PULSED LASER DEPOSITION OF HIGHLY ORIENTED LiCoO₂ AND LiMn₂O₄ THIN FILMS FOR MICROBATTERY APPLICATIONS

Abstract

Thin films of LiCo0 2 and LiMn20 4 were prepared by pulsed laser deposition technique. The influence of deposition parameters on the structure and surface morphology of the films were studied. The LiCo0 2 films deposited in oxygen partial pressure of 100 mTorr and at substrate temperature of 300 °C exhibited predominantly (003) orientation of the hexagonal R-3m phase indicating that the growth occurs perpendicularly to the substrate surface with an average grain size of 80 ran. Whereas the films grown at higher substrate temperature were polycrystalline with the growth parallel to the substrate surface. The LiMn 2 0 4 thin films prepared at 300 °C exhibited predominantly (111) orientation indicating cubic spinel structure with Fd3m space group.

Pulsed Laser Deposited Films for Microbatteries

“…A spinel structure (Fd3m space group) was successfully prepared using different PLD conditions and applied as a positive electrode in thin-film lithium microbatteries (see, for example, [121]). Most prior works focused on the fundamental properties of PLD-grown LMO cathode films, aiming to deposit the highly structured and porous morphology required for a good operating electrode [7,[122][123][124][125][126][127][128][129][130][131][132][133][134][135][136] [123]. The electrochemical features of the Li cell showed a specific capacity as high as 120 mC·cm −2 ·µm −1 in the voltage range of 3.0 to 4.2 V vs. Li + /Li, which was attributed to the high degree of film crystallinity [7,123].…”

“…The Li deficiency occurs as a result of the different behavior of the species at elevated Ts. Hussain et al[132,133] obtained highly oriented LiMn2O4 thin films on oriented Si substrates heated in the range of 100 ≤ Ts ≤ 600 °C under PO₂ = 10 Pa and with a laser fluence of Φ =10 J·cm −2 . Grains with a spherical shape (around 230 nm in diameter) changed to a flake-like structure at Ts = 600 °C (Figure 8a).…”