LiFePO 4 thin films grown by pulsed laser deposition: Effect of the substrate on the film structure and morphology

Abstract

Well crystallized and homogeneous LiFePO 4/C (LFPO) thin films have been grown by pulsed laser deposition (PLD). The targets were prepared by the sol–gel process at 600 °C. The structure of the polycrystalline powders was analyzed with X-ray powder diffraction (XRD) data. The XRD patterns were indexed having a single phase olivine structure (Pnma). LFPO thin films have been deposited on three different substrates: aluminum (Al), stainless steel (SS) and silicon (Si) by pulsed laser deposition (PLD). The structure of the films was analyzed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). It is found that the crystallinity of the thin films depends on the substrate temperature which was set at 500 °C. When annealed treatments were used, secondary phases were found, so, one step depositions at 500 °C were made. Stainless steel is demonstrated to be the best choice to act as substrate for phosphate deposition. LiFePO 4 thin films grown on stainless steel plates exhibited the presence of carbon, inducing a slight conductivity enhancement that makes these films promising candidates as one step produced cathodes in Li-ion microbatteries.