Room temperature liquid metals (LM) such as gallium (Ga) own the potential to react with specific materials which would incubate new application categories. Here, diverse self‐organized ring patterns due to nonequilibrium reaction‐diffusion and spreading‐limitation of Ga‐based LM clusters on gold (Au) film are reported, among which diffusion is the controlling step and the self‐limiting oxide layer plays the role of kinetic barrier. Such phenomena, classically known as the Liesegang rings, mainly occur in electrolyte media. Unlike existing systems, the present periodic crystallization mechanism enables highly symmetric spatiotemporal periodic Liesegang rings on a smaller scale under ambient conditions. Typically, the Ga‐Au and eutectic gallium‐indium alloy (EGaIn)‐Au reaction‐diffusion‐spreading systems are constructed, obtaining the revert type and hybrid type concentric Liesegang patterns, respectively. The competitive patterning behavior of the intermediate phase products AuGa2 and AuIn2 in hybrid Liesegang patterns is further analyzed by altering the initial Ga/In mass ratio, first‐principles calculations, and molecular dynamic simulations. When the mass ratio of In in GaIn alloy exceeds 15%, it will preferentially react with Au. The discovery of LM Liesegang phenomenon is expected to be a flashpoint for self‐organized reaction‐diffusion systems and offers promising rules for diverse areas such as materials synthesis and the jewelry design industry.
As a promising third-generation semiconductor, gallium oxide (Ga2O3) is currently facing bottleneck for its p-type doping. The doping process of conventional semiconductors usually introduces trace impurities, which is a major technical problem in the electronics industry. In this article, we conceived that the process complexity could be significantly alleviated, and a high degree of control over the results could be attained using the selective enrichment of liquid metal interfaces and harvesting the doped metal oxide semiconductor layers. An appropriate mechanism is thus proposed to prepare the doped semiconducting based on multicomponent liquid metal alloys. Liquid metal alloys with the certain Cu weight ratios in bulk are utilized to harvest Cu-doped Ga2O3 films, which result in p-type conductivity. Then, field-effect transistors were integrated using the printed p and n-type Ga2O3 films and demonstrated to own excellent electrical properties and stability. Au electrodes fabricated on the printed Ga2O3 and Cu-doped Ga2O3 layers showed good Ohmic behavior. Furthermore, high-power diodes are realized using printed p and n-type Ga2O3 homojunction through combining van der Waals stacking with transfer printing. The fabricated Ga2O3 homojunction diode exhibited good efficiency at room temperature, involving a rectification ratio of 103 and forward current density at 10 V (J@10 V) of 1.3 mA. This opens the opportunity for the cost-effective creation of semiconductor films with controlled metal dopants. The process disclosed here suggests important strategies for further synthesis and manufacturing routes in electronics industries.
Outstanding wide‐bandgap semiconductor material such as gallium nitride (GaN) has been extensively utilized in power electronics, radiofrequency amplifiers, and harsh environment devices. Due to its quantum confinement effect in enabling desired deep‐ultraviolet emission, excitonic impact, and electronic transport features, 2D or ultrathin quasi‐2D GaN semiconductors have been one of the most remarkable candidates for future growth of microelectronic devices. Here, for the first time, the authors report a large area, wide bandgap, and room‐temperature quasi‐2D GaN synthesis and printing strategy through introducing the plasma medicated liquid metal gallium surface‐confined nitridation reaction mechanism. The developed direct fabrication and compositional process is consistent with various electronics manufacturing approaches and thus opens an easy going way for cost‐effective growth of the third‐generation semiconductor. In particular, the fully printed field‐effect transistors relying on the GaN thus made show p‐type switching with an on/off ratio greater than 105, maximum field‐effect hole mobility of 53 cm2 V−1 s−1, and a small sub‐threshold swing. As demonstrated, the present method allows to produce at room temperature the GaN with thickness spanning from 1 nanometer to nanometers. This basic method can be further extended, generalized, and utilized for making various electronic and photoelectronic devices in the coming time.
In order to optimize laser ablation performance of a micro-thruster with 1U dimensions, which employs a micro semiconductor laser, the impacts of pulse width and glycidyl azide polymer (GAP) thickness on thrust performance was researched. The results showed that with a GAP thickness of 200 μm, the single-pulse impulse (I) increased gradually with the increase in the laser pulse width from 50 to 800 μs, while the specific impulse (Isp), impulse coupling coefficient (Cm), and ablation efficiency (η) all reached optimal values with a 200 μs pulse width. It’s worth noting that the optimal pulse width is exactly the ignition delay time. Both Cm and η peaked with the pulse width of 200 μs, reaching 242.22 μN/W and 35.4%, respectively. With the increase in the GAP thickness, the I and the Cm increased gradually. The GAP of different thickness corresponded to different optimal laser pulse width. Under a certain laser pulse width, the optimal GAP thickness should be the most vertical thickness of the ablation pit, and the various propulsion performance parameters at this time were also optimal. With the current laser parameters, the optimal GAP thickness was approximately 150 μm, the Isp was approximately 322.22 s, and the η was approximately 34.94%.
Wide band gap semiconductor Ga 2 O 3 is a high potential material for fabricating next-generation power electronics. However, the low conductivity and carrier mobility of Ga 2 O 3 have been seen as large barriers for its practical application. For many years, the efficient and low cost doping process to enhance the conductivity of Ga 2 O 3 has always been a technological challenge. Here, we report a one-step synthesis strategy to prepare Ga 2 O 3 doped with In 2 O 3 and SnO 2 (GaInSnO) multilayers from the liquid Ga−In−Sn alloy surface. Large area, controllable thickness, and high conductivity GaInSnO multilayers can be facilely obtained by using van der Waals exfoliation at a low temperature of 200 °C. The printed GaInSnO multilayers are transparent and display band gaps above 4.5 eV. The field effect transistors (FETs) based on the printed GaInSnO multilayers show n-type switching with on/off ratio all exceeding 10 5 , a maximum field-effect mobility (μ eff ) of 65.40 cm 2 V −1 s −1 , and a minimum subthreshold swing (SS) of 91.11 mV dec −1 at room temperature. With rising Ga concentration in GaInSnO multilayers, the μ eff of a fabricated FET decreases, while the SS increases. The present method can be further extended to produce various doped Ga 2 O 3 films and utilized to fabricate electronic and optoelectronic devices based on modified Ga 2 O 3 in the coming time.
In the field of laser ablation micro-propulsion, the property of double-layer tape has significant impact on the propulsion performance. In this paper, low temperature plasma was used to treat the surface of polyethylene terephthalate (PET) to improve its adhesion with energetic polymer. The PET surface pre- and post-plasma treatment was characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), and the enhancement mechanism of the interface adhesion was discussed. In addition, the ablation performance of the double-layer tape after the plasma treatment was studied. The results showed that the plasma etching effect increased the root mean square roughness of the PET surface from 1.74 nm to 19.10 nm. In addition, after the plasma treatment, the number of C–OH/COOH bonds and O=C–O bonds increased, which also greatly improved the adhesion between the PET and energetic polymers. In the optimization of the ablation performance, the optimal laser pulse width was about 200 μs. The optimal values of the specific impulse (Isp), impulse coupling coefficient (Cm), and ablation efficiency (η) were 390.65 s, 250.82 μN/W, and 48.01%, respectively. The optimization of the adhesion of the double-layer tape and the ablation performance lay the foundation for the engineering application of laser ablation micro-thrusters.
In the process of pulsed laser drilling, the material properties in the heat-affected zone will change due to the thermal effect of the laser. To study the effect of this change on the material tensile strength, two lasers were used to punch the standard 6061 aluminum alloy specimens with millisecond and nanosecond pulse widths, and then the tensile test was carried out on the standard specimens with a tensile tester to measure the ultimate tensile strength of the aluminum alloy. Finally, the micro-morphology of the fracture was photographed by scanning electron microscopy (SEM), and the fracture mechanism of the aluminum alloy was analyzed. The experimental results show that the relationship between the rate of intensity change induced by the millisecond laser and the ablation area ratio is more linear than that of the nanosecond laser; with the increase of ablation area ratio, the rate of intensity changes induced by the nanosecond and millisecond lasers becomes increasingly closer; three types of fractures are produced with two types of laser ablation; the plasticity of the material rapidly decreases with laser drilling, and the main reason for decrease in plasticity was stress concentration. This study provides an important point of reference for how to ensure the strength and plasticity of the components after laser drilling.
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