Influence of deposition temperature on microstructure and gas-barrier properties of Al2O3 prepared by plasma-enhanced atomic layer deposition on a polycarbonate substrate

We prepared polymer-based encapsulation films by plasma-enhanced atomic layer deposition (PEALD) of Al2O3 film on a polycarbonate (PC) substrate at 80-160 degrees C to fabricate Al2O3/PC barrier films. The thermal and dynamic mechanical properties of the PC substrate, the structural evolution of PEALD Al2O3 films, the optical transmission, surface morphology, and gas-barrier properties of Al2O3/PC film are all studied in this work as a function of temperature. The glass transition temperature T-g of the PC substrate is about 140 degrees C, and the coefficient of thermal expansion increases significantly when the temperature exceeds T-g. Increasing the deposition temperature from 80 to 160 degrees C for Al2O3 film deposited over 300 cycles increases the density from 3.24 to 3.45 g cm(-3), decreases the thickness from 44 to 40 nm, and decreases the O/Al content ratio from 1.525 to 1.406. Al2O3/PC films deposited at 80-120 degrees C have no surface cracks, whereas surface cracks appear in samples deposited near or above 140 degrees C. Upon increasing the deposition temperature, the water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) of Al2O3/PC films decrease significantly at temperatures below T-g, and then increase at temperatures near to or above T-g due to cracks in the films. The optimal deposition temperature is 120 degrees C, and the minimum WVTR and OTR of Al2O3/PC film are 0.00132 g per (m(2) 24 h) and 0.11 cm(3) per (m(2) 24 h 0.1 MPa), respectively. The gas-barrier properties of the Al2O3/PC films are attributed to both the densification of the Al2O3 film and the cracks, which are caused by the shrinkage of the PC substrate.

Automated summary

In this study, polymer-based encapsulation films were prepared by plasma-enhanced atomic layer deposition (PEALD) of Al2O3 film on a polycarbonate (PC) substrate. The properties of the PC substrate, the structure of PEALD Al2O3 films, and the optical transmission, surface morphology, and gas-barrier properties of the Al2O3/PC film were investigated as a function of temperature. The optimal deposition temperature was found to be 120°C, and the minimum water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) of the Al2O3/PC film were 0.00132 g/(m^2 24 h) and 0.11 cm^3/(m^2 24 h 0.1 MPa), respectively. The gas-barrier properties of the Al2O3/PC film were attributed to both the densification of the Al2O3 film and the cracks caused by the shrinkage of the PC substrate.