Tunable Emission from Europium-Doped Silicon Oxynitride Thin Films

This work reports tunable emission of Eu 3+ and Eu 2+ from SiO x N y films fabricated by integrated electron cyclotron plasma enhanced chemical vapor deposition and magnetron sputtering. The photoluminescence (PL) spectra of intense red emission from Eu 3+ around 600 nm and blue broadband emission from 400 to 750 nm of Eu 2+ are observed under daylight conditions with the naked eye. The findings of this work are promising toward the realization of europium doped Si-based materials for photonics and lighting technologies. Silicon (Si) based optoelectronic components are becoming very important for the advanced silicon photonic industry 1 . These optoelectronics components are also highly desirable for biochemical sensor applications in medicine and environmental control 2 . 3,4 However, the indirect band gap of bulk Si has limited its light emission efficiency . Several methods have been developed to engineer Si into an efficient light emitter, and among them, doping Si with rare earth ions has earned significant interest due to their excellent luminescent and chemical stability. Europium (Eu) is one of the promising rare earths that exhibits two optically active states, Eu 2+ and Eu 3+ , making it suitable for a wide range of color emission from the blue to the red spectral region 5 . The emission lines of Eu 3+ correspond to the transitions from the excited 5 D 0 level to the 7 F J (J= 0 to 6) level of the 4f n configuration and generate sharp peaks in the red spectral range. On the other hand, the emission from Eu 2+ occursdue to the electronic transitions from the 4f 6 5d 1 level to the 4f 7 shell, and emission happens between 400 to 800 nm 6 . Thus, Eu is very attractive in the fields of silicon photonics, along with solid state lighting, display, senor and photovoltaic applications 7 . In this study, we have investigated the optical properties and compositions of Eu-doped Si oxynitride thin films prepared by integrated electron cyclotron resonance plasma enhanced chemical vapor deposition and magnetron sputtering (ECR–PECVD) on p-type Si substrates. Different samples were fabricated by varying nitrogen and oxygen flow to understand the effect of the surrounding matrix on the luminescence. Post-deposition annealing was performed at different temperatures ranging from 600 to 1200 O C. The dependencies of the PL properties on Eu concentrations and annealing temperatures were investigated in detail. It is found that films annealed at a temperature higher than 1000 O C produced bright red emission from Eu 3+ and bright blue emission from Eu 2+ , which can be seen under daylight conditions with the naked eye. Furthermore, the existence of Eu-containing phases is confirmed by high-resolution X-ray diffraction spectroscopy (XRD). The stoichiometry of the films is analyzed by Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA). The optical constants and thickness of the films are analyzed by variable angle spectroscopic ellipsometry (VASE). This work highlights the tunable luminescence property of Eu doped SiO x N y thin films, making them promising candidates in light emission systems for optoelectronic platforms. Acknowledgements: This work is funded by NSERC Discovery Grant RGPIN-2019-06023 and ORF Grant ORF-RE 09-051. References Wang Z, Abbasi A, Dave U, et al., Laser Photon Rev . 2017;11(4). doi:10.1002/lpor.201700063 Germer S, Cherkouk C, Rebohle L, Helm M, Skorupa W., SPIE 8767, Integrated Photonics: Materials, Devices, and Applications II . 2013;8767:1-13. doi:10.1117/12.2017275 Tian Y, Chen B, Hua R, et al., J. Appl. Phys . 2011; 109 (5): 53511. doi:10.1063/1.3551584 Tian Y, Chen B, Hua R, et al., Cryst. Eng. Comm . 2012; 14 (5): 1760-1769. doi:10.1039/C1CE06232H Lin Z, Huang R, Wang H, et al., J. Alloys Compd . 2017; 694: 946-951. doi:10.1016/j.jallcom.2016.10.132 Azmi F, Gao Y, Khatami Z, Mascher P., J. Vac. Sci. Technol. A 2022; (043402). doi:10.1116/6.0001761 Bellocchi G, Franzò G, Iacona F, et al., Opt. Express . 2012; 20 (5): 5501-5507. doi:10.1364/OE.20.005501