Influence of deposition temperature on microstructure and gas-barrier properties of Al(2)O(3) 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 Al(2)O(3) film on a polycarbonate (PC) substrate at 80–160 °C to fabricate Al(2)O(3)/PC barrier films. The thermal and dynamic mechanical properties of the PC substrate, the structural evolution of PEALD Al(2)O(3) films, the optical transmission, surface morphology, and gas-barrier properties of Al(2)O(3)/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 °C, and the coefficient of thermal expansion increases significantly when the temperature exceeds T(g). Increasing the deposition temperature from 80 to 160 °C for Al(2)O(3) 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. Al(2)O(3)/PC films deposited at 80–120 °C have no surface cracks, whereas surface cracks appear in samples deposited near or above 140 °C. Upon increasing the deposition temperature, the water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) of Al(2)O(3)/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 °C, and the minimum WVTR and OTR of Al(2)O(3)/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 Al(2)O(3)/PC films are attributed to both the densification of the Al(2)O(3) film and the cracks, which are caused by the shrinkage of the PC substrate.