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Effect of deposition rate on the growth mechanism of microcrystalline silicon thin films using very high frequency PECVD
摘要： The intrinsic microcrystalline silicon thin films were deposited by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD). Two series of films with different deposition rate 0.30 nm/s and 1.94 nm/s were prepared. The film surface and gas phase reaction growth processes were monitored with real-time spectroscopic ellipsometry and optical emission spectroscopy. The effect of deposition rate on the microcrystalline silicon thin film growth mechanism has been studied. The microcrystalline silicon surface growth was analyzed with KPZ model. The results show that the growth exponent of β is 0.448 for the films with low deposition rate, and the growth exponent of β is 0.302 for the films with high deposition rate. The growth exponent does not increase with deposition rate, but declines. And the reasons for this phenomenon were explained.
关键词： Real time spectroscopic ellipsometry,Microcrystalline silicon,High rate deposition,Optical emission spectrum,Growth mechanism
更新于2025-09-09 09:28:46
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Physical Properties, Ligand Field and Judd-Ofelt Intensity Parameters of Bio-silicate Borotellurite Glass System Doped with Erbium Oxide
摘要： A glass series containing bio-silicate borotellurite (BSBT) doped with erbium oxide with composition of {[(TeO2)0.8 (B2O3)0.2]0.8 (SiO2)0.2}1-y (Er2O3)y, y= 0.01, 0.02, 0.03, 0.04, 0.05 mol fraction were fabricated using the melt quenching technique. In this glass composition, the bio-silicate was extracted from the rice husk. The X-ray fluorescence (XRF), X-ray diffraction (XRD), molar volume, density, optical absorption and luminescence properties and excitation of the glass sample were investigated. Result of x-ray diffraction (XRD) confirmed the amorphous nature of the glass. The X-ray fluorescence (XRF) verified the achievement of 98.6% of silicate from rice husk. The density is found to be increasing from 3.845 g/cm3 to 4.142 g/cm3 with the increase in the concentration of Er3+. The molar volume is also found to be increasing with concentration of Er3+, but later decreases at 0.04 and 0.05 mol fraction of erbium. The decrease may be due to the tightly packed atom giving rise to a denser glass. The obtained values of the Racah parameters are derived from the absorption spectra region with higher energy. The bonding parameters are found to increase with the increase in the concentration of Er3+ from 0.002789 to 0.002835 while the Racah parameters and nephelauxetic ratio decreased. The increase in crystal field strength also shows a strong field sites. The Judd-Ofelt (J-O) intensity parameters are derived from the UV-Vis spectra and the results showed ?2>?4>?6 trend with the exception of Erbium at 0.04 mol fraction which showed ?2>?6>?4 trend. The appearance of higher values of ?2 and ?6 indicate the presence of a stronger covalency and lower symmetry around Er3+ ions. MacCumber theory was used to determine the stimulated emission cross section from the calculated absorption cross section for 4I13/2 to 4I15/2 transition. The glass displayed intense green and a week red emission under 380 nm excitation. The width of the gain is found to shift towards the shorter wavelength which proves that this glass system is a good material for photonics and laser applications.
关键词： Bio-silicate,Bonding parameters,Judd-Ofelt,emission cross section,Luminescence
更新于2025-09-09 09:28:46
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Aggregation-Induced Emission (AIE) Polymeric Micelles for Imaging-Guided Photodynamic Cancer Therapy
摘要： Photodynamic therapy (PDT) is a noninvasive treatment for selectively killing malignant tumor cells. The photosensitizer is a necessary component of photodynamic nanomedicine. Many efforts have been made to develop new photosensitizers for efficient cancer photodynamic therapy. In this work, we report a novel nano photosensitizer, polymeric micelles (AIE-M) with aggregation induced emission characteristic, for photodynamic cancer therapy. AIE-M with sub-20 nm particle size is prepared by the self-assembly of salicylaldazine-incorporated amphiphilic polymer (AIE-1), which can produce reactive oxygen species (ROS) with light irradiation in solution. After uptake by cancer cells, AIE-M can specially sojourn in plasma membranes of cancer cells at the early stage and predominantly accumulate in the mitochondria of cancer cell at the late stage. The phototoxicity of AIE-M, resulting from the generation of intracellular ROS with light irradiation, can efficiently cause cancer cells death by apoptosis and necrosis. The advantages of AIE-M as a nano photosensitizer include the small size, highly colloidal stability in the process of preparation and storage, and high cell penetration. The ultra-low Critical Micelle Concentration (CMC) of AIE-1, negligible dark toxicity and super phototoxicity of AIE-M suggest its promising potential for image-guided PDT.
关键词： polymeric micelles,imaging,photodynamic,aggregation induced emission,cancer therapy
更新于2025-09-09 09:28:46
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Photometric and spectroscopic variability of the Be star 48 Lib: The relation between photometric variations and rotation
摘要： The purpose of this paper is to determine the origin of the photometric variations of 48 Lib using the data from the STEREO and to investigate their relations with the disk structure. The photometric data comprise a period of five years from 2007 to 2011. The spectroscopic data covering the same time interval are provided from the BeSS database. The Hα lines are examined by measuring their equivalent widths and line intensities. Hα variations are then compared with those displayed by the photometric data. From the photometry, high-precision results (10?4 mag in amplitude) are obtained. It is detected that the star has shown 24 frequencies, mainly clustered around the peaks at 2.48896(1) and 5.08150(2) c d?1. The analysis reveals that the photometric frequencies are not due to pulsation, but caused by the rotation, and that the remaining frequencies arise from transient activities on or just above the photosphere. Also, it is shown that the spectroscopic data exhibit a significant Hα variability, and that the Hα line variation depends on the variation of frequency and amplitude, something which has been often proposed in the literature but has never before been demonstrated observationally. This proves that the disk structure and photometric variations are related.
关键词： stars: emission line, Be,stars: rotation,methods: data analysis,stars: individual: 48 Lib
更新于2025-09-09 09:28:46
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4H-SiC 1200 V Junction Barrier Schottky Diodes with High Avalanche Ruggedness
摘要： A state-of-the art family of 1200 V junction barrier Schottky (JBS) diodes was developed. These devices are highly competitive in switching applications thanks to low specific series resistance (1.8 mΩ.cm2 at current rating) and low capacitive charge (1420 nC.cm-2 at 800 V). A uniform avalanche distribution over the active area combined with an optimized high-voltage termination provides industry-leading UIS capabilities. Stringent reliability tests were performed to meet the qualification requirements for the industrial market.
关键词： junction barrier Schottky diode,4H-SiC,emission microscopy,TCAD,unclamped inductive switching
更新于2025-09-09 09:28:46
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Blue-Emitting CsPbCl <sub/>3</sub> Nanocrystals: Impact of Surface Passivation for Unprecedented Enhancement and Loss of Optical Emission
摘要： High-energy-emitting CsPbCl3 nanocrystals have shown significant loss and enhancement of their emission intensity (～40?50 folds) during purification and surface treatments, respectively. This confirms that the surfaces of these nanocrystals are very sensitive. In this Letter, physical insights of the interface bindings on the surface of these blue-emitting CsPbCl3 nanocrystals with different passivating agents and their impact on purification are investigated. Using various metal chlorides consequential irrespective of the charge and size of the metal ions, metal acetates, and nonmetal chloride, the predominant influence of chloride ions in helping retrieve/intensify the blue emission is established. The purification processes are observed to be very delicate, and successive purifications with introduction of polar nonsolvents led to the transformation of an emitting cubic CsPbCl3 phase to nonemitting tetragonal CsPb2Cl5 phase nanocrystals irreversibly. The impact of various salt additions only temporarily helped in enhancing the emission, but the phase change remained inevitable upon successive purification. However, as a remedy, by in situ use of alkylammonium chloride salt in high-temperature reactions, the surface binding was improved, and significant emission as well as the phase could be retained with successive purifications.
关键词： surface passivation,purification,optical emission,CsPbCl3 nanocrystals,blue-emitting
更新于2025-09-09 09:28:46
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Characteristics of krypton ion emission from a gas field ionization source with a single atom tip
摘要： A scanning ion beam instrument equipped with a gas ?eld ionization source (GFIS) has been commercialized, but only helium and neon are currently available as GFISs. The characteristics of krypton ion emission from a single atom tip (SAT) have not been reported yet. In this study, the characteristics of krypton ion emission were investigated by ?eld ion microscopy. At 65 K, the krypton ion emission current reached approximately 40 pA, which is 1 order of magnitude higher than that at 130 K. As the krypton gas pressure was increased, the krypton ion current increased. At a pressure of 0.3 Pa, the emission current was anticipated to reach 200 pA, which may be high enough for nanofabrication. The variation of the krypton ion current was as low as 5% in one hour. We concluded that a krypton ion beam instrument equipped with a GFIS will be a powerful tool for nanofabrication.
关键词： gas field ionization source,field ion microscopy,nanofabrication,single atom tip,krypton ion emission
更新于2025-09-09 09:28:46
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in light filaments
摘要： We present our results on the emissions from N2+ pumped with ultrafast filaments using high-resolution pump probe. Our result shows the phase relation between transition lines at earlier delays. We show that the gain on transition lines extends beyond the time when coherence is lost.
关键词： stimulated emission,N2+,rotational wave packet,light filaments,ultrafast pump probe
更新于2025-09-09 09:28:46
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Ultrafast nuclear dynamics in the doubly-core-ionized water molecule observed via Auger spectroscopy
摘要： We present a combined experimental and theoretical study of the Auger-emission spectrum following double core ionization and excitation of gas-phase water molecules with hard-x-ray synchrotron radiation above the O K ?2 threshold. We observe an indication of ultrafast proton motion occurring within the 1.5 fs lifetime of the double-core-hole (DCH) states in water. Furthermore, we have identi?ed symmetric and antisymmetric dissociation modes characteristic for particular DCH states. Our results serve as a fundamental reference for state-of-the-art studies of DCH dynamic processes in liquid water both at synchrotron and free-electron-laser facilities.
关键词： double core ionization,Auger-emission spectrum,synchrotron radiation,ultrafast proton motion,DCH states
更新于2025-09-09 09:28:46
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Quantitative FRET measurement based on spectral unmixing of donor, acceptor and spontaneous excitation-emission spectra
摘要： Quantitative FRET measurement based on spectral unmixing of donor, acceptor and spontaneous excitation-emission spectra. The SPEES-FRET method we developed here is very robust against cellular autofluoresence. SPEES-FRET method can obtain stable and accurate E and RC values for FRET tandem constructs with high or low FRET efficiency in HEK293 cells with strong autofluorescence, and can also obtain consistent results for the bright and dim cells expressing FRET constructs or co-expressing Cerulean and Venus or co-expressing CFP-Bax and YFP-Bax. Therefore, the SPEES-FRET is applicable to the quantitative FRET measurements for the live cells with strong autofluorescence, and must become a powerful and robust tool for monitoring the weak protein-protein interaction in living cells.
关键词： spontaneous excitation-emission spectra,FRET,living cells,quantitative measurement,spectral unmixing
更新于2025-09-09 09:28:46