DQMP Forum - Effect of strain on LaNiO3 nickelates films - Novel domain configurations in ferroelectric superlattices under tensile strain

28.05.2019 13:00 – 14:00

Effect of strain on LaNiO3 nickelates films
Ivan Ardizzone (group of Prof. van der Marel)

Due to competition between lattice distortion and electronic correlations, rare earth nickelates
exhibit a very rich structural, electronic and magnetic phase diagram. Rare-earth substitution
can be used to tune the ground state but strain may also be an interesting option, especially on
films.
In the present study, we measured terahertz transmission, Far- and Mid-infrared reflectivity and
visible light spectroscopic ellipsometry on LaNiO3 films grown on different substrates to
investigate electronic properties. Film/substrate lattice mismatch begets tensile or compressive
strain that induces strong structural and electronic perturbations. Through the redistribution of
optical spectral weight as strain varies, we aim to disentangle the electron-lattice from the
electron-electron interactions.
Electronic and structural theoretical predictions allow us to deeper understand the evolution of
the optical conductivity and spectral weight regarding combined effects of electron correlations,
lattice distortion and orbital hybridization.



Novel domain configurations in ferroelectric superlattices under tensile strain
Marios Hadjimichael (group of Prof. Triscone)

Domains in ferroelectric materials have been at the forefront of recent scientific research,
mostly due to the fascinating properties of their boundaries, domain walls. As well as enhancing
the macroscopic properties of ferroelectrics, such as permittivity and piezoelectric coefficients,
domain walls exhibit symmetry and properties different from the bulk material, offering novel
functionality. To take advantage of this functionality and further advance the field of domain wall nanoelectronics, reproducible and scalable methods to control dense domain wall structures are needed, with one leading method being epitaxial strain.
In this talk, I will present studies performed on superlattices of ferroelectric PbTiO3 and
metallic SrRuO3 under tensile strain. The superlattices are epitaxially grown on DyScO3
substrates and were studied using X-ray diffraction, piezoresponse force microscopy and
transmission electron microscopy. It was found that the domain structures in these films are
extremely sensitive to electrical and mechanical boundary conditions and adopt highly nonuniform
polarization configurations. I will show that, by exploiting strain fields imposed by both
the underlying substrate and different layers in these heterostructures, novel domain
configurations can be stabilised.


Forum Committee: C. Lichtensteiger, N. Ubrig, A. Tamai (20.05.2019)

Lieu

Bâtiment: Ecole de Physique

Auditoire Stückelberg

entrée libre