Effects of post-annealing on tensile properties of indium tin oxide thin films

Abstract

Indium tin oxide (ITO) thin film has been extensively used for transparent electrodes in electronic devices because of its unique optical, electrical, and chemical properties. However, the ITO thin film easily fails by a small deformation due to its brittle nature. Therefore, intrinsic tensile properties of ITO thin films are required to analyze the mechanical behavior of the ITO layers for a reliable design. In addition, there is a lack of systematical studies on the annealing dependence of the tensile properties though the annealing has been broadly conducted to improve the electrical and optical properties. In this thesis, we performed a direct tensile test of the freestanding ITO thin films afloat on the water surface to reveal the intrinsic tensile properties. In addition, the ITO thin films were annealed at the various temperature (100 $^\circ C$ - 200 $^\circ C$) and time (0.5 h - 6 h) to investigate the annealing effects on the tensile properties. As a result of the structural and crystallographic change, the tensile properties of the ITO thin films varied significantly. Especially, the highest elongation and tensile strength were observed at the 150 $^\circ C$, 1 h-annealed samples. On the other hand, the 200 $^\circ C$-annealed samples showed increased Young's modulus while the elongation and tensile strength severely decreased after the annealing process. Based on this study, we expect to understand the intrinsic mechanical properties of ITO thin films regarding the annealing conditions, thereby contribute to the mechanically robust design of electronic devices.