Amorphous carbon membranes were successfully synthesized onto a SiO₂–ZrO₂/α-Al₂O₃ nanoporous substrate via plasma-enhanced chemical vapor deposition (PECVD) at room temperature. PECVD-derived amorphous carbon membranes exhibited molecular sieving properties, showing ideal selectivities of 23 and 1750 for He/N₂ and He/SF₆, respectively, at 25 °C. The membrane maintained high selectivity even at high temperatures as high as 200 °C, indicating considerable stability of the plasma-deposited amorphous carbon layer.