Anisotropic stress mechanisms for different dielectric multi-layer films deposited by ion-beam assisted deposition on flexible substrates

• Published in: Thin solid films Vol. 782; p. 140026
• Main Authors: Chen, Hsi-Chao, Lu, Yu-Ru, Chen, Sheng-Bin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2023
• Subjects: Flexible electronics; Interferometry; Ion-beam assisted deposition; Multilayer; Stress behavior; Multilayer; Flexible electronics; Ion-beam assisted deposition; Stress behavior; Interferometry
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2023.140026

•Three multilayer films are deposited on flexible substrates with ion-beam assisted deposition.•A phase-shifting shadow moiré interferometer used to measure the residual stress.•The different relative elasticity could potentially be used for stress relief.•The anisotropic stress of these multilayer films are analyzed with Mohr circle method. This study simulates and tests various prototype multi-layer films on polyethylene terephthalate (PET) and polycarbonate (PC) substrates. The optical and stress response properties of three commonly used optoelectronic anti-reflector (AR) coatings (TiO2/SiO2)2, (Ta2O5/SiO2)2 and (Nb2O5/SiO2)2 were determined. A lab-designed phase-shifting shadow moiré interferometer and Mohr circle approach were used to collect and interpret data. Results showed that the refractive indices of the four different dielectric films were 2.24(TiO2) > 2.23(Nb2O5) > 2.1(Ta2O5) > 1.44(SiO2). The transmittances of the three different AR coatings, in decreasing order, were 95.28%(Ta2O5/SiO2)2 > 94.86%(TiO2/SiO2)2 > 94.03%(Nb2O5/SiO2)2. The maximum shear stress of three different AR coatings, in decreasing size, were (Nb2O5/SiO2)2 > (Ta2O5/SiO2)2 > (TiO2/SiO2)2, for both the PET and PC substrate; however, the maximum principal stresses of three different AR coatings were tensors for the PET substrate, and compressive for the PC substrate. The principal stresses recorded were -916 MPa (Nb2O5/SiO2)2 > 438 MPa (Ta2O5/SiO2)2 > 346 MPa (TiO2/SiO2)2 for PET, and -951 MPa (Nb2O5/SiO2)2 > -838 MPa (Ta2O5/SiO2)2 > -766 MPa (TiO2/SiO2)2 for PC. The different elasticity moduli (ΔE) and relative elasticity between the different film layers may potentially be used to mitigate stress relief in multilayer coatings.