Epitaxial growth of Co/Cu[100] and [111] superlattices via rf sputtering on sapphire (1120)-substrates
- PDF / 1,462,275 Bytes
- 12 Pages / 612 x 828 pts Page_size
- 76 Downloads / 221 Views
Co/Cu superlattices with total thicknesses ranging from 10 nm to 60 nm and with periodicities of 1.6—8.5 nm were sputtered on single-crystalline sapphire (ll20)-substrates. Sputtering with low rates at room temperature yields samples of high epitaxial and crystalline quality. By careful choice of the sputtering parameters, either the fee [100] or the fee [111] orientation can be selected as growth direction on one and the same substrate orientation. The preference for a particular film orientation appears to be kinetically driven. In all cases, the average lattice spacings d and the appearance of satellite reflections in x-ray Bragg-scans point to coherent growth up to thicknesses of 30 nm. X-ray small angle reflectivity measurements reveal clear oscillations and satellites indicative for smooth interfaces. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations supplement the characterization of the films.
I. INTRODUCTION In recent years growing attention has been paid to artificial metallic superlattices because of their intriguing structural, magnetic, and transport properties.1"3 Co/Cu is a member of the group of 3d ferromagnetic/ nonmagnetic metals and, therefore, the main interest in these superlattices is focused on their magnetic behavior, in particular the exchange coupling through nonmagnetic layers.4 Research in magnetism of superlattices requires a detailed knowledge of their structural properties. This is particularly true for the Co/Cu system for which magnetic measurements on sputtered polycrystalline multilayers5 and MBE single crystals6"8 with different orientations have been published with, in part, conflicting results. This paper is concerned with the overall structural properties of Co/Cu superlattices prepared by sputter methods which, nevertheless, have high single crystalline structural qualities. Concomitant magnetic measurements of the [100] oriented superlattices are presented in a subsequent paper, and those of the [111]superlattices are published elsewhere.9 Another point of interest is the deposition method itself. While many groups employ well-equipped MBE machines for the preparation of thin films and superlattices, this study is based on samples grown by conventional rf-sputter methods.10 It is well known that the sputter deposition process differs drastically from that occurring in molecular beam epitaxy (MBE). 11 Apart from generally poorer vacuum conditions, sputter deposition provides enhanced surface migration leading to sharper interfaces. Furthermore, using proper growth parameters and single crystal substrates, high quality films and superlattices can be grown which rival their MBE 570
http://journals.cambridge.org
J. Mater. Res., Vol. 9, No. 3, Mar 1994
Downloaded: 13 Mar 2015
counterparts. Nevertheless, sputtering is a comparatively easy process to handle, and it is only a small step from laboratory to industrial applications. In MBE growth it is well known that the single crystalline substrate together with a suitable buffer layer se
Data Loading...
