Abstract
Thermochromic
La
1
−
x
Sr
x
Mn
O
3
(
x
=
0.1
, 0.175, and 0.3) (LSMO) smart coatings were synthesized on (100) silicon and (0001) sapphire substrates by means of reactive pulsed laser deposition process at relatively low substrate temperature
(
500
°
C
)
and without postannealing. X-ray diffraction patterns indicated that all deposited LSMO films have polycrystalline structures. The energy dispersive x-ray spectroscopy analysis indicated approximately the same
La
∕
Sr
ratio in the formed LSMO coatings as in their corresponding targets. While, the x-ray photoelectron spectroscopy analysis of the LSMO/sapphire revealed that the strontium segregate at the film surface. The thermochromism of LSMO coatings was investigated by measuring their infrared reflectance as a function of temperature (up to
160
°
C
). It was observed that the reflectance decreased as the temperature increased. Reflectance switching of about 25% was achieved in
La
0.7
Sr
0.3
Mn
O
3
∕
Si
at a wavelength of
5
μ
m
. The sheet electrical resistivity as a function of temperature (up to
130
°
C
) of LSMO/sapphire was investigated by means of the standard four-point probe technique. The resistivity decreased with increasing the temperature and no metallic-to-insulator transition was observed. However, it is found that the resistivity is very sensitive to the concentration level of Sr dopant: the resistivity decreased as the concentration of Sr increased. In addition, at room temperature, a higher temperature coefficient of resistance of
−
2.30
%
∕
°
C
was achieved in
La
0.9
Sr
0.1
Mn
O
3
thin films. Finally, these LSMO smart coatings are promising materials for optical switching and IR uncooled bolometer devices.