Investigation of the Effects of AR Stacks on the Structure, Optical and Mechanical Properties of Transparent Conductive Oxide Thin Films

摘要

SiO_2 overcoat and Al_2O_3 undercoat were added to ITO film to improve its visible transmittance. While the SiO_2 overcoat has little impact on the microstructure of ITO film, Al_2O_3 undercoat decreases the lattice parameter and grain size of ITO layer, and increases the number of oxygen vacancies, and in turn, increases the infrared reflectance of ITO film. The detachment behavior of ITO film with and without AR coatings was investigated by nano-scratch and nanoindenta-tion tests. The ITO with top and bottom AR coatings showed significant improvement in scratch resistance against severe damage, such as delamination and chipping. To understand the mechanism, hardness H, elastic modulus E, intrinsic stress and thermal stress were systematically investigated. It was found that the improved scratch resistance is attributable mainly to the increased the value of H~3/E~(*2) and decreased residual stress when overcoat and undercoat were added. The increased hardness and decreased elastic modulus for ITO sandwiched between SiO_2 and Al_2O_3 suggest that there is a possibility to tailor the mechanical properties of material by making multilayer composite.