Annealing temperature dependence of tensile cracking of indium tin oxide films on polycarbonate substrates

Abstract

Indium tin oxide (In₂O₃:Sn, ITO) films deposited on rigid polycarbonate (PC) substrates exhibit susceptibility to microcracking under mechanical loading and thermal cycling conditions, compromising the mechanical durability of aerospace transparencies. To address this issue, this study systematically investigated the influence of annealing on tensile cracking behavior and crack resistance of 500 nm ITO films on PC substrates. ITO films were subjected to annealing temperatures of 80 °C to 130 °C for 1 h. In situ electrical resistance test under uniaxial tension was employed to characterize the conductive failure strain (ε_c), a key indicator of crack initiation resistance. The results revealed that ε_c demonstrate a non-monotonic relationship with increasing annealing temperature, with a peak ε_c of 1.01 ± 0.01 % achieved at 120 °C. This temperature-dependent behavior of ε_c is principally governed by the competing effects of thermal compressive stress (resulting from the coefficient of thermal expansion mismatch) and intrinsic tensile stress (associated with microstructural evolution). Furthermore, fracture toughness evaluation through the energy release rate method revealed maximum critical energy release rate values for 120 °C-annealed specimens, indicating optimal crack propagation resistance at this annealing condition.