Highly-selective wettability on organic light-emitting-diodes patterns by sequential low-power plasmas

Patterned organic light-emitting-diode substrates were treated by oxygen (O-2) and tetrafluoromethane (CF4) radio-frequency (rf, 13.56 MHz) plasmas of low-power (close to 1 W) that were capacitively-coupled. An unexpected wettability contrast (water contact angle difference up to 90 degrees) between the indium-tin-oxide anode and the bank resist regions was achieved, providing excellent conditioning prior to the ink-jet printing. This selectivity was found to be adjustable by varying the relative exposure time to the O-2 and CF4 sequential plasmas. Static contact angle measurements and extensive x-ray photoelectron spectroscopy analyses showed that the wetting properties depend on the carbon and fluorine chemical functional groups formed at the outermost surface layers, whereas atomic force microscopy images did not show a morphological change. Plasma optical emission spectroscopy and ion mass spectroscopy suggested that surface functionalization was initiated by energy transfer from ionic species (O+, O-2(+), CF+, CF2+, and CF3+) and excited neutrals (O* and F*). The absolute ion fluxes measured on the substrates were up to 10(14) cm(-2) s(-1) and the ion energies up to 20 eV, despite the low powers applied during the process. (C) 2010 American Institute of Physics. [doi:10.1063/1.3371697]