Papers by Keyword: Raman Spectroscopy

Abstract: In this work, a solar cell structure of nitrogen-doped nanocrystalline diamond (NCD:N)/p-type silicon was fabricated using microwave plasma jet chemical vapour deposition technique. The effects of nitrogen doping level on the structure, optical, and electrical of the as-grown NCD:N was discussed. The results showed that the micro structure, surface roughness, electrical properties, and optical properties were affected by the nitrogen doping. Additionally, the agglomeration of the film was increased with the higher concentration of CN species when the ratio of doped nitrogen increased. The roughness of the film was Rms:16.5 nm ~ 20.4 nm and the wettability was increased (contact angle 94.4^o ~ 64.6^o). The optical transmittance was decreased (87% ~ 72%) with the higher nitrogen. The results of Hall measurements showed that the carrier concentration increased 2 order (1016 cm^-3 to 1018 cm^-3) through nitrogen doping. The solar cell was made by NCD: N compound with p-type silicon. The photoelectric conversion efficiency was 2.8%. The open-circuit voltage was 0.52 V. The short-circuit current was 3 mA and the fill factor was 0.38.

Abstract: Copper (II) oxide graphene composite materials were prepared on the electrode surface at the solution of CuCl₂. The resulting composite material was characterized by cyclic voltammetry on surface of the glassy carbon electrode. Prepared copper (II) oxide graphene nanocomposite was scraped from the electrode surface and was measured Raman spectra by optical tweezers combined with micro Raman spectroscopy. This composite nanomaterial was used on determination of glucose and can be used to construct bio batteries too.

Abstract: The most expensive and principal step in the process of converting cellulosic biomass into biorenewables and biofuel is the pretreatment during which lignin and cellulose crystalline structure is broken down. In this study, TiO₂ nanoparticles were utilized as photocatalyst in addition to alkaline (ammonia and sodium hydrate) treatment of corn stover biomass to improve delignification ability and reduce the energy and chemical loadings to make the process more environmentally friendly. Raman Spectroscopic imaging, as an accurate and rapid chemical characterization method, was utilized to investigate the molecular compositional and structural changes occurring during the pretreatment process in the corn stover biomass qualitatively. Lignin characteristic peaks at 1,600, 1,620 and 1,690 cm^-1 as well as cellulose characteristic peaks at 1,059 and 2,888 cm^-1 were identified through Raman Spectroscopic measurement as indicators of the effects of the pretreatment. Real-time quantitative analysis of these functional peaks revealed the molecular structural changes during delignification, potentially may lead to optimization of the processing parameters to reduce the processing cost in the future.

Abstract: Crystallographic structures of 8H-and 10H-SiC crystals were analyzed by the Raman spectroscopy and diffraction methods. Two and four transverse-optical modes for 8H-and 10H-SiC were observed, and their values were different from those of 4H-and 6H-SiC. Crystallinity for the wide and narrow areas of these crystals was analyzed by the Laue diffraction and the transmission electron microscope, respectively. Based on these results, the stacking sequences of these polytype were discussed.

Abstract: Persistent conductivity in n-type 3C-SiC is investigated in a wide temperature range down to 3 K by Hall effect, admittance spectroscopy, low temperature photoluminescence (LTPL) and Raman spectroscopy. We propose a model, which clearly explains the persistent behavior of the electron density n below 50 K. It is experimentally verified that the persistent conductivity results from doped SF bunches, which can be considered as nanopolytype inclusions in 3C-SiC.

Abstract: The aim of this work is to develop the bulge test technique combined with the micro-Raman analysis and a refined load-deflection model for high quality 3C-SiC squared-membranes. By the minimization of the total elastic energy, starting from the isotropic relation between the stress tensor and the strain tensor, it is possible to calculate the relationship between the maximum deflection and the applied pressure, in both regime of small and large deflection. Furthermore, the relationship between the measured shift of Raman Transverse Optical (TO) phonon modes and the total residual strain (Δa/a) within the epitaxial 3C-SiC layer was found and in order to understand the stress distribution within the membrane, TO Raman shift maps were performed along the corner and the border of the membrane.

Abstract: The optical properties of isotope-pure ²⁸Si¹²C, natural SiC and enriched with ¹³C isotope samples of the 4H polytype are studied by means of Raman and photoluminescence spectroscopies. The phonon energies of the Raman active phonons at the Γ point and the phonons at the M point of the Brillouin zone are experimentally determined. The excitonic bandgaps of the samples are accurately derived using tunable laser excitation and the phonon energies obtained from the photoluminescence spectra. Qualitative comparison with previously reported results on isotope-manipulated Si is presented.

Abstract: We investigated the effect of ion-beam irradiation of the 3C-SiC(111) surface on the growth of graphene by the SiC surface-decomposition method. When a 3C-SiC(111) surface was irradiated by 1 keV Ar⁺ ions at a dose of 4.5 × 10¹⁵ cm² in an ultra-high-vacuum chamber and then annealed at 1200 °C for 1 min, the formation of graphene layers was promoted in comparison with that in the absence of ion-beam irradiation. X-ray photoelectron spectroscopy studies showed that Ar ion bombardment of the 3C-SiC(111) caused breakage of surface bonds and helped Si atoms to desorb from the surface.

Abstract: We examined the warpage structure in epitaxial 4H-SiC wafers subjected to phosphorus-ion (P⁺) implantation and post-annealing with varying implantation and annealing temperatures, using glazing-incidence monochromatic synchrotron X-ray topography. Using Raman spectroscopy, we then studied the relationship between the warpage of the crystal plane in the underlying epilayer and the recovery of lattice disorder in the implanted layer. We determined that the warpage structure of the underlying SiC epilayer was closely correlated with the recovery of lattice disorder in the implanted layer.

Abstract: To provide the quality assurance for various samples test, fast testing methods of the performance of laser confocal micro-Raman spectroscopy system for cell analysis are developed. The silicon wafer was used on the performance test of LabRam INV system produced by Horiba JY. The silicon wafer can not only be used for system calibration (the band of 520.7cm^-1), but also for the evaluation of the system performance. The curves of the intensity at the band of 520.7 cm^-1 as a function of laser intensity radiated on the sample, pinhole and time were achieved. The results show that the intensity at the band of 520.7 cm^-1 change linearly with the laser intensity, which can be used to evaluate the laser intensity radiated on the sample. The intensity changes with pinhole can be used to determine the size of pinhole for different purpose. The stability of Raman system can be determined by the variation of the intensity at the band of 520.7 cm^-1 with time, which helps to decide whether it is suitable for other sample test.