PhD Thesis_RuiMSMartins.pdf - RUN UNL

In-situ XRD studies during growth of Ni-Ti SMA films and their complementary ex-situ characterization
1500
Intensity (arb. units)
1000
500
*
B2(100)
B2(110)
R-phase
*
*
R-phase
B2(200)
B2(310)
470°C
Substrate holder
RT
0
10 15 20 25 40 42
Scattering angle 2θ (deg)
Fig. 3.4: XRD spectra from a Ni-Ti sample deposited with a V b of −45 V on naturally
oxidized Si(100), during annealing after deposition stop at 470°C and at RT.
The deposition of Ni-Ti on naturally oxidized Si(111) substrates without applying a
substrate bias voltage was also studied. The net areas calculated from the B2(110) and
B2(200) diffraction peaks recorded as a function of time during the film growth, as well as the
values calculated for a o , are shown in Fig. 3.5. There was a preferential development of the
B2(200) peak intensity when compared with the B2(110) peak. The presence of faint
intensities of the B2(310) were detected by performing a measurement in a higher 2θ range
during annealing after the deposition is stopped (results not shown here). The values obtained
for a o as calculated from B2(110) and B2(200) show a convergence to a common value
(≈ 0.303 nm), which is lower than the values observed in the experiments using naturally
oxidized Si(100) substrates with and without V b .
Chapter 3 – Results 104