The structural and thermal properties of Pb nanoprecipitates embedded in a Si wafer, synthesized by high-fluence ion implantation and subsequent annealing, have been experimentally investigated. X-ray diffraction (XRD), synchrotron small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM) have been used to study the orientation, size, strain and melting point of the nanoparticles. Samples with different implantation fluences and annealing time intervals were annealed at 600°C in a N₂ atmosphere. After annealing, the formation of fcc-structured Pb nanoparticles was identified by using a combination of XRD and TEM. The Pb nanoprecipitates with their average diameter ranging from 9 to 13 nm are epitaxially oriented within the Si wafer, apart from a fraction (~ 50%) of Pb particles that are rotated by 60° in the (111) plane.

The average radius of Pb nanoparticles scales with implantation fluences f and thermal annealing time interval t as f^1/2 and t^1/3 was identified, which is attributed to diffusional growth and Ostwald ripening regime of precipitation during the ion implantation and subsequent annealing，respectively.

Unlike the theoretical prediction and previous experiments for free-standing metallic nanoparticles and nanoparticles embedded in or on amorphous substrates, the crystalline Pb nanoparticles in Si show a dilation of lattice parameters. The experimental XRD data was used to deduce the isotropic un-elastic strain with e^∥ ≈ e^⊥ ranging from 0.6% to 0.2% with increasing size of the nanoparticles. Quasi-pseudomorphism can be invoked to explain this result. 

 

 

Huan Wang, Instituut voor Kern- en Stralingsfysica K.U.Leuven, Belgium
Jo Cuppens, Laboratorium voor Vaste-Stoffysica en Magnetisme and INPAC, K. U. Leuven, Belgium
Margriet Van Bael, Laboratorium voor Vaste-Stoffysica en Magnetisme and INPAC, K. U. Leuven, Belgium
Ellen Biermans, Dept. Fysica, Universiteit Antwerpen, EMAT, University of Antwerp, Belgium
Sara Bals, Dept. Fysica, Universiteit Antwerpen, EMAT, University of Antwerp, Belgium
Kristina Kvashnina, DUBBLE @ ESRF, Grenoble, France
Lucia Fernandez-Ballester, DUBBLE @ ESRF, Grenoble, France
Wim Bras, DUBBLE @ ESRF, Grenoble, France
Werner Knaepen, Department of Solid State Sciences, Ghent University, Belgium
Christophe Detavernier, Department of Solid State Sciences, Ghent University, Belgium
Kristiaan Temst, Instituut voor Kern- en Stralingsfysica and INPAC, K. U. Leuven, Belgium
André Vantomme*, Instituut voor Kern- en Stralingsfysica and INPAC, K. U. Leuven, Belgium

*presenting author