Microscopic study of local thermal, electrical and structural properties of ZnMgO thin films on different substrates

Abstract

In this work we combine a group of scanning microscopy methods to investigate correlations between structural, thermal and electrical properties of ZnMgO thin films, influenced by the substrate material. The ZnMgO layers, grown by means of molecular beam epitaxy, were deposited on r- and m-plane Al₂O₃ and Si (111) substrates. The X-ray diffraction measurements were introduced to verify crystallinity of investigated ZnMgO layers. We demonstrate the possibilities offered by combining selected scanning microscopy methods to gain deeper and more comprehensive insight into the interrelationship of structural and thermo-electrical properties of thin ZnMgO layers. Using atomic force microscopy, we analyzed the morphology, basic surface parameters and surface grains. Additionally, the Kelvin probe force microscopy allowed us to analyze the surface electron properties, such as the local contact potential difference and work function distribution. We used scanning thermal microscopy to determine local thermal conductivity values. Finally, the scattering-type scanning near-field optical microscopy provided us with information about the local free-carrier concentration. While maintaining a spatial resolution above 100 nm, proposed approach provides valuable information on the possibilities of using the studied layers in various nanosystems and devices for which the surface structure and thermo-electric properties play a key role.