Synthesis of Doped-ZrO2 Thin Films by Metallo-organic Decomposition via a Low-Toxicity Chemical Solution

Witte, Pim (2021) Synthesis of Doped-ZrO2 Thin Films by Metallo-organic Decomposition via a Low-Toxicity Chemical Solution. Bachelor's Thesis, Chemistry.

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Abstract

Since the discovery of hafnia- and zirconia-based ferroelectrics in 2011, ferroelectricity has been reported for ZrO2 and HfO2 thin films with several dopants, synthesized with both physical and chemical deposition methods. The ferroelectricity in ZrO2 and HfO2 is attributed to a polar, orthorhombic phase. This relatively new class of ferroelectrics is considered to be suitable for non-volatile memory applications, energy-related applications, and microelectromechanical systems. Because physical methods to deposit electronic thin films, like pulsed laser deposition, often require a vacuum and long preparation time, they are unsuitable techniques for industrial-scale production of thin films for electronics applications. In the transition to applying zirconia- and hafnia-based ferroelectrics in commercial applications, it is, therefore, useful to consider chemical solution deposition methods to synthesize these thin films. Because hafnium is currently only being produced as a byproduct of refining zirconium, and it is demand is increasing due to its applications in nuclear applications, its supply will likely be outpaced. Because ZrO2 and HfO2 have very similar chemical and physical properties, this work focuses on the deposition of ZrO2 as a suitable alternative to decrease costs. In this work, a low-toxicity chemical solution for the deposition of doped-ZrO2 thin films for future piezo- and/or ferroelectric applications is successfully used to deposit uniform thin films in a high symmetry phase on Si. Structural characterization has shown that the annealing temperature is a key parameter in determining the crystalline phase, with cubic or tetragonal, and monoclinic phases obtained at low (500°C) and high (800°C) annealing temperatures respectively. At intermediate temperatures, a mixture of these phases is obtained. Estimations of the crystallite size further support this, showing crystallite sizes of ~10 nm which corresponds to literature reports for the cubic and tetragonal phases of ZrO2. The root mean square roughness of the thin films was determined to be between 0.5 and 2 nm by atomic force microscopy. The roughness increased as the annealing temperature was increased for pure ZrO2 films. Doping ZrO2 with 5% Ca or Mg decreased the roughness of the films. The smoothness of the films makes them suitable for electrode deposition, electronic testing, and applications. Therefore, these results show that the precursor solution used here gives rise to was the successful deposition of ZrO2 thin films that show great promise for being used in piezo- and ferroelectric applications. This removes the need for dangerous compounds such as 2-methoxyethanol and carboxylic anhydrides, or the use of carboxylic acids as solvents in the deposition of the films as so far reported.

Item Type:	Thesis (Bachelor's Thesis)
Supervisor name:	Noheda, B. and Badillo Avila, M.A. and Acuautla Meneses, M.I.
Degree programme:	Chemistry
Thesis type:	Bachelor's Thesis
Language:	English
Date Deposited:	16 Jul 2021 08:01
Last Modified:	20 Mar 2025 07:38
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/25269

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