| 1. |
- Salamania, Janella, 1992-, et al.
(författare)
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Elucidating dislocation core structures in titanium nitride through high-resolution imaging and atomistic simulations
- 2022
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 224
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Tidskriftsartikel (refereegranskat)abstract
- Although titanium nitride (TiN) is among the most extensively studied and thoroughly characterizedthin-film ceramic materials, detailed knowledge of relevant dislocation core structures is lacking. Byhigh-resolution scanning transmission electron microscopy (STEM) of epitaxial single crystal (001)-oriented TiN films, we identify different dislocation types and their core structures. These include, besidesthe expected primary a/2{110}h110i dislocation, Shockley partial dislocations a/6{111}h112i and sessileLomer edge dislocations a/2{100}h011i. Density-functional theory and classical interatomic potentialsimulations complement STEM observations by recovering the atomic structure of the different disloca-tion types, estimating Peierls stresses, and providing insights on the chemical bonding nature at the core.The generated models of the dislocation cores suggest locally enhanced metal–metal bonding, weakenedTi-N bonds, and N vacancy-pinning that effectively reduces the mobilities of {110}h110i and {111}h112idislocations. Our findings underscore that the presence of different dislocation types and their effects onchemical bonding should be considered in the design and interpretations of nanoscale and macroscopicproperties of TiN.
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| 2. |
- Salamania, Janella, et al.
(författare)
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High temperature decomposition and age hardening of single-phase wurtzite Ti1−xAlxN thin films grown by cathodic arc deposition
- 2024
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Ingår i: Physical Review Materials. - : AMER PHYSICAL SOC. - 2475-9953. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Wurtzite TmAlN (T-m = transition metal) themselves are of interest as semiconductors with tunable band gap, insulating motifs to superconductors, and piezoelectric crystals. Characterization of wurtzite TmAlN is challenging because of the difficulty to synthesize them as single-phase solid solution and such thermodynamic, elastic properties, and high temperature behavior of wurtzite Ti1-xAlxN is unknown. Here, we investigated the high temperature decomposition behavior of wurtzite Ti1-xAlxN films using experimental methods combined with first-principles calculations. We have developed a method to grow single-phase metastable wurtzite Ti1-xAlxN (x = 0.65, 0.75, 085, and 0.95) solid-solution films by cathodic arc deposition using low duty-cycle pulsed substrate-bias voltage. We report the full elasticity tensor for wurtzite Ti1-xAlxN as a function of Al content and predict a phase diagram including a miscibility gap and spinodals for both cubic and wurtzite Ti1-xAlxN. Complementary high-resolution scanning transmission electron microscopy and chemical mapping demonstrate decomposition of the films after high temperature annealing (950 degrees C), which resulted in nanoscale chemical compositional modulations containing Ti-rich and Al-rich regions with coherent or semicoherent interfaces. This spinodal decomposition of the wurtzite film causes age hardening of 1-2 GPa.
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| 3. |
- Salamania, Janella, et al.
(författare)
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Influence of nitrogen vacancies on the decomposition route and age hardening of wurtzite Ti1−xAlxNy thin films
- 2023
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 41:6
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Tidskriftsartikel (refereegranskat)abstract
- The wurtzite phase of TiAlN has been known to form in industrial grade coatings with high Al content; yet, a significant knowledge gap exists regarding its behavior at high temperatures and the impact of defects on its properties. Specifically, its response to high temperatures and the implications of defects on its characteristics are poorly understood. Here, the high-temperature decomposition of nitrogen-deficient epitaxial wurtzite Ti1-xAlxNy (x = 0.79-0.98, y = 0.82-0.86) films prepared by reactive magnetron sputtering was investigated using x-ray diffractometry and high-resolution scanning transmission electron microscopy. The results show that wurtzite Ti(1-x)Al(x)Ny decomposes by forming intermediary MAX phases, which then segregate into pure c-TiN and w-AlN phases after high-temperature annealing and intermetallic TiAl nanoprecipitates. The semicoherent interfaces between the wurtzite phase and the precipitates cause age hardening of approximately 4-6 GPa, which remains even after annealing at 1200 degrees C. These findings provide insight into how nitrogen vacancies can influence the decomposition and mechanical properties of wurtzite TiAlN.
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