On the potential of Er-doped AlN film as luminescence sensing layer
for multilayer Al/AlN coating health mo nitoring
Liping Fang, Anyi Yin, Shengfa Zhu
*
, Jingjing Ding, Lin Chen, Dongxu Zhang, Zhen Pu,
Tianwei Liu
**
Institute of Materials, China Academy of Engineering Physics, Mianyang, 621700, PR China
article info
Article history:
Received 12 June 2017
Received in revised form
16 August 2017
Accepted 17 August 2017
Available online 19 August 2017
Keywords:
Aluminum nitride
Erbium doping
Magnetron sputtering
Photoluminescence
Luminescence sensing
abstract
Luminescence sensing is an attractive approach for in-situ monitoring the health and integrity of
multilayered surface protective coatings on highly active metals. In this work, we demonstrate the po-
tential of erbium (Er) doped aluminum nitride (AlN) films to be applied as luminescence sensing layer in
the Al/AlN multilayered coating system. The AlN:Er films were prepared by radio-frequency magnetron
sputtering from Al targets doped with varied concentrations (from 0.5 at.% to 2.5 at.%) of Er. The chemical
composition, surface morphology, crystal structure, chemical state and optical properties of the depos-
ited AlN:Er films were investigated. We found that the crystal structure, surface roughness and optical
properties of the AlN:Er films have strong correlations with the Er doping level. The as-deposited AlN:Er
films showed the characteristic photoluminescence emission lines of the trivalent Er ions in the visible
frequency range and quenching was observed when the Er doping level increased to 2.5 at.%. This work
signifies the viabil ity of AlN:Er film as luminescence sensing layer and the optimal Er doping concen-
tration of the Al sputtering target is 2.0 at.% for practical applications.
© 2017 Elsevier B.V. All rights reserved.
1. Introduction
Luminescence sensing [1e5] is an attractive approach for eval-
uating the wear and corrosion of protective coatings deposited on
reactive metals. This concept was initially proposed for in-situ
monitoring the health of ceramic thermal barrier coatings depos-
ited on metal blades and other hot components in gas turbines. Our
work studies the probability of using such luminescence sensing
technique to monitor the integrity of protective coatings deposited
on reactive metals. Basically, there are two approaches to apply this
idea: a layer of ceramic material doped with luminescent ions could
be deposited under the protective coating, and luminescence could
be detected when the protective coating was deteriorated by wear
or corrosion; the luminescent layer itself functions as the protective
coating, reduced or even no luminescence signal could be detected
when the luminescent layer is worn or eroded away, and this sig-
nifies the failure of the protective coating. This non-destructive
sensing technique is quite useful for in-situ monitoring the health
and integrity of the surface protective coatings deposited on highly
active metals. The hidden initial cracks or delamination sites of the
protective coating could be identified and remedial approaches
could be applied before worse failure occurs.
AlN is a hard and chemical inert material, which could be
applied as surface protective coatings for active metals [2,6,7]. And
AlN films bear the potential to enhance the wear and corrosion
resistance by forming multilayer Al/AlN coatings with the merits of
higher density, better adhesion property, and lower residual stress
than the two single layer coatings alone [6e9]. The investigation of
the viability of AlN:Er film as a luminescence sensing layer which
could be incorporated into the Al/AlN multilayer coating is the main
intention of our work.
A number of previous studies have been performed on doping
AlN films with rare earth or common metallic ions for various
purposes [10e20]. And reactive radio-frequency magnetron sput-
tering is the most favorable approach due to the fact that high
quality films could be obtained with relatively low cost. However,
little literature has indicated the relationship between the doping
concentration of the sputtering target and the performance of the
luminescent AlN:Er films, which is important for practical appli-
cations of the AlN:Er luminescence sensing layer.
In this work, we investigated the effect of Er doping in the
* Corresponding author.
** Corresponding author.
E-mail addresses: zhushf-306@163.com (S. Zhu), liutw30@163.com (T. Liu).
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: http://www.elsevier.com/locate/jalcom
http://dx.doi.org/10.1016/j.jallcom.2017.08.174
0925-8388/© 2017 Elsevier B.V. All rights reserved.
Journal of Alloys and Compounds 727 (2017) 735e743