Artigos de revistas: "Raman/PL"

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Pavić, Ivan, Joško Šoda, Vlatko Gašparić e Mile Ivanda. "Raman and Photoluminescence Spectroscopy with a Variable Spectral Resolution". Sensors 21, n.º 23 (28 de novembro de 2021): 7951. http://dx.doi.org/10.3390/s21237951.

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Raman and photoluminescence (PL) spectroscopy are important analytic tools in materials science that yield information on molecules’ and crystals’ vibrational and electronic properties. Here, we show results of a novel approach for Raman and PL spectroscopy to exploit variable spectral resolution by using zoom optics in a monochromator in the front of the detector. Our results show that the spectral intervals of interest can be recorded with different zoom factors, significantly reducing the acquisition time and changing the spectral resolution for different zoom factors. The smallest spectral intervals recorded at the maximum zoom factor yield higher spectral resolution suitable for Raman spectra. In contrast, larger spectral intervals recorded at the minimum zoom factor yield the lowest spectral resolution suitable for luminescence spectra. We have demonstrated the change in spectral resolution by zoom objective with a zoom factor of 6, but the perspective of such an approach is up to a zoom factor of 20. We have compared such an approach on the prototype Raman spectrometer with the high quality commercial one. The comparison was made on ZrO2 and TiO2 nanocrystals for Raman scattering and Al2O3 for PL emission recording. Beside demonstrating that Raman spectrometer can be used for PL and Raman spectroscopy without changing of grating, our results show that such a spectrometer could be an efficient and fast tool in searching for Raman and PL bands of unknown materials and, thereafter, spectral recording of the spectral interval of interest at an appropriate spectral resolution.

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Suga, Keishi, Ying-Chen Lai, Miftah Faried e Hiroshi Umakoshi. "Direct Observation of Amyloid β Behavior at Phospholipid Membrane Constructed on Gold Nanoparticles". International Journal of Analytical Chemistry 2018 (2 de dezembro de 2018): 1–7. http://dx.doi.org/10.1155/2018/2571808.

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Amyloid β (Aβ) is a potential biomarker of Alzheimer’s disease (AD), and its fibrillation behavior is of interest and value. In this study, the Aβ behaviors on phospholipid membranes were observed by Membrane Surface-Enhanced Raman Spectroscopy (MSERS) method. Phospholipid (PL) membranes, consisting of DMPC and DMPS with a molar ratio of 9:1, were fabricated on gold nanoparticles with diameter of 100 nm (Au@PL). Enhancement of the Raman intensity of Au@PL was increased by Aβ, with enhancement factor about 40. The H-bonding network was disturbed in presence of NaCl which covered Au@PL and made Au@PL away from one another. When Aβ was applied with Au@PL, the H-bonding network was disturbed just after mixing. As the reaction reaches to equilibrium, Aβ attracted neighbouring Au@PL and induced aggregation of Au@PL which blocked the aggregation prone site of Aβ to inhibit further fibrillation. Based on our method, the Aβ behaviors at lipid membrane surface can be directly observed via enhanced Raman signals.

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CHUAH, L. S., Z. HASSAN, F. K. YAM e H. ABU HASSAN. "STRUCTURAL AND OPTICAL FEATURES OF POROUS SILICON PREPARED BY ELECTROCHEMICAL ANODIC ETCHING". Surface Review and Letters 16, n.º 01 (fevereiro de 2009): 93–97. http://dx.doi.org/10.1142/s0218625x09012342.

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Porous silicon (PS) samples were prepared by electrochemical anodic etching of n-type (111) silicon wafers in HF solution. The structural, optical, and chemical features of the PS were investigated in terms of different etching durations. The porous samples were investigated by scanning electron microscopy (SEM), photoluminescence (PL), and Raman scattering. SEM images indicated that the pores increased with the etching duration; however, the etching duration has significant effect on the shape of the pores. PL measurements revealed that the porosity-induced PL intensity enhancement was only observed in the porous samples. Raman spectra showed shifting of PS Raman peak to lower frequency relative to non-porous silicon Raman peak.

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ZHANG, WEI-FENG, QIAN XING e YA-BIN HUANG. "MICROSTRUCTURES AND OPTICAL PROPERTIES OF STRONTIUM TITANATE NANOCRYSTALS PREPARED BY A STEARIC-ACID GEL PROCESS". Modern Physics Letters B 14, n.º 19 (20 de agosto de 2000): 709–16. http://dx.doi.org/10.1142/s0217984900000896.

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SrTiO3 nanocrystals with grain sizes from 26 to 86 nm were prepared by stearic-acid gel method. The microstructures, lattice vibration and luminescence spectra were examined by X-ray diffraction, infrared, Raman and photoluminescence (PL) spectroscopies. Hydroxyl defects were clearly found by infrared spectroscopy in the SrTiO3 nanocrystals. Raman measurement results showed that internal stress exists in the SrTiO3 nanocrystals, which induces first-order Raman scattering processes. Strong visible PL near 2.62 eV was observed under 3.54 eV light excitation in small SrTiO3 nanocrystals. Grain-size dependence of the PL spectrum is investigated and the origin for the PL is attributed to a charge transfer via intrinsic defects inside an oxygen octahedron.

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AMIRHOSEINY, M., Z. HASSAN e S. S. NG. "EFFECT OF CURRENT DENSITY ON OPTICAL PROPERTIES OF ANISOTROPIC PHOTOELECTROCHEMICAL ETCHED SILICON (110)". Modern Physics Letters B 26, n.º 20 (5 de julho de 2012): 1250131. http://dx.doi.org/10.1142/s021798491250131x.

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Photoelectrochemical etched Si layers were prepared on n-type (110) oriented silicon wafer. The photoluminescence (PL), Fourier transformed infrared (FTIR) absorption and Raman spectroscopies of etched Si (110) at two different current densities were studied. Both samples showed PL peak in the visible spectral range situated from 650 nm to 750 nm. The corresponding changes in Raman spectra at different current density are discussed. The blue shift in the PL and Raman peaks is consequent of the quantum confinement effect and defect states of surface Si nanocrystallites complexes and hydrogen atoms of the photoelectrochemical etched Si (110) samples. The attenuated total reflection (ATR) results show both hydrogen and oxygen related IR modes in the samples which can be used to explain the PL effect.

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Zhang, Xiangzhe, Renyan Zhang, Xiaoming Zheng, Yi Zhang, Xueao Zhang, Chuyun Deng, Shiqiao Qin e Hang Yang. "Interlayer Difference of Bilayer-Stacked MoS2 Structure: Probing by Photoluminescence and Raman Spectroscopy". Nanomaterials 9, n.º 5 (24 de maio de 2019): 796. http://dx.doi.org/10.3390/nano9050796.

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This work reports the interlayer difference of exciton and phonon performance between the top and bottom layer of a bilayer-stacked two-dimensional materials structure (BSS). Through photoluminescence (PL) and Raman spectroscopy, we find that, compared to that of the bottom layer, the top layer of BSS demonstrates PL redshift, Raman E 2 g 1 mode redshift, and lower PL intensity. Spatial inhomogeneity of PL and Raman are also observed in the BSS. Based on theoretical analysis, these exotic effects can be attributed to substrate-coupling-induced strain and doping. Our findings provide pertinent insight into film–substrate interaction, and are of great significance to researches on bilayer-stacked structures including twisted bilayer structure, Van der Waals hetero- and homo-structure.

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Bleisteiner, Bernd. "Raman- und PL-Spektroskopie an Kohlenstoffnanoröhren". Nachrichten aus der Chemie 55, n.º 4 (abril de 2007): 430–32. http://dx.doi.org/10.1002/nadc.200747533.

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Gu, Kai, Ming Sun e Yang Zhang. "Tip-Enhanced Raman Spectroscopy Based on Spiral Plasmonic Lens Excitation". Sensors 22, n.º 15 (28 de julho de 2022): 5636. http://dx.doi.org/10.3390/s22155636.

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In this study, we proposed the idea of replacing the traditional objective lens in bottom-illumination mode with a plasmonic lens (PL) to achieve tip-enhanced Raman spectroscopy (TERS). The electric field energy of surface plasmon polaritons (SPPs) of the spiral PL was found to be more concentrated at the focal point without any sidelobe using the finite-difference time domain (FDTD) method compared with that of a symmetry-breaking PL. This property reduces far-field background noise and increases the excitation efficiency of the near-field Raman signal. The disadvantage of only the near-field Raman scattering of samples at the center of the structure being detected when using an ordinary PL in TERS is overcome by using our proposed method of changing only the polarization of the incident light.

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Han, Tao, Hongxia Liu, Shulong Wang, Shupeng Chen, Kun Yang e Zhandong Li. "Synthesis and Spectral Characteristics Investigation of the 2D-2D vdWs Heterostructure Materials". International Journal of Molecular Sciences 22, n.º 3 (27 de janeiro de 2021): 1246. http://dx.doi.org/10.3390/ijms22031246.

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Due to the attractive optical and electrical properties, van der Waals (vdWs) heterostructures constructed from the different two-dimensional materials have received widespread attention. Here, MoS2/h-BN, MoS2/graphene, WS2/h-BN, and WS2/graphene vdWs heterostructures are successfully prepared by the CVD and wet transfer methods. The distribution, Raman and photoluminescence (PL) spectra of the above prepared heterostructure samples can be respectively observed and tested by optical microscopy and Raman spectrometry, which can be used to study their growth mechanisms and optical properties. Meanwhile, the uniformity and composition distribution of heterostructure films can also be analyzed by the Raman and PL spectra. The internal mechanism of Raman and PL spectral changes can be explained by comparing and analyzing the PL and Raman spectra of the junction and non-junction regions between 2D-2D vdWs heterostructure materials, and the effect of laser power on the optical properties of heterostructure materials can also be analyzed. These heterostructure materials exhibit novel and unique optical characteristics at the stacking or junction, which can provide a reliable experimental basis for the preparation of suitable TMDs heterostructure materials with excellent performance.

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Li, Chun Ping, Jian Zhang, Hua Min Yu e Li Zhong Zhang. "Raman and Photoluminescence Properties of ZnO Nanorods with Wurtzite Structure". Key Engineering Materials 538 (janeiro de 2013): 50–53. http://dx.doi.org/10.4028/www.scientific.net/kem.538.50.

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Raman, resonant Raman and photoluminescence (PL) properties of ZnO nanorods that produced by simple solution chemical process are reported in this paper. The transmission electron microscopy measurements show that the obtained ZnO nanorods have well-proportioned distribution with diameters about 30 nm, and the maximal lengths up to more than 2.2 μm. The micro-Raman and resonant Raman spectrum of nanorods show the obvious differences from that of the commercial bulk phase ZnO samples. The PL with intense UV emission indicates the good quality of the obtained ZnO nanorods.

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Xu, Qiang, Hua Yang Sun, Cheng Chen, Ling Yun Jang, E. Rusli, Suwan P. Mendis, Chin Che Tin et al. "4H-SiC Wafers Studied by X-Ray Absorption and Raman Scattering". Materials Science Forum 717-720 (maio de 2012): 509–12. http://dx.doi.org/10.4028/www.scientific.net/msf.717-720.509.

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Synchrotron radiation X-ray absorption and UV 325 nm excitation Raman scattering- photoluminescence (PL) have been employed to investigate a series of 4H-SiC wafers, including bulk, epitaxial single or multiple layer structures by chemical vapor deposition. Significant results on the atomic bonding and PL-Raman properties are obtained from these comparative studies.

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G, Munkhbayar, e Otgonbaatar M. "Study of Exfoliated Molybdenum Disulfide (MoS2)". Физик сэтгүүл 20, n.º 438 (13 de março de 2022): 85–89. http://dx.doi.org/10.22353/physics.v20i438.132.

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In this study, We demonstrate mono and few layers MoS2 samples on the SiO2 (270nm)/Si substrate from bulk MoS2 crystal by micromechanical exfoliation technique. We also report that the Raman and PL intensity can be thermally modulated by annealing 1L, 2L and 7LMoS2 in a vacuum or air. We have systematically studied Atomic Force Microscopy, Raman and PL properties of mono and few layer MoS2 on the SiO2 (270nm)/Si substrate. First, we find that the number of layer values dependent the Raman and PL emission. First, Raman intensity area ratio of the MoS2 E12g, Ag1 and 2LA modes to that area of the Si substrate increased linear with increasing number of layers MoS2. Second, Normalized PL intensity area of the (A) peak decreased linear with increasing number of layers MoS2. The value of those graphs is a method to understand the number of layers the exfoliated MoS2. Third we found that some effects of the few layers MoS2after thermal annealed (vacuum and air 3000C for 40 min).

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Munkhbayar, G., S. Palleschi, F. Perrozzi, M. Nardone, J. Davaasambuu e L. Ottaviano. "A Study of Exfoliated Molybdenum Disulfide (MoS₂) Based on Raman and Photoluminescence Spectroscopy". Solid State Phenomena 271 (janeiro de 2018): 40–46. http://dx.doi.org/10.4028/www.scientific.net/ssp.271.40.

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In this study, We demonstrate mono and few layers MoS2 samples on the SiO2(270nm)/Si substrate from bulk MoS2 crystal by micromechanical exfoliation technique. We have systematically studied Atomic Force Microscopy, Raman and PL properties of mono and few layer MoS2 on the SiO2(270nm)/Si substrate. First, we find that the number of layer values dependent the Raman and PL emission. First, Raman intensity area ratio of the MoS2E12g, A1g and 2LA modes to that area of the Si substrate increased linear with increasing number of layers MoS2. Second, Normalized PL intensity area of the (A) peak decreased linear with increasing number of layers MoS2. The value of those graphs is a method to understand the number of layers the exfoliated MoS2.

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McCormick, Terri L., W. E. Jackson e R. J. Nemanich. "The characterization of strain, impurity content, and crush strength of synthetic diamond crystals". Journal of Materials Research 12, n.º 1 (janeiro de 1997): 253–63. http://dx.doi.org/10.1557/jmr.1997.0033.

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This study addresses the correlation of the macroscopic and microscopic characteristics of synthetic diamond crystals produced by high pressure, high temperature conditions. Microscopic properties were characterized using Raman spectroscopy, birefringence, and photoluminescence (PL). Macroscopic properties characterized included inclusion content and crush force. Raman measurements detected measurable stress shifts in only two samples. The PL measurements indicated an increased presence of the H3 center in areas of high strain. The absence of the H3 center and the presence of the N-V PL center was correlated to lower average crush force. A hierarchy has been developed that relates microscopic properties to average crush force.

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Ali, Wajid, Ye Liu, Ming Huang, Yunfei Xie e Ziwei Li. "Temperature-Dependent Phonon Scattering and Photoluminescence in Vertical MoS2/WSe2 Heterostructures". Nanomaterials 13, n.º 16 (16 de agosto de 2023): 2349. http://dx.doi.org/10.3390/nano13162349.

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Transition metal dichalcogenide (TMD) monolayers and their heterostructures have attracted considerable attention due to their distinct properties. In this work, we performed a systematic investigation of MoS2/WSe2 heterostructures, focusing on their temperature-dependent Raman and photoluminescence (PL) characteristics in the range of 79 to 473 K. Our Raman analysis revealed that both the longitudinal and transverse modes of the heterostructure exhibit linear shifts towards low frequencies with increasing temperatures. The peak position and intensity of PL spectra also showed pronounced temperature dependency. The activation energy of thermal-quenching-induced PL emissions was estimated as 61.5 meV and 82.6 meV for WSe2 and MoS2, respectively. Additionally, we observed that the spectral full width at half maximum (FWHM) of Raman and PL peaks increases as the temperature increases, and these broadenings can be attributed to the phonon interaction and the expansion of the heterostructure’s thermal coefficients. This work provides valuable insights into the interlayer coupling of van der Waals heterostructures, which is essential for understanding their potential applications in extreme temperatures.

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Munkhbayar, G., Erdenebat Nomin-Erdene e Jav Davaasambuu. "Thermal Annealing Effects on the Raman and Photoluminescence Properties of Mono and Few-Layer MoS<sub>2</sub> Films". Key Engineering Materials 943 (29 de março de 2023): 173–78. http://dx.doi.org/10.4028/p-lpbn39.

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In this study, we report that the thermal treatment effects on the Raman and photoluminescence (PL) spectra of mono and few-layer MoS2 films by annealing in the vacuum and air at 300°C, respectively. The MoS2 film samples were prepared on silicon substrate by exfoliating from a bulk MoS2 crystal with a micromechanical exfoliation. For characterization of structural properties of the MoS2 films and identification of the Raman active modes, Raman spectrometer equipped with a He-Ne laser source and an optical microscope has been used. The results show that the vacuum annealing 7L MoS2 decreases the Full Width at Half Maximum (FWHM) of the Raman active modes as E12g, A1g and the vacuum annealing 1L MoS2 increases the PL intensity and peak energy, for 60% and 13.3meV, respectively also air annealing bilayer MoS2 increased the PL intensity (IA) and peak energy (EA), respectively for 85% and 15.4 meV (300°C for 40 min). After thermal annealing (vacuum and air), we observe that the indirect bandgap of the few-layer MoS2 was changed.

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El Filali, Brahim, e Aaron I. Díaz Cano. "Size dependent optical properties in ZnO nanosheets". MRS Proceedings 1617 (2013): 95–100. http://dx.doi.org/10.1557/opl.2013.1170.

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ABSTRACTPhotoluminescence (PL), scanning electronic microscopy (SEM) and Raman scattering have been studied in crystalline ZnO nanosheets with different sizes after the thermal annealing at 400 °C for 2 hours in ambient air. ZnO nanosheets were created by the electrochemical (anodization) method using the variation of the etching durations with obtained ZnO nanosheet sizes from the range 40-360 nm. Earlier it was shown using the X ray diffraction (XRD) method that thermal annealing performed the ZnO oxidation and crystallization with the creation of the wurtzite crystal lattice. Four PL bands are revealed in PL spectra with the PL peaks at 1.60, 2.08, 2.50 and 3.10 eV. Size decreasing of ZnO nanosheets stimulates tremendous changes of ZnO optical parameters. It is shown that decreasing the ZnO nanosheet sizes is accompanied by the intensity increase of a set of Raman peaks and the surface defect related PL bands. The reasons of emission transformation and the nature of optical transitions have been discussed as well.

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Akilbekov, Abdirash, Daurzhan Kenbayev, Alma Dauletbekova, Elena Polisadova, Victor Yakovlev, Zhakyp Karipbayev, Alexey Shalaev, Edgars Elsts e Anatoli I. Popov. "The Effect of Fast Kr Ion Irradiation on the Optical Absorption, Luminescence, and Raman Spectra of BaFBr Crystals". Crystals 13, n.º 8 (16 de agosto de 2023): 1260. http://dx.doi.org/10.3390/cryst13081260.

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In this work, using photoluminescence (PL), optical absorption (OA), Raman spectroscopy (RS), and atomic force microscopy (AFM), the radiation damage of BaFBr crystals irradiated with 147 MeV 84Kr ions to fluences (1010–1014) cm2 was investigated. The manifestations of the oxygen impurity contained in the studied crystals on the effects associated with ion irradiation are also considered. In unirradiated crystals, the PL spectra exhibited bands related to the oxygen impurity. Moreover, it was found that quenching and a shift of the PL maximum occur, which is due to the fact that, with increasing dose, aggregation of defects occurs. Electronic and hole aggregate color centers appear mainly in the bromide sublattice. A detailed study of the Raman spectra and comparison with the corresponding data for KBr single crystals made it possible to reveal the corresponding manifestations of the Raman modes of complex Br3−-type hole centers.

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Cetinel, A., N. Artunç, G. Sahin e E. Tarhan. "Influence of applied current density on the nanostructural and light emitting properties of n-type porous silicon". International Journal of Modern Physics B 29, n.º 15 (25 de maio de 2015): 1550093. http://dx.doi.org/10.1142/s0217979215500939.

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Effects of current density on nanostructure and light emitting properties of porous silicon (PS) samples were investigated by field emission scanning electron microscope (FE-SEM), gravimetric method, Raman and photoluminescence (PL) spectroscopy. FE-SEM images have shown that below 60 mA/cm 2, macropore and mesopore arrays, exhibiting rough morphology, are formed together, whose pore diameter, pore depth and porosity are about 265–760 nm, 58–63 μ m and 44–61%, respectively. However, PS samples prepared above 60 mA/cm 2 display smooth and straight macropore arrays, with pore diameter ranging from 900–1250 nm, porosity of 61–80% and pore depth between 63–69 μ m . Raman analyses have shown that when the current density is increased from 10 mA/cm 2 to 100 mA/cm 2, Raman peaks of PS samples shift to lower wavenumbers by comparison to crystalline silicon (c-Si). The highest Raman peak shift is found to be 3.2 cm -1 for PS sample, prepared at 90 mA/cm 2, which has the smallest nanocrystallite size, about 5.2 nm. This sample also shows a pronounced PL, with the highest blue shifting, of about 12 nm. Nanocrystalline silicon, with the smallest nanocrystallite size, confirmed by our Raman analyses using microcrystal model (MCM), should be responsible for both the highest Raman peak shift and PL blue shift due to quantum confinement effect (QCE).

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Dalal, Aditya, Animesh Mandal, Shubhada Adhi e Kiran Adhi. "Study on integration of aluminum-doped zinc oxide (AZO) thin films with graphene oxide (GO)". International Journal of Modern Physics B 32, n.º 19 (18 de julho de 2018): 1840044. http://dx.doi.org/10.1142/s0217979218400441.

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Aluminum (0.5 at.%)-doped ZnO (AZO) thin films were deposited by pulsed laser deposition technique (PLD) in oxygen ambient of 10[Formula: see text] Torr. The deposited thin films were characterized by x-ray diffraction (XRD), photoluminescence (PL), Raman spectroscopy and uv–visible spectroscopy (UV–vis). Next, graphene oxide (GO) was synthesized by Hummers method and was characterized by XRD, UV–vis spectroscopy, Raman spectroscopy and transmission electron microscopy (TEM). Thereafter, GO solution was drop-casted on AZO thin films. These films were then characterized by Raman Spectroscopy, UV–vis spectroscopy and PL. Attempt is being made to comprehend the modifications in properties brought about by integration.

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ZENG, JUN, PENG TAO, CHANGEN XU, SEN WANG e JINCHENG XU. "A NOVEL METHOD FOR PREPARING ZnSnO NANOFIBERS". Modern Physics Letters B 23, n.º 23 (10 de setembro de 2009): 2755–61. http://dx.doi.org/10.1142/s0217984909020825.

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This paper reports that ZnSnO nanofibers (ZSNFs) were synthesized by thermal oxidation of ZnSn alloys. ZnSn alloys were prepared by cold press and sintering (powder metallurgy). The structure and optical properties were characterized by X-ray diffraction (XRD), micro-Raman scattering technology, field emission scanning electron microscopy (FESEM) and photoluminescence (PL) spectrum. The micro-Raman scattering spectra of ZSNFs show four Raman peaks at 574, 1156, 1729 and 2330 cm-1. The diameter and length of ZSNFs are about 50 nm and 60 μm, respectively. The room temperature PL spectra of ZSNFs shows the near-band-edge emission at ~391 nm and a broad green emission at ~493 nm.

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Feng, Zhe Chuan, Jiamin Liu, Deng Xie, Manika Tun Nafisa, Chuanwei Zhang, Lingyu Wan, Beibei Jiang et al. "Optical, Structural, and Synchrotron X-ray Absorption Studies for GaN Thin Films Grown on Si by Molecular Beam Epitaxy". Materials 17, n.º 12 (14 de junho de 2024): 2921. http://dx.doi.org/10.3390/ma17122921.

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GaN on Si plays an important role in the integration and promotion of GaN-based wide-gap materials with Si-based integrated circuits (IC) technology. A series of GaN film materials were grown on Si (111) substrate using a unique plasma assistant molecular beam epitaxy (PA-MBE) technology and investigated using multiple characterization techniques of Nomarski microscopy (NM), high-resolution X-ray diffraction (HR-XRD), variable angular spectroscopic ellipsometry (VASE), Raman scattering, photoluminescence (PL), and synchrotron radiation (SR) near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. NM confirmed crack-free wurtzite (w-) GaN thin films in a large range of 180–1500 nm. XRD identified the w- single crystalline structure for these GaN films with the orientation along the c-axis in the normal growth direction. An optimized 700 °C growth temperature, plus other corresponding parameters, was obtained for the PA-MBE growth of GaN on Si, exhibiting strong PL emission, narrow/strong Raman phonon modes, XRD w-GaN peaks, and high crystalline perfection. VASE studies identified this set of MBE-grown GaN/Si as having very low Urbach energy of about 18 meV. UV (325 nm)-excited Raman spectra of GaN/Si samples exhibited the GaN E2(low) and E2(high) phonon modes clearly without Raman features from the Si substrate, overcoming the difficulties from visible (532 nm) Raman measurements with strong Si Raman features overwhelming the GaN signals. The combined UV excitation Raman–PL spectra revealed multiple LO phonons spread over the GaN fundamental band edge emission PL band due to the outgoing resonance effect. Calculation of the UV Raman spectra determined the carrier concentrations with excellent values. Angular-dependent NEXAFS on Ga K-edge revealed the significant anisotropy of the conduction band of w-GaN and identified the NEXAFS resonances corresponding to different final states in the hexagonal GaN films on Si. Comparative GaN material properties are investigated in depth.

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Коншина, Е. А., Д. П. Щербинин e M. M. Aboud. "Усиление фотолюминесценции и комбинационного рассеяния в гибридных тонкопленочных структурах a-C:H с наночастицами серебра". Журнал технической физики 128, n.º 3 (2020): 422. http://dx.doi.org/10.21883/os.2020.03.49070.314-19.

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n this work, we studied changes in the spectra of optical density, photoluminescence (PL) and Raman spectra of hybrid thin-film structures based on a-C: H and granular silver films before and after annealing of samples at 200 ° C. The hypsochromic shift of the main plasmon peak, the formation of double resonance spectra, and an increase in the band intensity were observed after annealing of samples with the gravimetric Ag film thickness of 10 nm. The influence of both the morphology of the nanostructure of Ag films and the features of the electronic structure of a-C: H films were observed on the plasmon enhancement of the PL and Raman spectra. For samples based on a-C:H with an optical gap Eg = 0.4 eV, a more effective PL enhancement was observed after annealing of the samples. At the same time, in the samples with Eg = 2.7 eV, the PL intensity practically did not change, remaining higher. The amplification of resonant Raman scattering was selective. It was associated with scattering by polycyclic aromatic groups predominant in the structure of the a-C: H film with a narrower optical gap.

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Mahmood, Ainorkhilah, Zainuriah Hassan, Naser Mahmoud Ahmed, Fong Kwong Yam, Lee Siang Chuah, Marina Mokhtar, Nurul Huda Mohd Noor e Siti Azlina Rosli. "Structural and Optical Studies of Undoped Porous GaN Prepared by Pt-Assisted Electroless Etching". Materials Science Forum 846 (março de 2016): 358–65. http://dx.doi.org/10.4028/www.scientific.net/msf.846.358.

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Porous GaN structures were formed from crystalline GaN on conducting AL2O3 substrate using Pt-assisted electroless etching in HF: CH3OH: H2O2 = 1:4:4 under illumination of 500 W UV lamp. Scanning electron microscope (SEM) photoluminescence (PL) and Raman spectra measurements evidenced important features of the pore morphology, nanostructures and optical properties. According to the SEM micrographs, the three-dimensional ridge structure appears with the formation of porous material between the ridges. The porous layer exhibited a substantial PL intensity enhancement with red-shifted band-edge PL peaks associated with the relaxation of compressive stress. The shift of E2(high) to the lower frequency in Raman spectra of the porous GaN films further confirms such a stress relaxation.

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Le, Kim Cuong, Saga Bergqvist, Jonatan Henriksson e Per-Erik Bengtsson. "Observation of Structural Changes during Oxidation of Black and Brown Soot Using Raman Spectroscopy". C 10, n.º 2 (15 de abril de 2024): 38. http://dx.doi.org/10.3390/c10020038.

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In this study, Raman spectroscopy has been used to evaluate the evolution of the structural modification of soot during oxidation processes at various preset temperatures up to 700 °C. Two types of well-characterized mini-CAST soot, representing black soot and brown soot, were examined. The major difference between the signals from the two types of soot was the higher photoluminescence (PL) signal for brown soot compared with black soot, in addition to some variations in the first-order Raman signatures such as oxygenated groups and their evolutions during thermal oxidation treatment. An interesting observation was the increase in the PL signal for brown soot at increasing temperatures up to 150 °C probably due to the formation of small oxidized polycyclic aromatic hydrocarbon and defects, followed by a decrease in the PL signal until the soot was fully oxidized. We also demonstrated that brown soot is prone to oxidation in ex situ measurements, a factor that should be considered in the Raman analysis of soot.

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THANGADURAI, P., S. RAMASAMY e R. KESAVAMOORTHY. "HIGH FREQUENCY RAMAN MODES IN NANOCRYSTALLINE LEAD (II) FLUORIDE". International Journal of Nanoscience 05, n.º 04n05 (agosto de 2006): 585–91. http://dx.doi.org/10.1142/s0219581x06004838.

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Nanocrystalline PbF 2 was prepared by inert gas condensation technique. Structural studies using X-ray diffraction showed that as-prepared and annealed samples contained both orthorhombic and cubic phases of PbF 2. The annealed samples contain dominantly the cubic phase. For the first time Raman scattering and PL experiments were carried out on these nano- PbF 2. In addition to regular lattice vibrational modes such as T2g for cubic phase and Ag and B1g for orthorhombic phases, a few new Raman modes have been observed at high frequencies. PL studies confirmed that the new Raman modes are due to the presence of electronic centers. The regular modes agree well with the theoretically calculated values and previously reported experimental values.

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Kumar, Pushpendra. "Effect of Silicon Crystal Size on Photoluminescence Appearance in Porous Silicon". ISRN Nanotechnology 2011 (7 de julho de 2011): 1–6. http://dx.doi.org/10.5402/2011/163168.

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The photoluminescence (PL) study in porous silicon (PS) with decreasing Si crystallites size among the pores was reported. The PL appearance is attributed to electronic confinement in columnar-like (or dotlike) structures of porous silicon. Three different pore diameter PS samples were prepared by electrochemical etching in HF-based solutions. Changes in porous silicon and Si crystallite size were studied by observing an asymmetric broadening and shift of the optical silicon phonons in Raman scattering. Fourier transform infrared spectroscopy (FTIR) was used to study the role of siloxene or other molecular species, for example, in the luminescence mechanism. This mechanism was further studied by thermal annealing of PS at different temperatures. The PL of PS sample annealed at ≥300°C for 1 hr shows that trap electronic states appear in the energy gap of the smaller nano-crystal when Si–O–Si bonds are formed. From the observation of PL, Raman, and FTIR spectroscopy, the origin of PL in terms of intrinsic and extrinsic properties of nanocrystalline silicon was discussed.

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Volodin, Vladimir A., E. B. Gorokhov, D. V. Marin, A. G. Cherkov, Anton K. Gutakovskii e M. D. Efremov. "Ge Nanoclusters in GeO₂: Synthesis and Optical Properties". Solid State Phenomena 108-109 (dezembro de 2005): 83–90. http://dx.doi.org/10.4028/www.scientific.net/ssp.108-109.83.

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Ge nanocrystals (NCs) in GeO2 films obtained with the use of two methods were studied. The first method is a film deposition from supersaturated GeO vapor with subsequent dissociation of metastable GeO on heterophase system Ge:GeO2. The second method is growth of anomalous thick native germanium oxide layers with chemical composition GeOx(H2O) during catalytically enhanced Ge oxidation. The obtained films were studied with the use of photoluminescence (PL), Raman scattering spectroscopy, high-resolution electron microscopy (HREM). Strong PL signals were detected in GeO2 films with Ge-NCs at room temperature. “Blue-shift” of PL maximum was observed with reducing of Ge excess in anomalous thick native germanium oxide films. Also a correlation between reducing of the NC sizes (estimated from position of Raman peaks) and PL “blue-shift” was observed. The Ge NCs presence was confirmed by HREM data. The optical gap in Ge-NCs was calculated with taking into account quantum size effects and compared with the position of the experimental PL peaks. It can be concluded that a Ge-NC in GeO2 matrix is a quantum dot of type I.

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КАЛАЧЕВ, И. В., И. А. МИЛЁХИН, Е. А. ЕМЕЛЬЯНОВ, В. В. ПРЕОБРАЖЕНСКИЙ, В. С. ТУМАШЕВ, А. Г. МИЛЁХИН e А. В. ЛАТЫШЕВ. "RAMAN SCATTERING AND PHOTOLUMINESCENCE OF GAAS NANOWIRES". Автометрия 59, n.º 6 (29 de dezembro de 2023): 3–11. http://dx.doi.org/10.15372/aut20230601.

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Представлены экспериментальные данные по изучению фононных и оптических свойств нанопроволок GaAs ориентации (111), расположенных на золотой подложке с помощью методов спектроскопии комбинационного рассеяния света (КРС) и фотолюминесценции (ФЛ). Структурные параметры нанопроволок были определены методами атомно-силовой (АСМ) и сканирующей электронной микроскопии (СЭМ). В спектрах микроКРС и микроФЛ отдельной нанопроволоки GaAs наблюдаются моды оптических фононов GaAs и их обертонов, вплоть до третьего порядка, и полоса экситонной фотолюминесценции. В спектрах микроФЛ проявляется анизотропия интенсивности ФЛ в нанопроволоках, причём максимальный/минимальный сигнал наблюдается при направлении вектора поляризации вдоль/поперёк проволоки. Выполнено картирование наноФЛ отдельной нанопроволоки GaAs с пространственным разрешением 20 нм, что существенно меньше дифракционного предела. При переходе к нанометровым масштабам обнаружено плазмонное усиление сигнала ближнепольной экситонной наноФЛ, обусловленное металлизированной АСМ-иглой. The paper presents experimental data on phonon and optical properties of (111)-oriented GaAs nanowires on a gold substrate studied by means of Raman scattering and photoluminescence (PL). The structural parameters of the nanowires are determined by atomic force and scanning electron microscopy (AFM and SEM, respectively). In the micro-Raman and micro-PL spectra of a single GaAs nanowire, phonon modes of GaAs and their overtones up to the third order and an exciton photoluminescence band are observed. In the micro-PL spectra, anisotropy of the PL intensity in nanowires is revealed, and the maximum/minimum signal is observed when the polarization vector is directed along/across the wire. Nano-PL maps of a single GaAs nanowire with a spatial resolution of 20 nm are obtained, which is significantly smaller than the diffraction limit. Plasmon enhancement of the near-field exciton nano-PL in the vicinity of the metallized tip of the AFM microscope is detected.

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Shu, Xiang Ping, Cheng Chen, Yi Ting He, Zhi Ren Qiu, Dong Sing Wuu e Zhe Chuan Feng. "Optical Probe in MgZnO Alloys with Varied Mg Ratios by Metalorganic Chemical Vapor Deposition". Advanced Materials Research 746 (agosto de 2013): 406–10. http://dx.doi.org/10.4028/www.scientific.net/amr.746.406.

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We present a study on five MgxZn1-xO samples with varied x (x = 0, 0.01, 0.06, 0.10 and 0.14), grown on sapphire substrate by Metalorganic Chemical Vapor Deposition (MOCVD). Combined photoluminescence (PL) and Raman scattering studies were carried out over a temperature range of 80K-470K, under the excitation of UV 325 nm. Temperature dependence of the PL for MgZnO with x = 0, 0.01 and 0.06 are shown. The resonance Raman longitudinal optical (LO) multiple modes are exhibited for MgZnO with x = 0.06, 0.10 and 0.14 over all temperature range. Raman shifts exhibit a quadratic dependence on temperature in the measured temperature range. These dependences can be calculated, based upon a model involving three-and four-phonon coupling. We attribute both the thermal expansion and four-phonon terms in the four-phonon anharmonic processes to describe the change of Raman shift with temperature.

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31

Tingzon, Philippe Martin, Horace Andrew Husay, Neil Irvin Cabello, John Jairus Eslit, Kevin Cook, Jonas Kapraun, Armando Somintac et al. "Indirect stress and air-cavity displacement measurement of MEMS tunable VCSELs via micro-Raman and micro-photoluminescence spectroscopy". Semiconductor Science and Technology 37, n.º 3 (28 de janeiro de 2022): 035013. http://dx.doi.org/10.1088/1361-6641/ac4abc.

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Abstract We employ micro-Raman spectroscopy to optically infer the stress experienced by the legs of a bridge-type microelectromechanical systems (MEMS) used in high contrast gratings tunable vertical cavity surface emitting lasers (VCSELs). We then employ micro-photoluminescence (PL) spectroscopy to indirectly measure the air cavity displacement of the same MEMS structure. Results from micro-Raman showed that electrostatically actuating the MEMS with a DC bias configuration yields increasing residual stress on the endpoints of the MEMS with values reaching up to 0.8 GPa. We simulated a finite element model via Comsol Multiphysics which agrees with the trend we observed based on our micro-Raman data. Our micro-PL spectroscopy showed that change in the air cavity of the VCSEL structure resulted in a change in the full width of the PL peak emitted by the layer consisting of four pairs of distributed Bragg reflectors. The change in the full width of the PL peak was due to the change in the optical cavity induced by displacing the MEMS via externally applied bias and agrees with our transfer matrix convolution simulation. These optical characterization tools can be used for failure analysis, MEMS design improvements, and monitoring of MEMS tunable VCSEL devices for mass production and manufacturing.

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Lu, Xin Zhen, Yan Yan Chang, Ming Tao Xu e Bo Peng. "Microstructures of ZnO Electrospun Nanofibers on AZO Glass". Advanced Materials Research 936 (junho de 2014): 439–43. http://dx.doi.org/10.4028/www.scientific.net/amr.936.439.

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ZnO electrospun nanofibers were considered to be potential novel materials in applications of photovoltaic devices and sensors. AZO glass was usually used in those devices as transparent electrodes. ZnO nanofibers on AZO glass were synthesized by electrospinning and calcination process. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and photoluminescence (PL) spectrum was employed to investigate the morphology, structure and optical performance of ZnO nanofibers. Network structure composed of sheet ZnO was observed. Raman spectra and PL spectrum indicated the existence of defect states in the ZnO nanofibers.

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Батаев, М. Н., М. С. Кузнецова, Д. В. Панькин, М. Б. Смирнов, С. Ю. Вербин, И. В. Игнатьев, И. А. Елисеев, В. Ю. Давыдов, А. Н. Смирнов e Е. В. Колобкова. "Электрон-фононное взаимодействие в нанокристаллах перовскитов во фторфосфатном стекле". Физика и техника полупроводников 57, n.º 5 (2023): 313. http://dx.doi.org/10.21883/ftp.2023.05.56196.14k.

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The photoluminescence (PL) spectra of CsPbBr3 perovskite nanocrystals grown in a fluorophosphate glass matrix exhibit phonon replicas of the exciton line. The dependence of intensity of the phonon sidebands are simulated taking into account the difference in the curvature of the excited and ground adiabatic potentials. The Raman spectra of CsPbBr3 nanocrystals are measured. Calculations based on the density functional theory is performed to obtain the spectrum of phonon states of these crystals in the orthorhombic phase. The phonon frequencies observed in the PL and Raman spectra are compared with the calculation results.

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Daescu, Monica, Adelina Matea, Catalin Negrila, Constantin Serbschi, Alina C. Ion e Mihaela Baibarac. "Photoluminescence as a Valuable Tool in the Optical Characterization of Acetaminophen and the Monitoring of Its Photodegradation Reactions". Molecules 25, n.º 19 (7 de outubro de 2020): 4571. http://dx.doi.org/10.3390/molecules25194571.

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In this work, new evidence for the photodegradation reactions of acetaminophen (AC) is reported by photoluminescence (PL), Raman scattering and FTIR spectroscopy. Under excitation wavelength of 320 nm, AC shows a PL band in the spectral range of 340–550 nm, whose intensity decreases by exposure to UV light. The chemical interaction of AC with the NaOH solutions, having the concentration ranging between 0.001 and 0.3 M, induces a gradual enhancement of the photoluminescence excitation (PLE) and PL spectra, when the exposure time of samples at the UV light increases until 140 min, as a result of the formation of p-aminophenol and sodium acetate. This behavior is not influenced by the excipients or other active compounds in pharmaceutical products as demonstrated by PLE and PL studies. Experimental arguments for the obtaining of p-aminophenol and sodium acetate, when AC has interacted with NaOH, are shown by Raman scattering and FTIR spectroscopy.

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Chen, Hong, W. Z. Shen e W. S. Wei. "Photoluminescence and Raman Studies on Boron-Doped Nanocrystalline Si:H Thin Films". Solid State Phenomena 121-123 (março de 2007): 933–38. http://dx.doi.org/10.4028/www.scientific.net/ssp.121-123.933.

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We report on room-temperature visible photoluminescence (PL) of B-doped hydrogenated nanocrystalline Si (nc-Si:H) thin films grown by plasma enhanced chemical vapor deposition. It is found that with increasing the boron doing ratio, the PL peak energy blue shifts while the PL intensity first increases and then decreases. The PL profiles can be well reproduced by using the model of Islam and Kumar [J. Appl. Phys. 93, 1753 (2003)] which incorporates the effects of quantum confinement and localized surface states, together with a log-normal rather than normal crystallite size distribution. The yielded microstructural information is in good agreement with the Raman analysis, revealing that B doping tends to reduce the size of Si nanocrystals and the PL intensity is jointly determined by the amount of amorphous Si:H phase and the fraction of B-doped Si nanocrystals. These results also provide implications to realize control of PL properties of nc-Si:H by B doping under optimized growth conditions.

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WEI, XIAN QI, e BAO-YUAN MAN. "DEPENDENCE OF TEMPERATURE ON THE STRUCTURE AND PHOTOLUMINESCENCE OF ZnO THIN FILMS FABRICATED BY PULSED Nd:YAG LASER DEPOSITION ON SAPPHIRE SUBSTRATES". International Journal of Modern Physics B 21, n.º 11 (30 de abril de 2007): 1851–60. http://dx.doi.org/10.1142/s0217979207037090.

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Zinc oxide ( ZnO ) thin films were grown on sapphire substrates at different deposition temperatures by pulsed laser deposition (PLD). The structure, composition and optical properties of deposited thin films have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Raman and photoluminescence (PL) spectra. The results show that the ZnO thin films deposited at 500°C have the best crystalline quality with hexagonal structure, surface morphology and stoichiometric composition. The PL spectrum reveals that the sample possesses the strongest ultraviolet (UV) emission at 370 nm and the weakest blue emission at 459 nm under this condition. Raman spectra and weak blue emission of PL spectra show that very few oxygen vacancies exist in the ZnO thin films.

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Kumar, Shiv, Kandasami Asokan, Ranjan Kumar Singh, Sandip Chatterjee, Dinakar Kanjilal e Anup Kumar Ghosh. "Investigations on structural and optical properties of ZnO and ZnO:Co nanoparticles under dense electronic excitations". RSC Adv. 4, n.º 107 (2014): 62123–31. http://dx.doi.org/10.1039/c4ra09937k.

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Matthews, Samantha, Chuan Zhao, Hao Zeng e Frank V. Bright. "Effects of Acetone Vapor on the Exciton Band Photoluminescence Emission from Single- and Few-Layer WS2 on Template-Stripped Gold". Sensors 19, n.º 8 (23 de abril de 2019): 1913. http://dx.doi.org/10.3390/s19081913.

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Two-dimensional (2D) materials are being used widely for chemical sensing applications due to their large surface-to-volume ratio and photoluminescence (PL) emission and emission exciton band tunability. To better understand how the analyte affects the PL response for a model 2D platform, we used atomic force microscopy (AFM) and co-localized photoluminescence (PL) and Raman mapping to characterize tungsten disulfide (WS2) flakes on template-stripped gold (TSG) under acetone challenge. We determined the PL-based response from single- and few-layer WS2 arises from three excitons (neutral, A0; biexciton, AA; and the trion, A−). The A0 exciton PL emission is the most strongly quenched by acetone whereas the A− PL emission exhibits an enhancement. We find the PL behavior is also WS2 layer number dependent.

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Jia, X., Z. Lin, T. Zhang, B. Puthen-Veettil, T. Yang, K. Nomoto, J. Ding, G. Conibeer e I. Perez-Wurfl. "Accurate analysis of the size distribution and crystallinity of boron doped Si nanocrystals via Raman and PL spectra". RSC Advances 7, n.º 54 (2017): 34244–50. http://dx.doi.org/10.1039/c7ra04472k.

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Litrico, Grazia, Nicolò Piluso e Francesco La Via. "Detection of Crystallographic Defects in 3C-SiC by Micro-Raman and Micro-PL Analysis". Materials Science Forum 897 (maio de 2017): 303–6. http://dx.doi.org/10.4028/www.scientific.net/msf.897.303.

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A new technique with micro-Raman and micro-PL analysis is proposed to detect defects in 3C-SiC epitaxial films. The high-power of an above band-gap laser is used to increase locally the free carriers density in un-doped epitaxial material (n < 1016 cm-3). The electronic plasma couples with the longitudinal optical (LO) Raman mode determining the so-called LOPC effect. The Raman shift of the LO phonon-plasmon-coupled mode (LOPC) changes as the free carriers density is modified. Crystallographic defects induce a modification of the free carriers density determining a change in the Raman shift of LO mode and in the PL emission from the 3C-SiC gap. Thus we suppose that the results observed are connected to crystallographic defects and we propose this technique as a methodology to analyze extended defects in 3C-SiC material because a detailed study of defects in 3C-SiC has not yet been performed.

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Гамбарян, М. П., Г. К. Кривякин, С. Г. Черкова, M. Stoffel, H. Rinnert, M. Vergnat e В. А. Володин. "Проявление квантоворазмерных эффектов в нанокристаллах и аморфных нанокластерах германия в плeнках GeSixOy". Физика твердого тела 62, n.º 3 (2020): 434. http://dx.doi.org/10.21883/ftt.2020.03.49010.600.

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The non-stoichiometric germanosilicate films of two types GeOx[SiO](1-x) and GeOx [SiO2](1-x) were obtained by high-vacuum evaporation of GeO2 and either SiO or SiO2 powders and sputtering on a cold Si (001) substrate. The as-deposited and annealed (550 and 650 oC, 1 hour) samples were studied by IR spectrocopy, electron microscopy, Raman spectroscopy and photoluminescence (PL). From an analysis of Raman spectra, it was found that the as-deposited GeO[SiO2] film did not contain germanium clusters, and the as-deposited GeO[SiO] film contained amorphous germanium clusters; according to electron microscopy, it’s size was ~3 nm. According to IR spectroscopy, the films contained Si-O, Ge-O, and Si-O-Ge bonds. After annealing at 550 °C, amorphous germanium clusters were detected in both films, and after annealing at 650 °C, germanium nanocrystals were observed. A wide PL band with a maximum of 1050 nm was found in the as-deposited films at low temperatures. PL is probably due to defects, presumably oxygen vacancies and excess germanium atoms. Annealing causes a transformation of both film structure and PL spectra. In films containing germanium nanoclusters, PL is observed with a maximum of 1500–1600 nm. In this case, the PL signal from defects decreased. The temperature dependence of the intensity of the PL peaks was studied; it decreased with increasing temperature but remained at temperatures up to 200 K. The contribution to the PL from germanium nanocrystals formed during annealing is discussed.

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Hari, Parameswar, Jared Seay, Kevin Farmer e Ken Roberts. "Cobalt Doped ZnO Nanorods Fabricated by Chemical Bath Deposition Technique". Advances in Science and Technology 77 (setembro de 2012): 280–84. http://dx.doi.org/10.4028/www.scientific.net/ast.77.280.

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ZnO nanorods are currently studied for variety optoelectronic applications. Typically, thin film and bulk ZnO show a strong light absorption in the ultra violet (UV) range. For devices that operate in the visible and infrared range such as optoelectronic sensors and photovoltaic cells, it is necessary to modify the absorption profile from UV to higher wavelengths in the visible region. In this study we investigate optical absorption of ZnO nanorods doped with cobalt using a modified chemical bath deposition technique. The light absorption properties of Cobalt doped ZnO nanorods were studied using Photoluminescence (PL) and Raman Spectroscopy. For doping of Cobalt ranging from 3 to 10 percentage of the total weight, the PL intensity shows a suppression of the prominent UV peak at 383 nm with increase in doping concentration. This reduction in PL intensity at 383 nm is accompanied by an increase in the PL intensity at 429 nm and 469 nm. We will discuss details of ZnO-Cobalt structures using Raman spectroscopy on cobalt doped ZnO nanorod samples of 1 -20% doping concentration.

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Chen, Guangxu, Sibin Chen, Zewen Lin, Rui Huang e Yanqing Guo. "Enhanced Red Emission from Amorphous Silicon Carbide Films via Nitrogen Doping". Micromachines 13, n.º 12 (22 de novembro de 2022): 2043. http://dx.doi.org/10.3390/mi13122043.

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The enhanced red photoluminescence (PL) from Si-rich amorphous silicon carbide (a-SiCx) films was analyzed in this study using nitrogen doping. The increase in nitrogen doping concentration in films results in the significant enhancement of PL intensity by more than three times. The structure and bonding configuration of films were investigated using Raman and Fourier transform infrared absorption spectroscopies, respectively. The PL and analysis results of bonding configurations of films suggested that the enhancement of red PL is mainly caused by the reduction in nonradiative recombination centers as a result of the weak Si–Si bonds substituted by Si–N bonds.

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Eremin, Timofei, Valentina Eremina, Yuri Svirko e Petr Obraztsov. "Over Two-Fold Photoluminescence Enhancement from Single-Walled Carbon Nanotubes Induced by Oxygen Doping". Nanomaterials 13, n.º 9 (6 de maio de 2023): 1561. http://dx.doi.org/10.3390/nano13091561.

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Covalent functionalization of single-walled carbon nanotubes (SWCNTs) is a promising way to improve their photoluminescent (PL) brightness and thus make them applicable as a base material for infrared light emitters. We report as high as over two-fold enhancement of the SWCNT PL brightness by using oxygen doping via the UV photodissociation of hypochlorite ions. By analyzing the temporal evolution of the PL and Raman spectra of SWCNTs in the course of the doping process, we conclude that the enhancement of SWCNTs PL brightness depends on the homogeneity of induced quantum defects distribution over the SWCNT surface.

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CETINEL, A., M. OZDOGAN, G. UTLU, N. ARTUNC, G. SAHIN e E. TARHAN. "THE EFFECT OF THICKNESS OF SILVER THIN FILM ON STRUCTURAL AND OPTICAL PROPERTIES OF POROUS SILICON". Surface Review and Letters 24, n.º 06 (9 de novembro de 2016): 1750074. http://dx.doi.org/10.1142/s0218625x17500743.

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In this study, porous silicon (PS) samples were prepared on [Formula: see text]-type silicon (100) wafers by electrochemical etching method, varying the current density from 20 to 100[Formula: see text]mA/cm2 and keeping constant HF concentration (10%) and etching time of 15[Formula: see text]min. Then, Ag thin films, which have 10, 50 and 100[Formula: see text]nm film thicknesses, were deposited on PS layers by using thermal evaporation to investigate the influence of Ag film thickness on structural and optical properties of PS. The structural and optical properties of PS and Ag deposited PS layers have been investigated by XRD, FE-SEM, Raman and photoluminescence (PL) spectroscopy. FE-SEM XRD and Raman analyzes indicate that average pore size and porosity of PS layers increase with the increasing current density. Further, Ag nanoparticles have embedded in pore channel. PL measurement reveals that higher porosity of PS would be better to form the Ag–PS nano-composite material leading to stronger PL band. The PL spectra of PS and Ag–PS samples indicate that PL bands show blue shift with increasing current density and film thickness. Consequently, it has been found that the structural and optical properties of PS depend on current density and Ag film thickness individually.

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Matthews, Samantha, e Frank V. Bright. "Interplay Between Silicon Nanocrystal Size and Local Environment Within Porous Silicon on the Analyte-Dependent Photoluminescence Response". Applied Spectroscopy 73, n.º 10 (25 de julho de 2019): 1218–27. http://dx.doi.org/10.1177/0003702819864606.

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Porous silicon (pSi) exhibits strong photoluminescence (PL) and its PL is often exploited for chemical sensor development. However, the sensor response is not uniform across a pSi specimen. We use co-localized confocal PL and Raman scattering mapping to establish a relationship between the analyte-induced PL response and the silicon nanocrystallite size, size distribution, and amorphous silicon (aSi) contribution across a pSi specimen. Using toluene as a model analyte, high analyte-induced PL response is associated with areas within the specimen that have (i) low aSi content, (ii) silicon nanocrystallites having diameters between 2 and 5 nm, and (iii) silicon nanocrystallites that exhibit a narrow size distributions (≤1% relative standard deviation).

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Ma, Ying, Zhili Qiu, Xiaoqin Deng, Ting Ding, Huihuang Li, Taijin Lu, Zhonghua Song, Wenfang Zhu e Jinlin Wu. "Chinese Colorless HPHT Synthetic Diamond Inclusion Features and Identification". Crystals 12, n.º 9 (6 de setembro de 2022): 1266. http://dx.doi.org/10.3390/cryst12091266.

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Chinese HPHT diamonds have improved dramatically in recent years. However, this brings a challenge in identifying type IIa colorless diamonds. In this study, eleven HPHT and three natural, colorless, gem-quality IIa diamonds were analyzed using magnified observation, Raman, PL and chemical element analysis. The results show that only HPHT samples possessed kite-like inclusions and lichenoid inclusions, as verified by their complex Raman spectra (100–750 cm−1). Through PL mapping, HPHT and natural IIa diamonds were distinguished by their growth environments, which were reflected by PL peaks at 503, 505, 575, 637, 693, 694 and 737 nm. The chemical components of HPHT IIa diamond carbide inclusions are mainly Fe, Co, Ni and Mn, but those of Natural IIa are mainly Fe and Ni. As a result, the chemical components can be used to distinguish a natural colorless IIa diamond from a synthetic diamond.

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Гонгальский, М. Б., У. А. Цурикова, К. А. Гончар, Г. З. Гвинджилия e Л. А. Осминкина. "Квантово-размерный эффект в кремниевых нанокристаллах при их растворении в модельных биологических жидкостях". Физика и техника полупроводников 55, n.º 1 (2021): 43. http://dx.doi.org/10.21883/ftp.2021.01.50386.9517.

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In present work, we studied the mechanisms of dissolution of porous silicon nanoparticles (PSi NPs) during their incubation in model liquids, i.e. water and phosphate buffered saline (PBS) at 37 С. The methods of transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, and Raman spectroscopy were used. According to TEM images, PSi NPs consist of silicon nanocrystals (nc-Si) 2-10 nm in size and pores. It is shown that incubation of PSi NPs in water leads to enhancement of their PL, accompanied by a slight decrease in the size of nc-Si, which is associated with the passivation of defects and stabilization of the oxide shell of nanocrystals. During incubation in PBS, a significant quenching of PL and disappearance Raman signal of the PSi NPs took place. That indicates rapid dissolution of PSi NPs. We presented phenomenological model describing how quantum-confinement effect affects properties of nc-Si during their dissolution.

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Koutu, Vaibhav, Lokesh Shastri e M. M. Malik. "Effect of NaOH concentration on optical properties of zinc oxide nanoparticles". Materials Science-Poland 34, n.º 4 (1 de dezembro de 2016): 819–27. http://dx.doi.org/10.1515/msp-2016-0119.

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AbstractIn the present work, powder zinc oxide samples were prepared by varying NaOH concentration (0.1 M – 0.4 M) using wet-chemical co-precipitation method. As-synthesized ZnO was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence (PL) and Raman spectroscopy. Formation of hexagonal wurtzite structure of the ZnO samples has been revealed from XRD studies. This study further suggests reduction in crystallite size from 40 nm to 23 nm with an increase in NaOH concentration which is confirmed by FESEM. PL and Raman spectroscopy studies of these samples show significant peak shift towards the higher and lower energy respectively, with maximum PL emission between 400 nm and 470 nm region of the visible spectrum. Noticeable inverse relationship between optical properties of ZnO nanoparticles and NaOH concentration may be attributed to the rapid nucleation during the synthesis process. With these remarkable properties, ZnO nanoparticles may find applications in nanoelectronic devices, sensors, nanomedicine, GATE dielectrics, photovoltaic devices, etc.

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Liu, Qianqian, Xiaoxuan Chen, Hongliang Li, Yanqing Guo, Jie Song, Wenxing Zhang, Chao Song, Rui Huang e Zewen Lin. "Effect of Thermal Annealing on the Photoluminescence of Dense Si Nanodots Embedded in Amorphous Silicon Nitride Films". Micromachines 12, n.º 4 (25 de março de 2021): 354. http://dx.doi.org/10.3390/mi12040354.

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Luminescent amorphous silicon nitride-containing dense Si nanodots were prepared by using very-high-frequency plasma-enhanced chemical vapor deposition at 250 °C. The influence of thermal annealing on photoluminescence (PL) was studied. Compared with the pristine film, thermal annealing at 1000 °C gave rise to a significant enhancement by more than twofold in terms of PL intensity. The PL featured a nanosecond recombination dynamic. The PL peak position was independent of the excitation wavelength and measured temperatures. By combining the Raman spectra and infrared absorption spectra analyses, the enhanced PL was suggested to be from the increased density of radiative centers related to the Si dangling bonds (K0) and N4+ or N20 as a result of bonding configuration reconstruction.

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