PhD Thesis_RuiMSMartins.pdf - RUN UNL

More documents

Recommendations

Info

In-situ XRD studies during growth of Ni-Ti SMA films and their complementary ex-situ characterization 1E8 1E8 Intensity (arbitrary units) Deposition TiN (3 min) Thickness ≈ 15 nm Deposition TiN (3 min) Thickness ≈ 15 nm o After deposition After 90 min 1 (a) 0.5 1.0 1.5 Incident angle θ (deg) 1 (b) 0.5 1.0 1.5 Incident angle θ (deg) Fig. 3.30: Typical XRR spectra; (a) for a 3 min deposition of a TiN buffer layer (black line) with the fitting curve (red line), (b) obtained immediately after deposition (black line) and obtained 90 min after deposition of TiN (blue curve). A V b of −30V was applied during the growth of the TiN layers. Figure 3.31 shows results obtained from the in-situ XRD data for the Ni-Ti depositions on top of the three different TiN buffer layers (three different TiN thickness values: ≈ 15, ≈ 80 and ≈ 215 nm). Represented are: (a) the variation of the net area of the B2(110) peak for all samples and additionally the variation of the net area of the B2(211) peak for the sample with a TiN layer of thickness ≈ 15 nm, (b) the variation of the a 0 values (as calculated from the lattice constant, d, according to the B2(110) and B2(211) peak positions), versus time. The Ni-Ti film deposited on the TiN layer with thickness ≈ 215 nm shows a preferential growth of oriented grains of the Ni-Ti B2 phase from the beginning of the deposition, with a constant growth rate during the whole deposition. For the Ni-Ti film deposited on a TiN layer of thickness ≈ 15 nm, the B2(110) diffraction peak also appeared from the beginning of the deposition, but much less intense. In this latter case, the B2(211) peak was also detected with a crossover from oriented grains dominating at small thicknesses to oriented grains taking over at larger thicknesses. Despite an initial stronger increase, the net area of the B2(110) peak, for the Ni-Ti film deposited on a TiN buffer layer with ≈ 80 nm thickness, approached the one of the B2(110) peak of the previous sample (with a TiN layer of thickness ≈ 15 nm) after ≈ 85 min [in the case of the sample with a TiN layer of ≈ 80 nm, the B2(211) peak was not monitored in situ]. These experiments have also shown that the B2(200) diffraction peak did not assume an important relevance (in contrast to the depositions on oxidized Si substrates) and, thus, not considered for this representation. Chapter 3 – Results 127
In-situ XRD studies during growth of Ni-Ti SMA films and their complementary ex-situ characterization Net Area (arb. units) 1100 1000 900 500 400 300 200 B2(110): B2(211): 100 Deposition Annealing 0 0 25 50 75 100 125 150 175 200 (a) Time (min.) TiN ≈ 215 nm ≈ 80 nm ≈ 15 nm ≈ 15 nm Lattice parameter, a 0 (nm) 0.308 0.307 0.306 0.305 0.304 0.303 0.302 Deposition B2(211): TiN ≈ 215 nm ≈ 80 nm ≈ 15 nm ≈ 15 nm 0 25 50 75 100 125 150 175 200 (b) Time (min.) B2(110): Annealing Fig. 3.31: In-situ XRD results for Ni-Ti films deposited without V b on three different TiN buffer layers; (a) net areas of the diffraction peaks of the B2 phase recorded as a function of time, (b) a 0 values as obtained from the positions of the diffraction peaks as a function of time. Figure 3.31(b) shows the variation of the a 0 values of the Ni-Ti films during the deposition and annealing steps. A continuous decrease was perceptible during the whole film deposition. In the case of the film with a TiN buffer layer of thickness ≈ 80 nm, when the propensity for the development of the diffraction peak B2(110) is noticeable, a 0 of B2 phase, as calculated from d (110) , shows lower values, when compared with the film deposited on the TiN buffer layer with ≈ 15 nm. Nevertheless, when the net areas of the B2(110) diffraction peak of both samples approached the same value (approximately after 85 min), also the calculated a 0 values approached each other. 3.3.1.2. Effect of the substrate bias voltage on the structure of Ni-Ti films deposited on TiN The effect of a V b of −45 V during the deposition of a Ni-Ti film on a TiN buffer layer with a thickness of ≈ 15 nm (a dominating orientation could not be identified for this TiN layer, i.e. primarily and oriented grains nucleate and grow) was tested [Fig. 3.32(b)]. The development of the oriented grains of the Ni-Ti B2 was suppressed when compared with the sample deposited without bias [Fig. 3.32(a)]. In the case of the Ni-Ti film deposited with an ion bombardment promoted by the applied V b , the oriented grains dominated since the beginning. This extra parameter favoured the stacking of (110) planes of the B2 phase parallel to the substrate surface. Chapter 3 – Results 128
Page 1 and 2:
RUI MIGUEL DOS SANTOS MARTINS IN-SI
Page 3 and 4:
ACKNOWLEDGEMENTS The research work
Page 5 and 6:
At CENIMAT, Luís Pereira also carr
Page 7 and 8:
SUMÁRIO O fabrico de películas fi
Page 9 and 10:
LIST OF SYMBOLS AND ABREVIATIONS α
Page 11 and 12:
TABLE OF CONTENTS Introduction ....
Page 13 and 14:
LIST OF FIGURES Fig. 1.1: Power/wei
Page 15 and 16:
Fig. 2.3: Calculated integrated pho
Page 17 and 18:
Fig. 3.25: Pole figures of Ni-Ti B2
Page 19 and 20:
Fig. 3.66: SAED pattern obtained on
Page 21 and 22:
LIST OF TABLES Tab. 1.1: Factors af
Page 23 and 24:
In-situ XRD studies during growth o
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98: In-situ XRD studies during growth o
Page 147: In-situ XRD studies during growth o
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
Page 225 and 226:
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
Page 241 and 242:
Page 243 and 244:
Page 245 and 246:
Page 247 and 248:
Page 249 and 250:
Page 251 and 252:
Page 253 and 254:
Page 255 and 256:
Page 257 and 258:
Page 259:
show all

PhD Thesis_RuiMSMartins.pdf - RUN UNL

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?