PhD Thesis_RuiMSMartins.pdf - RUN UNL

In-situ XRD studies during growth of Ni-Ti SMA films and their complementary ex-situ characterization
Resistivity (µΩ
µΩ.m)
1.0
0.9
0.8
0.7
0.6
M s
R f
M f
M f
M s
R f
R s
Cooling
R s
no Vb
- 45 V
Heating
A s A
R' f
A f
R' f As
A f
R' s
R' s
no Vb
- 45 V
0.5
-110 -90 -70 -50 -30 -10 10 30 50 70 90 110
Temperature (°C)
(a)
-110 -90 -70 -50 -30 -10 10 30 50 70 90 110
(b)
Temperature (°C)
Fig. 3.39: Dependence of the ER with temperature for the Ni-Ti samples, deposited without and with a
V b of −45 V on a TiN buffer layer of thickness ≈ 15 nm; (a) during cooling and (b) heating. The result
from Fig. 3.38 has been inserted for comparison.
For the Ni-Ti sample deposited without V b , the ER values of R-phase and B2 phase
are higher than for deposition with V b = −45 V. Additionally, it has been observed that for the
samples deposited with V b = −45 V, the transformations temperatures are lower when
compared with the Ni-Ti sample deposited without V b .
1.0
Cooling
Heating
Resistivity (µΩ
µΩ.m)
0.9
0.8
0.7
M f
M f
M f
M s
M s
M s
R f
R s
R f
R f
R s
R s
no Vb
-45 V
-90 V
R' A
R' As f s
f
R'
R' f Af
A s
f
A s
R'
A
s
f
R's
no Vb
-45 V
-90 V
0.6
-110 -90 -70 -50 -30 -10 10 30 50 70 90 110
Temperature (°C)
(a)
-110 -90 -70 -50 -30 -10 10 30 50 70 90 110
Temperature (°C)
(b)
Fig. 3.40: Dependence of the ER with temperature for the Ni-Ti samples deposited without V b , with −45 and
−90 V on a TiN buffer layer of thickness ≈ 215 nm; (a) during cooling and (b) during heating.
Chapter 3 – Results 135