Lipon thin films grown by plasma-enhanced metalorganic chemical vapor deposition in a N2–H2–Ar gas mixture

Lithium phosphorus oxynitride (Lipon) thin films have been deposited by a plasma-enhanced metalorganic chemical vapor deposition method. Lipon thin films were deposited on approximately 0.2 μm thick Au-coated alumina substrates in a N2–H2–Ar plasma at 13.56 MHz, a power of 150 W, and at 180 °C using triethyl phosphate [(CH2CH3)3PO4] and lithium tert-butoxide [(LiOC(CH3)3] precursors. Lipon growth rates ranged from 10 to 42 nm/min and thicknesses varied from 1 to 2.5 μm. X-ray powder diffraction showed that the films were amorphous, and X-ray photoelectron spectroscopy (XPS) revealed approximately 4 at.% N in the films. The ionic conductivity of Lipon was measured by electrochemical impedance spectroscopy to be approximately 1.02 μS/cm, which is consistent with the ionic conductivity of Lipon deposited by radio frequency magnetron sputtering of Li3PO4 targets in either mixed Ar–N2 or pure N2 atmosphere. Attempts to deposit Lipon in a N2–O2–Ar plasma resulted in the growth of Li3PO4 thin films. The XPS analysis shows no C and N atom peaks. Due to the high impedance of these films, reliable conductivity measurements could not be obtained for films grown in N2–O2–Ar plasma.