A Microstructural Study of Iron Carbides Formed by Plasma-Enhanced Chemical Vapor Deposition (50-800 nm thick)
- PDF / 1,363,639 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 94 Downloads / 137 Views
A Microstructural Study of Iron Carbides Formed by Plasma-Enhanced Chemical Vapor Deposition (50-800 nm thick) H. Siriwardane," W.J James,' O.A. Pringle* and J.W. Newkirk, Departments of *Physics, *Chemistry, and 'Metallurgical Engineering and the *Graduate Centerfor Materials Research, University of Missouri-Rolla, Rolla, MO 65401 (U.S.A.) Thin mirror-like iron carbide films were prepared by introducing iron pentacarbonyl [Fe(CO) 5] and hydrogen [H2] into a glow discharge. The deposition temperatures were varied from 200-5000C. The iron to carbon ratios of the resulting films were controlled by adjusting the gas flow ratios. The microstructure and phase transformations occurring in these films were studied before and after annealing at 4000C for four hrs. Characterization techniques used included x-ray diffraction, electron diffraction, Auger spectroscopy and atomic force microscopy. X-ray diffraction data of plasma-deposited films on glass substrates maintained at 400'C showed the presence of only Fe3C. However, the x-ray diffraction data of films on carbon coated glass, and transmission electron microscopy selected area diffraction patterns of films on carbon coated copper grids indicated the presence of a second phase, the closely related metastable Fe7C3, as well as small amounts of Fe3 O4. Atomic force microscopy of crystallites on the surface of films deposited at 400'C and annealed at 400'C for four hours revealed a periodic structure of oblate spheroids. The measured spacings and angle, when compared to projected models of high reticular density planes, suggested the surface to have a structure corresponding to that of bulk Fe3C or Fe7 C3. However the data were not of sufficient quality to unambiguously determine such. 1. INTRODUCTION
Thin iron-carbide films of FeTC 3 and Fe 3C are readily deposited in a cold plasma by introducing the vapor of iron pentacarbonyl and H2 into a glow discharge.1 ' 2 Possible applications of these films are in wear and corrosion resistant coatings, and magnetic storage. 3 The conventional bulk forms of these phases are produced at pressures of thousands of atmospheres and temperatures of thousands of degrees centigrade.4 On the other hand, the plasma-formed analogues are produced at low temperatures and low pressures, typically 200o400*C and 50-100 milliTorr. To exploit the potential uses of plasma deposited films, it is necessary to understand how the film microstructure, atomic structure, and magnetic structure relate to its properties. The aim of the present study is to understand the microstructure of these Plasma Enhanced Chemical Vapor Deposited (PECVD) films. 2. EXPERIMENTAL
The Fe3 C3 and Fe3C films were prepared by introducing iron pentacarbonyl [Fe(CO) 5], and H2 vapor into an inductively coupled glow discharge tubular reactor. The reactor system was the same as that used by Lin et al. 5 The starting materials were, iron pentacarbonyl from the Alpha division of Morton Thiokol Inc., and H2 from the Matheson Gas Group Inc.. Iron pentacarbonyl was degassed prior to us
Data Loading...
