Electron-emission properties of silicon field-emitter arrays treated with trifluoromethane plasma (Si:C-FEA) were evaluated under H-2, CH4, CO, CO2, O-2, and C2H4 ambients. Oxidizing gases, including O-2 and CO2, make shortened the lifetime. However, reductive gases such as H-2 and CH4 lengthened the lifetime longer. On the other hand, C2H4 caused a decrease of the emission current, despite the fact that C2H4 is considered to be one of the reductive gases. Furthermore, emission properties can be recovered by the aging process in an ultrahigh vacuum. This is probably attributable to physisorption and desorption of C2H4 molecules or decomposed molecules onto the emitter surface of the Si:C-FEA. (c) 2008 American Vacuum Society.