Structural and emission properties of Tb³⁺-doped nitrogen-rich silicon oxynitride films

Abstract

Terbium doped silicon oxynitride host matrix is suitable for various applications such as light emitters compatible with CMOS technology or frequency converter systems for photovoltaic cells. In this study, amorphous Tb ion doped nitrogen-rich silicon oxynitride (NRSON) thin films were fabricated using a reactive magnetron co-sputtering method, with various N flows and annealing conditions, in order to study their structural and emission properties. Rutherford backscattering (RBS) measurements and refractive index values confirmed the silicon oxynitride nature of the films. An electron microscopy analysis conducted for different annealing temperatures (T ) was also performed up to 1200 °C. Transmission electron microscopy (TEM) images revealed two different sublayers. The top layer showed porosities coming from a degassing of oxygen during deposition and annealing, while in the region close to the substrate, a multilayer-like structure of SiO and SiN phases appeared, involving a spinodal decomposition. Upon a 1200 °C annealing treatment, a significant density of Tb clusters was detected, indicating a higher thermal threshold of rare earth (RE) clusterization in comparison to the silicon oxide matrix. With an opposite variation of the N flow during the deposition, the nitrogen excess parameter (N) estimated by RBS measurements was introduced to investigate the Fourier transform infrared (FTIR) spectrum behavior and emission properties. Different vibration modes of the Si-N and Si-O bonds have been carefully identified from the FTIR spectra characterizing such host matrices, especially the 'out-of-phase' stretching vibration mode of the Si-O bond. The highest Tb photoluminescence (PL) intensity was obtained by optimizing the N incorporation and the annealing conditions. In addition, according to these conditions, the integrated PL intensity variation confirmed that the silicon nitride-based host matrix had a higher thermal threshold of rare earth clusterization than its silicon oxide counterpart. Analysis of time-resolved PL intensity versus T showed the impact of Tb clustering on decay times, in agreement with the TEM observations. Finally, PL and PL excitation (PLE) experiments and comparison of the related spectra between undoped and Tb-doped samples were carried out to investigate the impact of the band tails on the excitation mechanism of Tb ions.

First down converter multilayers integration in an industrial Si solar cell process

“…One can notice that the increase of RFP Tb leads to the decrease of both LO and TO vibration modes of Si─N bonds. The absence of vibration modes peaking at around 1080 and 1250 cm −1 attests of the absence of any oxygen‐based compound as previously observed in similar host matrix . The analysis of the Figure C reveals a decrease of the Si─N bond quantity with RFP Tb because all the multilayers produced here have the same total thickness.…”

“…The absence of vibration modes peaking at around 1080 and 1250 cm −1 attests of the absence of any oxygen-based compound as previously observed in similar host matrix. 36,40 The analysis of the Figure 1C 36 Such an empirical approach is in agreement with the law proposed by Makino,42 assuming that our produced sputtering layers do not contain any hydrogen species. The result is displayed in the inset of Figure 1C Figure 2A.…”

The nitrogen concentration effect on Ce doped SiOxNy emission: towards optimized Ce3+ for LED applications

“…Indeed, the Si 3 N 4 has much higher RE ions solubility in comparison to SiO x counterpart, thus inhibiting RE ions clustering. 21,22 Moreover, its lower bandgap (4-5 eV) 23 can improve both electrical conductivity and the onset voltage for the electroluminescence signal. 24,25 Since the presence of oxygen is crucial for a Ce 3+ emission, 26 one possibility is to combine advantages of SiO 2 (i.e.…”

Down-shifting Si-based layer for Si solar applications

“…It is worth mentioning that the Full Width at Half Maximum (FWHM) of the PLE band is much broader than the FWHM of typical f-d absorption bands of rare earth ions, which is another evidence for indirect excitation of these ions. The optimized Tb 3+ -doped SiN x layer obtained is compared to an optimized Tb 3+ -doped layer made with a silicon oxynitride matrix, SiO x N y previously studied in our team [25]. The Tb 3+ ions PL peaks at 285 nm excitation wavelength of our optimized sample is found to be 2.3 times more intense than the optimized sample obtained on the SiO x N y :Tb 3+ system (Fig.…”

“…In addition, some of those used materials were toxic because of the presence of fluorine [20] or of heavy metals such as cadmium [21], or lead [22]. Following this reasoning, various studies using a silicon oxynitride matrix, SiO x N y , doped with terbium ions (Tb 3+ ) have been carried out [23][24][25]. However, the presence of oxygen favors the rare earth clusters formation that is detrimental to an intense emission.…”