Al₂O₃/alucone Barrier Films Prepared By Pulsed Plasma Assisted Atomic Layer Deposition And Molecular Layer Deposition

Organic light-emitting diodes（OLEDs）,organic electronic devices,especially flexible devices,such as wearable electronic sensors,electronic display paper and flexible printing electronics,are vulnerable to water vapor erosion,reducing the service life.Therefore,the devices encapsulated by flexible barrier layer are indispensable.Atomic layer deposition（ALD）technique is one of thin film growth technologies based on self-limiting interface chemical reaction.Atomic layer technique is one of the major methods to prepare high barrier films because growth films are dense structure,high conformality,low defect density,excellent performance and good uniformity.In this thesis,plasma-assisted atomic layer deposition（PA-ALD）technique is used to deposit aluminum oxide（Al₂O₃）films on 50μm polyethylene terephthalate（PET）substrate with trimethylaluminum（Al（CH₃）₃,TMA）as aluminum source,and H₂O or O₂as oxidant for thermal atomic layer deposition（T-ALD）and plasma-assisted atomic layer deposition（PA-ALD）Al₂O₃,respectively.In the same equipment,meanwhile,molecular layer deposition（MLD）technique is used to prepare organic thin films polyethylene glycol aluminum（alucone）using trimethylaluminum（Al（CH₃）₃,TMA）and ethylene glycol（EG）as precursors.Furthermore,inorganic-organic composite films are prepared by combining the PA-ALD and PA-MLD.The barrier properties are investigated in detailed.The main results are as follows:（1）After comparing of aluminum oxide（Al₂O₃）prepared by thermal atomic layer deposition（T-ALD）,continuous plasma-assisted atomic layer deposition（continuous PA-ALD）and pulsed plasma-assisted atomic layer deposition（pulsed PA-ALD）.It is resulted that under the same parameters,pulsed plasma promotes the growth of Al₂O₃ films,and the pulsed PA-ALD Al₂O₃ contains few impurities with a smooth surface and a good barrier performance.（2）After optimizing the process parameters in pulsed PA-ALD Al₂O₃,including substrate temperature,peak power,duty cycle and Ar/O₂ ratio.It is resulted that at 60℃-75℃substrate temperature,20W peak power,20%duty cycle,and Ar/O₂=80:10,Al₂O₃films are the smoothest（RMS～1.22 nm）with the best barrier performances.The water vapor transmission rate（WVTR）of PET coated with 35 nm Al₂O₃ films is～1.7×10^-2g/（m~2·day）,which is two orders of magnitude lower than that of the original PET film（～4.89 g/（m~2·day））.（3）Combining pulsed PA-ALD and pulsed plasma-assisted molecular layer deposition（pulsed PA-MLD）to prepare Al₂O₃/alucone inorganic-organic composite films,the barrier properties of PET are further improved,the WVTR value is as small as～2.9×10^-3 g/（m~2·day）.Compared with single Al₂O₃ coating,the flexibility is improved,and the high transparency is remained reaching 99.95%in the visible light region after coated with 50 nm Al₂O₃/alucone composite films.