  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. An
excellent particle identification (PID) capability is one of the most important
requirements for the detector at the STCF. A 3$\sigma$ $\pi$/K separation power
at the momentum of 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 herein presented. The PID
performance of the detector is studied using Geant4 simulation. With a proper
reconstruction algorithm, an overall time resolution of ~50 ps is achieved for
the detector with an optimum geometry when convoluting contributions from all
other sources, including the transit time spread (TTS) of the photodetector,
electronic timing accuracy, and an assumed precision (~40 ps) of the event
start time. A $\pi$/K separation power of better than 4$\sigma$ at the momentum
of 2 GeV/c is achieved over the entire sensitive area of the DTOF detector,
thereby fulfilling the physics requirement of the PID detector for the
experiment at the STCF.
