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 a t 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 wa s applied to the substrate during deposition. The structural and elect rical properties of the films were studied as a function of V-s by X-r ay photon electron spectroscopy, cross-section transmission electron m icroscopy and by measurements of the temperature coefficient of electr ical 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 no rmally the fee structure epitaxially grown with the NiCo(001)parallel to MgO(001) and NiCo[010]parallel to MgO[010] relationship. Misfit dis locations are induced at the interface to relax the strain energy due to the lattice mismatch between Ni87Co13 and MgO. In addition, the cry stal 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 Elsevie r Science S.A.