Role of a buried ultrathin amorphous interlayer on the growth of Co films on different metal substrates

Thin films of different metals M (M = Ti, Zr, Hf, Nb, Fe, and Ni) of thickn ess around 10 nm are deposited on Si(100) substrates and a similar to 30 nm Co film is deposited on these metal films using the magnetron sputtering m ethod. Cross-sectional transmission electron microscopy (XTEM) shows the pr esence of a similar to2 nm buried ultrathin amorphous interlayer at the int erface between the Co layer and the M layers (M=Ti, Zr, Hf, and Nb). X-ray reflectivity is used to determine the electron density of this buried ultra thin amorphous interlayer. X-ray diffraction (XRD) is used to determine the crystalline quality of the deposited Co film on these various metal film s ubstrates. The XRD peaks of Co(111) and Co(222) are observed when Ti, Zr, H f, and Nb are used as substrates. Pole figure measurements confirm that the Co film is highly textured on such metallic substrates. On the other hand no characteristic XRD peaks of cobalt are observed when Ni and Fe are used as the substrate, however, XTEM shows the presence of the Co film on those substrates. Theoretically, the heat of mixing (-DeltaH) has been calculated for Co-M systems. The local temperature rise is estimated using the averag e heat capacity and the calculated heat of mixing of the amorphous interfac e compound (Co3M). The local temperature rise due to the amorphous phase fo rmation and hence better mobility of the further deposited metal atoms is t he cause of highly textured Co thin films on such metal substrates. (C) 200 1 American Institute of Physics.