Epitaxial growth of SrTiO 3 (00 h ), (0 hh ), and ( hhh ) thin films on buffered Si(001)
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Epitaxial growth of SrTiO3 (00h), (0hh), and (hhh) thin films on buffered Si(001) F. S´anchez, R. Aguiar, V. Trtik,a) C. Guerrero, C. Ferrater, and M. Varela Departament de F´ısica Aplicada i Electr`onica, Universitat de Barcelona, Avda. Diagonal 647, E-08028 Barcelona, Spain (Received 27 June 1997; accepted 21 January 1998)
Epitaxial SrTiO3 (STO) thin films have been grown successfully on Si(001) buffered with single and double buffer layers by pulsed laser deposition. Depending on the buffer structure and under appropriate substrate temperature and oxygen pressure values, epitaxial films are grown with single orientations. Epitaxial STO films with (0hh), (00h), and (hhh) out-of-plane orientation have been obtained for the first time on yttria-stabilized zirconia (YSZ)ySi(001), CeO2yYSZySi(001), and TiNyYSZySi(001), respectively. Secondary ion mass spectrometry analyses show sharp interfaces and good uniformity of the elements in each layer. The films are practically free of droplets, and the rms value of roughness is smaller than 0.5 nm.
SrTiO3 (STO) is a paraelectric material which has many potential applications because of its high thermal stability and high dielectric constant (higher than 300 at room temperature). STO has a cubic perovskite structure with a lattice constant of 0.3905 nm, so it is highly compatible with most ferroelectric perovskites, the superconductor YBa2 Cu3 O7 (YBCO), the conducting oxide Sr12x Cax RuO3 , as well as important insulating oxides such as yttria-stabilized zirconia (YSZ) or CeO2 . STO has been proposed to replace conventional dielectrics in capacitors for dynamic random access memories.1,2 It is commonly used in superconducting field-effect transistors,3 and it has been used as seed layer to grow epitaxial ferroelectric Pb(Zr, Ti)O3 films on silicon.4,5 STO films directly deposited on silicon are polycrystalline.6 High quality epitaxial growth is not possible because STO reacts with silicon to form an amorphous layer before epitaxy occurs. There are few works reporting epitaxial growth of STO on silicon. Mori and Ishiwara7 successfully proposed to deposit a thin metallic strontium layer before the STO deposition. Other approaches include using epitaxial buffer layers, such as SrVO3 ,8 fluorides,9,10 or TiN.4,11,12 The best reported properties correspond to STO films deposited on TiN buffer layers.11,12 In this paper, we report for the first time the epitaxial growth of STO on Si(001) covered with various single or double buffer layers: YSZ, CeO2yYSZ, and TiNyYSZ. The use of each particular structure and the optimization of the technological parameters have allowed the epitaxial growth of STO films with single (00h), (0hh), and
a)
Permanent address: Institute of Physics, Academy of Sciences of Czech Republic, Na Slovance 2, 18040 Prague 8, Czech Republic.
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http://journals.cambridge.org
J. Mater. Res., Vol. 13, No. 6, Jun 1998
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(hhh) orientations. These results can be very interesting to extend the
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