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Direct Imaging of Current‐Induced Transformation of a Perovskite/Electrode Interface
摘要： Formamidinium-lead-iodide (FAPbI3) perovskite films are subjected to a long-term action of the constant electrical current in the dark, using planar vacuum-deposited gold electrodes. The current-induced transformation is monitored by the time-of-flight secondary ion mass spectrometry (ToF-SIMS) mapping complemented by microscopic, spectroscopic methods, and X-ray diffraction. The migration of chemical species inside the lateral interelectrode gap is clearly visualized by ToF-SIMS. Those species correspond to both electrode material and perovskite itself, so that the perovskite/electrode interface becomes disrupted. As a result, the interelectrode gap shrinks, which is reflected in the surface images.
关键词： interfaces,dark current,gold electrodes,perovskites,ToF-SIMS mapping
更新于2025-11-25 10:30:42
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Chemical imaging of buried interfaces in organic-inorganic devices using FIB-ToF-SIMS
摘要： Organic-inorganic hybrid materials enable the design and fabrication of new materials with enhanced properties. The interface between the organic and inorganic materials is often critical to the device’s performance and therefore chemical characterization is of significant interest. Since the interfaces are often buried, milling by focused ion beams (FIB) to expose the interface is becoming increasingly popular. Chemical imaging can subsequently be obtained using secondary ion mass spectrometry. However, the FIB milling process damages the organic material. In this study, we make an organic-inorganic test structure to develop a detailed understanding of the processes involved in FIB milling and SIMS imaging. We provide an analysis methodology that involves a “clean-up” process using sputtering with an argon gas cluster ion source to remove the FIB induced damage. The methodology is evaluated for two additive manufactured devices, an encapsulated strain sensor containing silver tracks embedded in a polymeric material and a copper track on a flexible polymeric substrate created using a novel nanoparticle sintering technique.
关键词： FIB,additive manufacturing,hybrid interfaces,ToF-SIMS,polymer,Argon cluster,milling
更新于2025-09-23 15:22:29
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High-voltage regrown nonpolar m-plane vertical p-n diodes: A step toward future selective-area-doped power switches
摘要： We report high-voltage regrown nonpolar m-plane p-n diodes on freestanding GaN substrates. Secondary-ion mass spectroscopy (SIMS) measurements indicate O and Si spikes at the regrowth interfaces with maximum concentration ~ 5×1017 cm-3, which is similar to previously published c-plane studies. A high blocking voltage of 540 V at ~ 1 mA/cm2 (corresponding to an electric field of E ~ 3.35 MV/cm), turn-on voltages between 2.9-3.1 V, specific on-resistance of 1.7 mΩ.cm2 at 300 A/cm2, and a minimum ideality factor of 1.7 were obtained for the regrown diodes. Our results suggest that Si, O and C interfacial impurity levels up to 2×1017 cm-3, 8×1017 cm-3, and 1×1019 cm-3, respectively, at the metallurgical junction of m-plane p-n diodes do not result in very early breakdown in the reverse bias, although the off-state leakage current in forward bias is affected. The impact of growth interruption/regrowth on diode performance is also investigated.
关键词： Selective-area doping,GaN,Specific on-resistance,Impurity incorporation,Avalanche breakdown,Leakage currents,Ideality factor,Nonpolar,SIMS,Vertical p-n diodes
更新于2025-09-23 15:22:29
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Comparative Analysis of Defects in Mg-Implanted and Mg-Doped GaN Layers on Freestanding GaN Substrates
摘要： Inefficient Mg-induced p-type doping has been remained a major obstacle in the development of GaN-based electronic devices for solid-state lighting and power applications. This study reports comparative structural analysis of defects in GaN layers on freestanding GaN substrates where Mg incorporation is carried out via two approaches: ion implantation and epitaxial doping. Scanning transmission electron microscopy revealed the existence of pyramidal and line defects only in Mg-implanted sample whereas Mg-doped sample did not show presence of these defects which suggests that nature of defects depends upon incorporation method. From secondary ion mass spectrometry, a direct correspondence is observed between Mg concentrations and location and type of these defects. Our investigations suggest that these pyramidal and line defects are Mg-rich species and their formation may lead to reduced free hole densities which is still a major concern for p-GaN-based material and devices. As freestanding GaN substrates offer a platform for realization of p-n junction-based vertical devices, comparative structural investigation of defects originated due to different Mg incorporation processes in GaN layers on such substrates is likely to give more insight towards understanding Mg self-compensation mechanisms and then optimizing Mg doping and/or implantation process for the advancement of GaN-based device technology.
关键词： Line defects,Pyramidal defects,SIMS,GaN,STEM
更新于2025-09-23 15:22:29
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A detailed comparison of measured and simulated optical properties of a short-period GaAs/Al <sub/><i>x</i> </sub> Ga <sub/> 1a?? <i>x</i> </sub> As distributed Bragg reflector
摘要： A 6-period GaAs/Al0.9Ga0.1As distributed Bragg re?ector (DBR) has been grown and its optical properties have been both measured and simulated. Incremental improvements were made to the simulation, allowing it to account for internal consistency error, incorrect layer thicknesses, and absorption due to substrate doping to improve simulation accuracy. A compositional depth pro?le using secondary-ion mass spectrometry (SIMS) has been taken and shows that the Al fraction averages 88.0% ± 0.3%. It is found that the amplitude of the transmission is signi?cantly affected by absorption in the n-doped GaAs substrate, even though the energy of the transmitted light is well below the GaAs band gap. The wavelength of the features in the transmission spectrum are mostly affected by DBR layer thicknesses. On the other hand, the transmission spectrum is found to be relatively tolerant to changes to Al fraction.
关键词： optical simulation,AlGaAs,distributed Bragg re?ector,SIMS,cross section,telecoms,vertical cavity
更新于2025-09-23 15:21:01
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Comparison of quantitative analyses using SIMS, atom probe tomography, and femtosecond laser ablation inductively coupled plasma mass spectrometry with Si <sub/>1a??X</sub> Ge <sub/>X</sub> and Fe <sub/>1a??X</sub> Ni <sub/>X</sub> binary alloys
摘要： Due to their electrical and physical properties, Si1?XGeX materials are widely used in microelectronic devices. In particular, the Ge component found within Si1?XGeX compounds is important for enhancing carrier mobility and altering the lattice constant of metal-oxide-semiconductor field-effect transistors. In this study, magnetic sector secondary ion mass spectrometry (magnetic sector SIMS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to determine the accurate concentrations of major compositions present within binary alloy samples. However, quantitative SIMS analysis is limited by the matrix effect, which influences the sputter yield of an element in a compound and alters the secondary ionization yields. Quantitative deviations that were due to the matrix effect were reduced by using Cs cluster ions (MCs+ and MCs2+) instead of elemental ions; the SIMS results using the elements were, therefore, compared with those using MCs+ and MCs2+ cluster ions. In the case of Fe1?XNiX alloys that have a less matrix effect compared to Si1?XGeX alloys, both the Cs primary ion beam (Cs+) and an oxygen primary ion beam (O2+) were used to measure the Fe1?XNiX compositions. The quantitative results from the two different primary ion beams were then compared to understand the ionization process. Deviations in the quantitative values gained with the O2+ beam were lower than those obtained using the Cs+ primary ions, meaning that using oxygen as the primary ion improves the accuracy in quantifying Fe1?XNiX compounds. Other reliable tools for analysis such as atom probe tomography and femtosecond laser ablation inductively coupled plasma mass spectrometry were also used in the quantitative analysis, with results that were consistent with the most accurate results obtained using magnetic sector SIMS and ToF-SIMS.
关键词： Si1?XGeX,femtosecond laser ablation inductively coupled plasma mass spectrometry,atom probe tomography,SIMS,Fe1?XNiX,binary alloys
更新于2025-09-23 15:21:01
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Decoupling Contributions of Chargea??Transport Interlayers to Lighta??Induced Degradation of pa??ia??n Perovskite Solar Cells
摘要： Perovskite solar cells (PSCs) have demonstrated impressive performance, while their operation stability still requires substantial improvements before this technology can be successfully commercialized. There is a growing evidence that stability of PSCs is strongly dependent on the interface chemistry between the absorber films and adjacent charge transport layers, while the exact mechanistic pathways remain poorly understood. Here we present a systematic approach for decoupling the degradation effects induced by the top electron transport layer (ETL) of the fullerene derivative PC61BM and various bottom hole-transport layer (HTL) materials assembled in p-i-n perovskite solar cells configurations. We show that chemical interaction of MAPbI3 absorber with PC61BM most aggressively affects the operation stability of solar cells. However, washing away the degraded fullerene derivative and depositing fresh ETL leads to restoration of the initial photovoltaic performance when bottom perovskite/HTL interface is not degraded. Following this approach and refreshing ETL after light soaking of the samples and before completing the solar cell architectures, we were able to compare the photostability of stacks with various HTLs. It has been shown that PEDOT:PSS and NiOx induce significant degradation of the adjacent perovskite layer under light exposure, while PTAA provides the most stable perovskite/HTL interface. ToF-SIMS analysis of fresh and aged samples allowed us to identify chemical origins of the interactions between MAPbI3 and HTLs. The proposed research methodology and the revealed degradation pathways should facilitate future development of efficient and stable perovskite solar cells.
关键词： hole transporting materials,perovskite solar cells,TOF-SIMS,stability,interfacial degradation
更新于2025-09-23 15:21:01
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Successes and Challenges Associated with Solution Processing of Kesterite Cu2ZnSnS4 Solar Cells on Titanium Substrates
摘要： Roll-to-roll (R2R) processing of solution-based Cu2ZnSn(S,Se)4 (CZT(S,Se)) solar cells on flexible metal foil is an attractive way to achieve cost-effective manufacturing of photovoltaics. In this work we report the first successful fabrication of solution-processed CZTS devices on a variety of titanium substrates with up to 2.88% power conversion efficiency (PCE) collected on flexible 75 μm Ti foil. A comparative study of device performance and properties is presented aiming to address key processing challenges. First, we show that a rapid transfer of heat through the titanium substrates is responsible for the accelerated crystallisation of kesterite films characterised with small grain size, a high density of grain boundaries and numerous pore sites near the Mo/CZTS interface which affect charge transport and enhance recombination in devices. Following this, we demonstrate the occurrence of metal ion diffusion induced by the high temperature treatment required for the sulfurization of the CZTS stack: Ti4+ ions are observed to migrate upwards to the Mo/CZTS interface whilst Cu1+ and Zn2+ ions diffuse through the Mo layer into the Ti substrate. Finally, residual stress data confirm the good adhesion of stacked materials throughout the sequential solution process. These findings are evidenced by combining electron imaging observations, elemental depth profiles generated by secondary ion mass spectrometry, and x-ray residual stress analysis of the Ti substrate.
关键词： SIMS,titanium,CZTS,solar cell,stress
更新于2025-09-23 15:19:57
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Highly Luminous Ba2SiO4a???′N2/3?′:Eu2+ Phosphor for NUV-LEDs: Origin of PL-Enhancement by N3a??-Substitution
摘要： Ba2SiO4?δN2/3δ:Eu2+ (BSON:Eu2+) materials with different N3? contents were successfully prepared and characterized. Rietveld refinements showed that N3? ions were partially substituted for the O2? ions in the SiO4-tetrahedra because the bond lengths of Si-(O,N) (average value = 1.689 ?) were slightly elongated compared with those of Si-O (average value = 1.659 ?), which resulted in the minute compression of the Ba(2)-O bond lengths from 2.832 to 2.810 ?. The average N3? contents of BSON:Eu2+ phosphors were determined from 100 nm to 2000 nm depth of grain using a secondary ion mass spectrometry (SIMS): 0.064 (synthesized using 100% α-Si3N4), 0.035 (using 50% α-Si3N4 and 50% SiO2), and 0.000 (using 100% SiO2). Infrared (IR) and X-ray photoelectron spectroscopy (XPS) measurements corroborated the Rietveld refinements: the new IR mode at 850 cm?1 (Si-N stretching vibration) and the binding energy at 98.6 eV (Si-2p) due to the N3- substitution. Furthermore, in UV-region, the absorbance of N3?-substituted BSON:Eu2+ (synthesized using 100% α-Si3N4) phosphor was about two times higher than that of BSO:Eu2+ (using 100% SiO2). Owing to the N3? substitution, surprisingly, the photoluminescence (PL) and LED-PL intensity of BSON:Eu2+ (synthesized using 100% α-Si3N4) was about 5.0 times as high as that of BSO:Eu2+ (using 100% SiO2). The compressive strain estimated by the Williamson?Hall (W?H) method, was slightly increased with the higher N3? content in the host-lattice of Ba2SiO4, which warranted that the N3- ion plays an important role in the highly enhanced PL intensity of BSON:Eu2+ phosphor. These phosphor materials could be a bridgehead for developing new phosphors and application in white NUV-LEDs field.
关键词： N3? substitution,Ba2SiO4:Eu2+,IR,PL,SIMS,XPS
更新于2025-09-23 15:19:57
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Influence of Silicon Layers on the Growth of ITO and AZO in Silicon Heterojunction Solar Cells
摘要： In this article, we report on the properties of indium tin oxide (ITO) deposited on thin-film silicon layers designed for the application as carrier selective contacts for silicon heterojunction (SHJ) solar cells. We find that ITO deposited on hydrogenated nanocrystalline silicon (nc-Si:H) layers presents a significant drop on electron mobility μe in comparison to layers deposited on hydrogenated amorphous silicon films (a-Si:H). The nc-Si:H layers are not only found to exhibit a larger crystallinity than a-Si:H, but are also characterized by a considerably increased surface rms roughness. As we can see from transmission electron microscopy (TEM), this promotes the growth of smaller and fractured features in the initial stages of ITO growth. Furthermore, secondary ion mass spectrometry profiles show different penetration depths of hydrogen from the thin film silicon layers into the ITO, which might both influence ITO and device passivation properties. Comparing ITO to aluminum doped zinc oxide (AZO), we find that AZO can actually exhibit superior properties on nc-Si:H layers. We assess the impact of the modified ITO Rsh on the series resistance Rs of SHJ solar cells with >23% efficiency for optimized devices. This behavior should be considered when designing solar cells with amorphous or nanocrystalline layers as carrier selective contacts.
关键词： secondary ion mass spectrometry (SIMS),indium tin oxide (ITO),series resistance,Aluminum doped zinc oxide (AZO),transparent conductive oxide (TCO),transmission electron microscopy (TEM),silicon heterojunction (SHJ)
更新于2025-09-16 10:30:52