Papers by Keyword: Raman Spectroscopy

Abstract: Er³⁺ doped SrMoO₄ (SrMoO₄:Er³⁺) and Er³⁺/Yb³⁺ co-doped SrMoO₄ (SrMoO₄:Er³⁺/Yb³⁺) particles were successfully synthesized by a cyclic microwave-assisted metathetic (MAM) route followed by heat treatment. The microstructures exhibited well-defined and homogeneous morphology with particles sizes of 100500 nm. With excitation at 980 nm, SrMoO₄:Er³⁺ and SrMoO₄:Er³⁺/Yb³⁺ particles exhibited a strong 525-nm emission band and a weak 550-nm emission band in the green region and a weak 655-nm emission band in the red region. The Raman spectra of SrMoO₄:Er³⁺ and SrMoO₄:Er³⁺/Yb³⁺ particles indicated the detection of additional strong peaks at both higher frequencies (564, 524, 456, and 403 cm^-1) and lower frequencies (294, 251, and 220 cm^-1).

Abstract: Titanium Dioxide, TiO₂ is one of the potential semiconductor materials. TiO₂ has much application such as for pigments, oxygen sensors, and photocatalyst. Recently, the researcher study on the other application and revealed that this material has a great potential to be use in nanocoating area. The objective of this paper is to produce TiO₂ nanostructured prepared by sol-gel method. Sol-gel was carried out using tetra (IV) isopropoxide (TTIP), absolute ethanol, Acetic Acid Glacial (GAA), Triton-X-100 and deionized water and all the solution was mixing by continuous stirring and heating. After finished prepare the sol-gel, solution will be spin coated onto glass substrate and annealed with different temperature for 2 hours. The particles were analyzed using Raman Spectroscopy to observe the crystallographic phase, and the morphology was evaluated through Atomic Force Microscopy (AFM). As a result, TiO₂ that annealed at 450°C shows the better nanostructured compared to other annealing temperature. Keywords: Titanium Dioxide (TiO₂); Sol-gel method ; Spin-coating ; Annealing process ; Raman spectroscopy

Abstract: Single-walled carbon nanotubes (SWCNT) were synthesized by using a simple evaporating method and a double furnace system. Ethanol was chosen as a carbon precursor because it has an evaporating temperature of 78 °C and was reported to produce a high purity of CNTs. Evaporated ethanol can be used as a precursor for carbon nanotubes (CNTs) synthesis. Ethanol was evaporated at 80 °C and channeled directly into a double furnace system. Furnace 1 was maintained at 180 °C and furnace 2 was set at 700 °C, 800 °C and 900 °C. The CNTs were then characterized by thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and Raman spectroscopy. Helical CNTs were observed at 700°C, webs of hollow tubes at 800 °C, and long tube structures at 900 °C based on FESEM. The diameter of CNTs that were synthesized ranged between 54 - 200 nm. Raman spectrum revealed that the G-band was 1590 cm^-1 and the D-band was about 1350 cm^-1. SWCNT was determined by RBM (radial breathing mode) to be between 200 - 300 raman shifts (cm^-1). The modified CVD (chemical vapor deposition) system set up in the present study is successfully used for large scale synthesis of CNTs from an aqueous precursor such as ethanol.

Abstract: The effect of calcination temperature for Fe₂O₃/MgO catalysts on the formation of carbon nanotubes (CNTs) was examined. CNTs were synthesized over Fe₂O₃/MgO catalysts calcined at different temperatures by catalytic decomposition of methane at 1000°C. The synthesized CNTs were investigated by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The results show that the effect of calcination temperatures greatly governed the diameter and the quality of the SWCNTs formed. The catalysts calcined at 500, 600 and 700°C produced CNTswith the diameters of 1.53, 1.95 and 2.97nm, respectively. Generally, an increase in the calcination temperature increases the average diameter and decreases the quality of the CNTs produced.

Abstract: Three-dimensional graphene foam (GF) is synthesized by chemical vapor deposition (CVD) at ~1000°C under ambient pressure. Then it is characterized by scanning electron microscopy (SEM) and laser Raman spectroscopy, the results indicate that GF has changed the surface morphology of Ni foam, and ~ 98% of the GF are fewlayer. At last, the surface wettability of GF is investigated, which shows that it is hydrophobic. The special three-dimensional structure and excellent properties of GF make it a candidate for a range of applications.

Abstract: In this research the composition of polyurethane open cell (PUOC) with two concentrations of SiO₂ nanoparticles (1 and 2wt. %) have been prepared. Optical microscopy imaging, watering uptake, FTIR and Raman spectroscopy of the synthesized samples were measured. The optical microscopy imaging of samples showed differences in the appearance of matrix by applying of different amount of SiO₂ nanoparticles. Variations of the water uptake of specimens were related to the function of SiO₂ nanoparticles (NPs) and their concentrations. The degree of phase separation and the hydrogen bonding index in samples were evaluated in terms of their FTIR spectroscopy data. The apparent and real densities of foams were measured and then total porosity, open porosity and close porosity of samples were calculated. According to creating voids in polyurethane, the apparent and real density has different behavior by adding of SiO₂ nanoparticles (NPs). The open porosity of samples is increased by adding the amount of nanoparticles but the close and total porosity are decreased.

Abstract: Phase characterization is critical in material properties probing. In this study, Raman scattering was employed to identify the phase of YSZ co-doped with CeO₂/Gd₂O₃. As a comparing, XRD for co-doped YSZ was also measured. The results show that introducing a small amount of CeO₂/Gd₂O₃ into YSZ can lead to a change on Raman spectroscopy. Raman peaks appear with co-doping is attributed to the local structure change which caused by the re-distribution of vacancy. Comparing to XRD, Raman spectroscopy shows a more sensitive on the phase identify for the YSZ with a small amount dopant.

Abstract: The properties of the absorber layer of solar cell CuInSe₂(CIS) thin film made by electro-depostied method were researched in this article. Different concentration of reactant and voltage was applied to prepare the CIS film. The micro-Raman spectroscopy and X-ray diffraction (XRD) of CIS film was carried out. A correlation between the linewidth A₁ mode of Raman spectrum and the XRD line and the voltage of electro-deposition technology was found.

Abstract: Many quantum optical and optoelectronic achievements have been obtained by using quantum coherence effects occurred in four-level quantum systems. Here we report a systemic study on the 1^st, 2^nd and 3^rd order subschemes of the four-level scheme with the aid of Boolean algebra, and find 7 1^st order subschemes and 53 2^nd order subschemes in total. Further it is found that 472 3^rd-order subschemes may appear in the realistic optical quantum coherence experiments when the applied lasers are distinguished only by the strong and weak field intensities.

Abstract: Epitaxial lateral overgrowth (ELO) was performed to grow cubic GaN layers on stripe-patterned GaAs (001) substrates via metalorganic vapor phase epitaxy. Growth time was varied from 10 to 120 minutes to investigate an evolution of growth morphologies and crystal structures of GaN, which were respectively analyzed by scanning electron microscopy and micro-Raman scattering spectroscopy. Growth features of ELO cubic GaN for [1-10] oriented mask stripe-pattern showed the {113} side-wall facets. On the other hand, the {111} side-wall facets were observed for ELO cubic GaN grown on the [110] oriented mask stripe-pattern. In case of [100] oriented mask stripe-pattern, growth feature with top rough surface and unclear side-wall facets was obtained. Micro-Raman spectroscopy was used as a tool to identify both cubic and hexagonal GaN structures performed on surface of the top and side-wall facets of the GaN stripes. ELO cubic GaN layer with growth time of 60 min along the [1-10] oriented mask stripe-pattern exhibited the highest ratio of cubic to hexagonal GaN, which was examined from an integrated intensity of LO phonon mode at 738 cm^-1 for cubic GaN comparing with that of hexagonal GaN, appearing at A₁ (TO) 538 cm^-1, E₁ (TO) 558 cm^-1 and E₂ (high) 568 cm^-1.