Optimal composition of europium gallium oxide thin films for device applications

Abstract

Europium gallium oxide ͑Eu x Ga 1-x ͒ 2 O 3 thin films were deposited on sapphire substrates by pulsed laser deposition with varying Eu content from x = 2.4 to 20 mol %. The optical and physical effects of high europium concentration on these thin films were studied using photoluminescence ͑PL͒ spectroscopy, x-ray diffraction ͑XRD͒, and Rutherford backscattering spectrometry. PL spectra demonstrate that emission due to the 5 D 0 to 7 F J transitions in Eu 3+ grows linearly with Eu content up to 10 mol %. Time-resolved PL indicates decay parameters remain similar for films with up to 10 mol % Eu. At 20 mol %, however, PL intensity decreases substantially and PL decay accelerates, indicative of parasitic energy transfer processes. XRD shows films to be polycrystalline and beta-phase for low Eu compositions. Increasing Eu content beyond 5 mol % does not continue to modify the film structure and thus, changes in PL spectra and decay cannot be attributed to structural changes in the host. These data indicate the optimal doping for optoelectronic devices based on ͑Eu x Ga 1-x ͒ 2 O 3 thin films is between 5 and 10 mol %.

Doping of Ga2O3bulk crystals and NWs by ion implantation

“…The spectra in Fig. 4 were normalized to the main Eu 3+ emission peak at ~611 nm attributed to the 5 D 0 → 7 F 2 intraionic transition in agreement with previous reports in Eu-doped Ga 2 O 3 films and nanostructures [4][5][6][7][8] . The annealing temperature has a strong effect on the Eu 3+ lines as seen in Fig.…”

“…In particular, Eu-doping has been studied with view to its application in phosphors due to the intense red intra-4f 6 transitions of the Eu 3+ ions 4 . In these studies Eu was successfully incorporated and optically activated in polycrystalline thin films 5 , nanopowders 6 or nanowires (NWs) 7 . REs incorporation into single crystals, in contrast, remains challenging due their low solubility in the crystalline matrix.…”

Optical properties of LFZ grown β-Ga2O3:Eu3+ fibres

“…Furthermore, the wide band gap of ␤-Ga 2 O 3 makes this TCO a suitable host for phosphor applications [11][12][13][14][15][16][17][18][19][20][21][22]. As an example, high luminance was obtained in thin-film electroluminescent displays when gallium oxide is activated with europium ions [12].…”

“…As an example, high luminance was obtained in thin-film electroluminescent displays when gallium oxide is activated with europium ions [12]. However, due to poor crystallization of the gallium oxide films [13][14][15], the rare earth ion emission lines are very broad and little is known about the mechanisms behind the intraionic Eu 3+ luminescence in the crystalline Ga 2 O 3 environment. More recently, nanostructured ␤-Ga 2 O 3 has been synthesized by different routes and intentionally activated with rare earth ions for nanophosphor applications [17][18][19][20][21][22].…”

“…More recently, nanostructured ␤-Ga 2 O 3 has been synthesized by different routes and intentionally activated with rare earth ions for nanophosphor applications [17][18][19][20][21][22]. As for the thin films [13][14][15], large full width at half maximum of the main 5 D 0,1 → 7 F J transitions of the Eu 3+ ions in the nanopowders [18,20] for the emitting ions in crystalline environments, from where the identification of the number of emitting Eu centres and site symmetry could be explored via the Stark level splitting due to the crystal field effect. Although the Eu 3+ emission has been reported for thin films and nanopowders [11][12][13][14][15][16][17][18][19][20][21][22], information on the rare earth ion spectroscopic properties in bulk ␤-Ga 2 O 3 remains scarce and constitutes an important issue to clarify the ion properties inside this TCO material.…”