Photoluminescence and Raman spectroscopy studies of low-temperature γ-Al2O3 phases synthesized from different precursors

Pulsed laser deposition and structural evolution of BaF2 nanolayers in Eu-doped BaF2/Al2O3 layered optical nanocomposite thin films

“…In our case, the defects were possibly caused by the implantation of oxygen ions/atoms into the BaF2 layer during the deposition of EuOx and Al2O3 layers. The fact that this peak is lowest for sample D, which has the thinnest BaF2 layer, is consistent with the data shown in Table 2, which indicate that there is very little BaF2 in sample D. It is also possible that the broad peak may have some contribution from Al2O3, as the PL spectrum from a pure Al2O3 film shows a broad peak centering at ~430 nm, which could be attributed to oxygen vacancy defects such as F-centers, as observed in previous literatures [75,76]. It should be noted that the narrow intense peak at 693 nm is likely a spurious signal that results from the UV objective used in the custom-built microscope for PL data collection, because this 693 nm peak was seen in the background spectrum (no samples) with the objective but not seen in the background spectrum without the objective.…”

The search for defects in undoped SrAl2O4 material

“…The luminescence of Fcenters in pure α -Al2O3 is at ∼440 nm (2.8 eV) [15][16][17], in turn the luminescence of F2centers is at 517 nm (2.4 eV) [18]. Important is the F2centers luminescence band position is found the very close, even the same in both α -Al2O3 and γ -Al2O3 [19,20] showing weak influence from the structure. There is a strong possibility, that in the SrAl2O4 material these defects might Fig.…”

CoFe2O4 Nanoparticles Grown within Porous Al2O3 and Immobilized on Graphene Nanosheets: A Hierarchical Nanocomposite for Broadband Microwave Absorption

“… 30 , 31 In the case of PA, the absence of any distinct peak in 200–1200 cm –1 indicated the γ phase of Al 2 O 3 , and the broad peak that is centered at ∼1309 cm –1 ( Figure S3c ) can be assigned as the Al–O bending vibrations in the octahedral structure. 32 In the case of the (60PA-40CF) 90 -Gr 10 sample ( Figure 1 b), the peaks were observed at 474 cm –1 ( T 2g of CF), 694 cm –1 (Al–O bond in tetrahedral AlO 4 in γ-Al 2 O 3 ), 1331 cm –1 (D band of graphene), and 1578 cm –1 (G band of the graphene in-plane vibration mode of sp 2 carbon). The broad peak ranging from ∼1000 to 2250 cm –1 also indicated the presence of γ-Al 2 O 3 in the nanocomposite.…”

“…The single and sharp 2D peak indicated the almost single-layer nature of this Gr. The Raman spectrum of CF (Figure S3b) displayed peaks at 456 cm –1 ( T 2g vibrational mode of octahedral iron), 589 cm –1 (vibrational mode of an oxygen anion at tetrahedral sites (MO 4 )), and 662 cm –1 (A 1g vibrational mode of tetrahedral cobalt). , In the case of PA, the absence of any distinct peak in 200–1200 cm –1 indicated the γ phase of Al 2 O 3 , and the broad peak that is centered at ∼1309 cm –1 (Figure S3c) can be assigned as the Al–O bending vibrations in the octahedral structure . In the case of the (60PA-40CF) 90 -Gr 10 sample (Figure b), the peaks were observed at 474 cm –1 ( T 2g of CF), 694 cm –1 (Al–O bond in tetrahedral AlO 4 in γ-Al 2 O 3 ), 1331 cm –1 (D band of graphene), and 1578 cm –1 (G band of the graphene in-plane vibration mode of sp 2 carbon).…”