High Resolution Leed Study of The Fe Growth Mode on Cu(100), Cu(110) and Cu (111) Surfaces
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HIGH RESOLUTION LEED STUDY Cu(ll0) AND Cu(lll) SURFACES
OF
THE
Fe
GROWTH
MODE
ON
Cu(100),
1
1 YUQUN CAO AND PEDRO A. MONTANO ,2 1) Department of Physics, Brooklyn College and CUNY Center, Brooklyn, NY 11210. 2) MSD, Argonne National Laboratory, Argonne Il 60439.
Graduate
ABSTRACT. We have investigated the growth mode of iron on clean Cu(100), Cu(ll0) and Cu(lll) surfaces using high resolution LEED. We studied the effect of substrate temperature on the growth of epitaxial fcc iron. Iron metal was evaporated from an electron beam source under UHV conditions and deposited on the copper single crystal surfaces at three different temperatures ( 173 K, 300 K and 473 K ) . A high resolution LEED system was used to measure the diffraction spot profiles. The samples were studied as a function of temperature after deposition on the copper substrates. The clean Cu surfaces were also measured and used as references for the Fe:Cu system. The diffraction spot profiles show Gaussian line shape before and after the Fe deposition. The effect of iron grown on the Cu surface is to reduce the coherent length. This effect is observed for all the copper surfaces. The intensity of the diffraction spots exhibit a sudden increase above 470 K, simultaneously a larger coherent length is observed. This effect occurs for all copper surfaces. The epitaxial growth of Fe is better on Cu(100) than on the other surfaces. The best epitaxial growth is obtained for the highest substrate temperature. A careful Auger study reveals that the anomalous increase observed on the intensity of the diffraction spots is related to the evaporation of iron from the copper surface. The spot profiles at low temperature are very broad and are suggestive of very poor epitaxy, random islands growth with a high probability of bcc iron inclusions. Introduction There is great interest in the study of the epitaxial growth of metals on single crystal substrates. They offer the possibility of stabilizing new crystallographic phases with novel physical properties[l-6]. There is special interest in the epitaxial growth of iron due to the competition between the bcc and fcc structures. The bcc a-Fe phase is ferromagnetic and the crystallographic structure exists up to about 1183 K, where a phase transformation occurs to fcc y-Fe. The fcc iron face is antiferromagnetic at low temperatures, as observed by Mossbauer spectroscopy in y-Fe precipitates in Cu [7], and more recently on Fe epitaxially grown on Cu(100) [8]. There are several reports in the literature [911 that suggest the presence of a metastable ferromagnetic phase. The presence of a metastable ferromagnetic phase at 363 K, with the Fe magnetic moment parallel to the Cu(100) surface was
Mat. Res. Soc. Symp. Proc. Vol. 237. @1992 Materials Research Society
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of publication [11) . The presence an earlier observed in a ferromagnetism at low temperatures has been reported in publication by Pescia et al (9) . They observed that the iron magnetic moment was perpendicular to the Cu(100) plane. We have also rep
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