Epitaxial Integration of Functional Oxides
with Silicon Using Pulsed-Laser Deposition
Danilo Suvorov
Professor of Materials Science, Jozef Stefan Institute

Epitaxial integration of transition metal oxides with semiconductors offers various phenomena for novel device applications, specifically bringing ferroelectric, ferromagnetic, electro-optic, photocatalytic, multiferroic, piezoelectric and other properties to the well-established silicon platform. A convenient way of integrating functional oxides with Si(001) substrate is through a SrTiO3 (STO) intermediate layer, which can be fabricated on Si(001) in epitaxial form and with high crystallinity using mainly molecular beam epitaxy (MBE) and atomic-layer deposition (ALD) methods. However, slow deposition processes and difficult stoichiometry control make these methods inappropriate from an industrial point of view.
The epitaxial growth of functional oxides on silicon substrates requires atomically defined surfaces, which are most effectively prepared using SrO- or Sr-induced deoxidation and passivation. As-prepared surfaces enable overgrowth with various oxides for novel device applications. In our work pulsed laser deposition (PLD) was used to integrate oxides with silicon. We showed the ability to prepare highly-ordered sub-monolayer SrO- and Sr-based surface structures, including two-domain (2×3)+(3×2) pattern at 1/6 ML Sr coverage as determined by the reflection high-energy electron diffraction (RHEED) technique. On the passivated silicon surface epitaxial layers of STO was grown by the method of kinetically controlled sequential deposition, with out-of plane relationship of STO(001)∥Si(001) and in-plane relationship of STO[110]∥Si[100]. Detailed study of initial deposition parameters in terms of background gas pressure, deposition temperature, fluence, and oxidation proved to be extremely important in achieving epitaxial relation of STO with the underlying substrate. On as-prepared pseudo-substrate Pb[Mg1/3Nb2/3]O3-PbTiO3 (PMN-PT) films were gown for applications in microelectromechanical systems, due to its high values of longitudinal piezoelectric coefficients and electromechanical coupling. In this presentation growth peculiarities of PMN-PT thin films, including the effect of lead surplus and bottom electrode will also be outlined.