Orientation alignment of epitaxial LiCoO2 thin films on vicinal SrTiO3 (100) substrates

LiCoO2 is epitaxially grown on SrTiO3 (100) substrates with (104) orientation. Because the LiCoO2 film is grown with its c-axis parallel to four equivalent 〈111〉 axes of the SrTiO3, the (104)-oriented film exhibits four-domain structure on the SrTiO3 (100) substrate. Introducing off-cut angle to the substrate surface breaks the equivalency between the four 〈111〉 axes of the SrTiO3 substrate to induce preferential growth of specific orientation with the c-axis in a descending direction of off-cut surface. Increasing off-cut angle and lowering deposition rate promote the preferential growth, because they facilitate step-flow growth mode, and finally align the c-axes in the domains completely into one 〈111〉 direction of the SrTiO3 substrate. The LiCoO2 film delivers a discharge capacity of 90 mAh g−1 at a low discharge rate of 0.01 C, and 25% of capacity is kept even at a high rate of discharge with 100 C.