RADIOFREQUENCY MAGNETRON SPUTTERING OF PURE AND MIXED TARGETS OF LI4SIO4, LI3PO4, AND LI2O

Pure and mixed targets of Li4SiO4, Li3PO4, and Li2O were sputtered in both argon and argon/oxygen process gases using a 1-in. diam radio-frequency planar magnetron source. The appearance of the sputter target, the self-bias voltage of the target, the film deposition rate, and the optical emission of the plasma were monitored during film growth. The films were analyzed by energy dispersive x-ray spectrometry, proton induced gamma emission, and atomic spectrometry. Films grown from targets of Li3PO4 were found to be near stoichiometric. In contrast, films grown from targets of, or containing, Li4SiO4 were lithium deficient due to the decomposition and segregation of Li2O away from the sputtered area on the surface of the target. A similar redistribution of material was observed for Li2O targets as well. Reproducible and homogeneous film compositions with stoichiometric lithium concentrations can best be achieved by codeposition with independently controlled sputter sources onto a rotating substrate.