Grazing-incidence X-ray fluorescence analysis of Sn0.9Cu0.1O2 films,

A.M. MUDARRA NAVARRO, F. GOLMAR, C. PEREZ AND C.E. RODRÍGUEZ TORRES

Campinas, Brasil

Congreso; 6th International Conference on Synchrotron Radiation in Materials Science (SRMS-6); 2008

Dilute magnetic semiconductors DMS produced by doping transition metal ions into nonmagnetic semiconductors are of interest for potential applications in spin electronics. High temperature ferromagnetism has been reported in several oxide materials such as ZnO, TiO2, SnO2 doped with different transition metals (Co, Fe, Cu, Mn, etc.). The ferromagnetism is usually only found in thin films, at doping levels below the percolation threshold for nearest-neighbour cation interactions, although the results are not very reproducible, with different conditions and preparation methods leading to different moments or ordering temperatures. Then a careful examination of extrinsic effects, such as inhomogeneous dopant distribution it is necessary to understand the magnetic behaviours observed in these systems.In this work we present a Grazing-Incidence X-Ray Fluorescence (GIXRF) analysis of  Sn0.9Cu0.1O2 thin films deposited by pulse laser deposition (PLD) on different substrates: LaAlO3 (LAO), STO (TiSrO3) and Si. The main purpose of this work is to study the depth distribution of dopant and their interaction with the substrate. All films were deposited simultaneously. The substrate temperature, laser energy density, oxygen pressure, and pulse repetition rate were 650 °C, 2 J/cm2, 4 Pa, and 10 Hz, respectively. The films thickness was estimated at approximately 200 nm. The GIXRF measurements were carried out at the XRF Fluorescence beamline of the LNLS (Campinas, Brazil), using a monochromatic X-ray beam of 9.5 keV and performing an angular scan around the critical angle of total (external) reflection for the thin film material.  Fig 1 shows the angular dependence of the fluorescence intensity of the elements contained in the film for different substrates. It can be seen in the case of LAO and Si substrates that copper concentration continuously increase in depth reaching a maximum value at the film-substrate interface, whereas in STO substrate the copper rich zone appears near the surface of the film. Some consideration based on epitaxial relation between SnO2 and the substrates and interface enthalpies between the constituents will be employed in order to interpretate these results.