Elaboration de couches minces ZnO par ablation laser et caractérisation physique

Abstract

Our thesis aims to achieve and study of the physical properties (Structural, morphological, optical and electrical) of conductive and transparent thin layers of undoped zinc oxide (ZnO) and doped aluminum (AZO) prepared by the pulsed laser deposition technique (PLD) on glass and silicon substrates heated to 450°C. The source used is a KrF excimer laser (248 nm, 25 ns, 2 J/cm2). The structural study by X-ray diffraction (XRD) showed that these layers has a hexagonal crystal structure with a preferential growth according to the (002) orientation, and a decrease in grain sizes of about 40 to 25 nm with increasing aluminum doping rates of 0 to 5 at%. leading to a deterioration of the crystalline quality of the layers. The Atomic Force Microscope AFM was used to study the state of the surfaces and their roughness which was found to be between 3 and 15 nm. Rutherford backscattering spectroscopy RBS was used to determine the chemical composition and thickness of the prepared films, the layer thickness ranges from about 179-366 nm. Study by UV-visible spectrophotometry showed that the transmittance of the samples is around 75% in visible with an optical band gap varying from 3.23 to 3.36 eV when the content of Al doping increases from 0 to 5 at.%. Analysis by (M-Lines) helped us to extract approximate values for the refractive index of these layers, which is between 1.83 and 1.97, and thicknesses very close from those estimated by the RBS analysis, as well as the possibility of using the layers in the field of the optical waveguide. In addition to these results, the electrical measurements by (Hall Effect) have shown that all the layers prepared in this study are n-type semiconductor, and that, the aluminum doping increases the concentration of charge carriers and reduces resistance.