EPITAXIAL GROWTH OF Pt ( 001 ) THIN FILMS ONMgO ( 001 ) UNDER OXIDIZING CONDITIONS

Epitaxial Pt(001) thin films have been grown on MgO(001) substrates using dc magnetron sputtering with an Ar/0 2 mixture at 700'C. The width (FWHM) of the rocking curve of the Pt(002) peak is between 0.160 and 0.200, which is only 0.05' wider than that of the MgO (002) peak of the cleaved substrate. The film surface roughness is about 1 nm (rms) for a 240 nm thick Pt film. No grain structure could be observed using SEM. In contrast, the films deposited at 700 'C with pure Ar, have both Pt(111) and Pt(001) oriented growth, as shown by XRD e 2 0 scans, with the Pt(111) peak having the largest intensity. BaTiO3 epitaxial films have also been deposited on Pt(001)/MgO(001). The width (FWHM) of the rocking curve of the BaTiO3(200) peak is 0.40. The surface morphology of the epitaxial BaTiO3(100) thin films on Pt(001)/MgO(001) is featureless. XRD pole figure measurements on PtIBaTiO3/Pt trilayer shown a very good in-plane alignment of all layers. The epitaxial growth relationship was also confirmed by TEM electron diffraction and cross-section imaging. The Pt/BaTiO 3/Pt epitaxial trilayer could serve as a prototype for ferroelectric capacitors and may be able to improve the electrical properties of the capacitors. INTRODUCTION In multilayer systems, epitaxial growth has been an important issue for high quality multilayer structures and of great interest for applications. Epitaxial growth of metallic films is also important in oxidizing environments employed in the deposition of ferroelectric, magnetic oxides and HTSC films. Recently, Lairson et al. [1] reported epitaxial growth of Pt films on MgO(001), MgO(110), MgO(111), and A120 3(0001) substrates using a sputtering technique. In a pure argon atmosphere of 3.0 mTorr, the relative intensity of Pt(111) to the total Pt(111) and Pt(200) peak intensity varied from nearly 100% for temperatures below 550'C to 0.1% at a deposition temperature of 6800C when MgO(001) substrates were used. In a mixture of 10 mTorr Ar and 5 mTorr oxygen, epitaxial growth of Pt(001) on MgO(001) at 680'C was demonstrated. In this report, we present data showing the epitaxial growth of Pt(001) on MgO(001) at 7000C with a mixture of 6 mTorr Ar and 5 mTorr 02 . Pt(111) and Pt(200) oriented growth was observed when Pt was deposited in pure Ar at the same temperature. The epitaxial Pt(001) films grown under oxidizing conditions have mirror-like surfaces with a surface roughness of 1 nm (rms), single crystal-like structure and rocking curve widths as low as 0.2'. These films have been shown to be suitable for subsequent growth of epitaxial films and multilayers of ferroelectric materials. DEPOSITION PROCESS A vacuum chamber was equipped with a 2" magnetron sputtering gun which can be operated in a dc or rf mode, and with a 2" resistance heater ( US Mat. Res. Soc. Symp. Proc. Vol. 310. 01993 Materials Research Society