Improved Flexibility of Alumina Ultrathin Barrier Films by Nano-Lamination

Ultra-thin ceramic films deposited by atomic layer deposition (ALD) can provide an excellent oxygen and moisture barrier for diverse applications, such as organic light emitting devices, micro heat pipes, vacuum packaging, and flexible electronics. Due to their nano-scale thickness, these films exhibit a certain degree of flexibility despite being ceramic. Above a critical strain, the ALD films will crack, and this cracking has been shown to be governed by a fracture mechanics model. This paper shows the critical cracking strain of Al₂O₃ deposited on polymers can be improved by incorporating the ceramic film into a nano-laminate (NL) structure, with alternating layers of ALD Al₂O₃ and a compliant polymer film. We find that the critical cracking strain depends on the elastic modulus of the polymer film. We experimentally demonstrate a factor of 2 improvement in critical cracking strain using an 8-layer polymer/ALD NL, with 3 different polymers, independent of the polymer thickness.