INTENSE

Ferroelectrics are a fascinating class of materials both from a fundamental standpoint and for their potential applications such as a gate oxide in field-effect transistors for low power logic. The key functionality of ferroelectrics arises because their polarization can be switched between two-stable orientations by application and reversal of an electrical field. However, in epitaxial ultrathin films on a semiconductor, a perpendicular polar state may not be switchable due to incomplete screening and depolarization field issues. The project INTENSE is devoted to the study of ferroelectric nanodomains in the complex oxide BaTiO3 epitaxially grown on semiconductor planar- or nanowire-platform. The overarching objective is to understand and control, in ultrathin films (< 50 unit cells), the conditions favoring a bi-stable perpendicular polar state and engineer the nanodomain pattern for their future integration. The challenges to be solved are diverse: i) there are materials issues related to thermal strain, lattice mismatch and depolarization field effects – ii) there are nanocharacterization challenges as both the crystalline and ferroelectric domains on semiconductors appear to be non-periodic and display nanometer size. In addition, phenomena at interfaces such as surface rumpling and ionic contributions to screening are of paramount importance. To address these different challenges, the consortium gathers three academic laboratories (INL, CEMES, IMEP-LAHC) to leverage their unique and complementary expertises in i) epitaxy by both MBE and CVD/ALD for monolithic integration of oxides on semiconductors, ii) structural nanocharacterization using advanced TEM techniques such as HRTEM, dark holography or High Angle Annular Dark Field imaging and iii) advanced electrical and electro-mechanical nanocharacterization based on atomic force microscopy. Within INTENSE, we address for the first time the ferroelectricity of BaTiO3 on various semiconductor substrates: planar Si1-xGex (0