Probe size study of apatite irradiation in stem

¹ Unité des Matériaux et Transformation (UMET), Université des Sciences et Technologies de Lille, Bâtiment C6, 59650 Villeneuve d’Ascq, France
² École Nationale Supérieure des Ingénieurs en Arts Chimiques et Technologiques Cirimat-Ensiacet, Ensiacet 4 allée Émile Monso, BP44362, 31030 Toulouse cedex 4, France
³ Laboratoire de Recherche en Nanosciences LRN EA4682, UFR Sciences Université de Reims, 21, rue Clément Ader, 51685 Reims cedex 02, France

^a e-mail: etienne.bres@univ-lille1.fr

Received: 25 February 2013
Revised: 31 October 2013
Accepted: 5 June 2014
Published online: 1 August 2014

Abstract

The effect of electron beam irradiation of stoichiometric hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAP) is investigated using electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) mode equipped with a LaB₆ gun. Initial irradiation at 160 A cm⁻² dose rate shows no modification of the low loss spectra. No difference of mass loss for Ca, O and P is observed for two different probe diameters: 4 nm (dose rate = 160 A cm⁻²) and 24 nm (dose rate = 70 A cm⁻²). Furthermore no formation of CaO is observed for both experimental conditions. It is proposed that the low values of both electron dose rates and doses (from 350 to 2400 C cm⁻²) avoid mass loss. At the higher dose rate obtained with a field emission gun (FEG), transformations are observed for the lowloss signal as well as for the Ca, P and O signals. These results might be very useful for the future studies of apatite particles at the nanoscale.