-generated bubbles, such microswarms could overcome the tremendous and chaotic drag force from extensive and disordered bubble generation in single units. Tubular MnO2 micromotor individuals headed by self-generated oxygen bubbles are ultrasonically driven to swim rapidly in surfactant-free H2 O2 solutions. A large bubble core fused from multiple microbubbles is excited to oscillate and the resultant local intensified acoustic field attracts the individual micromotors to school around it, leading to a simultaneous growth of dandelion-like microswarms. The bubble-carried micromotor groups driven by ultrasound could swarm at a zigzag pattern with an average speed of up to 50 mm s-1 , which is validated in low H2 O2 concentrations. Additionally, such superfast locomotion could be ultrasonically modulated on demand. The ultrafast microswarm growth and locomotion strategy offers a new paradigm for constructing distinct dynamic assemblies and rapid transmission of artificial microrobots, paving the way to a myriad of promising applications.

Growth of ultrafast, super dense ZnO nanorods using microwaves for piezoelectric MEMS applications

We report a successful integration of a crystalline ZnO thin film with nanorod morphology into a piezoelectric MEMS device. We grow ZnO nanorods using a hydrothermal process in a domestic microwave that ensures ultrafast growth while preserving the high crystal quality of the nanorods. The integration of ZnO as the active layer into a piezo MEMS device requires high crystallinity for better piezoelectric properties and growth on a metallic layer for the bottom electrode functionality. We, therefore, first identify the optimal substrate for ZnO growth and then optimize the seed layer for best crystal orientation as ascertained by HRXRD ω-scan (2.63°) and a super dense morphology to ensure no pinholes or electrode shorting paths. The realization of a membrane MEMS structure incorporating ZnO as the active piezo layer involves another process innovation where we do not pattern the top electrode, as is typical in such piezo MEMS devices, but rather, pattern the bottom electrode using a lift-off process and leave the top electrode as a conformal metallic layer. We describe the entire process of growth and device fabrication in this paper with special attention to the compatibility of the process with MEMS fabrication.

Ultra-fast growth of copper oxide (II) thin films using hydrothermal method

In this paper we present the extremely fast growth of polycrystalline CuO thin films using a modified hydrothermal method. The process takes place in an open system, at a low temperature (below 100 °C) and in a very short time (in the range of 6 min–38 s). The growth technology does not require the use of toxic precursors or sophisticated equipment. The reaction solution used consists only of deionized water and copper (II) acetate. Sodium hydroxide is used as a pH regulator. The method developed makes it possible to control the thickness of the films over a wide range. The impact of individual parameters: pH, heating power, process duration and Cu(II) concentration, on layer thickness is discussed.The obtained films consist of monoclinic CuO, which was proved by XRD and is consistent with EDX measurements. The structure of the layers is polycrystalline with nanocrystallites of 7–12 nm in size, which was extracted from SEM images and XRD data. The optical energy band gap estimated from transmittance measurements is in the range of 1.82–1.87 eV.The innovative method described is very promising for many applications, especially photovoltaic ones. Its simplicity, low cost, and high efficiency make this approach very interesting and competitive to commonly used technologies.

Ultrafast nucleation and growth of high-quality monolayer MoSe2 crystals via vapor-liquid-solid mechanism

The controlled production of two-dimensional atomically thin transition metal dichalcogenides (TMDs) is fundamentally important for their device applications. However, the synthesis of large-area and high-quality TMD monolayers remains a challenge due to the lack of sufficient understanding of growth mechanisms, especially for the chemical vapor deposition (CVD). Here we report molten-salt assisted CVD growth of highly crystalline MoSe2 monolayers via a novel vapor-liquid-solid (VLS) mechanism. Our results show that the growth rate of the VLS-grown monolayer MoSe2 is about 40 times faster than that of MoSe2 grown via the vapor-solid (VS) mechanism, which makes the fabrication of 100 μm domains for ∼2 min and a uniform monolayer film within 5 min. The ultrafast growth of monolayer MoSe2 crystals benefits from the synergic effect of one-dimensional VLS growth and two-dimensional VS edge expansion. Moreover, these MoSe2 monolayers exhibit high crystal quality and enhanced photoluminescence due to efficient Se-vacancy repairing by the doping of halogen atoms. These findings provide a new understanding of MoSe2 growth and open up an opportunity for the rapid synthesis of high-quality TMD monolayers and heterostructures.

Ultrafast Growth of a Cu(OH)2–CuO Nanoneedle Array on Cu Foil for Methanol Oxidation Electrocatalysis

A swift potentiostatic anodization method for growing 5-7 µm tall nanoneedle array of Cu(OH)2-CuO on Cu foil within 100 s has been developed. This catalytic electrode when screened for methanol oxidation electrocatalysis in 1 M KOH with 0.5 M methanol, delivered a current density as high as 70 ± 10 mA cm-2 at 0.65 V vs. Hg/HgO which is superior to the performance of many related catalysts reported earlier. Observed activity enhancement is attributed to the formation of both Cu(OH)2-CuO nanoneedle array of high active surface area over the metallic Cu foil. In addition, Cu(OH)2-CuO/Cu electrode had also exhibited excellent stability upon prolonged potentiostatic electrocatalytic oxidation of methanol while retaining the charge transfer characteristics. Growth of such highly ordered assembly of Cu(OH)2-CuO nanoneedles has never been achieved before within a minute. When compared to its OER activity, the addition of 0.5 M methanol has lowered the overpotential at 10 mA cm-2 by 334 mV which is significant. This encourages the use of methanol as a sacrificial anolyte for energy-saving production of H2 from water electrolysis.

Ultrafast growth kinetics of titanium dendrites investigated by electrostatic levitation experiments and molecular dynamics simulations

An ultrafast crystal growth velocity of 122 m/s for β–Ti dendrites was achieved at a liquid undercooling of 352 K (0.18Tm) by electrostatic levitation technique. In contrast, most refractory metals attained slower dendrite growth velocities but displayed similar power laws with liquid undercooling. A combined analysis by current dendrite growth theory with molecular dynamics simulation indicates that liquid thermal diffusion rather than solid-liquid (S/L) interface kinetics is still the dominant factor to control dendrite growth. Besides, the atomic-scale thickness of the S/L interface layer may determine the dendrite growth velocity difference for various refractory metals.

Ultrafast transient liquid assisted growth of high current density superconducting films

The achievement of high growth rates in YBa2Cu3O7 epitaxial high-temperature superconducting films has become strategic to enable high-throughput manufacturing of long length coated conductors for energy and large magnet applications. We report on a transient liquid assisted growth process capable of achieving ultrafast growth rates (100 nm s−1) and high critical current densities (5 MA cm−2 at 77 K). This is based on the kinetic preference of Ba-Cu-O to form transient liquids prior to crystalline thermodynamic equilibrium phases, and as such is a non-equilibrium approach. The transient liquid-assisted growth process is combined with chemical solution deposition, proposing a scalable method for superconducting tapes manufacturing. Additionally, using colloidal solutions, the growth process is extended towards fabrication of nanocomposite films for enhanced superconducting properties at high magnetic fields. Fast acquisition in situ synchrotron X-ray diffraction and high resolution scanning transmission electron microscopy (STEM) become crucial measurements in disentangling key aspects of the growth process.

Ultrafast growth of large single crystals of monolayer WS2 and WSe2.

Monolayer transition metal dichalcogenides (TMDs) have attracted considerable attention as atomically thin semiconductors for the ultimate transistor scaling. For practical applications in integrated electronics, large monolayer single crystals are essential for ensuring consistent electronic properties and high device yield. The TMDs available today are generally obtained by mechanical exfoliation or chemical vapor deposition (CVD) growth, but are often of mixed layer thickness, limited single crystal domain size or have very slow growth rate. Scalable and rapid growth of large single crystals of monolayer TMDs requires maximization of lateral growth rate while completely suppressing the vertical growth, which represents a fundamental synthetic challenge and has motivated considerable efforts. Herein we report a modified CVD approach with controllable reverse flow for rapid growth of large domain single crystals of monolayer TMDs. With the use of reverse flow to precisely control the chemical vapor supply in the thermal CVD process, we can effectively prevent undesired nucleation before reaching optimum growth temperature and enable rapid nucleation and growth of monolayer TMD single crystals at a high temperature that is difficult to attain with use of a typical thermal CVD process. We show that monolayer single crystals of 450 μm lateral size can be prepared in 10 s, with the highest lateral growth rate up to 45 μm/s. Electronic characterization shows that the resulting monolayer WSe2 material exhibits excellent electronic properties with carrier mobility up to 90 cm2 V−1 s−1, comparable to that of the best exfoliated monolayers. Our study provides a robust pathway for rapid growth of high-quality TMD single crystals.