Compositional analysis by RBS, XPS and EDX of ZnO:Al, Bi and ZnO:Ga, Bi thin films deposited by d.c. magnetron sputtering. (March 2019) - Ribeiro, J.M.
Abstract: Rutherford backscattering spectrometry, X-ray photoelectron and X-ray energy dispersive spectroscopies were employed to analyse Bi incorporation into ZnO:Al and ZnO:Ga transparent and electrically conductive thin films deposited by d.c. magnetron sputtering, with thickness in the range of 300–400 nm. Sputtering was performed in an argon atmosphere from two targets in confocal geometry being one composed of either ZnO:Al2 O3 or ZnO:Ga2 O3 composites and the other a Bi metal target. The content of bismuth dopant in the ZnO matrix was controlled by the respective target current density (JBi ) in order to attain a high optical transparency (>80%) in the visible region. For ZnO:Al, Bi films Bi content varied from 0.1 to a maximum of 1.5 at.% when varying JBi from 0.06 to 0.26 mA cm −2 . However, for ZnO:Ga, Bi films, deposited in similar conditions, Bi reached a maximum overall layer content of 2.4 at.%, with a surface enrichment content that varied from 1.3 to 8.8 at.%. It was also observed that the Bi content in the topmost layers of the films is slightly depleted due to thermal evaporation upon thermal annealing in vacuum at 350 °C. It is envisaged applications for these films as transparent photoelectrodes and thermoelectric materials. Highlights: ZnO:Al, Bi and ZnO:Ga, Bi optically transparent thin films were deposited by confocal magnetron sputtering. In-depth composition analysis of Bi dopant by combined RBS/PIXE, XPS and EDX. In thermal annealed films Bi is depleted from top of deposit due to thermal evaporation. Applications in transparent photoelectrodes and thermoelectric materials.