Metallic indium segregation control of InN thin films grown on Si(1?0?0) by plasma-enhanced atomic layer deposition

摘要： InN thin films were grown on Si(1 0 0) substrates by plasma-enhanced atomic layer deposition (PEALD). In this work, It is found that the island growth of InN on Si(1 0 0) easily happens at the initial PEALD period. The PEALD parameters have been systematically investigated to optimize the size, density, coalescence and distribution uniformity of InN grains with good crystallinity and no metallic indium clustering. Especially, indium segregation of PEALD-grown InN has a direct dependence on the deposition temperature (T), the supply of tri-methylindium (TMIn) precursor and nitrogen plasma (NP) source. Based on our proposed PEALD mechanism of InN, a polycrystalline hexagonal InN thin film in the thickness of 24.2 nm has been well deposited at the growth per cycle (GPC) of 0.8 ?/cycle. And it shows a (0 0 2) preferential orientation and no any structural phase of metallic indium segregation. As a result, it may provide a useful guide for deeply understanding the PEALD growth mechanism of InN and In-rich nitrides, which further extends the promising applications in high-efficiency photovoltaics and high speed electronic devices.

Highly tin doped GaAs at low growth temperatures using tetraethyl tin by metal organic vapor phase epitaxy

摘要： GaAs layers with a high tin (Sn) doping concentration and a smooth surface morphology were successfully grown at temperatures as low as 425 °C using tetraethyl tin (TESn) by metal organic vapor phase epitaxy (MOVPE). The samples grown at 650 °C showed Sn-rich droplets even with a low TESn molar flow rate of 0.06 μmol/min, indicating that Sn atoms were not incorporated into the GaAs film but segregated and accumulated on the film surface. Droplet formation was suppressed at a low growth temperature of 425 °C. This suggests that the segregation process is kinetically-limited, with the segregation mechanism is slow compared to the growth rate at low growth temperatures. Uncorrected Hall effect measurements found an electron concentration of ～1 × 1019 cm?3, which is close to the maximum reported doping-limit obtainable in GaAs:Sn grown by MOVPE, while avoiding droplet formation and maintaining a smooth surface morphology. The electron mobility is dominated by the ionized impurity scattering. The sample possesses a generally flat Sn profile extending from the substrate to the film surface. Secondary ion mass spectroscopy indicates that the Sn is electrically active but compensated by carbon acceptors to yield the measured carrier concentration.

Microstructure and Performance of Laser-Welded GH3128/Mo Dissimilar Joints

摘要： Laser beam offset welding of GH3128 and molybdenum (Mo) dissimilar joints was studied with an emphasis on the role of laser beam offset (LBO). It was found that the change of LBO significantly affected the properties of GH3128/Mo dissimilar joints. When the LBO increased from 2 0.1 mm (i.e., laser spot was centered on Mo surface) to + 0.3 mm (i.e., laser spot was centered on GH3128 surface) at the step size of 0.1 mm, the amount of melted Mo gradually declined; the welding mode gradually changed from fusion welding to welding–brazing; macro-segregation of Mo-rich phases in fusion zone (FZ) gradually disappeared; the average microhardness of FZ significantly decreased, and therefore, microhardness distribution in FZ became more uniformly; the quantity of grain boundary liquation observed in heat-affected zone (HAZ) of GH3128 side gradually decreased; and recrystallization of grains in the HAZ of Mo was gradually suppressed. Joints with the optimal LBO of + 0.2 mm reached the maximum tensile strength of about 560 MPa. When using a small LBO, i.e., LBOs were + 0.1, 0, 2 0.1 mm, the HAZ of Mo was greatly softened and embrittled. When adopting a large LBO, i.e., LBO was + 0.3 mm, the melt near Mo-FZ interface might fail to moisten Mo surface and spread on Mo surface, thus resulting in the reduction in tensile strength.

Ba-induced phase segregation and band gap reduction in mixed-halide inorganic perovskite solar cells

摘要： All-inorganic metal halide perovskites are showing promising development towards efficient long-term stable materials and solar cells. Element doping, especially on the lead site, has been proved to be a useful strategy to obtain the desired film quality and material phase for high efficient and stable inorganic perovskite solar cells. Here we demonstrate a function by adding barium in CsPbI2Br. We find that barium is not incorporated into the perovskite lattice but induces phase segregation, resulting in a change in the iodide/bromide ratio compared with the precursor stoichiometry and consequently a reduction in the band gap energy of the perovskite phase. The device with 20 mol% barium shows a high power conversion efficiency of 14.0% and a great suppression of non-radiative recombination within the inorganic perovskite, yielding a high open-circuit voltage of 1.33 V and an external quantum efficiency of electroluminescence of 10?4.

Progress in Research and Application of Micro-Laser-Induced Breakdown Spectroscopy

摘要： The technique of micro-laser-induced breakdown spectroscopy (μLIBS) usually refers to analyzing the surface of the sample using a compact focused laser beam in the optical microscope range. Compared to conventional laser-induced breakdown spectroscopy (LIBS), it can provide more abundant form, structure, and content information on a smaller, less sample condition. Hence, the application field is very wide. In this paper, the basic status of μLIBS in the selection of laser source and the structure of optical path system is introduced, and its application in metal, semiconductor, animal and plant fields is reviewed. The existing problems and potential development direction is pointed out.

Corrigendum: Impact of Polymer Backbone Fluorination on the Charge Generation/Recombination Patterns and Vertical Phase Segregation in Bulk Heterojunction Organic Solar Cells

Segregation and activation of Sb implanted in Si by UV nanosecond-laser-anneal-induced non-equilibrium solidification

摘要： In advanced logic devices, access resistance to transistors is dominated by metal–semiconductor contact resistivity. Recent studies report values below 1 × 10?9 ohm cm2, realizing metastable incorporation of dopants into epitaxially grown semiconductor materials. In this study, we have investigated segregation and activation of antimony (Sb) implanted in silicon (Si) epilayers by using UV nanosecond pulsed laser annealing (LA). The Sb-implanted Si epilayers were partially or fully molten by LA, followed by the analysis of atomic and electrically active dopant concentrations as well as the observation of surface morphology evolution. To discuss the impact of the solute trapping phenomenon on substitutional incorporation of the Sb atoms, we also simulated the evolution of solidification front velocity in the LA-induced non-equilibrium solidification. It is noteworthy that the active level of the Sb atoms largely surpasses their reported equilibrium solubility limit (～2.6 × 1020 at./cm3 compared to ～6.8 × 1019 at./cm3) when the non-equilibrium solidification approaches a near-complete solute trapping regime.

[IEEE 2018 22nd International Conference on Ion Implantation Technology (IIT) - Würzburg, Germany (2018.9.16-2018.9.21)] 2018 22nd International Conference on Ion Implantation Technology (IIT) - Super Activation of Highly Surface Segregated Dopants in High Ge Content SiGe Obtained by Melt UV Laser Annealing

摘要： Activation of surface segregated dopants above the solid solubility limit in a high Ge content SiGe substrate has been demonstrated by nanosecond melt UV laser anneal. This exceeds the activation possible with conventional solid-phase annealing technics. The segregation effects, strongly amplified by the phase changing of the partial melting of the sample during the annealing, play a key role explaining dopant profile redistribution in Si-Ge alloys and activation.

Trap States, Electric Fields, and Phase Segregation in Mixeda??Halide Perovskite Photovoltaic Devices

摘要： Mixed-halide perovskites are essential for use in all-perovskite or perovskite–silicon tandem solar cells due to their tunable bandgap. However, trap states and halide segregation currently present the two main challenges for efficient mixed-halide perovskite technologies. Here photoluminescence techniques are used to study trap states and halide segregation in full mixed-halide perovskite photovoltaic devices. This work identifies three distinct defect species in the perovskite material: a charged, mobile defect that traps charge-carriers in the perovskite, a charge-neutral defect that induces halide segregation, and a charged, mobile defect that screens the perovskite from external electric fields. These three defects are proposed to be MA+ interstitials, crystal distortions, and halide vacancies and/or interstitials, respectively. Finally, external quantum efficiency measurements show that photoexcited charge-carriers can be extracted from the iodide-rich low-bandgap regions of the phase-segregated perovskite formed under illumination, suggesting the existence of charge-carrier percolation pathways through grain boundaries where phase-segregation may occur.

Structural Origins of Light-Induced Phase Segregation in Organic-Inorganic Halide Perovskite Photovoltaic Materials

摘要： Light-induced phase segregation in mixed-halide perovskite photovoltaic materials results in the formation of low-band-gap regions that limit the voltage of devices. This work explores the dependence of this light instability on crystal structure and maps it across the cubic-tetragonal solvus in the (CsyFA1?y)Pb(BrxI1?x)3 phase diagram.