Title: Nanoindentation-induced structural phase transformations in crystalline and amorphous germanium

Authors: Maha M.O. Khayyat, M. Munawar Chaudhri, G. Patriarche, E. Le Bourhis

Addresses: Department of Physics, Faculty of Applied Science, UQU, P.O. Box 12582, Makkah, Kingdom of Saudi Arabia; IBM T J Watson Research Centre, Yorktown Heights, NY 10598, USA. ' Cavendish Laboratory, Department of Physics, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK. ' Laboratoire de Photonque et de Nanostructures, CNRS UPR 20, Route de Nozay, 91460 Marcoussis, France. ' Laboratoire de Metallurgie Physique, Universite de Poitiers, UMR 6630 CNRS, SP2MI, Teleport 2, Boulevard Marie et Pierre Curie, Boite Postale 30179, 86962 Futuroscope-Chasseneuil Cedex, France

Abstract: During hardness indentation with a diamond indenter, materials are subjected to highly localised pressures. These pressures may cause a complete change of atomic arrangement of the material within the indented zone. This paper reports that when a Berkovich or Vickers nanoindenter is loaded onto a submicrometer thick film of amorphous germanium (a-Ge) and germanium single crystals (Ge-I), they undergo structural phase transitions. These observations are based on Raman scattering investigations, and high resolution transmission electron microscopy. The results show that a-Ge transforms to a face centred cubic (FCC) Ge-I, and simple tetragonal ST12-phase (Ge-III). On the other hand, single crystals of germanium Ge-I transforms to Ge-III and a-Ge phases. It also shows that Ge-III phase is sensitive to the power of the exciting laser beam. It has been shown that structural phase transitions occur at a nanozone close to the indenter tip, where the plastic strain is the highest.

Keywords: germanium crystals; amorphous germanium; nanoindentation; high-resolution transmission electron microscopy; HRTEM; Raman spectroscopy; phase transition; phase transformations; nanotechnology; plastic strain.

DOI: 10.1504/IJNBM.2009.027701

International Journal of Nano and Biomaterials, 2009 Vol.2 No.1/2/3/4/5, pp.91 - 99

Published online: 08 Aug 2009 *

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