PUMA
Istituto dei materiali per l'elettronica ed il magnetismo     
Pattini F. Growth of oxide thin films for devices by Pulsed Electron Deposition.
 
 
Abstract
(English)
In this Thesis, the worldwide situation about energy consumption and production is presented and some solution based on superconductor (YBCO) and semiconductor (CIGS) materials have been studied. The former can be used to reduce electrical waste and to enhance the efficiency of electrical generators using HTS-CC. The latter is the base for PV solar cell devices. However both devices present several issues, in particular high production costs. In order to reduce these problems, we studied a single buffer layer architecture to substitute the complex and multi-buffer layer structure used for HTS-CC devices. We investigated the structural properties of Yb-, Sm-, Zr- and Ta-doped CeO2 layers deposited by e-beam evaporation and by Pulsed Electron Deposition (PED) on cube-textured Ni-W substrates. We found that doping can significantly improve the mechanical resistance of the buffer layer. Best results were obtained using Yb45%- and 15%Zr-doped CeO2 layers where no cracks were detected in films thicker than 200 nm for e-beam deposition and thicker than 700 nm for films grown by PED. These represent remarkable progresses as compared to the maximum thickness of 100 nm found in pure CeO2 layers. Thanks to these thicknesses, we completely prevent any atomic diffusion from the substrate to the YBCO and its de-oxygenation. In addition, such doped buffer layers do not affect the excellent structural and superconducting properties of the YBCO films obtained previously, using undoped layers. YBCO deposited on these single buffer layers by TCE and PLD shows high electrical an structural properties. In parallel we investigated ZnO-based materials as suitable TCO thin film for 2nd generation solar cells. Remarkable and reproducible results have been obtained for PED-grown Al-doped ZnO thin films with an optical transmittance higher than 80% and resistivity values in the order of 10-4 Ohm*cm. In addition, some deposition of CIGS have been performed in view of an all-PED thin films solar cell. Preliminary results show the goodness of the choice of PED for depositing CIGS thin films because it is clear that the generally applied "post-deposition selenization step" can be avoided. The devices for energy application based on the materials studied in these three years seem to be very promising to enhance the renewable resources use for higher efficiency in electricity production and energy transport.
Subject PED
buffer layers
ceria
ybco
ZnO
solar cells


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