Artifacts in the characterization of skin layers and ultrathin films by X-ray diffraction X. Marti, V. Holy Charles University, Prague P. Ferrer, T. Schulli ESRF, Grenoble J. Herrero-Albillos BESSY, Berlin J. Narvaez, G. Catalan CIN2, Barcelona N. Barrett, CEA, Gif-sur-Yvette M. Alexe MPI, Halle EMRS, Warsaw, SEPT D. Pesquera, F. Sanchez, G. Herranz, J. Fontcuberta ICMAB, Barcelona Substrate Thin film, t < 10 nm Out-of-plane parameter? 12 Conventional XRD Grazing incidence diffraction

EMRS, Warsaw, SEPT 2011 Substrate Thin film, t < 10 nm Incoming X-rays

EMRS, Warsaw, SEPT 2011 Substrate Thin film, t < 10 nm Incoming X-rays

EMRS, Warsaw, SEPT 2011 Substrate Thin film, t < 10 nm Incoming X-rays

EMRS, Warsaw, SEPT 2011 Substrate Thin film, t < 10 nm Incoming X-rays

EMRS, Warsaw, SEPT 2011 Substrate Thin film, t < 10 nm Incoming X-rays

EMRS, Warsaw, SEPT 2011 Substrate Thin film, t < 10 nm Incoming X-rays

EMRS, Warsaw, SEPT 2011 |E SL (w)| 2 = |E S (w) + E L (w)| 2 |E 0 SL (w)| 2 = |E S (w)| 2 + |E L (w)| 2

EMRS, Warsaw, SEPT 2011 |E SL (w)| 2 = |E S (w) + E L (w)| 2 |E 0 SL (w)| 2 = |E S (w)| 2 + |E L (w)| 2

EMRS, Warsaw, SEPT 2011 How relevant this issue could be (1/2): Samples grown at ICMAB

EMRS, Warsaw, SEPT 2011 Samples grown at ICMAB |E SL (w)| 2 = |E S (w) + E L (w)| 2 |E 0 SL (w)| 2 = |E S (w)| 2 + |E L (w)| 2

EMRS, Warsaw, SEPT 2011 How relevant this issue could be (1/2): Samples grown at ICMAB

EMRS, Warsaw, SEPT 2011 How relevant this issue could be (2/2): Samples courtesy of A. Gruverman I0I0 Measured peak is at … …w = deg The corresponding “c” is at … deg !!!

EMRS, Warsaw, SEPT 2011 How relevant this issue could be (2/2): Samples courtesy of A. Gruverman True lattice parameter Apparent lattice parameter I0I0 Measured peak is at … …w = deg The corresponding “c” is at … deg !!!

EMRS, Warsaw, SEPT 2011 How relevant this issue could be (2/2): Sample courtesy of A. Gruverman I0I deg  4.14 Angstrom (fit) deg  4.07 Angstrom (peak-pick) Measured peak is at … …w = deg The corresponding “c” is at … deg !!! FE Measurement courtesy of P. Zubko

1.Small changes of the out-of-plane parameter 2.…and confined in a few (?) nm thick topmost surface Single crystal αiαi EiEi EMRS, Warsaw, SEPT 2011 Scenario # 2: a thin skin layer of a substrate

EMRS, Warsaw, SEPT 2011 Correction for refraction

To circumvent refraction we scanned both energy and incidence angle EMRS, Warsaw, SEPT 2011 Color scale indicates the information depth For the particular case of BiFeO 3, for instance:

Measured Corrected BULKSKIN Q Q Changing the energy (no refraction correction required) EMRS, Warsaw, SEPT 2011

Measured Corrected Changing the angles BULKSKIN Changing the energy (no refraction correction required) EMRS, Warsaw, SEPT 2011

Concluding remarks 1)For the extraction of lattice parameters it is highly recommended to fit simultaneously both the substrate and the thin film using a dynamical or semi-kinematical model. 2)For the determination small changes of lattice parameters, in grazing incidence geometry, changing the energy may be more useful than changing the angles Thank you very much for your attention! EMRS, Warsaw, SEPT 2011