Characteristics of in-situ annealed LiMn2O4 thin films for a MEMS power system

LiMn2O4 films were deposited by using rf magnetron sputtering. To obtain the spinel phase, we heated the stainless-steel substrate to 450 degreesC during deposition (in-situ annealing). The films deposited at ambient temperature had an amorphous phase. At lower substrate temperatures (below 400 degreesC), the phase of the films was Li2MnO3. The spinel-phase film was obtained when the film was deposited at 450 degreesC. The deposited films were oxygen-rich and lithium-poor in the spinel phase. These spinel films had a preferred orientation in the (111) plane. In the electrochemical test, the initial volumetric capacity value was lower than the theoretical volumetric capacity (63 muAh/cm(2)- pm). However, the in-situ annealed films had good cyclability. The electrochemical properties of the spinel-phase thin films were improved by increasing the substrate temperature during deposition. The in-situ annealing process could be suitable for MEMS device fabrication.