Epitaxial growth structure and physical properties of Fe film biased dc-plasma sputter deposited on MgO(001)

Abstract

One hundred-nm-thick Fe film has been deposited on MgO(001) substrate at 250 °C by biased dc-plasma sputtering at 2.9 kV in Ar gas. A dc bias voltage Vs between 0 and −160 V was applied to the substrate during deposition. Reflection high energy electron diffraction, x-ray diffraction, cross sectional transmission electron microscopy (XTEM) and high resolution XTEM were used to investigate the structure of the films. Electrical resistivity at room temperature was measured by four-point probe method. Saturation magnetization of the films at room temperature was measured using a vibration sample magnetometer. As a result, when Vs=−140 V the Fe film could be epitaxially grown with Fe(001)[110]//MgO(001)[100] while the film retained a polycrystalline structure when Vs was higher or lower than −140 V. The minimum electrical resistivity and the maximum saturation magnetization were achieved at Vs=−140 V consistent with the result of the growth structure. In conclusion, when Vs=−140 V the Fe film can be epitaxially grown with the lower defect density under the bombardment of energetic Ar particles accelerated by Vs to increase the mobility of Fe adatoms and to resputter impurity species during the film formation.