Optical and structural studies in Eu-implanted AlN films

Self Cite

AlN films grown on sapphire were implanted with 300 keV Eu ions to fluences from 3 ϫ 10 14 to 1.4ϫ 10 17 atoms/ cm 2 in two different geometries: "channeled" along the c-axis and "random" with a 10°angle between the ion beam and the surface normal. A detailed study of implantation damage accumulation is presented. Strong ion channeling effects are observed leading to significantly decreased damage levels for the channeled implantation within the entire fluence range. For random implantation, a buried amorphous layer is formed at the highest fluences. Red Eu-related photoluminescence at room temperature is observed in all samples with highest intensities for low damage samples ͑low fluence and channeled implantation͒ after annealing. Implantation damage, once formed, is shown to be stable up to very high temperatures.

Section: Introductionmentioning

confidence: 94%

Optical doping and damage formation in AlN by Eu implantation

Lorenz

Alves

Gloux

et al. 2010

Self Cite

“…The same is also observed for Eu-implanted GaN and AlN films prepared under similar conditions. 25,26 The fits to the experimental scans are also shown in Fig. 6 and used vibration amplitudes of 0.18͑2͒ Å, 0.20͑2͒ Å, and 0.28͑2͒ Å for Al, Ga, and Eu, respectively, for the ͗0001͘ direction, and 0.21͑2͒ Å, 0.24͑2͒ Å, and 0.4͑1͒ Å for the ͗2113͘ direction.…”

Section: -3mentioning

confidence: 99%

“…29,30 Furthermore, Eu 3+ ions are known to give rise to multiple active centers in the binary systems. 31,32 In this context, it is important to emphasize the difference of the lattice site location of Eu ͑Eu is known to be incorporated into near-substitutional Ga and Al sites in GaN and AlN, respectively 25,26 ͒ and the different optically active centers ͑often also called "sites"͒ which depend on the local symmetry around the substitutional Eu ͑which can for example be influenced by next neighbor defects͒. Figure 7 presents the PL spectra showing the main 5 D 0 → 7 F 2 transition excited using the 325 nm laser line of all SL samples as well as GaN, AlN, and Al 0.5 Ga 0.5 N epilayers implanted with 1 ϫ 10 15 cm −2 and annealed.…”

Section: B Optical Analysismentioning

confidence: 99%

Functionalizing self-assembled GaN quantum dot superlattices by Eu-implantation

Magalhães

Peres

Fellmann

et al. 2010

Self Cite

Self-assembled GaN quantum dots ͑QDs͒ stacked in superlattices ͑SL͒ with AlN spacer layers were implanted with Europium ions to fluences of 10 13 , 10 14 , and 10 15 cm −2 . The damage level introduced in the QDs by the implantation stays well below that of thick GaN epilayers. For the lowest fluence, the structural properties remain unchanged after implantation and annealing while for higher fluences the implantation damage causes an expansion of the SL in the ͓0001͔ direction which increases with implantation fluence and is only partly reversed after thermal annealing at 1000°C. Nevertheless, in all cases, the SL quality remains very good after implantation and annealing with Eu ions incorporated preferentially into near-substitutional cation sites. Eu 3+ optical activation is achieved after annealing in all samples. In the sample implanted with the lowest fluence, the Eu 3+ emission arises mainly from Eu incorporated inside the QDs while for the higher fluences only the emission from Eu inside the AlN-buffer, capping, and spacer layers is observed.

“…6,7 It is also regarded as a potential candidate for photoluminescence and electroluminescence devices due to its wide bandgap (6.2 eV). 8 Many groups have reported rare-earth or transition metal doped AlN but most of them focused on thin films, [9][10][11][12][13][14] very few studies investigated powder phosphors. Although the luminescent properties of rare-earth doped AlN films have been extensively studied, it is still not clear where these luminescent ions locate in the wurtzite AlN lattice as there is not enough space for a large cation to occupy the tetrahedral Al sites.…”

Section: Introductionmentioning

confidence: 99%

Europium location in the AlN: Eu green phosphor prepared by a gas-reduction-nitridation route

Yin

Zhu

et al. 2012

Eu doped aluminum nitride phosphors were successfully synthesized by a novel gas-reduction-nitridation route with a reaction temperature of 1400 C and a soaking time of 3 h. The obtained AlN:Eu phosphors were analyzed to elucidate the location of the Eu luminescent center. High-resolution transmission electron microscopy and transmission electron microscopy-energy dispersive spectra proved that Eu was located in the crystal lattice of AlN, then EXAFS revealed that Eu occupied a highly distorted Al site coordinated by four nitrogen at about 2.30-2.40 Å , and the second nearest neighbors of Eu were 12 Al. This could be confirmed by the first-principles calculations based on the obtained local structure around the Eu luminescence center, where the theoretical absorption spectrum was similar to the experimental excitation spectrum. X-ray appearance near edge structure showed that Eu existed in terms of both Eu 3þ and Eu 2þ ions, which could be related to the limited location space of Eu. High temperature treatment could significantly increase the amount of Eu 2þ by the expansion of the crystal lattice, leading to an increased green luminescence of the obtained AlN:Eu phosphors. V