Raman spectroscopy is a proven versatile tool for characterization of materials spanning almost all areas of science because of its ability to non-invasively extract information about materials. This technique is able to detect any perturbation in a system that can affect the phonons. A detailed discussion on various factors that affect the Raman line shape for a material has been summarized here by taking the example of silicon. Methods to identify the actual reason(s) behind the observed Raman spectral line shape have also been briefly discussed. Raman line shape obtained from silicon nanostructures when analyzed closely along with their bulk counterparts, reveals important information about the quantum confinement in such systems characterized by the Bohr's exciton radius. Raman line-shape parameters are analyzed closely to understand the influence of any perturbation like quantum confinement, heavy doping, temperature rise, pressure, excitation wavelength, electron–phonon interaction, and so on. Current review briefly deals with the origin of asymmetric Raman line shapes in (nano-) silicon due to various physical perturbations and their interplays, which becomes the origin of different line shapes. Advantages of using Raman microscopy in analyzing subtler physical processes taking place in a semiconductor have also been underlined. 相似文献
Cubic-silicon carbide crystals have been grown from carbon-rich silicon solutions using the travelling-zone method. To improve the growth process, we investigated the effect of controlling more tightly some of the growth parameters. Using such improved growth conditions, our best sample is a 12 mm diameter and 3 mm long 3C–SiC crystal. It is grown on a (0001) 2 off, 6H–SiC seed and has 111-orientation. The low amount of silicon inclusions results in a reduced internal stress, which is demonstrated by the consideration of μ-Raman spectra collected at room temperature on a large number of samples. 相似文献
The carbon‐rich hydrogenated amorphous silicon carbide (a‐Si1−xCx:H) films were deposited by plasma enhanced chemical vapor deposition using silane (diluted to 10% in hydrogen) and ethylene as the gas sources. To observe surface enhanced Raman scattering (SERS), some samples were prepared on sputtered Ag films on Si substrates. A variety of techniques including ellipsometer, Fourier transform infrared spectroscopy, Raman scattering, scanning electron microscope, and photoluminescence (PL) spectroscopy were used to characterize the grown films. With enormous enhancement in Raman spectral intensity of carbon related phases and Si C bonds, SERS is proved to be a powerful method to investigate carbon‐rich a‐Si1−xCx:H films. Multiphase structure of the grown a‐Si1−xCx:H films is confirmed which possesses hydrogenated sp3 Si C network and sp2 amorphous carbon clusters. Blue–green multiband PL are observed at room temperature. A possible PL mechanism is suggested: the PL originates from exciton‐like and geminate recombination of excited electron–hole pairs through localized tail states within sp2 clusters and gap states related to sp3 Si C network. 相似文献
The fluorescence spectra of Cr,Tm,Ho:YAG crystal have been detected at the temperature from 65 to 295 K with interval of 10 K. The width and the shift of Ho3+ lines at 4959.6 cm-1 (at 65 K) have been investigated and interpreted in terms of the interactions between lattice vibration (phonons) and ions. The results showed that the line broadening with the temperature was mainly due to the Raman scattering of phonons,and the line shift with temperature was mainly due to the emission and absorption of virtual phonons. 相似文献
The fluorescence spectra of Cr,Tm,Ho∶YAG crystal have been detected at the temperature from 65 to 295 K with interval of 10 K.The width and the shift of Ho3+ lines at 4959.6 cm-1 (at 65 K) have been investigated and interpreted in terms of the interactions between lattice vibration (phonons) and ions.The results showed that the line broadening with the temperature was mainly due to the Raman scattering of phonons,and the line shift with temperature was mainly due to the emission and absorption of virtual phonons. 相似文献
The carrier lifetime in epilayers of n‐type 4H‐SiC with low concentrations of the Z1/2 lifetime killer has been investigated over a wide range of temperature under low injection conditions. It was found that in addition to the primary initial decay dominated by surface recombination (SR), as determined by previous work, in some samples a slow decay component is observed, exhibiting a thermally activated recombination rate. Such a slow tail on the carrier decay can be of concern in high voltage switching devices. The slow decay was well accounted for by the thermal emission of minority carriers trapped on a defect. The resulting analysis has determined that the responsible trap is located ≈Ev + (0.37–0.58) eV with relatively small capture cross‐sections for both electrons and holes: σp ≈ (0.5–12) × 10−17 cm2; σn < (0.3–8) × 10−18 cm2. Comparing these characteristics with reports in the literature for as‐grown materials, the most likely candidates for the responsible defects are the D‐ and/or i‐centers, which have similar ionization energies and capture cross‐sections. 相似文献
Crystalline–amorphous core–shell silicon nanowires (SiNWs) grown separately on glass and stainless steel substrates were investigated by Raman spectroscopy. Raman spectra confirmed the presence of crystalline and amorphous silicon phases in both samples. With respect to bulk silicon, the crystalline Raman peaks for the nanowires grown on a glass substrate showed much larger red shift and spectral broadening as compared to that of the nanowires grown on stainless steel. The Raman shift was attributed to local heating which was further confirmed by the reduction in red shift of the Raman spectrum at lower incident powers for both samples. For a low input power of 0.8 mW, the nanowires grown on stainless steel showed no shift in the first order Raman peak as compared to bulk silicon, however a small spectral broadening was still observed.
