Structural and electrical properties of Ni-Co films DC-biased plasma-sputter-deposited on MgO(001)

Ni-Co alloy films 180-nm thick were deposited on MgO(001) substrates at 280 degrees C by de plasma-sputtering at 2.5 kV in pure Ar gas using a Ni90Co10 target. A bias voltage, V-s, of 0, -110, -140 or -180 V was applied to the substrate during deposition. The structural and electrical properties of the films were studied as a function of V-s by X-ray photon electron spectroscopy, cross-section transmission electron microscopy and by measurements of the temperature coefficient of electrical resistance (TCR), eta, from 150 to 300 K as well as resistivity, rho(r), at 10 K, The composition inside the film is uniformly Ni87Co13 with no detectable impurity independently of V-s. The films retain normally the fee structure epitaxially grown with the NiCo(001)parallel to MgO(001) and NiCo[010]parallel to MgO[010] relationship. Misfit dislocations are induced at the interface to relax the strain energy due to the lattice mismatch between Ni87Co13 and MgO. In addition, the crystal lattice of the film near the interface is expanded. eta increases and rho(r) decreases by applying V-s, suggesting that the application of V-s could improve the crystallinity of the films, (C) 1998 Elsevier Science S.A.