Special Materials Science & Engineering Seminar
Wednesday, December 5, 2012 - 2:00pm - 3:00pm
Columbia University Morningside Campus S.W. Mudd, Room 210 (APAM Conference Room)
Dr. Catherine Dubourdieu
Grenoble - Institut des Nanotechnologies
"Integration of ferroelectric oxides on silicon - Towards negative capacitance field-effect devices"
As the conventional transistor approaches its ultimate physical limits, there is a need for new switches operating at lower voltages. In 2008, Salahuddin and Datta proposed that introducing a ferroelectric as a gate oxide could decrease the sub-threshold slope below the thermodynamic limit of 60 mV/dec in field-effect transistors (FETs) operating at room temperature thanks to negative capacitance contribution. So far, this effect has not been demonstrated experimentally in a FET using a ferroelectric oxide. The reason for the lack of experimental demonstration resides in the major difficulties to integrate ferroelectric oxides on Si with a high quality interface and - just as importantly - to obtain a polarization perpendicular to the Si surface. Although the ability to grow epitaxial SrTiO3 on Si by molecular beam epitaxy has opened up the route, more than a decade ago, to the integration of perovskite oxides on Si platform, a very limited number of perovskite compounds have been successfully grown. Hence, integrating ferroelectric functionality on silicon remains a major and unresolved challenge.
In this talk, I will briefly introduce ferroelectric materials. I will then present a study on BaTiO3 films epitaxially grown on Si(001) by MBE. We investigated the crystalline structure and the associated domain structure for a large range of thicknesses (1.2 - 40 nm). The electrical properties of these films will be discussed. Finally, I will show that ferroelectricity is evidenced by piezoforce microscopy with polarization pointing perpendicular to the silicon substrate. This is the first unambiguous proof of ferroelectricity in these materials. I will conclude with ongoing perspectives on new field-effect devices that aim at resolving the flaws of the original device.
Catherine Dubourdieu received her Engineer University in 1995. She received the Diplome d'Habilitation a Diriger des Recherches in 2002 from Grenoble Polytechnic Institute. She spent 18 months as a post-doctoral fellow and Adjunct Assistant Professor at Stevens Institute of Technology in Hoboken (New Jersey) and worked on the in situ characterization of gas phase and film growth by optical spectroscopies during chemical vapor deposition (CVD). She joined CNRS in 1997, where she is now Directrice de Recherche since 2007.
Her research interests are on the synthesis by CVD and on the properties of oxides heterostructures and nanostructures in relation with their micro/nanostructure. In particular, she investigates size and strain effects on the crystalline, electronic and magnetic properties of functional oxides and work on strain engineering in thin films to finely tune their properties. Her current focus is, on one hand, on ferroelectric and multiferroic materials, and, on the other hand, on high-k dielectrics. She has investigated various aspects of CVD/ALD techniques: precursors benchmarking, process optimization, plasma use for low-temperature deposition. She also works on the integration of functional oxides in micro- and nano-electronics.
She has been teaching at Undergraduate, Graduate and advanced levels at various locations such as Stevens Institute of Technology, Grenoble Institute of Technology, Joseph Fourier University, College de l'Ecole Polytechnique (Palaiseau) and the company Altis Semiconductors. She has supervised or co-supervised 14 PhD students and 11 post-doctoral researchers.
From May 2009 until May 2012, she was invited as a Visiting Scientist at the T.J. Watson Research Center of IBM in Yorktown Heights, where she worked on the integration of ferroelectric oxides on silicon and on the Atomic Layer Deposition of novel oxides.
In June 2012, she joined the Institut des Nanotechnologies de Lyon (INL-CNRS). She currently works on the monolithic integration of functional oxides on semiconductors (Si, III/V, Ge) using molecular beam epitaxy (MBE).
She is currently a member of the Bureau of the GDR CNRS 'Materiaux Multiferroiques' and a member of the ITRS (International Technology Roadmap for Semiconductors) working in the Emerging Research Materials group.