Invited Paper EM2-WeM10
Ferroelectric Devices

Wednesday, November 12, 2014, 11:00 am, Room 314

Novel methods of deposition developed over the past decade or so, enabled fabrication of thin films of ferroelectric materials, such as BaTiO₃ (BTO), of very high crystal quality. This has resulted in renewed interest in ferroelectric field effect transistors and in addition, led to new device architectures, such as negative capacitance devices. Thanks to very high Pockels coefficient, thin films of BTO may find applications in Si nano-photonics.

In this talk I will describe our recent efforts on integration of BTO (and other ferroic oxides) on semiconductors using a SrTiO₃ (STO) buffer. More specifically, I will describe integration of BaTiO₃ on Si (001) and Ge (001) using molecular beam epitaxy (MBE) and atomic layer deposition (ALD). We employ first principles modeling to both guide the crystal growth and analyze the characterization data. By modeling core level spectroscopy and comparing it with the x-ray photoemission data we are able to identify the Zintl growth template for STO on Si and Ge. Comparing theoretical spectral functions with the angle resolved photoemission spectra (ARPES), provides us with a better understanding of the SrTiO₃ buffer surface. Using this strategy we stabilized ferroelectric state with out-of-plane polarization in BaTiO₃ (BTO) grown on Si with an STO buffer. And we demonstrate both out-of-plane in-plane polarized BTO growth on Ge (001). Annular dark field microscopy is used to elucidate the atomic structure of the semiconductor/oxide interface that is used in subsequent first principles calculations of the band alignment at the interface. We use a combination of polarization force and microwave impedance microscopies to investigate the ferroelectric response and field effect in our structures.