Chemical composition and crystalline phases in F-doped tin oxide films grown by DC reactive sputtering

We study by x-ray diffraction (XRD) the structural variations on a series o f SnOx:F films grown by dc reactive sputtering from a metallic tin target i n an Ar-O-2-Freon plasma. We found that the films tend to be crystalline wh en the stoichiometry approaches to that of SnO or SnO2, being amorphous in between. We fitted the x-ray diffractograms and found that films are compos ed by a mixture of compounds, i.e. SnO, Sn3O4, Sn2O3 and SnO2, given by the simultaneous presence of Sn+2 and Sn+4. From the analysis of the deconvolu ted areas under the x-ray diffractograms we calculate the Sn+2/Sn and Sn+4/ Sn molar fraction present in the films. The same calculations are done for the x-ray photoelectron spectroscopy (XPS) results. By applying a combinato ry model we fitted the general behavior of SnO. films with different oxygen content versus the Sn+2/Sn and Sn+4/Sn molar fraction. Both XRD and XPS re sults are compared with the theoretical curve, showing a well agreement.