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Influence of bath temperatures on physical and electrical properties of potentiostatically deposited Cu2O thin films for heterojunction solar cell applications
摘要： In the present work, the influence of bath temperatures on structural, morphological, vibrational, optical, electrical and photo response properties of the electrochemically deposited cuprous oxide (Cu2O) thin films on fluorine doped tin oxide substrate is extensively investigated with the help of X-ray diffraction (XRD), scanning electron microscopy (SEM), Micro Raman spectroscopy, photo luminescence (PL) spectroscopy, UV–visible spectroscopy, LCR measurement, Keithley 4200 semiconductor characterization system respectively. XRD patterns reveal that the deposited Cu2O films have cubic structure grown along the preferential (111) orientation and the film deposited at 40 °C shows better crystalline nature when compared at 55 and 70 °C. The micro structural properties of films such as crystallite size (D), dislocation density (δ), micro strain (ε) and stacking fault probability (α) were calculated and discussed in detail. SEM displays a well-defined three side pyramid shaped morphology for the film deposited at 40 °C. Micro Raman and PL spectra reveal the film deposited at 40 °C by being better crystalline at a higher acceptor concentration. UV–Visible study shows that the optical energy band gap increases from 2.05 to 2.17 eV with an increase in bath temperature from 40 to 70 °C. The frequency-temperature dependence of impedance analysis shows a higher electrical conductivity for a film deposited at 40 °C compared to other bath temperatures. I-V measurement illustrates a good photoconductivity response for Cu2O thin film deposited at 40 °C compared to films deposited at 55 and 70 °C.
关键词： Micro Raman spectroscopy,X-ray diffraction,Photoconductivity,Cuprous oxide,Pyramid shape
更新于2025-11-19 16:46:39
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Raman analysis of strained graphene grown on dewetted cobalt
摘要： Graphene grows onto cobalt by means of diffusion of carbon atoms during the isothermal stage of exposure to hydrocarbon precursor, followed by precipitation during cooling. This method, largely applied with nickel catalyst, is known to produce continuous, but not uniform, layers with the concurrent presence of mono‐ and poly‐graphene areas. With the aid of Raman mapping of graphene still lying onto its catalyst, we are able to consider the possible origins for the observed distortions of the phonon modes with respect to the well‐known picture of the monolayer material. Optical effects, doping, the presence of multi‐layered islands, and strain are kept into account. It is shown that some isotropic observations can be interpreted in terms of the occurrence of strain with the uniaxial component superimposed at the metal discontinuities. Strain is proposed to originate from the difference between the thermal expansion coefficients of graphene and cobalt. The present paper shows that inhomogeneities in graphene grown onto catalysts with high C solubility are not always directly related to excess of precipitation. The observation of strain in as‐grown graphene opens the possibility of tailoring the electronic density of states via strain engineering directly during growth.
关键词： strain,graphene,micro‐Raman,cobalt,chemical vapor deposition
更新于2025-09-23 15:23:52
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Near-ultraviolet Raman and micro-Raman analysis of electronic materials
摘要： Raman and micro-Raman analysis methods have been extensively investigated for the study of materials used in electronic and photonic devices. Raman studies are used to understand fundamental phonon properties, along with effects related to the crystal structure, disorder, doping, and external factors such as temperature and stress. Micro-Raman extends these investigations to the micron scale. This article reviews diverse benefits of Raman measurements when carried out using laser excitation in the near-ultraviolet wavelength range, nominally 400 to 325 nm. Micro-Raman methods in the near ultraviolet exploit the key advantage of reduced focal spot size, achievable at shorter wavelengths when using diffraction-limited optics, for mapping with high spatial resolution. There are distinct advantages common to Raman and micro-Raman spectroscopy in the near ultraviolet when compared to the widely used visible excitation. One advantage exploits the shallower optical penetration depth in select materials for probing near-surface regions or interfaces. A second advantage is related to tuning of the excitation photon energy relative to the electronic levels of a material for investigating resonance effects. Finally, the application of Raman scattering to materials which exhibit strong fluorescence requires tuning to a wavelength range away from the potentially obscuring emission. This article overviews several examples of these key advantages to study diverse applied physics problems in electronic and photonic materials. Topics covered include stress mapping in silicon and related materials, stress and thermal effects in gallium nitride and other group-III-nitride semiconductors, and carbon materials ranging from graphite and graphene to diamond grown using chemical vapor deposition. The fundamental effects of stress- and temperature-induced shifts in phonon energies and their application to study epitaxy and device-related effects are also briefly reviewed.
关键词： near-ultraviolet,stress mapping,carbon materials,chemical vapor deposition,phonon properties,Raman spectroscopy,electronic materials,micro-Raman,gallium nitride
更新于2025-09-23 15:21:01
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Different material modifications in laser-induced damage of optical films in air and vacuum environments
摘要： A combination study of material modifications for the catastrophic laser-induced damage by 12 ns, 1064 nm laser pulse irradiation was investigated in air and vacuum environments. The samples were observed by optical microscope, scanning electron microscopy, laser micro-Raman spectroscopy, photoluminescence spectrum; moreover 2D numerical calculations were performed. According to our results, vacuum pumping induced higher laser field intensities, accompanying with more absorption of laser energy in the laser-induced damage process. All of these resulted in the material melting and subsequent re-solidification in the laser-damaged core in vacuum. While, in the air conditions, plasma expanding due to material heating and associated thermal expansion induced a large stress field, which caused the material deformation and formation of delamination and crack in the laser-damage region.
关键词： Vacuum,Photoluminescence spectrum,Laser-induced damage,Laser micro-Raman spectroscopy
更新于2025-09-23 15:21:01
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Characterization of the chips generated by the nanomachining of germanium for X-ray crystal optics
摘要： Micro-Raman spectroscopy, scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM) were used to study the effect of cutting speed and cutting depth on the mode of the single-point diamond fly cutting of Ge(110) surface via crystallinity of the chips. Reducing the cutting depth from 15 to 2 μm and concurrently cutting speed from 10 to 2 mm/min at 2000 rpm, the content of amorphous phase in the chips increased at the expense of the crystalline one from 28 to 46%. Simultaneously, the chip morphology visible by SEM suggested transition from a brittle to a mixed brittle-ductile mode of nanomachining. The damage transition line indicates 1/3 portion of the ductile component at 2-μm cutting depth that produced twisted lamellae of a width of 18–20 μm without any signs of a fracture. As the feed rate here was 1 μm/rev, the tool made 18–20 revolutions while passing the same point of the nanomachined surface that was enough to gradually remove the surface region damaged by the brittle cutting component along with the entire amorphous region beneath, both being delaminated by the chips. This explains the dislocation-free single-crystal lattice beneath the Ge(110) surface machined under these conditions. A close relationship between the brittle mode of nanomachining and crystallinity of the chips observed by micro-Raman spectroscopy and SEM was confirmed by HR-TEM showing dense occurrence of nanocrystals in the chips coming from the nanomachinings with 5-μm and 15-μm cutting depths. These results demonstrate potential of the single-point diamond machining for the preparation of high-quality X-ray surfaces with undistorted single-crystal lattice beneath for next-generation X-ray crystal optics.
关键词： Micro-Raman spectroscopy,X-ray crystal optics,Scanning electron microscopy,Germanium,Transmission electron microscopy,Single-point diamond machining
更新于2025-09-19 17:15:36
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Crystal defects in monocrystalline silicon induced by spot laser melting
摘要： Laser processing of monocrystalline silicon has become an important tool for a wide range of applications. Here, we use microsecond spot laser melting as a model experiment to investigate the generation of crystal defects and residual stress. Using Micro-Raman spectroscopy, defect etching, and transmission electron microscopy, we find no dislocations in the recrystallized volume for cooling rates exceeding jdT=dtj ? 2 (cid:2) 107 K/s, and the samples remain free of residual stress. For cooling rates less than jdT=dtj ? 2 (cid:2) 107 K/s, however, the experiments show a sharp transition to a defective microstructure that is rich in dislocations and residual stress. Moreover, transmission electron microscopy indicates dislocation loops, stacking-fault tetrahedra, and voids within the recrystallized volume, thereby indicating supersaturation of intrinsic point defects during recrystallization. Complementing photoluminescence spectroscopy indicates even three regimes with decreasing cooling rate. Spectra of regime 1 do not contain any defect related spectral lines. In regime 2, spectral lines appear related to point defect clusters. In regime 3, the spectral lines related to point defect clusters vanish, but dislocation-related ones appear. We propose a quantitative model explaining the transition from dislocation-free to dislocation-rich recrystallization by means of the interaction between intrinsic point defects and dislocations.
关键词： monocrystalline silicon,transmission electron microscopy,laser melting,micro-Raman spectroscopy,crystal defects,residual stress,photoluminescence spectroscopy
更新于2025-09-16 10:30:52
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Raman scattering of impact diamonds
摘要： We report the results of a study of the polycrystalline powder of the diamond-lonsdaleite from the Popigai crater (Siberia) using UV micro-Raman spectroscopy and high-resolution synchrotron X-ray diffraction. By subtracting two experimental Raman spectra of diamond-lonsdaleite samples with close amounts of diamond and lonsdaleite, we were able to identify the polytypic composition of impact diamonds in contrast to the method of X-ray diffraction. We have managed to get for the first time the spectrum of "pure" lonsdaleite. Its deconvolution has allowed us to identify all the three Raman - active vibrational modes E2g, A1g, and E1g whose positions agree well with the results of ab initio calculations.
关键词： Raman scattering,polytypic composition,impact diamonds,synchrotron X-ray diffraction,lonsdaleite,UV micro-Raman spectroscopy
更新于2025-09-10 09:29:36
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Surface-enhanced Raman spectroscopy (SERS) in cotton fabrics analysis
摘要： This article presents some aspects of application the dispersive Micro-Raman Spectroscopy in textile fibers analysis. Research were dedicated to the methodology of surface enhancement Raman spectroscopy (SERS) studies on cotton fabric and possibility of its application in fibers characterization. Studies were carried out on dyed cotton fabrics modified by silver nanowires (AgNWs). Three reactive dyes (blue, yellow, red) and four color intensities (0.5%, 1%, 2% and 5%) were used. AgNWs colloid was deposited on undyed and dyed cotton fabrics by dipping and drying method. Dyed fabrics were examined by spectroscopic methods: FTIR ATR, Raman, UV-Vis Diffuse Reflectance Spectroscopy, Fluorescence Spectroscopy. Raman signal enhancement phenomena occurring on the silver nanoparticles increases the possibility of fiber and dye identification especially in the case of dyes used in cotton dyeing reveals fluorescence.
关键词： UV-Vis Diffuse Reflectance Spectroscopy,SERS,Fluorescence Spectroscopy,reactive dyes,FTIR ATR,Micro-Raman spectroscopy,Cotton fibers
更新于2025-09-09 09:28:46
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Raman fingerprint of two terahertz spin wave branches in a two-dimensional honeycomb Ising ferromagnet
摘要： Two-dimensional (2D) magnetism has been long sought-after and only very recently realized in atomic crystals of magnetic van der Waals materials. So far, a comprehensive understanding of the magnetic excitations in such 2D magnets remains missing. Here we report polarized micro-Raman spectroscopy studies on a 2D honeycomb ferromagnet CrI3. We show the definitive evidence of two sets of zero-momentum spin waves at frequencies of 2.28 terahertz (THz) and 3.75 THz, respectively, that are three orders of magnitude higher than those of conventional ferromagnets. By tracking the thickness dependence of both spin waves, we reveal that both are surface spin waves with lifetimes an order of magnitude longer than their temporal periods. Our results of two branches of high-frequency, long-lived surface spin waves in 2D CrI3 demonstrate intriguing spin dynamics and intricate interplay with fluctuations in the 2D limit, thus opening up opportunities for ultrafast spintronics incorporating 2D magnets.
关键词： micro-Raman spectroscopy,CrI3,spintronics,2D magnetism,spin waves
更新于2025-09-09 09:28:46
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Residual stress in underlying silicon at the fixed end of SiO <sub/>2</sub> microcantilevers?— A micro-Raman study
摘要： In this work, nature of the residual stress developed in the convex corners created in underlying Si at the fixed end of SiO2 microcantilevers (MCs) fabricated by wet chemical etching method was investigated using micro-Raman spectroscopy with visible excitation. It revealed the presence of tensile stress near the sharp edge of the convex corner and is attributed to the localized stress generated in the neighborhood of the discontinuities, acting as stress concentration region. Residual stress estimated by micro-Raman technique across the convex corner was also validated by FEM simulations. Micro-Raman also revealed the presence of tensile stress on the etched Si surface, which is explained on the basis of stress induced by native oxide shells covering the etched features.
关键词： SiO2 microcantilever,convex corner in Si,micro-Raman spectroscopy using visible excitation,residual stress
更新于2025-09-04 15:30:14