Field emission (FE) currents were measured for prinstine single-walled carbon nanotubes (SWCNTs), and after encapsulation of electron withdrawing and donating molecule, i.e., 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) and tetrathiafulvalene (TTF). X-ray photoelectron spectrometer, infrared, and Raman spectrometer were used to confirm encapsulation. TCNQ-doped SWCNTs (TCNQ-SWCNT) enhanced, and TTF-doped SWCNTs (TTF-SWCNT) decreased FE properties compared with pristine SWCNTs. The turn-on field of the pristine SWCNTs, TCNQ-SWCNT, and TTF-SWCNT were calculated to be 2.5, 2.3, and 3.2 V/mu m, respectively, and the maximum currents were obtained, in turn, 180, 329, and 21 mu A/cm(2) at the electric field of 3.6 V/mu m. To explain the FE properties, the work function of doped SWCNTs were calculated from Fowler-Nordheim equation, and also the resistivity of three samples was measured by four-point probe method and compared with each other. (c) 2008 American Vacuum Society.