Plasma diagnostic in LiMn₂O₄ thin film process for Li-ion battery application

This work reports an advanced plasma-material process comprising the process design, plasma characterization, and surface engineering of LiMn₂O₄ films deposited by dual RF magnetron sputtering (MS). Several plasma diagnostic techniques integrated with the MS system were carefully utilized for the in-situ process monitoring to control the plasma parameters. Glancing angle deposition is used to create uniform plasma, which assists excellent film uniformity in the central region. Various standard techniques such as XRD, Raman, TEM, and AFM were used to study the characteristic properties of the deposited films. High plasma density that assists high ion energy flux (IF) and high energy tails in the EEPF, deposition of total energy-in-flux (EF) on the substrate, and high optical emission intensities characterized by the excited species of Mn, O, Li, and Ar, respectively, measured by the radio frequency compensated Langmuir probe (LP), energy flux probe, and optical emission spectroscopy (OES) methods at pressures of 0.93 Pa and 1.33 Pa produced LiMn₂O₄ films with superior crystallinity and smooth microstructure. This work also reports the collective effect of plasma parameters and thermal energy on the growth and properties of LiMn₂O₄ film intended for Li-ion battery application.