Temperature Dependent Raman Studies and Thermal Conductivity of Few Layer MoS2

We report on the temperature dependence of in-plane E2g and out of plane A1g Raman modes in high quality few layers MoS2 (FLMS) prepared using a high temperature vapor-phase method. The materials obtained were investigated using transmission electron microscopy. The frequencies of these two phonon modes were found to vary linearly with temperature. The first order temperature coefficients for E2g and A1g modes were found to be 1.32*10-2 and 1.23*10-2 cm-1/K, respectively. The thermal conductivity of the suspended FLMS at room temperature was estimated to be about 52 W/mK

Surface optical Raman modes in InN nanostructures

Raman spectroscopic investigations are carried out on one-dimensional nanostructures of InN,such as nanowires and nanobelts synthesized by chemical vapor deposition. In addition to the optical phonons allowed by symmetry; A1, E1 and E2(high) modes, two additional Raman peaks are observed around 528 cm-1 and 560 cm-1 for these nanostructures. Calculations for the frequencies of surface optical (SO) phonon modes in InN nanostructures yield values close to those of the new Raman modes. A possible reason for large intensities for SO modes in these nanostructures is also discussed.Comment: 13 pages, 4 figures, Submitted in Journa

Analytical Simulation and Experimental Investigation of Various Characteristics of Hole Quality During Micro Drilling of PCB

Achievement of good surface quality remains a concern during micro drilling of printed circuit board (PCB). Although a great deal of work is reported on micro drilling of PCB, information on effect of drilling parameters like feed on different characteristics of hole quality is relatively scarce. Although stresses during micro drilling of PCBs are critical issues, their correlation with hole quality is yet to be reported. The current work utilizes finite element analysis based simulation of deformation and stresses to explain the various parameters of hole quality such as diameter, delamination factor and burr thickness. Effect of feed on these parameters has also been established. Results indicated that stresses play a vital role in influencing hole qualities of PCB. Increase in feed rate resulted in reduction in hole diameter, whereas delamination factor and mean burr thickness increased with feed. The study is, therefore, expected to be of help in proper selection of feed in order to achieve acceptable hole quality after micro drilling of PCB

Excitation energy dependence of electron-phonon interaction in ZnO nanoparticles

Raman spectroscopic investigations are carried out on ZnO nanoparticles for various photon energies. Intensities of E1-LO and E2 modes exhibit large changes as the excitation energy varied from 2.41 to 3.815 eV, signifying substantially large contribution of Frohlich interaction to the Raman polarizability as compared to deformation potential close to the resonance. Relative strength of these two mechanisms is estimated for the first time in nanoparticles and compared with those in the bulk.Comment: 13 pages. 3 figures Journa

Confined Acoustic Phonon in CdS1-xSex Nanoparticles in Borosilicate Glass

We calculate low-frequency Raman scattering from the confined acoustic phonon modes of CdS1-xSex nanoparticles embedded in borosilicate glass. The calculation of the Raman scattering by acoustic phonons in nanoparticles has been performed by using third-order perturbation theory. The deformation potential approximation is used to describe the electronphonon interaction. The Raman-Brillouin electronic density and the electron-phonon interaction are found to increases with decreasing size of nanoparticle. A good agreement between the calculated and reported low-frequency Raman spectra is found.Comment: 13 pages, 3 figures. Journal of Nanoscience and Nanotechnology (In Press