The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Atomic Layer Deposition of Lanthanide Oxide Thin Films

Jani Päiväsaari

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Chemical Technology for public examination and debate in Auditorium V1 at Helsinki University of Technology (Espoo, Finland) on the 19th of May, 2006, at 12 noon.

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Abstract

This thesis describes the processing of thin films of lanthanide (Ln) oxides by atomic layer deposition (ALD) technique. Deposition of all binary lanthanide oxides was studied, excluding terbium oxide and the unstable promethium oxide. In addition, gadolinium oxide-doped cerium dioxide films were grown by combining the respective binary processes developed in this work. Films were characterized by a wide range of analytical techniques for structural, compositional, electrical, and surface properties. As background for the study, some promising application areas for lanthanide and rare earth (RE) oxide thin films are briefly introduced, and the ALD technique is explained. Reported ALD processes for RE oxides are then reviewed.

Ln(thd)3 and ozone were successfully utilized for deposition of most members of the Ln2O3 series. The deposited films were nearly stoichiometric Ln2O3 with only low concentrations of carbon, hydrogen, and fluorine impurities. Films were also uniform and smooth. Relative permittivity values were in the range of 8.4-11.1.

In addition to Er(thd)3, Er2O3 films were also grown with (CpMe)3Er and Er(tBu2amd)3 as metal precursors. All processes resulted in pure and nearly stoichiometric Er2O3 films. The growth rate of 1.5 Å/cycle obtained with the (CpMe)3Er/H2O process was approximately four and six times the rates measured for erbia films grown by the Er(tBu2amd)3/O3 and Er(thd)3/O3 processes, respectively.

Cerium dioxide films were successfully deposited with use of Ce(thd)4 or Ce(thd)3(phen) and ozone as precursors. Gadolinium oxide-doped CeO2 (CGO) films were then grown by combining the Ln(thd)x/O3 processes for the respective binary oxides. ALD-grown CGO films were dense and conformal, but the Ce:Gd ratio in the films could not be optimized to the level required in solid oxide fuel cells.

This thesis consists of an overview and of the following 7 publications:

  1. Päiväsaari, J., Putkonen, M., and Niinistö, L., A comparative study on lanthanide oxide thin films grown by atomic layer deposition, Thin Solid Films 472 (2005) 275-281.
  2. Kosola, A., Päiväsaari, J., Putkonen, M., and Niinistö, L., Neodymium oxide and neodymium aluminate thin films by atomic layer deposition, Thin Solid Films 479 (2005) 152-159.
  3. Päiväsaari, J., Putkonen, M., Sajavaara, T., and Niinistö, L., Atomic layer deposition of rare earth oxides: erbium oxide thin films from β-diketonate and ozone precursors, Journal of Alloys and Compounds 374 (2004) 124-128.
  4. Päiväsaari, J., Niinistö, J., Arstila, K., Kukli, K., Putkonen, M., and Niinistö, L., High growth rate of erbium oxide thin films in atomic layer deposition from (CpMe)3Er and water precursors, Chemical Vapor Deposition 11 (2005) 415-419.
  5. Päiväsaari, J., Dezelah, C. L., Back, D., El-Kaderi, H. M., Heeg, M. J., Putkonen, M., Niinistö, L., and Winter, C. H., Synthesis, structure and properties of volatile lanthanide complexes containing amidinate ligands: application for Er2O3 thin film growth by atomic layer deposition, Journal of Materials Chemistry 15 (2005) 4224-4233.
  6. Päiväsaari, J., Putkonen, M., and Niinistö, L., Cerium dioxide buffer layers at low temperature by atomic layer deposition, Journal of Materials Chemistry 12 (2002) 1828-1832.
  7. Gourba, E., Ringuedé, A., Cassir, M., Päiväsaari, J., Niinistö, J., Putkonen, M., and Niinistö, L., Microstructural and electrical properties of gadolinium doped ceria thin films prepared by atomic layer deposition (ALD), The Electrochemical Society Proceedings 2003-7 (2003) 267-274.

Keywords: precursors, rare earth oxides, ALD

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© 2006 Helsinki University of Technology

Last update 2011-05-26