UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2012 Meeting


Section: Solid State Physics and Materials Science


Title:
Mössbauer spectroscopy and magnetic study of Fe films grown on Si substrates. Effects of hydrogenation treatments


Authors:
Simona G. SANDU (1,2), P. PALADE (1), G. SCHINTEIE (1), A. BIRSAN (1), V. KUNCSER(1)


Affiliation:
1. National Institute of Materials Physics, 077125, Bucharest-Magurele, Romania

2. University of Bucharest, Faculty of Physics, 077125, Bucharest-Magurele, Romania


E-mail
simona.sandu@infim.ro


Keywords:
ferromagnetic-semiconducting interfaces, atomic inter-diffusion, RF sputtering, CEMS, XRR, MOKE.


Abstract:
Thin Fe films, with thicknesses in the range 1 – 10 nm, were grown on Si substrates via radio-frequency (RF) sputte ring. Local structural aspects and magnetic behavior were investigated by means of 57Fe conversion electron Mössbauer spectroscopy (CEMS) and magneto-optical Keer effect (MOKE), respectively. The films were deposited either directly on the Si substrate or on Cu buffer layers, in order to reduce the interatomic diffusion at the Fe/Si interface. Hydrogenation treatments were subsequently applied to improve the crystallinity and to reduce the oxidation of the Fe films. X ray reflectometry (XRR) was used to derive the thickness of the films. An oxidation layer was observed in all as deposited films, considerably decreasing in relative contribution with the deposition time. The Fe3+ based oxide layer is formed on the top of a quasiamorphous metallic layer. In addition, the thicker films presents also a magnetic silicide phase (Fe3Si) at the Fe/Si interface. Unexpectedly, introducing a Cu buffer layer is not sufficiently to diminuish either the interfacial diffusion or the oxidation process. On the other side, the hydrogenation process clearly induceses a better crystallinity, with well formed alpha-iron majoritary phase and almost no significant oxide layer for thicker (>3nm) films. Before hydrogenation treatment, the Fe films present an in plane magnetic texture. The hydrogenation treatment reduces the texture and increases considerably the coercive field. It is demonstrated via MOKE and CEMS measurements that hydrogenation treatments allow the modification of the film structure, phase composition, magnetic properties and interfacial diffusion more effectively than buffer Cu layers and might represent an efficient tool for engineering suitable ferromagnetic/semiconducting interfaces.