CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

Figure 38 (a) shows the emission spectra of b-Ga 2 O 3 doped with 0, 0.5, 1 and 2 at %
Tb 3+ obtained after excitation at 255 nm. Undoped (0 at % Tb) b-Ga 2 O 3 sample shows a
broad band centered around 455 nm and is assigned to emission from oxygen defect levels
present in the host matrix. The emission intensity reduces with increase in Tb 3+ percentage in
the sample. This is explained based on the energy transfer from host to Tb 3+ ions. The
excitation spectra corresponding to host and Tb 3+ emission are shown in Fig.38 (b).
Intensity (arb.units)
600
400
200
0
400
200
0
200
100
0
200
100
0
2% Tb
1% Tb
0.5% Tb
undoped
350 400 450 500 550 600 650
Wavelength (nm)
Normalised intensity
1.0
0.8
λ = 544 nm
em
λ em
= 460 nm
0.6
0.4
0.2
0.0
200 250 300 350 400
Wavelength (nm)
(a)
(b)
Fig.38 (a) Emission spectra of β-Ga 2 O 3 nanomaterials doped with 0, 0.5, 1 and 2 at % Tb 3+
ions. The corresponding excitation spectra for 1 at % Tb 3+ doped sample, monitored
at 460 and 544 nm emission, are shown in Fig. 38 (b)
The excitation spectra corresponding to host emission exhibits only one band at 255
nm whereas excitation spectra corresponding to Tb 3+ emission is characterized by strong
band at 275 nm having shoulder at 255 nm along with weak bands above 350 nm. The
broadband ~ 275 nm is assigned to 4f to 5d transition of Tb 3+ , the shoulder peak to host
absorption and peaks above 350 nm are due to f-f transitions of Tb 3+ ions. Based on the
excitation spectra, it is confirmed that energy transfer takes place from host to Tb 3+ ions in
these samples. This is further supported by the excited state lifetime values corresponding to
host emission observed from samples with different Tb 3+ contents. The corresponding decay
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