  The Super Tau-Charm Facility (STCF) is a future electron-positron collider
proposed in China with a peak luminosity of above 0.5$\times$10$^{35}$
cm$^{-2}$s$^{-1}$ and center-of-mass energy ranging from 2 to 7 GeV. Excellent
particle identification (PID) capability is one of the most important
requirements for the detector at the STCF. A 3$\sigma$ $\pi$/K separation up to
2 GeV/c is required within the detector acceptance. A DIRC-like time-of-flight
(DTOF) detector is proposed to meet the PID requirement for the endcap region
of the STCF. The conceptual design of the DTOF detector and its geometry
optimization is presented. The PID performance of the detector has been studied
with Geant4 simulation. With a proper reconstruction algorithm, an overall time
resolution of ~50 ps can be achieved for the detector with an optimum geometry,
when convoluting contributions from all other sources, including the transit
time spread (TTS) of photodetector, electronic timing accuracy, and an assumed
precision (~40ps) of the event start time. And a better than 4$\sigma$ $\pi$/K
separation power at the momentum of 2 GeV/c is achieved over the full sensitive
area of DTOF detector, fulfilling the physics requirement for the PID detector
of the experiment at the STCF.
