Phase Change during the Initial of Ni_(30)Fe_(70)(lnvar) Films on MgO(001) by DC-Biased Plasma-Sputter-Deposition

摘要

Ni100- xFex films were deposited on MgO(001) substrates at 250°C by dc plasma sputtering of the Ni30Fe70 (Invar) target at 2.5kV in pure Ar gas. A dc bias voltage Vs from 0 to -180V was applied to the substrate during deposition. The film thickness was controlled by changing the sputtering time t from 30sec to 5min. The initial growth structure and composition of the films were investigated by XPS and plan-vier-TEM. The resistance R and its temperature coefficient TCR (150K to 300K) were measured as a function of t and of Vs. The Ni 100 - x Fe x films where x ranges from 69 ± 3 to 71 ± 3 weakly dependent on Vs can be prepared. The films are initially grown in a BCC structure with NiFe(001)‖MgO(001) and NiFe[110] ‖ MgO[100] when t is 30sec As t reaches lmin, the FCC phase appears in the films. When t increases beyond 2 min, the films retain mainly the FCC-NiFe structure with NiFe(001) ‖ MgO(001) and NiFe[100] ‖ MgO[100].The films are not electrically continuous unless t reaches 2 min, 1 min, and 30 sec at Vs=0V, -120 V and -180 V, respectively . R decreases with an increase in t and in Vs, while TCR changes consistently with the change of R.