Bikowski, A.: The Relation between the Deposition Process and the Structural, Electronic, and Transport Properties of Magnetron Sputtered Doped ZnO and Zn1-xMgxO Films. , 2014
Humboldt-Universität zu Berlin
In this thesis, the relation between the structural, optical, and charge carrier transport properties of magnetron sputtered doped ZnO and Zn1-xMgxO films has been investigated in detail. The objective was to clarify the above mentioned relations, which allows to derive solutions for a deliberate improvement of the layer properties. The work first focusses on the growth of the ZnO layers to determine important structural properties like grain sizes and defect densities via X-ray diffraction and transmission electron microscopy investigations. These structural properties were then used as model parameters for the theoretical modelling of the charge carrier transport. The temperature dependent Hall, conductivity and Seebeck coefficient measurements show that the transport is mainly limited by grain boundary scattering and ionized impurity scattering. The theoretical description of the grain boundary scattering has been extended in this work to also include degenerate semiconductors. Based on the results on the structural and electronic properties, in a next step a qualitative model was developed which explains the correlation between the magnetron sputtering deposition process and the structural and electronic properties of the films. According to this model, the properties of the films are mainly influenced by the formation of electrically active acceptor-like oxygen interstitial defects at low deposition temperatures, which lead to a partial compensation of the extrinsic donors. These defects are caused by a bombardment of the growing film by high-energetic negative oxygen ions. At higher deposition temperatures, the formation of secondary phases or defect complexes, in which the dopant is electrically inactive, prevails.