A1 Journal article (refereed)
Mechanical and optical properties of as-grown and thermally annealed titanium dioxide from titanium tetrachloride and water by atomic layer deposition (2021)

Ylivaara, O. M., Langner, A., Liu, X., Schneider, D., Julin, J., Arstila, K., Sintonen, S., Ali, S., Lipsanen, H., Sajavaara, T., Hannula, S.-P., & Puurunen, R. L. (2021). Mechanical and optical properties of as-grown and thermally annealed titanium dioxide from titanium tetrachloride and water by atomic layer deposition. Thin Solid Films, 732, Article 138758. https://doi.org/10.1016/j.tsf.2021.138758

JYU authors or editors

Publication details

All authors or editors: Ylivaara, Oili M.E.; Langner, Andreas; Liu, Xuwen; Schneider, Dieter; Julin, Jaakko; Arstila, Kai; Sintonen, Sakari; Ali, Saima; Lipsanen, Harri; Sajavaara, Timo; et al.

Journal or series: Thin Solid Films

ISSN: 0040-6090

eISSN: 1879-2731

Publication year: 2021

Volume: 732

Article number: 138758

Publisher: Elsevier

Publication country: Netherlands

Publication language: English

DOI: https://doi.org/10.1016/j.tsf.2021.138758

Publication open access: Openly available

Publication channel open access: Partially open access channel

Publication is parallel published (JYX): https://jyx.jyu.fi/handle/123456789/76491

Abstract

The use of thin-films made by atomic layer deposition (ALD) is rapidly growing in the field of optical sensing. ALD TiO2 has been widely characterized for its physical and optical properties, but systematic information about the influence of thermal history to optical and mechanical properties of the film is lacking. Optical applications require planar surface and tunability of the refractive index and residual stress. In addition, mechanical properties such as elastic modulus and film hardness influence the performance of the layer, especially, when optics is integrated with microelectromechanical systems. In this work, optical properties, density, elemental analysis, residual stress, elastic modulus and hardness of as-grown ALD TiO2 thin films on silicon were studied at temperature range from 80 to 350 °C and influence of post-ALD annealing to films were studied on films annealed up to 900 °C. ALD TiO2 films were under tensile stress in the scale of hundreds of MPa. The stress depended both on the ALD temperature and film thickness in a complex way, and onset of crystallization increased the residual stress. Films grown at 110 and 300 °C were able to withstand post-ALD annealing at 420 °C without major change in residual stress, the refractive index or the extinction coefficient. Elastic modulus and hardness increased upon crystallization with increasing ALD temperature. The results presented here help to improve the design of the optical devices by choosing films with desired optical properties and help to design the post-ALD thermal budget so that films maintain their desired features.

Keywords: thin films; atomic layer deposition; titanium dioxide; physical properties; optical properties

Contributing organizations

Ministry reporting: Yes

VIRTA submission year: 2021

JUFO rating: 1