Atomic layer deposition of lanthanide oxide thin films

Jani Päiväsaari
Abstract & Cover

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.  

Source of Information
FinALD40 exhibition material,
Helsinki University of Technology, Department of Chemical Technology, Laboratory of Inorganic and Analytical Chemistry
(Espoo, Finland)
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