Hier finden Sie wissenschaftliche Publikationen aus den Fraunhofer-Instituten.

Speciation of deeply buried TiOx nanolayers with grazing-incidence x-ray fluorescence combined with a near-edge x-ray absorption fine-structure investigation

: Pollakowski, B.; Beckhoff, B.; Reinhardt, F.; Braun, S.; Gawlitza, P.


Physical Review. B 77 (2008), No.23, Art. 235408, 11 pp.
ISSN: 0163-1829
ISSN: 1098-0121
ISSN: 0556-2805
Journal Article
Fraunhofer IWS ()

Nondestructive methods based on electron emission may encounter serious difficulties when probing the chemical state of deeply buried nanolayers due to restricted information depth. The purpose of the present work is to evaluate to which extent photon emission can overcome these restrictions. Grazing-incidence x-ray fluorescence combined with a near-edge x-ray absorption fine-structure investigation (GIXRF-NEXAFS) offers access to depth-resolving analysis of buried nanolayers with respect to both the chemical speciation and the layer composition. By varying the angle of incidence, the penetration depth can be tuned from a few to several hundreds of nanometers. The information depth of the emitted fluorescence radiation is in the same general range as the soft x-ray regime. Initial measurements were performed on nominally 30 nm thick titanium nanolayers oxidized to different extents and buried below 5 nm carbon layers. These layered structures were produced by means of ion beam sputtering deposition. The plane grating monochromator beamline for undulator radiation in the laboratory of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY II provides tunable radiation of both well-known flux and high spectral purity for GIXRF-NEXAFS studies. The current results confirm that GIXRF-NEXAFS has the potential to substantially contribute to the speciation of deeply buried nanolayers. The analysis of measurements at a constant incident angle demonstrated that it is not possible to find an angle of incidence for the NEXAFS region to ensure a stable penetration depth. However, appropriate angular corrections can ensure a constant mean penetration depth, in particular, in the vicinity of absorption edges.