Increased Ordering in the Amorphous SiO x due to Hyperthermal Atomic Oxygen.
- PDF / 534,740 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 8 Downloads / 150 Views
NN9.5.1
Increased Ordering in the Amorphous SiOx due to Hyperthermal Atomic Oxygen. Maja Kisa, William G. Stratton*, Timothy K. Minton**, Klaus van Benthem***, Steve J. Pennycook***, Paul M. Voyles*, Xidong Chen#, Long Li and Judith C. Yang Materials Science and Engineering Department, 848 Benedum Hall, University of Pittsburgh, Pittsburgh, PA 15261 USA *Materials Science and Engineering Department, University of Wisconsin-Madison, 1509 University Avenue, Madison, WI 53706-1595, USA **Department of Chemistry and Biochemistry, 108 Gaines Hall, Montana State University, Bozeman, MT 59717, USA ***Condensed Matter Science Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831 # Department of Science and Mathematics, Cedarville University, 251 N Main St., Cedarville, OH 45314 # Materials Science Division, Argonne National Laboratory, 9700 Cass Ave, Argonne, IL 60439 ABSTRACT We had studied the effects of hyperthermal (5.1eV) atomic oxygen (AO) on the structural characteristics of the silica layer and Si/SiOx interface formed by the oxidation of Si-single crystal by a variety of microcharacterization techniques. A laser detonation source was used to produce atomic oxygen with 5.1eV kinetic energy. High Resolution Transmission Electron Microscopy (HRTEM) and Selected Area Electron Diffraction (SAED) demonstrated that the silica layer formed on Si(100) by atomic oxygen is thicker, more homogeneous, and less amorphous, compared to the oxide layer created by molecular oxygen (MO). High spatial resolution Electron Energy Loss Spectroscopy (EELS) study confirmed that the Si/SiOx interface created by atomic oxygen is abrupt containing no suboxides as opposed to the broad interface with transitional states formed by molecular oxygen. SAED technique was used to observe sharper diffraction rings present in the diffraction pattern of Si(100) oxidized by reactive atomic oxygen as opposed to the diffused haloes present in the diffraction pattern of Si(100) oxidized by molecular oxygen. Radial Distribution Function (RDF) analyses were performed on the SAED patterns of Si(100) oxidized in atomic and molecular oxygen, indicating that a more ordered oxide is formed by atomic oxygen. Initial Fluctuation Electron Microscopy (FEM) results confirmed an increased medium range ordering in SiOx formed by atomic oxygen when compared to the non-regular arrangement present in the amorphous oxide formed by the oxidation of Si(100) in molecular oxygen. INTRODUCTION Atomic oxygen is considered a hazardous factor causing rapid degradation of spacecraft materials exposed to a harsh environment present in the low earth orbit (LEO). LEO ranges from 200 to 700km in altitude, with average surface temperatures that vary between 200 and 400K [1]. The number density of atomic oxygen is low at these altitudes, but the atomic oxygen flux is very high (1014 atoms cm-2sec-1), due to the velocity of moving spacecrafts, i.e 8km/sec at 250km
NN9.5.2
altitude. Forward facing surfaces of the spacecraft encounter high fluxes of atoms, wit
Data Loading...
