We04 Seminar ...porous films from magnetron sputtering by Robin Dedoncker AND ...is the SrAl2O4:Eu,Dy enigma finally solved by David Van der Heggen

When
07-11-2019 from 16:00 to 17:00
Where
S9, multimediaroom
Language
English
Organizer
dr. Jonathan Leliaert
Contact
jonathan.leliaert@ugent.be
Website
https://www.ugent.be/we/solidstatesciences/en
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How can we get porous films from magnetron sputtering? - Robin Dedoncker Over two decades of research: is the SrAl2O4:Eu,Dy enigma finally solved - David Van der Heggen

This duo-seminar will consist of two talks given by Robin Dedoncker and David Van der Heggen and will take place this Thursday 7 November at 4PM in the multimediaroom in S9.

 How can we get porous films from magnetron sputtering? - Robin Dedoncker

Magnetron sputtering is typically characterized by the deposition of dense layers due to a high-energetic flux of incoming sputtered atoms and reflected neutrals. Although a dense film is often required in applications, it is not convenient to use sputtering when porous films are desired. Some strategies exist to overcome this inherent aspect of sputtering. However, most of the known techniques are non-scalable, environmentally harmfull or costly and not industrial applicable.
This presentation elucidates an alternative approach which has already shown promising results. The idea is based on sputter deposition from a powder target, consisting of a mixture of a metal and salt (NaCl). The powder target has a low thermal conductivity and the temperature on the target surface can in this way be controlled by the discharge power. At a certain point, the target will get so hot that NaCl sublimes from the target onto the substrate, while the metal is being sputtered. The result is a metal film containing NaCl crystals. A simple and short water treatment allows the removal of NaCl, and a porous structure remains. This approach offers all beneficial properties of magnetron sputtering and does not rely on aggressive chemicals.

Over two decades of research: is the SrAl2O4:Eu,Dy enigma finally solved - David Van der Heggen

The discovery of SrAl2O4:Eu,Dy as a long lasting afterglow phosphor over two decades ago marked the beginning of a relentless search for new, even better performing persistent phosphors. In his original paper from 1996, Matsuzawa proposed a model to explain the afterglow mechanism in SrAl2O4:Eu,Dy  and since then many authors have modified these models in order to explain experimental findings. The result after 23 years of research is that we are left with a plethora of models and a lot of experimental data but understanding of the actual afterglow mechanism in SrAl2O4:Eu,Dy  remains scattered. 
We will take a closer look at the physical mechanism behind the phosphor’s afterglow and try to find an answer as to why the storage capacity of the phosphor is limited.