Functionalizing window coatings with luminescence centers by combinatorial sputtering of scatter-free amorphous SiAlON:Eu2+ thin film composition libraries

Abstract

SiAlON window coatings are applied on an industrial scale to achieve e.g. scratch-resistance and anti-reflection. Doping these SiAlONs with rare-earths adds luminescent functionality, which could be applied in photovoltaics. By using a combinatorial reactive sputtering approach, an amorphous thin film composition library with a Si:Al ratio from 0.062 : 1 to 3.375 : 1 and a Eu doping from 4.8 at.% to 26 at.% is created. This library uniquely combines high absorption, strong emission and absence of light scattering. By combining position-dependent EDX measurements with transmission and emission spectra, properties like the index of refraction, absorption strength, emission wavelength and decay times of the library can directly be related to the composition. Throughout the library, an index of refraction of 1.63 ± 0.03 is observed, typical for a film with low nitrogen content. The library also shows a large absorption coefficient of 1294 ± 8 cm −1 at.% −1 . Laser-excited emission spectra show that the library has a strong redshift from 500 nm to 550 nm with increasing Al concentration. An increase in Eu concentration also causes a shift of the emission to red. Decay spectra show that a high degree of Si greatly improves the luminescence intensity. These functionalized SiAlON coatings can be of great interest for transparent and scatter-free luminescent solar concentrators applied as windows.

Distinguishing between Structural Models of β′-Sialons Using a Combined Solid-State NMR, Powder XRD, and Computational Approach

“…Hence, this observation strongly rules out the plane model from further consideration. The expansion of the unit cell observed experimentally is attributed to the difference in bond lengths (particularly, longer Al−O compared to Si−N), 10 the distribution of which within the models influences the resulting unit-cell parameters.…”

“…However, this then implies that full stochastic atomic mixing is unlikely and some type of local ordering/clustering occurs to maximize the number of Si–N and Al–O bonds. A detailed understanding of the atomic ordering is of real fundamental structural chemistry interest and has recently become practically and technologically much more important as sialons have started to be used in more functional applications, for example, doped with relevant ions to produce efficient phosphor materials. − For such applications, the crystal structure of the host material, in particular, the local coordination around the luminescence centers plays a crucial role.…”

Fabrication and Characterization of Transparent and Scratch-Proof Yttrium/Sialon Thin Films

“…Sialon thin films, which are a solid solution of Si, Al, O, and N, have received significant attention due to their unique mechanical properties including high wear resistance, low coefficient of friction, and high decomposition temperature [ 21 , 22 ]. Sialon thin films are already employed in the industry for various anti-reflection purposes and scratch-protection applications, owing to their reflective coatings’ mechanical strength, thermal resistance, and chemical inertness [ 21 , 23 , 24 , 25 ]. The surface of the Sialon thin films can be modified and imparted with added value by introducing alkaline earth/lanthanide metals into the surface.…”

“…Recently, Merkx et al [ 23 ] fabricated transparent Sialon:Eu thin films using three sputtering sources (Al, Eu, Si) in a reactive Ar + N 2 + O 2 at room temperature followed by rapid heat treatment to improve the optical properties of Sialon thin films. The sputtering technique, however, suffers from certain disadvantages such as a low deposition rate of the film and challenges in controlling the stoichiometry of the deposited material.…”