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Development of ultra-thin doped poly-Si via LPCVD and ex-situ tube diffusion for passivated contact solar cell applications
摘要： Rear side application of polycrystalline silicon (poly-Si) passivated contacts has demonstrated very high efficiencies for single-junction monocrystalline silicon (mono-Si) solar cells. To further improve the device performance, one possible approach is to apply the passivated contact concept to the front side of the solar cell as well. The front side application requires the use of ultra-thin poly-Si layer in order to suppress parasitic absorption. Suitable ex-situ diffusion process should be developed accordingly without damaging the passivation provided by the very thin interface oxide (iOx). In this work, we prepared symmetric lifetime samples of ultra-thin poly-Si (<30 nm) via low pressure chemical vapour deposition (LPCVD) method. Then we studied and optimised the ex-situ POCl3/BBr3 diffusion doping processes. An excellent passivation quality was demonstrated with a high implied open-circuit voltage (iVoc) of up to 730 mV (on symmetric n+ poly-Si lifetime samples) and 700 mV (on symmetric p+ poly-Si lifetime samples). For possible contact formation, we capped the poly-Si with sputter-deposited ZnO:Al, which shows good opto-electrical properties and firing stability at 650 °C.
关键词： Diffusion,ZnO:Al,Ex-situ doping,Ultra-thin poly-Si,Passivated contact
更新于2025-09-23 15:19:57
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Mechanisms of GaN quantum dot formation during nitridation of Ga droplets
摘要： We have examined the formation mechanisms of GaN quantum dots (QDs) via annealing of Ga droplets in a nitrogen ?ux. We consider the temperature- and substrate-dependence of the size distributions of droplets and QDs, as well as the relative roles of Ga/N diffusivity and GaN nucleation rates on QD formation. We report on two competing mechanisms mediated by Ga surface diffusion, namely, QD formation at or away from pre-existing Ga droplets. We discuss the relative roles of nucleation- and coarsening-dominant growth, as well as zincblende vs wurtzite polytype selection, on various substrates. These insights provide an opportunity for tailoring QD size distributions and polytype selection for a wide range of III-N semiconductor QDs.
关键词： polytype selection,surface diffusion,GaN quantum dots,nitridation,Ga droplets
更新于2025-09-23 15:19:57
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Dopant Activation of In Situ Phosphorusa??Doped Silicon Using Multia??Pulse Nanosecond Laser Annealing
摘要： Nanosecond laser annealing was performed on ISPD silicon in single- and multi-pulse modes. the active phosphorus concentration was increased with the laser power density and number of laser pulses and more phosphorus was activated with nanosecond lasers than with millisecond lasers. Moreover, almost all the incorporated phosphorus atoms were activated by the nanosecond laser without major strain loss when ISPD silicon melt
关键词： phosphorus-doped silicon,nanosecond laser annealing,diffusion,dopant activation,strain
更新于2025-09-23 15:19:57
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Laser induced breakdown spectroscopy application to reaction-diffusion studies in nuclear materials
摘要： We explore the possible use of Laser Induced Breakdown Spectroscopy (LIBS) to analyze active materials in hot cells or even inside nuclear reactors where high radiation levels prevent the use of conventional techniques. LIBS measurements of the reaction-diffusion process in alloys used in the nuclear industry were compared with standard techniques such as micrography, scanning electron microscopy, and energy dispersive X-rays spectroscopy. The LIBS capability to qualitatively detect the above process was established. Also, the average speed of the reaction-diffusion process was measured through a temperature-dependent effective parameter K.
关键词： Zirconium Alloys,LIBS,Nuclear Materials,Diffusion
更新于2025-09-23 15:19:57
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Highly accurate space-time coupled least-squares finite element framework in studying wave propagation
摘要： Simulation of stress wave propagation through solid medium is commonly carried using Galerkin weak-form cast over decoupled space and time domains. In this paper, accuracy of this commonly utilized framework is compared to that of the variationally-consistent least-squares form of the wave equation cast over space-time domain. The two formulations are tested for numerical dispersion and numerical diffusion, through two test cases. The first case studies the dispersion in harmonic shear wave propagation through a soil column over a wide range of forcing frequencies. The second test case investigates numerical diffusion in an axial wave propagation generated by constant force; which is removed after a certain time to allow free vibration to take place. Low numerical dispersion and numerical diffusion as well as high rates of convergence are the main advantages of the coupled least-squares (CLS) computational framework; when compared to the decoupled Galerkin (DG) framework. Based on studies presented here, CLS has low dispersion; yielding errors with one to two orders of magnitude less than that of DG. Also, the numerical diffusion present in DG framework causes a %40 error in DG’s prediction of the stress-wave intensity. Furthermore, accumulative error during evolution is virtually nonexistent for CLS, whereas, the error steadily increases as the solution evolves in DG framework. It is also demonstrated that CLS feature of temporal meshing allows for faster computations.
关键词： Shear wave propagation,Variational-consistency,Higher continuity hierarchical finite elements,Numerical diffusion,Least squares,Impact wave propagation,Space-time coupled,Numerical dispersion,Wave equation
更新于2025-09-23 15:19:57
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Achieving the hypsochromic electroluminescence of ultraviolet OLED by tuning excitons relaxation
摘要： Organic light emitting diode (OLED) has huge impact on display-related fields. Due to potential applications in information storage and backlight sources for full color display, ultraviolet OLED has attracted widespread attention. In this paper, we present an inverted UV OLED device with electroluminescence (EL) peak of 369 nm. The device employs zinc oxide (ZnO) as electron injection layer (EIL), revealing a relationship between the exciton diffusion and emitting peaks. The organic-inorganic interface in the device reduces the diffusion length of excitons and that can lead to a hampered relaxation of higher energy states, resulting in a hypsochromic shift of the EL spectrum. The existence of buffer layer will affect the relaxation process. Additionally, the emission peak of the UV-OLED can be adjusted from 369 nm to 384 nm by varying kinds and thickness of the organic functional layers.
关键词： Hypsochromic shift,OLED,Exciton relaxation,Ultraviolet emission,Wavelength regulation,Diffusion model
更新于2025-09-23 15:19:57
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Recovery kinetics in high temperature annealed AlN heteroepitaxial films
摘要： Based on the experimental dislocation annihilation rates, vacancy core diffusion-controlled dislocation climb was found as a dominant recovery mechanism in high temperature annealing of AlN heteroepitaxial films. Dislocation annihilation mechanisms via dislocation glide (with or without kinks) and vacancy bulk diffusion were found to be less significant. Cross-slip was also ruled out as a possible mechanism as a majority of dislocations in heteroepitaxial AlN films are threading edge dislocations. While dislocation climb through both vacancy bulk and core diffusion could offer a plausible explanation of the recovery process, the activation energy for the vacancy core diffusion-controlled dislocation climb was relatively low (4.3 ± 0.1 eV), as estimated from an Arrhenius plot. The validity of the vacancy core diffusion mechanism was also supported by a large vacancy mean free path (～240 nm), which was comparable to the sample thickness and thus the average dislocation length. Finally, the experimentally observed dislocation density reduction as a function of the annealing temperature and time was in good agreement with the vacancy core diffusion mechanism.
关键词： dislocation annihilation,high temperature annealing,AlN heteroepitaxial films,recovery kinetics,vacancy core diffusion
更新于2025-09-23 15:19:57
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Dynamic Diffusion of Disperse Dye in a Polyethylene Terephthalate Film from an Infrared Spectroscopic Perspective
摘要： The di?usion behavior of a typical disperse dye, disperse red 9 (DR 9), in the polyethylene terephthalate (PET) ?lm at di?erent temperatures was investigated by attenuated total re?ection?Fourier transform infrared spectroscopy and 2D correlation spectroscopy (2Dcos) analyses. According to the Fickian di?usion model, the calculated di?usion coe?cients of DR 9 in the PET ?lm at di?erent temperatures were observed to increase with temperature, which might be attributed to the increased free volume and thermal motion in the PET matrix and the rapid movement of DR 9 molecules at higher temperatures. In-detail analysis of the di?usion spectra discerned various kinds of molecular interactions, including intramolecular hydrogen bonding interactions of DR 9 and dipole?dipole and π?π interactions between DR 9 and PET. Among these, the dipole?dipole interactions between CO groups of DR 9 and PET occurred ?rst and played a vital role during the di?usion process of DR 9, as deduced from the sequence order of group motions in 2Dcos analysis.
关键词： ATR-FTIR spectroscopy,2D correlation spectroscopy,polyethylene terephthalate,diffusion,disperse dye
更新于2025-09-23 15:19:57
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Crystallization processes of quartz in a granitic magma: Cathodoluminescence zonation pattern controlled by temperature and titanium diffusivity
摘要： Quartz from a granitic pluton is found to have formed through sequential growth events under different mechanisms and crystallization temperatures, which can provide new insights into magmatic processes of granitic magmas that were eventually consolidified into plutons. The events were identified using 1) the description of crystal shape and occurrence, 2) the study of the internal structure with cathodoluminescence (CL), and 3) derivation of the crystallization temperatures based on TitaniQ thermometry. The magmatic quartz crystals from the Toki granite, central Japan, are characterized as having the following internal structures: oscillatory zonation, no-oscillatory zonation with luminescence gradation (gradational zonation), and heterogeneous CL. The quartz crystals with oscillatory zonation were formed in the temperature range of about 800 °C to below 700 °C, which is referred to as oscillatory zoning temperature (OZT) conditions. The CL zonation pattern was controlled by the temperature conditions and titanium diffusivity in the melt (magma). The crystallization process of quartz within the Toki granite reveals the cooling processes of the granitic pluton; the lithofacies with a high frequency of oscillatory-zoned quartz underwent slower cooling under the OZT conditions than those in other lithofacies.
关键词： diffusion-controlled growth,Toki granitic pluton,Cathodoluminescence characterization,Oscillatory zonation,Quartz,TitaniQ thermometer
更新于2025-09-23 15:19:57
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Tuning the Emission Colors of Self-Assembled Quantum Dot Monolayers via One-Step Heat Treatment for Display Applications
摘要： Homogeneously self-assembled colloidal semiconductor quantum dot monolayers (QD-SAMs) over large areas are promising materials for thin film optoelectronic device applications, especially for display. Although tuning of emission colors from QDs is generally achieved during wet chemical synthesis and before monolayer formation, we propose in this study a simple and effective method to adjust emission colors after the formation of QD-SAMs by a simple one-step heat treatment. CdSe-based core/shell or core/double shell structured QDs (CdSe/ZnS, CdSe/CdZnS, and CdSe/CdS/ZnS) covered with an optimal set of hydrophobic ligands can form homogeneous and stable QD-SAMs at the air-water interface. The QD-SAMs are subsequently transferred onto hydrophobized glass substrates by the Langmuir-Schaefer (LS) method and thermally treated in air. We found a blueshift of more than 35 nm for the emission wavelength (red to green) by a thermal treatment at 280 °C for 150 min with CdSe/ZnS QD-SAMs. The color can be adjusted by changing the heating temperature and the treatment time. The wavelength shift is in the order of CdSe/ZnS(4L) > CdSe/ZnS(6L) = (CdSe/CdZnS) > (CdSe/CdS/ZnS). The energy dispersive X-ray (EDX) microanalysis of a single QD reveals that the blueshift is mainly caused by atomic diffusion-induced alloying of core/shell type QDs. The main problem of this method is the decreasing emission intensity caused by oxidation during the heat treatment; however, this problem can be solved by use of a SiO2 protective coating on the QD-SAMs. We believe that this simple technique is useful for manufacturing RGB-colored ultrathin QD-SAM films for QDs displays such as QD film display, QD color-filter display, and QD light emitting diode.
关键词： QD Display,Quantum dots,Color tuning,Self-assembled monolayer,atomic diffusion-induced alloying,Thermal treatment
更新于2025-09-23 15:19:57