Effects of annealing process on morphology and mechanical properties of magnetron sputtered LiCoO₂ thin films

Abstract

LiCoO2 thin films were prepared on single crystal Si (100) by magnetron sputtering method and then annealed by different annealing temperatures, holding times and atmospheres. The effects of annealing processes on the surface morphologies, compositions, crystal structures and mechanical properties of LiCoO2 films were investigated. The results show that the surface average roughness of LiCoO2 film is reduced from 11.63 nm to 6.13 nm; annealing atmosphere has the greatest influence on the surface morphologies of LiCoO2 films. The LiCoO2 film composition is destroyed due to Li2O, CoO, Co3O4 by-products formed during annealing process. LiCoO2 film are crystallized under any annealing conditions, the average grain size is about 30 nm, annealing temperature has the greatest influence on the grain size and residual stress. After annealing, the hardness and young's modulus of LiCoO2 films are increased by an order of magnitude. Under the optimal annealing process (600 ℃, 60 min, pure O2 atmosphere), the ratio of H3/Er2 is 0.03 GPa, which shows excellent resistance to plastic deformation.

Keywords

• licoo₂ film
• surface topography
• hardness
• young’s modulus
• friction coefficient