Study of structural changes in krypton implanted silicon P. Dub cek a , B. Pivac a, * , O. Milat b , S. Bernstorff c , I. Zulim d a Rudjer Bo skovi c Institute, P.O. Box 180, Bijenicka c. 54, HR-10000 Zagreb, Croatia b Institute of Physics, P.O. Box 1010, HR-10000 Zagreb, Croatia c Sincrotrone Trieste, SS 14km 163.5, I-34012 Basovizza (TS), Italy d Faculty of Electrical and Mechanical Engineering, and Naval Architecture, University of Split, R. Bo skovi ca b.b., HR-21000 Split, Croatia Received 6 February 2003; received in revised form 9 July 2003 Abstract The structural changes induced in single crystal silicon implanted with krypton above the amorphisation threshold were studied by X-ray reflectivity together with grazing incidence small angle X-ray scattering technique. Silicon samples were implanted with krypton with two different ion energies. A well-defined layer of amorphous silicon, 220 nm thick, rich in krypton, was detected below the top, less disturbed layer. The studied series of samples consists of as- implanted, relaxed and several samples with increased level of defects induced by additional Kr implantation. Addi- tional implantation caused changes in layers structure and thickness, which was well evidenced in X-ray reflectivity, while only minor changes of surface roughness and critical angle were detected in GISAXS spectra. Ó 2003 Elsevier B.V. All rights reserved. 1. Introduction Energetic ion implantation in silicon single crystals leads to lattice damage production by energy transfer from impinging ions to the host lattice atoms. The point defects produced during this process are sufficiently mobile (at tempera- tures above 150 K); so that self-interstitials and vacancies created in the collision cascades are mostly annealed out by recombination. Neverthe- less, for higher doses the damage accumulates preferentially in regions where the maximum of the ion energy transfer occurs, and an amorphous layer is created, whose thickness depends on the ion dose. The amorphous silicon formed during such an implantation is strongly influenced by the im- plantation parameters and by subsequent thermal treatments. It has been shown that the thermody- namical state of ion implanted amorphous silicon (a-Si) changes progressively with low temperature (below the crystallization temperature) thermal annealing or after low dose ion implantation. Thermal treatment of as-implanted, i.e. unrelaxed a-Si produces a variation of its heat of crystalli- zation from a maximum of 18.5 kJ/mol for the fully derelaxed state to a minimum of 13.4 kJ/mol for the fully relaxed state [1,2]. Progressive tran- sitions from the derelaxed to the relaxed state can * Corresponding author. Tel.: +385-1-456-1068; fax: +385-1- 468-0114. E-mail address: pivac@rudjer.irb.hr (B. Pivac). 0168-583X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0168-583X(03)01818-4 Nuclear Instruments and Methods in Physics Research B 215 (2004) 122–128 www.elsevier.com/locate/nimb