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Issue 20, 2010
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Rare earth scandate thin films by atomic layer deposition: effect of the rare earth cation size

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Abstract

A series of amorphous REScO3 films was deposited by atomic layer deposition (ALD) using rare earth (RE) β-diketonate precursors RE(thd)3 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionato) together with ozone in an attempt to study the effect of the RE3+ cation size on various film properties. A clear correlation between the deposition rate and the RE3+ cation radius was established. REScO3 films with a metal ratio RE : Sc close to the stoichiometric one, viz. RE : Sc = 1, and a small excess of oxygen were realized by adjusting the metal precursor pulsing ratio. Small amount of carbon was found as impurity in all the films, concentrations varying from 1–3 at% (RE = La, Gd or Dy) to 0.4–0.5 at% (RE = Er or Lu). Also the crystallization temperature and the resulting phase were affected by the RE3+ cation size. The REScO3 films were found to crystallize either as an orthorhombic perovskite phase or as a solid solution of the cubic C-type oxides. High crystallization temperatures of 800–900 °C were observed for LaScO3, GdScO3 and DyScO3. All the films gave smooth CV curves with very small hysteresis (typically <35 mV). The highest dielectric constant (κ ≈ 24) was found for DyScO3. Also the leakage current densities were small, typically in a range of 10−6–10−9 A cm−2 at 1 V. The results confirm that REScO3 films deposited by ALD are potential candidates for new generation high-κ gate dielectrics.

Graphical abstract: Rare earth scandate thin films by atomic layer deposition: effect of the rare earth cation size

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Publication details

The article was received on 09 Feb 2010, accepted on 24 Mar 2010 and first published on 14 Apr 2010


Article type: Paper
DOI: 10.1039/C0JM00363H
Citation: J. Mater. Chem., 2010,20, 4207-4212
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    Rare earth scandate thin films by atomic layer deposition: effect of the rare earth cation size

    P. Myllymäki, M. Roeckerath, J. M. Lopes, J. Schubert, K. Mizohata, M. Putkonen and L. Niinistö, J. Mater. Chem., 2010, 20, 4207
    DOI: 10.1039/C0JM00363H

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