Dana Georgeta Popescu

By Dana Georgeta Popescu

X-ray absorption (XAS) and photoelectron spectroscopy (XPS or PES or ESCA—electronic structure for chemical analysis) are widely used techniques that allow to access the full electronic structure of the surfaces and buried interfaces offering complementary information on both the occupied (valence) and empty (conduction) states. XAS technique relies on measuring the signal corresponding to dipole-allowed transition, hence shines-up the unoccupied states’ investigation, which differs from XPS, where electrons are ejected from occupied states into the continuum, probing the occupied density of states. In the following, our purpose is to illustrate some of the potentials of XPS and XAS techniques by presenting some of the work where they were employed to study and describe bulk and interfacial phenomena in BaTiO3 systems.

Part of the book: Nanocomposites

By Cristina Chirila, Andra G. Boni, Lucian D. Filip, Mihaela Botea, Dana Popescu, Viorica Stancu, Lucian Trupina, Luminita Hrib, Raluca Negrea Ioana Pintilie and Lucian Pintilie

This chapter provides an overview of the versatile applications and properties of epitaxial ferroelectric materials obtained using the pulsed laser deposition technique. These materials can play a significant role in various electronic and sensing applications or energy harvesting. Materials that are ferroelectric and have a perovskite structure (ABO3 type) show spontaneous polarization that can be changed by an electric field, temperature, mechanical stress, or light. Here, we present results obtained on epitaxial ferroelectric thin films with different compositions, lead-based or lead-free, and the correlation with structural quality of the layers and with different electrostatic conditions induced either by the substrate or by the different dopants. Our studies revealed that the utilization of pulsed laser beam deposition technique is suitable for obtaining ultrathin films depositions with thicknesses measuring less than 5 nm. These results allowed us to reveal the impacts caused by polarization orientation on the band structure or the presence of self-doping phenomena. We also found that the conduction type can be modified by introducing 1% Fe and Nb on PbZrTiO₃ (PZT) epitaxial layers. In the last part of this chapter, we report on obtaining of a lead-free epitaxial thin film and its properties in the energy storage field.

Part of the book: Pulsed Laser Processing of Materials