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S.P. Krumdieck Department of Mechanical Engineering, University of Canterbury, Christchurch, Private Bag 4800, Christchurch, New Zealand (Received 11 January 2008; accepted 5 May 2008)

ZrO2 films deposited on silicon (100) substrates using pulsed-pressure metalorganic chemical vapor deposition (PP-MOCVD) with zirconium n-propoxide (ZnP) Zr(OC3H7)4 were dense and fully crystalline for substrate temperatures of 500 to 700 °C. Film thicknesses were 40 to 815 nm thick, measured after growth using ellipsometry and scanning electron microscopy (SEM). The growth rate was between 0.1 ␮m/h at 500 °C and 1 ␮m/h at 700 °C. Transmission electron microscopy (TEM) and x-ray diffraction (XRD) indicated an average grain size of 10 to 20 nm. There was a random orientation of cubic/tetragonal zirconia at the highest experimental temperature of 700 °C. SEM and atomic force microscopy (AFM) was used to characterize island height of discontinuous films in the initial stages of growth where defects in the substrate caused preferred nucleation of isolated particles. At later stages of growth, the average surface roughness of continuous films was 30 nm, which revealed a more uniform growth had developed. A growth model is proposed, and optimal growth conditions are suggested for targeted microstructures of ZrO2 films.

I. INTRODUCTION

The ability to tailor material microstructures by controlling zirconia film growth is highly desirable for a broad range of technological applications, from building microelectronics to creating solid-oxide electrolytes. Currently, a variety of deposition techniques are used to achieve the diverse material characteristics and microstructures required for different applications. Ultrathin films of zirconia on Si for high-k dielectric films can be made by rapid thermal chemical vapor deposition (CVD),1 atomic layer deposition (ALD),2 ultraviolet (UV)-ozone oxidation of Zr metal,3 or specialized sputtering techniques.4,5 Line-of-sight techniques such as electron beam physical vapor deposition (EB-PVD)6,7 and air plasma spraying (APS)8–10 are fabrication methods typically used in the deposition of zirconia for thermal-barrier coatings (TBC)11; however, the complex geometries of high-temperature components such as gas turbine blades make line-of-sight methods challenging to

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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0267 2202

http://journals.cambridge.org

J. Mater. Res., Vol. 23, No. 8, Aug 2008 Downloaded: 14 Mar 2015

use for uniform deposition. Screen printing is currently used for thick-film solid-oxide fuel cell (SOFC) planar electrolytes.12 However, as SOFC electrolytes are scaled down to thin films for enhanced efficiency, the fabrication of dense gas-impermeable materials becomes critical and alternative deposition techniques may be required. One option is CVD, a type of processing that can produce thin films on conformal surfaces. Low-pressure CVD, low-temperature kinetic-controlled CVD, and ALD all produce films with good uniformity, but also are metho