Transparent conducting oxides on polymeric substrates by pulsed laser deposition

This thesis describes the research on thin films of transparent conducting oxides (TCOs) on polymeric substrates manufactured by pulsed laser deposition\ud (PLD). TCOs are an indispensable part in optoelectronic applications such as displays, solar cells, light-emitting diodes, etc. At present, in many of these applications there is an increasing need for the use of flexible, cheap and lightweight substrates. Such polymer substrates however, limit the deposition temperature of thin films which results in deteriorated properties of the TCO. A\ud profound understanding of the fundamental aspects of transparent conductors is required in order to improve either the properties of existing materials, or design\ud new types of TCOs. These insights are of great scientific importance for the realization of high performance TCOs on polymer substrates.\ud This research focuses on thin film growth by PLD. This technique is a powerful tool for thin film research. A large freedom of choice in independently controllable deposition parameters allows one to quickly obtain results on the exploration and optimization of existing and new materials. The ablated species can be tuned over a large energetic range, enabling optimum conditions at lower\ud substrate temperatures normally used for high performance TCO materials. This makes the deposition of TCOs on heat resistive substrates possible. The substrates utilized in this research are all commercial available and commonly used materials such as translucent polyethylene terephthalate (PET). Analysis of the PLD grown films is done by a variety of tools to obtain information on the electrical, optical and structural properties as well as the thin film composition

Epitaxial PZT films for MEMS printing applications

Films of piezoelectric and ferroelectric oxides have been widely investigated for various applications, including microelectromechanical systems (MEMS) for printing. Pb(Zr,Ti)O3 is of particular interest due to its excellent piezoelectric properties. Control of the density, crystalline orientation, and compositional uniformity is essential to obtain these properties. In this article, we review recent progress on the fabrication of epitaxial Pb(Zr,Ti)O3films, in which the aforementioned control can be achieved. We discuss the different approaches used for the deposition of the epitaxial piezoelectric layer as well as the achieved degrees of the epitaxy. Furthermore, the integration of these piezoelectric layers in MEMS and the corresponding performance are discusse

Microwave Properties of Ba-Substituted Pb(Zr0.52_{0.52}Ti0.48_{0.48})O3_3 after Chemical-Mechanical Polishing

We have studied the effect of chemical-mechanical polishing (CMP) on the ferroelectric, piezoelectric, and microwave dielectric properties of Ba-substituted PZT (BPZT), deposited by pulsed laser deposition. CMP allowed for the reduction of the root mean square surface roughness of 600 nm thick BPZT films from 12.1nm to 0.79 nm. Ammonium peroxide (SC-1) cleaning was effective to remove Si CMP residuals. Measurements of the ferroelectric hysteresis after CMP indicated that the ferroelectric properties of BPZT were only weakly affected by CMP, while the piezoelectric d33 coefficient and the microwave permittivity were reduced slightly by 10%. This can be attributed to the formation of a thin dead layer at the BPZT surface. Moreover, the intrinsic dielectric permittivity at microwave frequencies between 1 and 25 GHz was not influenced by CMP, whereas the dead layer series capacitance decreased by 10%. The results indicate that the CMP process can be used to smoothen the BPZT surface without affecting the film properties strongly.Comment: 13 pages of text, 4 tables and 7 figures. This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No. 801055 "Spin Wave Computing for Ultimately-Scaled Hybrid Low-Power Electronics" - CHIRO

Thickness dependence of ferroelectric and piezoelectric properties in epitaxial PZT thin films

Epitaxial (110)-oriented Pb(Zr0.52,Ti0.48)O3 (PZT) thin films were fabricated on SrRuO3-coated (001) YSZ/Si and SrRuO3-coated (110) SrTiO3 (STO) substrates with various thicknesses ranging from 0.1 μm to 1.0 μm by pulsed laser deposition. The effects of the film thickness on the structure, ferroelectric and piezoelectric properties were systematically investigated as a function of the film thickness. On the STO substrate the remnant polarization of the films increased from 36.6 to 45.5 μC/cm2 with the increasing film thickness, while in the films on the silicon substrate the remnant polarization was in the range of 12.4 - 20.2μC/cm2. The improvement of the remnant polarization with increasing film thickness was due to the reduction of the film/electrode interface effect which leads to improve the switching of domains. The films on the STO substrate were in a compressive stress, while in the films on the silicon substrate a higher tensile stress was found. Compressive stress causes the ferroelectric domains to orient along the longitudinal direction (c-domain orientation), which in turn can result in an increase of the polarization. Moreover, the effective piezoelectric coefficient of the PZT thin films increased steady with increasing thickness. This effect is likely related to a mechanism of elastic domains that can move more easily in thicker film, and that give rise to out-ofplane piezoelectric displacement

Epitaxial PZT films for MEMS printing applications

Films of piezoelectric and ferroelectric oxides have been widely investigated for various applications, including microelectromechanical systems (MEMS) for printing. Pb(Zr,Ti)O3 is of particular interest due to its excellent piezoelectric properties. Control of the density, crystalline orientation, and compositional uniformity is essential to obtain these properties. In this article, we review recent progress on the fabrication of epitaxial Pb(Zr,Ti)O3films, in which the aforementioned control can be achieved. We discuss the different approaches used for the deposition of the epitaxial piezoelectric layer as well as the achieved degrees of the epitaxy. Furthermore, the integration of these piezoelectric layers in MEMS and the corresponding performance are discussed