Epitaxial Growth of Cerium Oxide Buffer Layers on MgO, YSZ and Sapphire Substrates
- PDF / 700,534 Bytes
- 6 Pages / 412.92 x 637.2 pts Page_size
- 28 Downloads / 296 Views
ABSTRACT We studied the epitaxial growth of CeO 2 thin films deposited onto MgO(100), YSZ(100) and A120 3( 1102 ) (r-plane sapphire) substrates by reactive dc magnetron sputtering of a Ce metal target in an Ar/0 2 plasma. The crystalline quality and biaxial alignment of the films was determined using x-ray diffraction techniques (0-20, w-scans, pole figures, 0-scans). The CeO 2/MgO(100) and CeO 2/Al 20 3( 1102) epitaxy was evident at 600'C and developed to nearly perfect biaxial alignment at 850'C with A0 = 5' and 90 respectively. The CeO 2/YSZ (100) epitaxy occurred below 300'C while deposition at _> 650'C led to single-crystal quality CeO 2 films with A0 = 0.20. INTRODUCTION Cerium oxide (CeO 2) is an attractive insulating material (- 6 eV band gap) that has a high dielectric constant (F = 26) and is very stable at high temperatures. Epitaxial CeO 2 thin films are currently of significant interest and relevance in several areas of thin film technology. In particular, CeO 2 is a desired buffer layer for the epitaxial growth of YBa 2Cu 30 7 superconducting films on a range of technical substrates. Examples include the growth of YBa 2Cu 307 thin films onto CeO 2 buffered large-area substrates such as A12O3(1102 ) (r-plane sapphire), MgO(l00) and YSZ(IO0) (yttria stabilised zirconia) for superconducting microwave
components (eg. filters, strip-line resonators) [1-3], and onto buffered Ni-based or hastelloy metal tapes for the manufacture of YBa 2 Cu 30 7 coated conductors [4-8]. Other areas of interest include the use of CeO 2 as a durable optical thin film coating or as an insulator in double barrier CeO 2/Si/CeO 2/Si(1 11) charge storage structures for DRAMs [9]. Furthermore, CeO 2 films doped with Y, Zr or Gd show promise as oxygen-storage components in catalytic converters and as composite electrodes in solid oxide fuel cells [10]. We report on the epitaxial growth of CeO 2 thin films on MgO(100), YSZ(100) and A120 3( 1102) substrates by reactive dc magnetron sputtering. The aim of this work has been to synthesise high quality films that are biaxially aligned to serve as templates for the growth of YBa 2Cu 30 7 thin films. EXPERIMENTAL METHODS The CeO 2 thin films were deposited by dc magnetron sputtering using a 75 mm diameter cerium metal target sputtered at 50 W in an Ar/0 2 gas mixture of 3:1. The target to substrate distance was 50 mm and the deposition rate was 10 nm/min. The substrates were clamped onto a substrate heater whose temperature could be raised to 850'C. We investigated the evolution of the hetero-epitaxy of CeO 2 thin films on polished MgO(100), YSZ(100) and A12 0 3( 1102 ) single crystal substrates as a function of growth temperature and film thickness. 191
Mat. Res. Soc. Symp. Proc. Vol. 619 © 2000 Materials Research Society
The crystalline quality of films was determined using x-ray diffraction techniques (0-20, wo-scans, pole figures, )-scans). The degree of c-axis or out-of-plane alignment was determined using the FWHM of w-scans of the (200) x-ray peak. F200, the fraction of (200) to
Data Loading...
