Magnetoresistive properties of cobalt thin films grown by plasma-assisted atomic layer deposition

Abstract

Cobalt thin films have been grown by plasma-enhanced atomic layer deposition using bis(cyclopentadienyl)cobalt(II) as cobalt precursor and NH3 plasma as a reducing agent. Electric and magnetic properties are investigated as a function of the growth temperature. A transition from a regime of temperature independent film thickness to a thermally-activated growth is observed at 340 °C. In the self-limited growth regime, magnetization increases and resistivity decreases with temperature. On the contrary, in the thermally-activated regime, magnetization decreases and resistivity increases with temperature. This results in an optimal growth temperature of 340 °C at which the magnetization equals bulk cobalt and the resistivity is 14 µΩ cm. Rotating magnetic field measurements show a magnetoresistance of 1.1% at room temperature ascribed to conventional anisotropic magnetoresistance. This study shows that magnetoresistive properties of cobalt thin films grown by atomic layer deposition are comparable to those obtained by physical vapor deposition and reveals that atomic layer deposition might be an alternative deposition technique for ferromagnetic layers in the field of spintronics.