Lithium Phosphate Thin Films Grown by Atomic Layer Deposition

Lithium phosphate, Li 3 PO 4 , has been considered a potential electrolyte material for lithium ion batteries and CO 2 sensors in particular if the films can be made dense and of high quality already at low thickness. In this work, Li 3 PO 4 thin films were deposited by atomic layer deposition (ALD) between 225 and 350°C using trimethyl phosphate and either of the two lithium sources, namely lithium hexamethyldisilazide or lithium tert-butoxide. The deposited films showed slightly crystalline Li 3 PO 4 structure in X-ray diffraction and the elastic recoil detection analysis confirmed this stoichiometry with some carbon and hydrogen impurities. The crystallinity and thermal stability of the films at elevated temperatures in N 2 were also examined. The long term stability of the deposited Li 3 PO 4 films under ambient air may be an issue for the applicability of these processes.