By Dr. Jutta Schwarzkopf, Leibniz-Institut für Kristallzüchtung, Berlin

16.05.2023 1:15 pm | Bd.600, R.301 CHyN

Abstract:

A promising way to tune the ferroelectric properties of complex oxides is to deliberately
modify the crystalline structure of these materials. This can be achieved by the deposition of thin oxide
films, where lattice strain is introduced by the heteroepitaxial growth on lattice mismatched
substrates. However, a directive tuning of the functional properties of thin films requires a detailed
understanding of the correlation between lattice strain and ferroelectric phase formation as well as the
availability of oxide substrates with tailored lattice mismatch. A very suitable growth method that
permits the growth of high-quality layers for this purpose is given by the metal-organic vapor phase
epitaxy (MOVPE) technique. It offers the advantages of high oxygen partial pressure, independent
control of all constituents, growth nearby thermodynamic equilibrium and large scale-up potential. In
my talk, I will discuss the influence of lattice strain in the material system Potassium-Sodium-Niobate
(K,Na)NbO3. (K,Na)NbO3 is a lead-free, environmentally friendly material which offers as bulk material
excellent piezoelectric and electromechanical properties, high Curie temperature and good thermal
stability. However, for most applications (like memory devices, actuators, sensors or RF devices),
reproducible growth of epitaxial films is necessary, which is still challenging due to the high volatility of
Na and K. Growth of epitaxially strained (K,Na)NbO3 thin films on IKZ own oxide substrates will be
discussed with regard to the impact of lattice strain on the ferro-/piezoelectric properties of the films.
As application example, the propagation of surface acoustic waves and the use of thin films in
biosensors are addressed.