Author:
Siriwardane, Haresh Gnaninda Samarasinghe.
Title:
MICROSTRUCTURE AND MAGNETIC PROPERTIES OF THIN IRON CARBIDE FILMS FORMED UNDER PLASMA-ENHANCED CHEMICAL VAPOR DEPOSITION (THIN FILMS).
Source:
Dissertation Abstracts International. Volume: 55-02, Section: B, page: 0553.
Abstract:
The microstructures of plasma-deposited
Fe7C3 and Fe3C films were investigated
by X-ray diffraction, transmission electron microscopy, scanning electron
microscopy, atomic force microscopy, and Auger electron spectroscopy.
According to X-ray diffraction, single phase Fe7C3 and
Fe3C
films were successfully produced on glass substrates at temperatures
of 300 degrees C and 400 degrees C, respectively. Electron
diffraction of films deposited on carbon coated copper grids showed
the presence of Fe7C3, Fe3C, and
Fe3O4 at all deposition
temperatures, suggesting that the films grown on glass probably contain
small quantities of secondary phases with extremely fine grains.
Two morphologies were observed with high resolution transmission
electron microscopy in films deposited on carbon-coated grids at
300 degrees C. The first morphology exhibited half-micron size platelets
of both Fe7C3 and Fe3C surrounded by 0.1-0.2 um crystals on
continuous film regions of the carbon support film on the copper grids.
The second morphology observed at the edges of torn carbon films
consists of grape-like clumps of 100-200 A size crystals each surrounded
with a uniform graphitic coating.
The magnetic
properties of the Fe7C3 and Fe3C films were
determined using a SQUID magnetometer. The magnetic moments of
films were found to be aligned perpendicular to the film surface.
After annealing the Fe7C3 film an increase in coercivity and
saturation magnetization was observed. In contrast, the coercivity of
the Fe3C film decreased after annealing. The effect of annealing on
coercivity is related to the particle sizes in theFe7C3 and
Fe3C films. Further, an approximate zero coercivity measured
for the Fe7C3 film at 300K is analogous to that of
superparamagnetic behavior of free particles.