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- Honnali, Sanath Kumar, 1996-
(författare)
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Energy-efficient physical vapor deposition of transition metal nitride thin films
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on providing insights into energy-efficient ways of growing protective thin films using physical vapor deposition (PVD) by magnetron sputtering, specifically high-power impulse magnetron sputtering (HiPIMS). This technique involves ionizing the material to be deposited to a high degree. The properties of the film for applications such as protective coatings could thus be controlled by modulating the energy and guiding the ions using electric and magnetic fields, respectively. The multiprincipal element TiZrNbTa nitride system is of interest for its corrosion-resistant coating applications. This material system consists of refractory metals that exhibit different ionic charge states with significant mass contrast. Thus, when sputtered with HiPIMS, the properties of the films strongly depend on the mass and energy of the bombarding metal ions. The transport of these ions to the substrate is influenced by the magnetic field distribution in the chamber. To demonstrate the influence of the magnetron arrangement, the deposition is performed without external heating. Two magnetron arrangements were chosen: a tilted closed-field design with four magnetrons and a single magnetron. The films exhibited different properties depending on the magnetron design used. The single magnetron design induces changes in the preferred orientation of the films from 111 to 200 along with film composition and density. A reduction in residual stress was observed with only a ~6 % degradation in the hardness compared to the closed-field design. I also demonstrate epitaxial growth of TiZrNbTaNx films without external heating. The films were grown with a single magnetron design on single crystal sapphire substrate. Applying a pulsed substrate bias with a long pulse width instead of a constant bias, resulted in low argon (~1 at. %) and oxygen (0.5 at. %) content in the films. In addition, the films exhibited a higher optical absorbance in the near-infrared region than the high-temperature grown films. The total energy consumption for film deposition was reduced by approximately 50 % compared to dc magnetron sputtering (DCMS) at 400°C growth temperature. This reduction is without considering the substrate heating and stabilization phase, which is shorter compared to the industry standard where the entire chamber is heated up to ~500-600°C. These findings are beneficial in designing film growth conditions for energy-efficient processes without compromising film quality. This could also address the challenges of growing high-quality films on temperature-sensitive substrates.
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| 2. |
- Pankratova, Daria, et al.
(författare)
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Enhanced Thermoelectric Properties by Embedding Fe Nanoparticles into CrN Films for Energy Harvesting Applications
- 2024
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society. - 2574-0970. ; 7:3, s. 3428-3435
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured materials and nanocomposites have shown great promise for improving the efficiency of thermoelectric materials. Herein, Fe nanoparticles were imbedded into a CrN matrix by combining two physical vapor deposition approaches, namely, high-power impulse magnetron sputtering and a nanoparticle gun. The combination of these techniques allowed the formation of nanocomposites in which the Fe nanoparticles remained intact without intermixing with the matrix. The electrical and thermal transport properties of the nanocomposites were investigated and compared to those of a monolithic CrN film. The measured thermoelectric properties revealed an increase in the Seebeck coefficient, with a decrease of hall carrier concentration and an increase of the electron mobility, which could be explained by energy filtering by internal phases created at the NP/matrix interface. The thermal conductivity of the final nanocomposite was reduced from 4.8 W m-1 K-1 to a minimum of 3.0 W m-1 K-1. This study shows prospects for the nanocomposite synthesis process using nanoparticles and its use in improving the thermoelectric properties of coatings.
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