| 초록 |
Recently, encapsulation techniques have been researched intensively for various applications such as food packaging, photovoltaic cells and organic light emitting diodes (OLEDs). Especially, organic devices require highly advanced permeation barrier layers because organic materials are easily degraded by H2O and O2. Currently glass is used for encapsulation of organic devices however it is not applicable due to the high brittleness under mechanical stress so many research groups have tried to improve permeation barrier properties. However, bare polymer films such as polyethersulfone (PES) in flexible devices exhibits high permeation rate. In a single inorganic protection layer, permeation is attributed to defects or pinholes in the film. To prevent such failures, a combination of protective coatings with multilayers of inorganic materials offers lower permeability than single film against gases. Atomic layer deposition (ALD) is well known as one of the most proper methods to deposit dense, conformal and pin-hole free passivation film. Especially, plasma-enhanced ALD (PEALD) is a very attractive technique for depositing oxide films because of its high chemical reactivity. However, the exposure of substrate to plasma during process could result in lattice damage by energetic ions. In this respect, remote plasma ALD (RPALD) was developed to minimize the plasma damage by generating the plasma remotely outside of chamber and the generated radicals and ions enter into the chamber by a downstream flow. In this paper, total 100nm of Al2O3, ZrO2 and Al2O3/ZrO2 multilayer films were deposited by RPALD followed by the measurement of WVTR by electrical Ca test at 50°C and 50% relative humidity to investigate the permeation barrier properties. It was observed that when more number of layers is deposited, it exhibited better barrier properties for encapsulation. In our results, single Al2O3 and ZrO2 films showed low 10-2g/m2day of WVTR but when they are deposited alternatively with 1 cycle of each layer, WVTR decreased to low 10-3g/m2day. To investigate the change of WVTR in detail, the properties of films were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). |
