Epitaxial growth of Fe/Mo/Fe(111) and Fe/Cr/Fe(111) on Si(111)
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Epitaxial body-centered cubic Mo and Cr films have been grown on the (111) surface of a-Fe films on Si(lll) at 300 and 575 K by electron beam evaporation in ultrahigh vacuum. X-ray diffraction and transmission electron microscopy show that the Mo films are oriented with the (111) plane parallel to the a - F e ( l l l ) plane and with the Mo[110] direction parallel to the Fe[110] direction in the plane of the substrate. The same orientation relationship holds for the Cr films epitaxially grown on a - F e ( l l l ) surfaces. Epitaxial Fe(lll)/Mo(lll)/Fe(lll) and Fe(lll)/Cr(lll)/Fe(lll) films have also been grown on Si(lll). This work provides new examples of low temperature epitaxy which can occur at a substrate temperature as low as 0.1 times the melting temperature of the deposited materials.
I. INTRODUCTION
Epitaxial growth of metallic thin films is an actively pursued area of research for fundamental studies of thin film growth processes and for applications in novel electronic and magnetic devices.1"5 The discovery of giant magnetoresistance in Fe/Cr superlattices has produced new interest in growing epitaxial metallic multilayers.6"21 Recently Purcell et al.s and Unguris et al.9 developed a method for growing [100] oriented epitaxial Fe/Cr multilayers using a Fe[100] whisker as a seed. Kamijo and Igarashi have grown epitaxial Fe(001)/Cr(001) superlattices with extremely flat interfaces by molecular beam epitaxy (MBE) at 650 °C on MgO(OOl) substrates.10 Folkerts et al. reported the epitaxial growth of Fe(100)/Cr(100) superlattices on Ge(100) substrates at 200 °C in a MBE system.11 Using sputtering techniques Window,18 Sato,19 and Brubaker et al.20 have grown crystalline multilayers of Fe/Mo with high coherency and almost perfect [110] texture in the growth direction on substrates, such as glass slides, silicon, and sapphire. Similarly, most of the Fe/Cr superlattices prepared by sputtering are [110] textured.12"17 Recently, Qiu et al. have grown epitaxial Fe(100)/Mo(100)/Fe(100) thin films on a Mo(100) single crystal substrate at room temperature by MBE.21 In this paper, we report a method for growing [111] oriented epitaxial Mo/Fe, Cr/Fe, Fe/Mo/Fe, and Fe/Cr/Fe structures on Si(lll) at 300 and 575 K using e-beam evaporation in ultrahigh vacuum. X-ray diffraction (XRD), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS) are used to characterize the as-grown structures. Additional information on the epitaxial growth of Mo on the a - F e ( l l l ) surface, including ion channeling measurements, can be found in Ref. 22. J. Mater. Res., Vol. 8, No. 7, Jul 1993
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We have recently reported the epitaxial growth of [111] oriented a-F e films on hydrogen-terminated Si(lll) substrates at temperatures between 300 and 600 K.23'24 Using this epitaxial a - F e layer as a seed, we have successfully grown epitaxial Nd/Fe multilayer structures.25 These observations encouraged us to explore the epitaxial growth of Mo and Cr on (111) oriented
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