Silicon nitride (SiNx) films deposited on Ar, N-2, and O-2 plasma-treated polycarbonate (PC) substrates have been investigated for transparent barrier applications. The details on different gas effects on PC surface and SiNx/PC properties were investigated in terms of the contact angle, free energy, roughness, adhesion, transmittance, water vapor transmission rate ( WVTR) and oxygen transmission rate (OTR). It was found that both Ar and N-2 plasma could improve the adhesion between SiNx films and PC substrates. When the roughness of plasma-treated PC substrates was decreased from 1.71 nm to 0.89 nm, the OTR data of SiNx/PC samples after 6000 times bending test was decreased from 0.61 to 0.1 cm(3)/m(2)/day. Moreover, the transmittance and permeation results of SiN,/PC plasma-treated samples also show great dependence. After Ar plasma treatment for 60 s, the WVTR and OTR of the 50-nm-thick SiNx barrier coating on PC substrate after 6000 times bending test can decrease to a value of near 0.01 g/m(2)/day and 0.1 cm(3)/m(2)/day, respectively. This result indicates that the SiNx films on Ar plasma-treated PC substrates have high potential for flexible organic light-emitting diode applications. (c) 2006 Elsevier B.V All rights reserved.