PhD Thesis_RuiMSMartins.pdf - RUN UNL

In-situ XRD studies during growth of Ni-Ti SMA films and their complementary ex-situ characterization
Intensity (arb. units)
10000
1000
*
TiN(111)
No bias
- 45V
- 90V
B2(110)
*
*
TiN(111)
No bias
- 45V
- 90V
R(112)
R(300)
B2(110)
*
R(202)
Substrate holder *
TiN(002)
Substrate holder *
15 16 18 19
(a)
Scattering angle 2θ (deg)
15 16 18 19
(b)
Scattering angle 2θ (deg)
Fig. 3.35: XRD spectra obtained for the Ni-Ti films deposited without V b , with −45 V and
−90 V on TiN buffer layers of thickness ≈ 215 nm; (a) after deposition at ≈ 470°C, (b) at RT.
A decrease of the full width at half maximum (FWHM) value with the increasing V b is
seen in Fig. 3.35(a). This suggests an overall trend of increasing coherence domain length
with increasing V b for the deposition of the Ni-Ti films on a TiN buffer layer of thickness
≈ 215 nm.
3.3.2. Ex-situ characterization
Typical bright field X-TEM micrographs for the Ni-Ti samples deposited without V b
on a TiN layer of thickness values of ≈ 15 and ≈ 215 nm are shown in Fig. 3.36. A columnar
structure was identified for the Ni-Ti films. In accordance with the Thornton structure model,
the TiN layers also show a columnar structure due to the substrate temperature of ≈ 470°C
when compared with the T m of ≈ 3000°C.
Chapter 3 – Results 131