CEA, LETI, MINATEC, 17 rue des Martyrs, Grenoble, France, CEA, LIST, Laboratoire National Henri Becquerel, France, CEA, LITEN, DTS, INES, 50 avenue du Lac Léman, Le Bourget-du-Lac, France, Atominstitut, Vienna University of Technology, Vienna, Austria

The optical and electrical properties of transparent conducting oxide (TCO) thin films are strongly linked with the structural and chemical properties such as elemental depth profile. In R&D environments, the development of non-destructive characterization techniques to probe the composition over the depth of deposited films is thus necessary. The combination of Grazing-Incidence X-ray Fluorescence (GIXRF) and X-ray reflectometry (XRR) is emerging as a fab-compatible solution for the measurement of thickness, density and elemental profile in complex stacks. Based on the same formalism, both techniques can be implemented on the same experimental set-up and the analysis can be combined in a single software in order to refine the sample model. While XRR is sensitive to the electronic density profile, GIXRF is sensitive to the atomic density (i. e. the elemental depth profile). The combination of both techniques allows to get simultaneous information about structural properties (thickness and roughness) as well as the chemical properties. In this study, we performed a XRR-GIXRF combined analysis on indium-free TCO thin films (Ga doped ZnO compound) in order to correlate the optical properties of the films with the elemental distribution of Ga dopant over the thickness. The variation of optical properties due to annealing process were probed by spectroscopic ellipsometry measurements. We studied the evolution of atomic profiles before and after annealing process. We show that the blue shift of the band gap in the optical absorption edge is linked to a homogenization of the atomic profiles of Ga and Zn over the layer after the annealing. This work demonstrates that the combination of the techniques gives insight into the material composition and makes the XRR-GIXRF combined analysis a promising technique for elemental depth profiling. © 2017 Elsevier B.V.

Depth profiling, GIXRF, Transparent conducting oxides, XRR

Annealing, Atoms, Chemical analysis, Chemical properties, Conductive films, Depth profiling, Doping (additives), Fluorescence, Gallium, Nondestructive examination, Optical properties, Oxide films, Reflection, Spectroscopic ellipsometry, Thickness measurement, Thin films, Elemental depth profiles, Elemental depth profiling, GIXRF, Nondestructive characterization, Optical and electrical properties, Spectroscopic ellipsometry measurements, Transparent conducting oxide, Transparent conducting oxide thin films, Optical films