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

One hundred-nm-thick Fe film has been deposited on MgO(001) substrate at 250 degrees C by biased de-plasma sputtering at 2.9 kV in Ar gas. A dc bias voltage V-s 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 V-s = -140 V the Fe film could be epitaxially grown with Fe(001)[110]//MgO(001)[100] while the film retained a polycrystalline structure when V-s was higher or lower than -140 V. The minimum electrical resistivity and the maximum saturation magnetization were achieved at V-s = -140 V consistent with the result of the growth structure. In conclusion, when V-s = - 140V the Fe film can be epitaxially grown with the lower defect density under the bombardment of energetic Ar particles accelerated by V-s to increase the mobility of Fe adatoms and to resputter impurity species during the film formation. (C) 2000 American Vacuum Society. [S0734-2101(00)02903-1].