X-ray absorption spectroscopy as a method for structural study of HfO2 and ZrO2 thin films

Raul Rammula 1,2Jaan Aarik 1Arvo Kikas 1Tanel Käämbre 1Hugo Mändar 3Teet Uustare 1Väino Sammelselg 1,2

1. Institute of Physics, University of Tartu, Riia str. 142, Tartu 51014, Estonia
2. Institute of Physical Chemistry, University of Tartu, Jakobi 2, Tartu 51014, Estonia
3. Department of Physics, University of Tartu, Tähe Street, Tartu 51010, Estonia

Abstract

Methods based on recording of photoelectrons excited by X-rays have frequently been used for composition studies of ultrathin films because of high surface sensitivity of the methods. It is not so well known, however, that a similar technique can be applied for structural characterization of thin films. This work continues our recent study of crystal phase effects on X-ray absorption spectra of HfO2 and ZrO2. HfO2 and ZrO2 films with different phases were deposited on Si (100) substrates in a flow-type hot-wall ALD reactor at temperatures of 180–600 °C using halide-based processes. X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy measurements were performed at beamline D1011 of MAX-II storage ring (Lund, Sweden). For the reference measurements of the phase composition RHEED and XRD methods were used.

In the XANES studies of the amorphous, cubic, monoclinic and tetragonal phases, the O 1s edge of HfO2 and ZrO2 was demonstrated to be more sensitive to the phase composition. The main bands in the spectra peaked at 532, 537, 541 and 543 eV. In case of amorphous sample, the peaks were not well resolved probably due to non-periodicity of local environment of oxygen atoms. In cubic and especially monoclinic phases the peak at 532 eV was split into two sub-peaks. Tetragonal phase gave very intense and well-resolved peak at 532 eV, but the second maximum at 537 eV was less intense and consisted of two overlapping maxima. XANES spectra of several cubic samples showed no significant differences, although the film thicknesses as well as precursors and growth temperatures differed markedly.

 

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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium C, by Raul Rammula
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-14 21:02
Revised:   2009-06-07 00:44