Hydoxyapatite films obtained by sol-gel and sputtering methods

Tionica Stoica 1Constantin Morosanu 1Adrian Slav 1Toma Stoica 1Petre Osiceanu 2Adrian Ghita 2Crina-Elena Anastasescu 2Mariuca Gartner 2Maria Zaharescu 2

1. National Institute for Materials Physics, Bucharest- Magurele 010555, Romania
2. Instituite of Physical Chemsitry (ICF), Splaiul Independentei 202, Bucharest 060021, Romania

Abstract

Hydroxyapatite (HA) biocoatings were obtained using two different deposition methods (sol-gel and sputtering). The depositions were performed on bare silicon or covered with a TiO2 buffer layer. Comparison of physico-chemical properties between different samples prepared by sputtering and sol-method, as well as between films deposited with and without TiO2 buffer layer is a main subject of this paper. The microstructural, chemical and optical characterizations of the films were performed by IR, XPS, UV-VIS Absorption and Ellipsometric Spectroscopies. The studied HA/Si films are highly transparent and colorless, owing to low refractive index of hydroxyapatite (1.556 at wavelength 590 nm, as estimated from ellipsometric data). Interference color, which depends on refractive index and thickness, was slightly observed increasing film thickness from 160 to 2500 nm. Ca/P atomic ratio of 1.7 (specific for HA) was evaluated from XPS spectra. Silicon signal derived from substrate or any other signals from impurities except carbon from surface were not observed. Similar FTIR spectra recorded on sputtering and sol-gel films were obtained. FTIR measurements showed two peaks from 550-600 cm-1 and 1000-1200 cm-1 which are attributed to the major absorption modes associated with the presence of phosphate (S. W. Russell et al., J. Am. Ceram. Soc. 79 (1996), 837). Films annealed at 400-5500C showed a band at 1600 cm-1 and one more faint at 861 cm-1 related to the CO32- ions. The OH- group was detected by XPS analysis after O1s line deconvolution. It was found that OH- group presents a relative concentration of about 15% from the total amount of oxygen. Although the investigated films show similar properties with previous published results, future improvements are necessary to reduce the carbon contamination due to organic residuals and to increase the stoichiometry of the films.

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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium H, by Mariuca Gartner
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-21 12:51
Revised:   2009-06-07 00:44
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