First-order Raman scattering in MgO microcrystals

Abstract

Raman scattering is observed in MgO microcrystals with three different particle sizes (105, 103, and 102 Å). The second-order Raman lines in the bulk crystals of MgO disappear in all the microcrystals, while new peaks emerge at 280, 446, and 1088 cm−1 except for specimen prepared by grinding a large single crystal. Raman lines with lower frequencies, which are enhanced with decrease of the particle size, are discussed as due to the first-order Raman scattering forbidden in the bulk crystals. The assignment is confirmed in terms of photon density of states in microcrystals. Another line with the highest frequency is coincident with a previously reported Raman line whose origin has been attributed to a surface phonon mode.

Magnesium Oxide in Nanodimension: Model for MRI and Multimodal Therapy

“…Raman peaks around 275.89, 442.15, and 1313.50 cm −1 (Figure 6(a)) are associated to the characteristics peaks of MgO and are found in good agreement with the previously reported research [46][47][48][49]. Generally, these bands are not present in the bulk MgO, so it confirms nanocrystalline phases within fabricated MgO [48] which is in concurrent to XRD analysis.…”

Fabrication and Raman Studies οf MgO/SnO2Core-Shell Heteronanowires

“…In addition, the line at 1080 cm −1 accompanied by line at 1121 cm −1 is observed. This rather broad band composed of two lines is similar to those observed from MgO microcrystals [15,17], being ascribed to the surface phonon modes in a TO-LO phonon gap. Figure 5b shows the Raman spectrum of the as--prepared MgO core/SnO 2 shell nanowires.…”

“…Figure 5a shows the room-temperature Raman spectrum of the core MgO nanowires. While the sharp peak at 520 cm −1 was identified as the TO phonon mode in the silicon (Si) crystal structure [13], presumably from the Si substrates, the peak centered at 939 cm −1 is associated with the surface phonon mode of amorphous silica, which should have been formed on the surface of Si sub- may coincide with the two prominent peaks in Chen's calculation in regard to MgO microcrystals [15,16]. Accordingly, it is supposed that the 290 cm −1 line is associated with a TA phonon at the zone boundary, whereas 448 cm −1 line with a TO phonon at the zone center.…”

Effect of Mg content on the structural and optical properties of Mg x Zn1−x O alloys

“…Except for sample F, all the samples show intense multi-phonon peaks in the range from 200 to 2500 cm -1 . Although the multiple phonon scattering processes have been observed in ZnO thin films [13][14][15][16], resonant Raman spectra of MgZnO thin films, to our knowledge, have not been reported up to now. Figure 5(a) shows the typical resonant Raman spectra of samples A and C. The Raman spectrum of sample A is composed of four sharp lines at 583.6, 1164.6, 1745.7 and 2327.1 cm -1 , which are from the 1st, 2nd, 3rd, and 4th longitudinal optical (LO) phonons of ZnO wurtzite structure, respectively.…”