Investigations at insulating thin films using XPS

Motivation and results

For the analysis of non-conducting material XPS is a favorable method because for excitation X-rays are used. Both the study of chemical bonding by peak shape analysis and the in-depth analysis with sputtering depth profiling is possible. Keeping always the knowledge of artifacts arising from the sputtering ions in mind, we have shown at a number of examples that chemical information can also derived then. Recent example was the study of La2Zr2O7 (LZO) layers as potential buffer layers for superconducting YBa2Cu3O7-x coated conductors deposited on Ni tapes. Chemical solution deposition was used for LZO layer preparation. XPS depth profiling was demonstrated to be an important method for layer characterization in addition to X-ray diffraction techniques. XPS measurements revealed layers that are homogeneous in depth, very smooth, and have no significant impurities. A slight difference to the nominal La:Zr stoichiometry is discussed in combination with structural defects that are suspected from spectral changes during ion sputtering.

Outlook

Studies of the behavior of oxide systems from the class of ferroic material.

References

S. Oswald, S. Baunack: Factor Analysis and XPS - Data Preprocessing for Non-Conducting Samples, Fres. J. Anal. Chem. 365 [1-3] (1999) 59-62 (doi:10.1007/s002160051445).

S. Oswald, W. Häßler, R. Reiche, J. Lindner, F. Weiss: XPS depth profile analysis of a thin non-conducting titanate superlattice, Mikrochim. Acta 133 [1-4] (2000) 303-306 (doi:10.1007/s006040070110).

S. Oswald, B. Schmidt, K.-H. Heinig: XPS investigation with factor analysis for the study of Ge Clustering in SiO2, Surf. Interface Anal. 29 [4] (2000) 249-254.

S. Oswald, R. Reiche: Binding state information from XPS-depth profiles - capabilities and limits, Appl. Surf. Sci. 179 [1-4] (2001) 307-315 (doi:10.1016/S0169-4332(01)00299-9 ).

S. Oswald, W. Brückner: XPS depth profile analysis of non-stoichiometric NiO films, Surf. Interface Anal. 36 [1] (2004) 17-22 (doi:10.1002/sia.1640).

R. Reiche, S. Oswald, F. Yubero. J.P. Espinos, J.P. Holgado, A.R. González-Elipe: Monitoring interface interactions by XPS at nanometric tin oxides supported on Al2O3 and Sb2Ox, J. Phys. Chem. B 108 [28] (2004) 9905-9913 (10.1021/jp031274m).

S. Oswald, K. Knoth, B. Holzapfel: XPS depth profiling investigations of La2Zr2O7 layers prepared by chemical solution deposition, Microchimica Acta 156 (2007) 121-124 (doi:10.1007/s00604-006-0600-3).

K. Knoth, R. Hühne, S. Oswald, L. Schultz, B. Holzapfel: Detailed investigations on La2Zr2O7 buffer layers for YBCO coated conductors prepared by chemical solution deposition, Acta Materialia 55 [2] (2007) 517-529 (doi:10.1016/j.actamat.2006.08.040).