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Three-dimensional Nanoscale Mapping of Porosity in Solution-Processed ITO Multilayer Thin Films for Patternable Transparent Electrodes
摘要： Indium tin oxide (ITO) films constitute components of many layered heterostructures used for emergent technologies beyond conventional optoelectronics. Compositional and morphological changes have a direct impact on the device’s performance. Hence control over the morphology with advanced multimodal characterization approaches are required to evaluate the devices. Herein multilayer ITO films deposited by spin coating were quantified in nanoscale detail in three dimensions by combining results from depth-sensitive neutron reflectometry (NR), non-contact topographic AFM images and cross-sectional SEM images. Films with different number of deposited layers were visually transparent even though the topmost layer was as high as 60% porous, with porosity gradually decreasing as the number of the underneath sublayers increased. Surface and interfacial roughness through the total film and individual layer thickness were obtained. NR data also furnished quantitative depth information on the films chemical composition and layer-by-layer bulk density, which has never been obtained before, providing a way to monitor and ultimately control the sheet resistivity via the pore network. When the same formulation is used for inkjet printing patterns, the larger pores disappear and the optical properties are improved to >90% transmittance at all visible wavelengths. All 5L films achieved sheet resistivities as low as 10-2 ?-cm and can therefore be used as patternable transparent electrodes for many devices including liquid crystal displays.
关键词： thin multilayer film,neutron reflectometry,depth density distribution,neutron absorption reflectometry,Indium tin oxide,porosity,structure chemical depth profile,off-specular neutron scattering,layer by layer deposition
更新于2025-11-19 16:56:35
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The electronic band structure analysis of OLED device by means of in situ LEIPS and UPS combined with GCIB
摘要： Low-energy inverse photoelectron spectroscopy (LEIPS) and ultraviolet photoelectron spectroscopy (UPS) incorporated into the multitechnique XPS system were used to probe the ionization potential and the electron affinity of organic materials, respectively. By utilizing gas cluster ion beam (GCIB), in situ analyses and depth profiling of LEIPS and UPS were also demonstrated. The band structures of the 10-nm-thick buckminsterfullerene (C60) thin film on Au (100 nm)/indium tin oxide (100 nm)/glass substrate were successfully evaluated in depth direction.
关键词： LEIPS–UPS,GCIB depth profile,OLED device,electronic band structure
更新于2025-09-23 15:21:01
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Characterization of Lattice Parameters Gradient of Cu(In1-xGax)Se2 Absorbing Layer in Thin-Film Solar Cell by Glancing Incidence X-Ray Diffraction Technique
摘要： In or Ga gradients in the Cu(In1-xGax)Se2 (CIGS) absorbing layer lead to change the lattice parameters of the absorbing layer, giving rise to the bandgap grading in the absorbing layer which is directly associated with the degree of absorbing ability of the CIGS solar cell. We tried to characterize the depth profile of the lattice parameters of the CIGS absorbing layer using a glancing incidence X-ray diffraction (GIXRD) technique, and then allows to determine the In or Ga gradients in the CIGS absorbing layer, and to investigate the bandgap grading of the CIGS absorbing layer. When the glancing incident angle increased from 0.50 to 5.00°, the a and c lattice parameters of the CIGS absorbing layer gradually decreased from 5.7776(3) to 5.6905(2) ?, and 11.3917(3) to 11.2114(2) ?, respectively. The depth profile of the lattice parameters as a function of the incident angle was consistent with vertical variation in the composition of In or Ga with depth in the absorbing layer. The variation of the lattice parameters was due to the difference between the ionic radius of In and Ga co-occupying at the same crystallographic site. According to the results of the depth profile of the refined parameters using GIXRD data, the bandgap of the CIGS absorber layer was graded over a range of 1.222 to 1.532 eV. This approach nondestructively guess the bandgap depth profile through the refinement of the lattice parameters using GIXRD data on the assumption that the changes of the lattice parameters or unit-cell volume follow a good approximation to Vegard’s law.
关键词： Vegard’s law,Cu(In1-xGax)Se2 absorbing layer,Depth profile,Bandgap grading,Glancing incidence X-ray diffraction technique
更新于2025-09-23 15:21:01
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Molecular Stacking Effect on Small-Molecular Organic Light-Emitting Diodes Prepared with Solution Process
摘要： The light emitting layer (EML) is generally prepared by mixing host and dopant to realize organic light emitting diode (OLED). However, phase separation is often observed during the fabrication process to prepare OLEDs depending on the structure of the host materials. In particular, phase separation due to π-π stacking is frequently observed during thermal annealing for the solution process. The annealing process is required for solvent removal and complete relaxation of the molecule. Hence, the materials with a high glass transition temperature (Tg) are ideal because phase separation occurs due to π-π stacking during annealing process if Tg is too low. To understand this phenomenon, we compared two host materials with similar molecular weights but different three-dimensional connectivity, which causes different rotational freedom. Then, we investigated the effect on the device properties depending on the annealing conditions. In both materials, when the annealing temperature rises above 120 °C, the dopant completely escaped from the EML. However, the material that does not disturb the molecular stacking order by annealing due to its limited free rotation through internal bond shows much better device characteristics even after annealing at a higher temperature than Tg. The results show that interdiffusion at the interface and unstable internal density distribution with annealing temperature are responsible for the device degradation behavior.
关键词： X-ray reflectivity,Depth profile,Free volume,Phase separation,Segmental motion,Small molecule,Solution process
更新于2025-09-23 15:19:57
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Characterization of multi-element impurity deposited on EAST divertor tile using laser-induced breakdown spectroscopy
摘要： Laser-induced breakdown spectroscopy (LIBS) has been applied for the depth-resolved identification of impurity deposited on EAST divertor tile. LIBS spectra show the presence of impurity elements (W, Mo, Li, Na, Ca, Cr) and tile material (C, Si, Ti) in the layer deposited on the graphite tile surface. The analysis of impurity deposition was performed in different positions on tile surface. The results indicate that the interaction of high heat plasma with plasma facing components (PFCs) leads to erosion of Mo from first wall and W from upper divertor. Depth profiling measurements show decay of impurity signals with successive laser shots and non-uniform impurity deposition in the different positions on tile surface. The impurity deposition was also measured at the different depths in the tile. The measurements show a non-uniform deposition at various depths in the deposition layer. Surface morphology and composition of tile were verified by SEM and EDX techniques. The study indicates that LIBS has potential to monitor the erosion and deposition of PFCs in fusion devices. The results obtained from LIBS technique are important for long pulse of H-mode plasma operation in EAST.
关键词： Depth profile,EDX,Graphite tile,Impurity deposition,LIBS,EAST,Plasma facing components
更新于2025-09-16 10:30:52
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Fluorescence imaging analysis of depth‐dependent degradation in photovoltaic laminates: insights to the failure
摘要： Accurate evaluation of the reliability of photovoltaic (PV) packaging materials is critically important for the long‐term safe operation of modules. However, the complexity of the laminated systems due to their multilayered and multicomponent structures and diverse aging mechanisms makes a thorough system evaluation very challenging, especially when the degradation is non‐uniform through the thickness. In such a case, neither surface nor bulk measurements can present a clear picture of the degradation profile. In this study, fluorescence imaging was developed to visualize the degradation depth‐profiles of an aged laminated PV system. A glass/ethylene vinyl acetate (EVA) encapsulant/poly(ethylene terephthalate) (PET)‐PET‐EVA (PPE) backsheet laminate was weathered with the glass‐side facing an ultra-violet (UV) light source for 3840 h. Cross‐sectional fluorescence images revealed a non‐uniform distribution of degradation species across the thickness of the EVA encapsulant, providing greater insight into the mechanisms of degradation, which are unavailable by traditional bulk‐based methods. In addition, strong fluorescence emissions were observed from the two thin adhesive layers of the aged backsheet, indicating severe degradation of the adhesives and a potential for interlayer delamination. This method is further confirmed with other microscale characterization techniques. The changes in optical (yellowness index), chemical (oxidation, UV absorber concentration), mechanical (Derjaguin‐Muller‐Toporov modulus), and thermal (melting enthalpy) properties of the EVA encapsulant were found to be related to fluorescence profiles, following the attenuation of UV light. This study highlights that fluorescence imaging is a spatially‐resolved and sensitive method for rapid failure assessment and in‐depth mechanism study for complex PV‐laminated system.
关键词： modulus,depth profile,UV aging,photovoltaic laminates,yellowness index,fluorescence imaging,degradation
更新于2025-09-16 10:30:52
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Micro-invasive depth profile analysis by laser-induced breakdown spectroscopy (LIBS): the case of mercury layers on Sasanian coins
摘要： Laser-Induced Breakdown Spectroscopy (LIBS) was used for depth-profile analysis of one Sasanian coin of the emperor Khusro II (591–628) from the Coin Collection of the Kunsthistorisches Museum of Vienna. The peculiarity of this coin, also found in analogous samples of the same and other collections, was the presence of an external Hg layer. The thickness and homogeneity of the Hg layer were characterized with the calibration-free inverse method, a variant of the classical calibration-free LIBS approaches in which one sample of known concentration is used to determine the plasma temperature. We demonstrated the feasibility of the inverse method also in cases of unknown samples with matrices different from that of the employed standard. In this work, the standard was a Cu-based alloy and the sample was an Ag-based alloy, also containing Hg and other minor components. The LIBS results were in good agreement with two previous independent micro-XRF measurements performed with a destructive approach, i.e. using a cross section of the same sample. This confirmed the applicability of the inverse method to unconventional matrices, for which the use of matrix-matched standards may be unfeasible. The conclusions of this work strongly support the use of laser ablation techniques for calibration-free and micro-invasive analysis of layered samples, in particular when the integrity of samples has to be preserved.
关键词： micro-invasive analysis,Laser-Induced Breakdown Spectroscopy,Hg layer,depth-profile analysis,calibration-free inverse method,Sasanian coin,LIBS
更新于2025-09-12 10:27:22
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Single shot laser ablation MC-ICP-MS for depth profile analysis of U isotopes in UO <sub/>2</sub> single crystals
摘要： An analytical procedure for determining the n(235U)/n(238U) amount ratio in consecutive layers of UO2 single crystals was developed and validated. A 25 mm circular shaped laser beam with a fluence of only 0.24 J cm?2 was employed for depth profiling 235U and 238U in UO2 single crystals with U isotopes being detected via MC-ICP-MS. The time-resolved 235U and 238U MC-ICP-MS signals obtained from individual laser shots were processed automatically using software specifically developed for this purpose. Downhole fractionation of the n(235U)/n(238U) amount ratio was excluded by shooting 80 laser pulses on a reference UO2 single crystal of known composition, revealing no measurable change in its U isotopic ratio during depth profiling. A linear relationship between the number of laser shots and the average depth of the laser ablation craters was established using confocal laser scanning profilometry. The ns-laser ablation system produced conical craters whose diameters were shown to increase with the number of laser pulses. The shape and roughness of the craters were studied as a function of both the number of pulses and focusing conditions. Using a dual beam focused ion beam (FIB), high resolution scanning electron microscopy (SEM) micrographs revealed the formation of rectangular “tiles” on the reference UO2 single crystal after as little as five laser shots. The ordered, rectangular structure disappeared progressively with increasing number of laser pulses, while simultaneously a sub-micrometric porosity developed. The depth profiling capabilities of the laser ablation system were applied to two UO2 single crystals produced under different experimental conditions involving solid state isotopic mixing of 235U and 238U in order to characterise U self-diffusion in UO2+x. Both UO2 single crystals featured a n(235U)/n(238U) ratio gradient, containing enriched U at the surface and depleted U in the bulk.
关键词： MC-ICP-MS,UO2 single crystals,depth profile analysis,laser ablation,U isotopes
更新于2025-09-11 14:15:04