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Evolution of the functional properties of titanium–silver thin films for biomedical applications: influence of in-vacuum annealing

Evolution of the functional properties of titanium–silver thin films for biomedical applications: influence of in-vacuum annealing
Evolution of the functional properties of titanium–silver thin films for biomedical applications: influence of in-vacuum annealing
In this work, the thermal stability of TiAgx thin films, deposited by magnetron sputtering, was evaluated, envisaging their application in biomedical devices, namely as electrodes for biosignal acquisition. Based on the composition and microstructural characterization, a set of four representative TiAgx thin films was selected in order to infer whether they are thermally stable in terms of functional properties. In order to achieve this purpose, the structural and morphological evolution of the films with annealing temperature was correlated with their electrical, mechanical and thermal properties. Two distinct zones were identified and two samples from each zone were extensively analysed. In the first zone (zone I), Ti was the main component (Ti-rich zone) while in the second, zone II, the Ag content was more significant. The selected samples were annealed in vacuum at four different temperatures up to 500 °C. For the samples produced within zone I, small microstructural changes were observed due to the recrystallization of the Ti structure and grain size increment. Also, no significant changes were observed with annealing temperature regarding the films' functional properties, being thermally stable up to 500 °C. For higher Ag contents (zone II) the energy supplied by thermal treatments was sufficient to activate the crystallization of Ti–Ag intermetallic phases. A strong increase of the grain size of these phases was also reported. The structural and morphological organization proved to be determinant for the physical responses of the TiAgx system. The hardness and Young's modulus were significantly improved with the formation of the intermetallic phases. The silver addition and annealing treatments also played an important role in the electrical conductivity of the films, which was once again improved by the formation of Ti–Ag phases. The thermal diffusivity of the films was practically unchanged with the heat-treatment. This set of results shows that this intermetallic-like thin film system has good thermal stability up to high temperatures (as high as 500 °C), which in case of the highest Ag content zone is particularly evident for electrical and mechanical properties, showing an important improvement. Hardness increases about three times, while resistivity values become half of those from the lowest Ag content zone. These sets of characteristics are consistent with the targeted applications, namely in terms of biomedical sensing devices.
TiAgx thin films, Heat-treatment, functional properties, biomedical applications
0257-8972
262-271
Lopes, C.
75ae989a-13d8-46e4-9781-14d7dfc32045
Gonçalves, C.
ee864a23-817d-4558-9b10-811d3f868af6
Borges, J.
c8e5c89d-68cf-454e-a7c3-4f4629f32120
Polcar, T.
c669b663-3ba9-4e7b-9f97-8ef5655ac6d2
Rodrigues, M.P.M.
644748a0-ef14-4478-bcb6-660b73db368d
Barradas, N.P.
8408c4b4-b978-4b33-be8a-99eaf6add1ca
Alves, E.
690fff18-b1ff-43a3-85fa-15f04a997f0c
Le Bourhis, E
3ed95b56-5bfe-4a90-a476-6f523947bc7d
Macedo, F
8ff422a2-ec9c-4449-bfe0-1a454bbb2b42
Conseca, C.
9798a2fe-464f-4ede-8928-6887cbf3268e
Vaz, F.
ba6841e6-8ce6-4015-a24e-8538df435147
Lopes, C.
75ae989a-13d8-46e4-9781-14d7dfc32045
Gonçalves, C.
ee864a23-817d-4558-9b10-811d3f868af6
Borges, J.
c8e5c89d-68cf-454e-a7c3-4f4629f32120
Polcar, T.
c669b663-3ba9-4e7b-9f97-8ef5655ac6d2
Rodrigues, M.P.M.
644748a0-ef14-4478-bcb6-660b73db368d
Barradas, N.P.
8408c4b4-b978-4b33-be8a-99eaf6add1ca
Alves, E.
690fff18-b1ff-43a3-85fa-15f04a997f0c
Le Bourhis, E
3ed95b56-5bfe-4a90-a476-6f523947bc7d
Macedo, F
8ff422a2-ec9c-4449-bfe0-1a454bbb2b42
Conseca, C.
9798a2fe-464f-4ede-8928-6887cbf3268e
Vaz, F.
ba6841e6-8ce6-4015-a24e-8538df435147

Lopes, C., Gonçalves, C., Borges, J., Polcar, T., Rodrigues, M.P.M., Barradas, N.P., Alves, E., Le Bourhis, E, Macedo, F, Conseca, C. and Vaz, F. (2015) Evolution of the functional properties of titanium–silver thin films for biomedical applications: influence of in-vacuum annealing. Surface and Coatings Technology, 261, 262-271. (doi:10.1016/j.surfcoat.2014.11.020).

Record type: Article

Abstract

In this work, the thermal stability of TiAgx thin films, deposited by magnetron sputtering, was evaluated, envisaging their application in biomedical devices, namely as electrodes for biosignal acquisition. Based on the composition and microstructural characterization, a set of four representative TiAgx thin films was selected in order to infer whether they are thermally stable in terms of functional properties. In order to achieve this purpose, the structural and morphological evolution of the films with annealing temperature was correlated with their electrical, mechanical and thermal properties. Two distinct zones were identified and two samples from each zone were extensively analysed. In the first zone (zone I), Ti was the main component (Ti-rich zone) while in the second, zone II, the Ag content was more significant. The selected samples were annealed in vacuum at four different temperatures up to 500 °C. For the samples produced within zone I, small microstructural changes were observed due to the recrystallization of the Ti structure and grain size increment. Also, no significant changes were observed with annealing temperature regarding the films' functional properties, being thermally stable up to 500 °C. For higher Ag contents (zone II) the energy supplied by thermal treatments was sufficient to activate the crystallization of Ti–Ag intermetallic phases. A strong increase of the grain size of these phases was also reported. The structural and morphological organization proved to be determinant for the physical responses of the TiAgx system. The hardness and Young's modulus were significantly improved with the formation of the intermetallic phases. The silver addition and annealing treatments also played an important role in the electrical conductivity of the films, which was once again improved by the formation of Ti–Ag phases. The thermal diffusivity of the films was practically unchanged with the heat-treatment. This set of results shows that this intermetallic-like thin film system has good thermal stability up to high temperatures (as high as 500 °C), which in case of the highest Ag content zone is particularly evident for electrical and mechanical properties, showing an important improvement. Hardness increases about three times, while resistivity values become half of those from the lowest Ag content zone. These sets of characteristics are consistent with the targeted applications, namely in terms of biomedical sensing devices.

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More information

Published date: 15 January 2015
Keywords: TiAgx thin films, Heat-treatment, functional properties, biomedical applications
Organisations: Engineering Mats & Surface Engineerg Gp

Identifiers

Local EPrints ID: 373893
URI: http://eprints.soton.ac.uk/id/eprint/373893
ISSN: 0257-8972
PURE UUID: 0ef7db1d-71e8-4a4a-9330-8c9cc08462fe
ORCID for T. Polcar: ORCID iD orcid.org/0000-0002-0863-6287

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Date deposited: 02 Feb 2015 14:28
Last modified: 15 Mar 2024 03:40

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Contributors

Author: C. Lopes
Author: C. Gonçalves
Author: J. Borges
Author: T. Polcar ORCID iD
Author: M.P.M. Rodrigues
Author: N.P. Barradas
Author: E. Alves
Author: E Le Bourhis
Author: F Macedo
Author: C. Conseca
Author: F. Vaz

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