共查询到20条相似文献,搜索用时 15 毫秒
1.
Raman scattering (RS) and field emission scanning electron microscopy (FESEM) have been used to extract microstructural information of RuO2 nanorods (NRs) and a two-phase system comprising NRs embedded in polycrystalline matrix deposited on different substrates by the metal-organic chemical vapor deposition method. The red shifts and asymmetric broadening of the Raman line shape for the NRs are analyzed by the spatial correlation model. The deduced spatial correlation length l is found to be much smaller than that of the average size L0 estimated from the FESEM images. The Raman features for the two-phase system can be resolved into two parts: a Lorentzian line shape feature corresponding to the polycrystallite at higher frequency side and an asymmetrically broadened NRs' signature located at lower frequency end. The volume fraction of NRs in the two-phase system can be determined from the analysis. These results demonstrate the significance of RS as a structural characterization method when used in conjunction with FESEM. 相似文献
2.
Silver nanocrystallites are obtained through immersion of porous silicon samples in AgNO3 solutions and a successive thermal annealing. The efficiency of nanostructures as surface enhanced Raman scattering (SERS) substrates is checked on cyanine-based dyes and horseradish peroxidase, evidencing detectable concentrations as low as 10−7 to 10−8 M. The substrate efficiency is strictly related to the Ag particle morphology, which could yield to either local surface plasmons (LSP) coupled to individual particles or to inter-particle short-range interaction. 相似文献
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4.
In this study we are able, using a copper grid substrate, to successfully grow separate nanowires with a high level of crystallinity, for a length of up to 10 μm. They were synthesized under various temperatures. We compare and contrast three types of geometries (micron-, nano-scale, and tip-like single CuO nanowires), to identify their potential for monitoring the size effects of quantum confinements. The confocal Raman spectrometry results confirm the expected outcome, that reducing of the diameter of a cylindrical cross-section of a single nanowire results in Raman frequency downshifts. The results can be explained by the bond polarizability model. The applicability of investigating the size effects of the quantum confinement of the tip-like geometry of a single nanowire without any preparation for different sizes of nanoparticles is possible because the detection is relatively straightforward and the reproduced Raman signals can be observed. 相似文献
5.
The paper reports a Raman spectral in-situ detection technique to measure the ethanol proportion in an ethanol-gasoline mixture rapidly and quantitatively. The transformed information of Raman spectra for different mixtures of gasoline and ethanol have been observed and recorded. The relative intensity ratio of two typical Raman peaks for ethanol and gasoline satisfies a linear relation with a variation in volume ratio which could be used as a quantitative measure. This method, compared with the direct intensity measurement of a Raman peak, may not only eliminate the random measurement error due to dark current, but also confirm the accurate the proportion of ethanol and gasoline. 相似文献
6.
We fabricated a silica optical fiber doped with InP sandwiched in the core and the inner cladding layers by using the conventional modified chemical vapor deposition process. We presented the experimental X-ray analysis on the optical properties and found that compound InP was contained in the fiber core after annealing process. Broadband photoluminescence observed in InP doped fiber was well coincided with those coming from the recombination of deep levels in InP. The occurrence of temperature-dependent photoluminescence both at the lower and room temperature would be related with the localized defects and their confinement in the micro-network structure of Si-O-Si. The Raman spectra reveal that Si-O-In vibration would disorder the silica ring structures and enervate their vibrations. 相似文献
7.
J.H. Jung 《Solid State Communications》2005,133(2):103-107
We have reported the Raman scattering and infrared absorption results on a t2g orbital ordered Ca2RuO4. At 10 K, a strong and clear peak was observed in Raman scattering near 1360 cm−1 with x′x′ geometry. In contrast to optic phonon modes, the peak does not show any frequency shift but rapidly decreases with increasing temperature. In addition, the peak is not observed in infrared absorption measurement. By comparing the previous Raman scattering results for several transition metal oxides, we have discussed the possible origins and ambiguities of the intriguing peak in Ca2RuO4. 相似文献
8.
Raman scattering (RS) has been used as a technique for characterization of IrO2 one dimensional (1D) nanocrystals (NCs) deposited on sapphire(100) and LiNbO3(100) substrates under various conditions. The IrO2 NCs were grown via metalorganic chemical vapor deposition method using (MeCp)(COD)Ir as the precursor and reactive magnetron sputtering using Ir metal target. The red-shifts and asymmetric broadening of the Raman lineshape for the NCs were analyzed by a modified spatial correlation (MSC) model, which includes the factor of stress induced shift. The proposed MSC model showed that the effects of stress and nanometric size can be separated in analyzing the observed Raman features. The usefulness of the experimental RS together with the MSC model analysis as a residual stress and structural characterization technique for 1D NCs has been demonstrated. 相似文献
9.
Colloidal CdSe nanoparticles (NPs), passivated with CdS and ZnS, were characterized by resonant Raman scattering and photoluminescence (PL). The effect of the passivating shell, its volume and formation procedure on optical and vibrational spectra is discussed. Analyzing the Raman peaks due to optical phonons inside the core and those related to the core-shell interface allows some understanding of the relation between the core-shell structure and its PL properties to be achieved. In particular, a compositional intermixing at the core/shell interface of the NPs was deduced from the Raman spectra, which can noticeably affect their PL intensity. 相似文献
10.
A systematic investigation on nanocrystalline LiCoO2 has been carried out using Raman spectroscopy. We synthesized nanocrystalline LiCoO2 (ca. 20-50 nm) through a combination of rapid thermal annealing at various annealing temperatures and a sol-gel method assisted with a triblock copolymer surfactant. Powder X-ray diffraction measurements revealed the formation of LiCoO2. The crystallite size of LiCoO2 from the Scherrer equation strongly depended on the annealing temperature. The crystallite size was confirmed by SEM and TEM measurements. Raman shifts of the A1g and Eg modes for nanocrystalline LiCoO2 exhibited a broadening and a frequency shift according to the crystallite size. While the frequency shift could be ascribed to a structural strain at the surface, the broadening was due to the phonon confinement effect produced by narrow crystal boundaries. 相似文献
11.
Yasutaka Hanada Koji Sugioka Ikuko Shihira Ishikawa Katsumi Midorikawa 《Applied Surface Science》2009,255(24):9893-9897
We demonstrate fabrication of microchips with microfluidic structures for dynamic analysis of living cells using a femtosecond (fs) laser. Fs laser direct writing followed by annealing and successive wet etching in dilute hydrofluoric (HF) acid solution resulted in formation of three dimensional (3D) hollow microstructures embedded in photostructurable glass. The embedded microchannel structure enabled us to analyze unique phenomenon of Cryptomonas, which suddenly swims very fast under certain condition. Vector analysis of the driving force for the rapid motion was also carried out by introducing nano-beads into the microchannel, in which Cryptomonas was encapsulated. We also fabricated a microchip for observation of Phormidium moving toward a seedling root, which accelerates growth of the seedling. Using the embedded microchannel in the microchip, observation of Phormidium assemblage to the seedling root was easily carried out. Such microchips with microfluidic structures, referred to as a nano-aquarium, realize the efficient and highly functional observation of living cells. 相似文献
12.
ZnWO4 powders, synthesized using co-precipitation technique and annealed in air at different temperatures in the range of 80-, were studied by Raman and photoluminescence spectroscopy. ZnWO4 single crystal was used for comparison. The interpretation of the observed variations of the Raman spectra and intrinsic photoluminescence band upon annealing is suggested. 相似文献
13.
We present a novel technique to fabricate deeply embedded microelectrodes in LiNbO3 using femtosecond pulsed laser ablation and selective electroless plating. The fabrication process mainly consists of four steps, which are (1) micromachining of microgrooves on the surface of LiNbO3 by femtosecond laser ablation; (2) formation of AgNO3 films on substrates; (3) scanning the femtosecond laser beam in the fabricated microgrooves for modification of the inner surfaces; and (4) electroless copper plating. The void-free electroless copper plating is obtained with appropriate cross section of microgrooves and uniform initiation of the autocatalytic deposition on the inner surface of grooves. The dimension and shape of the microelectrodes could be accurately controlled by changing the conditions of femtosecond laser ablation, which in turn can control the distribution of electric field inside LiNbO3 crystal for various applications, opening up a new approach to fabricate three-dimensional integrated electro-optic devices. 相似文献
14.
A free-running Er:YAG laser is used to ablate polyethylene glycol and the ablation yield is studied as a function of molecular weight (1000-10,000 g/mol) and laser fluence (8-25 J/cm2). A steady-state ablation mechanism is proposed which includes recoil-induced expulsion as the primary contributor to the ablation yield. It is also proposed that the formation of a molten layer is a necessary part of the ablation mechanism because the calculated tensile strengths for the solid polymer are too large to permit fracture of the target due to the laser-induced stress transient. The ablation yield is found to depend in a sigmoidal fashion upon laser fluence, thus implying a variable ablation enthalpy. Finally, the current results are compared with that obtained previously with a free electron laser. 相似文献
15.
The results of comparison of spectral position of the LF bands of g-As2S3 and g-As22S78 with theoretical calculations of vibrational spectra of different clusters (As2S4, As2S5, As2S6, AsS3-As3) in the LF region (10-85 cm−1) are given. The torsion type vibrations of the small chain-like clusters are located in the same spectral region as Boson peak of As-S glasses system. They can make several contributions to the LF spectrum. The cluster lengths by weight distribution functions f(L)*L are from 5.5 to 10.1 Å and from 4.5 to 7.5 Å for g-As2S3 and g-As22S78, respectively. The lognormal fittings of the f(L)*L functions give the most probably values about the 7.6 Å (for g-As2S3) and 6.2 Å (for g-As22S78). 相似文献
16.
Koichi Terashima Akihito Tanabe Kaoru Mori Junko Nakatsuru Manabu Ikemoto 《Applied Surface Science》2008,254(19):6165-6167
We fabricated Ge-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) by using replacement gate process and selective epitaxial growth. In our method, thin Ge layers were selectively grown on the channel region of MOSFETs after the removal of a sacrificial gate stack structure and the etching of the channel region. Ge layers with a smooth surface and a good morphology could be obtained by using the thin Si0.5Ge0.5 buffer layer. Dislocations were observed in the epitaxial layers and near the interface between the epitaxial layer and the substrates. We consider that these dislocations degrade the device performance. Although the electrical characteristics of the obtained MOSFETs need further improvement, our method is one of the promising candidates for the practical fabrication process of Ge-channel MOSFETs. 相似文献
17.
Tip-enhanced Raman spectroscopy in reflection mode makes possible the nanoscale characterization of non-transparent samples, such as silicon, inaccessible in transmission mode. However, a particular feature of this technique is the superposition of the far-field Raman signal with the near-field one generated in the tip vicinity sometimes resulting in a low near-field-to-far-field contrast. By using a polarized configuration and orientation optimization of a (0 0 1) crystalline Si sample we were able to enhance significantly the contrast through reducing the far-field contribution, reaching a value of about 40. This contrast enhancement method can be applied in principle to any crystalline sample. 相似文献
18.
Raman spectra of bismuth ferrite (BiFeO3) over the frequency range of 100-1500 cm−1 have been systematically investigated with different excitation wavelengths. The intensities of the two-phonon modes are enhanced obviously under the excitation of 532 nm wavelength. This is attributed to the resonant behavior when incident laser energy closes to the intrinsic bandgap of BiFeO3. The Raman spectra of BiFeO3 excited at 532 nm were measured over the temperature range from 77 to 678 K. Besides the abnormal changes of the peak position and the linewidth of the A1 mode at 139 cm−1, the prominent frequency shift, the line broadening and the decrease of the intensity for the two-phonon mode at 1250 cm−1 were observed as the temperature increased to Néel temperature (TN). All these results indicate the existence of strong spin-phonon coupling in BiFeO3. 相似文献
19.
Silica glass can be machined by irradiation with laser plasma soft X-rays on nano- and micrometer scale. We have investigated the ablation process of silica glass induced by laser plasma soft X-ray irradiation. We observed ionic and neutral species emitted from silica surfaces after irradiation. Dominant ions and neutrals are O+ and Si+ ions and Si, O, SiO and Si2 neutrals, respectively. The ions have kinetic energies of 13 and 25 eV, which are much higher than those of particles emitted by evaporation. The energy of laser plasma soft X-rays absorbed to silica glass at a fluence of 1.4 J/cm2 is estimated to be 380 kJ/cm3, which is higher than the binding energy of SiO2 of 76 kJ/cm3. These results suggest that the most of the bonds in silica glass are broken by absorption of laser plasma soft X-rays, that several percent of the atoms are ionized, and that neutral atoms are emitted together with repulsive ions. The process possibly enables us to fabricate nano structures. 相似文献
20.
We report on photoluminescence and Raman studies of Xe ion-implanted diamond. Several natural and high-purity artificial diamonds implanted within the wide dose range of 1010-5×1014 ion/cm2 were studied. The room temperature luminescence of the Xe center consists of two zero phonon lines, at 813 nm (strong) and 794 nm (weak). The dose dependences of photoluminescence and Raman spectra were studied. For doses less than 1013 ion/cm2, the luminescence intensity grows with the implantation dose linearly. The defect-induced photoluminescence quenching was observed for doses equal or more than 1013 ion/cm2. Possible models of the Xe center will be discussed. The nature of damages induced by ion implantation at different doses was analyzed using micro-Raman spectroscopy. 相似文献