A Cross-Sectional TEM Study of the Effects of Annealing Conditions on the Regrowth of Lead-Implanted Single Crystal Calc
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A CROSS-SECTIONAL TEX STUDY OF THE EFFECTS OF ANNEALING CONDITIONS ON THE REGROWTH QF LEAD-IMPLANTfD SINGLE CRYfTAL CALCIUM TIT4NATE Rankin , L.A. Boatner , C.W. White and L.W. Hobbs Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 +Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831.
ABSTRACT The atmospheric effects of oxygen and water vapor on the epitaxial regrowth behavior of ion-implanted CaTiO have been studied. Cross-sectional 3 transmission electry microsgopy (TEM) samples prepared from crystals 0 implanted with 1(10 ) Pb/cm at 540 KeV, were annealed at 450-650 C for 40 - 80 minutes, in environments containing different percentages of oxygen and water vapor. Regrowth was studied for implantation directions along both the and crystallographic directions of this orthorhombic TEM on unannealed crystals Perovskite structure, space group Pcmn. indicated the presence of an amorphous region extending approximately 190 nm Annealing in from the edge of the sample as a result of ion-implantation. The regrowth produced an epitaxial regrowth of the amorphous region. process began at the original amorphous/crystalline interface and proceeded It was found that the epitaxial outward to the surface of the sample. regrowth rate increased as the amount of water vapor in the annealing atmosphere was increased. In addition, it was observed that the amount of oxygen present during annealing did not alter the rate of recrystallization in this system.
INTRODUCTION Ion-implantation and annealing have been studied extensively in In recent years, semiconductors and covalently bonded materials [5,6]. however, investigations of these processes in ionic solids have been undertaken [1-4]. The introduction of energetic ions into ionic solids produces an amorphous near-surface region; the position and size of which are functions of the accelerating voltage and fluence of the incident ions 0 (see figure 1). Annealing at relatively low temperatures (-350 C) produces an epitaxial regrowth process that originates at the amorphous/crystalline Other work [2] interface and proceeds outward to the surface of the sample. has established that the epitaxial regrowth rate in CaTiO is a strong function of implantation and recrystallization directions. In a previous study [1], samples annealed in the vacuum of a TEM exhibited a slower regrowth rate than bulk samples annealed in air, for the These results suggest that the same time at the same temperature [2]. absence of oxygen and/or water vapor may retard the regrowth process in CaTiO The work presented here investigates the influence of oxygen and water vapor on the regrowth behavior of this material.
EXPERIMENTAL PROCEDURE All crystals were grown and implanted at Oak Ridge National Laboratory. Single crystals of calcium titanate were implanted at 1 liquid nitrogen temperature with 540 KeV Pb ions at a fluence of 1(10 )/cm , along either the or the direction. Transverse sections for TEM were prepared from bulk crystals
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