PhD Thesis_RuiMSMartins.pdf - RUN UNL

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In-situ XRD studies during growth of Ni-Ti SMA films and their complementary ex-situ characterization future fabrication of films with a combination of superelasticity and shape memory characteristics. The sputtering equipment installed at ROBL is also a very efficient instrument to deposit, and simultaneously follow in situ the evolution of the structure of ternary alloys like, NiTiHf films: - a preferential growth of oriented grains of the B2 phase from the beginning of the deposition could be obtained using a HfN buffer layer; - the increasing amount of Hf incorporated in NiTiHf films shifts the B2(110) peak towards lower 2θ (higher d-spacings) and decreases its intensity; - the higher transformation temperatures of the NiTiHf SMA, when compared to what was previously observed for Ni-Ti films, have been confirmed by XRD. 5.2. FUTURE WORKS Based on our experiences with the successful versatility of sputter deposition chambers with two magnetrons and in view of the potential of combining the deposition with energetic ion bombardment for growth assistance or amorphization, an additional ion gun (IQ 100 [175]) has been commissioned (during the final period of this <strong>PhD</strong> thesis work) to allow post-deposition ion irradiation or ion bombardment during sputter deposition (Fig. 5.1). The ion gun operating under a fixed incidence angle of 20° to the substrate normal can deliver energetic ions of ≤ 6 keV and up to 10 µA current. It has a sub-mm focus and a maximum scanning field of 10 × 10 mm 2 . Separate differential pumping allows its operation independent from the working pressure for magnetron sputtering, characteristically in the range from 0.1 to 1 Pa. The first experiments with in-situ XRD observation of film growth and post-deposition surface modification have been performed for the study of a Ni-Ti sample. Following the first experiments described in this thesis on the in-situ analysis of the sputtering of Ni-Ti films and the preliminary results obtained on the in-situ study of the energetic ion bombardment of this type of SMA films, it is suggested that future experiments should be dedicated to study changes of film properties by energetic ion irradiation during deposition. Energy and flux of the ions delivered by the gun can be varied independently of the ions and atoms from the magnetron targets. Chapter 5 – Conclusion and Future Works 203
In-situ XRD studies during growth of Ni-Ti SMA films and their complementary ex-situ characterization Fig. 5.1: Sputter deposition chamber inserted into the six-circles HUBER goniometer of ROBL viewed from the detector side with the ion gun (gas supply connected) and the two magnetrons on top (left); design study from the beam entrance side (right) with symmetric magnetrons, ion gun, viewport between Be entrance windows, one turbo pump (70 l/s) at a corner valve which can be used for throttling and substrate alignment [156]. Bellow first results obtained for the study of a Ni-Ti sample using the processing parameters given in Tab. 5.1 give an idea of the potential of this equipment. Ions → He Energy → 5 keV Incident angle → 20° Scanning field → 6 x 6 mm 2 Ion current → 6 µA Current density → ≈ 20 µA/cm 2 Ion flux → ≈ 1.2×10 14 He/cm 2 s Tab. 5.1: Process conditions for the in-situ ion bombardment (using an ion gun) of a near equiatomic Ni-Ti film deposited on a TiN buffer layer in the new sputtering chamber at ROBL. A Ni-Ti film with a preferential growth of oriented grains of the Ni-Ti B2 phase from the beginning of the deposition was deposited (at ≈ 470°C) on a TiN film with a topmost layer formed mainly by oriented grains (Fig. 5.2). The Ni-Ti film was then Chapter 5 – Conclusion and Future Works 204
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RUI MIGUEL DOS SANTOS MARTINS IN-SI
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ACKNOWLEDGEMENTS The research work
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At CENIMAT, Luís Pereira also carr
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SUMÁRIO O fabrico de películas fi
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LIST OF SYMBOLS AND ABREVIATIONS α
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TABLE OF CONTENTS Introduction ....
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LIST OF FIGURES Fig. 1.1: Power/wei
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Fig. 2.3: Calculated integrated pho
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Fig. 3.25: Pole figures of Ni-Ti B2
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Fig. 3.66: SAED pattern obtained on
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LIST OF TABLES Tab. 1.1: Factors af
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In-situ XRD studies during growth o
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