RBS and XAS Study of Lithium Nickel Cobalt Manganese Oxide/Lithium Lanthanum Zirconate/Zinc Ferrite Trilayer Structures Grown Using Radio Frequency Sputtering

This work elucidates the growth of lithium nickel cobalt manganese oxide (NCM)/lithium lanthanum zirconate (LLZO)/zinc ferrite (ZFO) films using X-ray diffraction (XRD), Rutherford backscattering (RBS), electron probe microanalysis (EPMA) and X-ray absorption spectroscopy (XAS). Prior to deposition of LLZO and NCM/LLZO, ZFO films (deposition times: 25 (NLZ25) and 100 min (NLZ100)) were deposited on silicon (100) substrates using radio frequency (RF) sputtering at a base pressure of 5.0 × 10−6 Torr. LLZO was deposited for 90 min at RF power of 40 W. Thereafter, an NCM layer was deposited on these bilayer structures for 100 min (RF power—35 W). Obtained trilayer structures were annealed at 900 °C for 1 h. XRD shows ZFO is able to attain crystalline phase of spinel structure for both NLZ25 and NLZ100. In the trilayer structures onsets of some impurity phases are observed. RBS analysis reveals that for NLZ25, NCM, LLZO, and ZFO layers have thicknesses of approximately 30, 60, and 70 nm. For NLZ100, the corresponding layer thicknesses are 40, 90, and 200 nm, respectively. The significant change in ZFO thickness is attributed to the longer deposition duration for later cases. The O K-edge near-edge X-ray absorption fine structure (NEXAFS) spectra of grown trilayer structures exhibit spectral features associated with ZFO, LLZO and NCM. The pre-edge region in the O K-edge NEXAFS spectra is strongly influenced by the interaction of ions from various layers in these structures. La M-edge NEXAFS spectra exhibit characteristic spectral features of La ions in LLZO and show the presence of La3+ in respective layers.