Nano Sized Defect Free Al2O 3 Thin Film for High Performance Gas Barrier

Abstract

Recently, our interests in flexible display for next generation have been increased. Plastic substrate is used for flexible display. However it has less chemical resistance, heat resistance, gas transmittance resistance characteristics than glass substrate. By these reasons, plastic substrate requires functional coatings. Because the OLED is degraded by moisture and oxygen, it requires intensely ultralow Water Vapor Transition Rate (WVTR) as 1ⅹ10-6gm-2day-1. To achieve the ultralow WVTR, defects must be prevented. Defects generated by particles can be prevented carefully controlling the process, but defects generated in grain boundary have to be annealed to get rid of them. Organic materials have weakness for heat so annealing process has to be avoid. In this study, we developed Al2O3 nano-structure single gas barrier layer using Neutral Beam Assisted Sputtering (NBAS) process. The NBAS process can be continuously changing crystalline structure from amorphous phase to nano-crystal phase of various grain sizes within single inorganic thin film. These NBAS process effect can lead to formation of nano-structure barrier layer which effectively passivate and healing gas diffusion pathways between grain boundaries. As a result, we confirmed nano-structure of NBAS processed Al2O3 single gas barrier layer through the dielectric constant measurement, Ellipsometry, AFM, and TEM analysis. Finally, WVTR property of Al2O3 nano-structure single gas barrier layer is measured under 1ⅹ10-6gm-2day-1. The Al2O3 nano- structure single gas barrier layer is very suitable in the OLED application.