A facile one-pot solvothermal route using the reaction of sputtered copper film and sulfur powder in ethanol solution at a low temperature of 90 °C for 12 hours has been implemented to in situ synthesize 2D hexagonal copper sulfide (CuS) nanoflakes. Their field electron emission (FE) characteristics were investigated and were found to have a close relationship with the copper film's thickness. The lowest turn on electric field (Eon) was 2.05 V μm(-1) and the largest field enhancement factor (β) was 7261 when the copper film's thickness was 160 nm. Furthermore, through a preferred edge growth route, patterned CuS nanoflakes were synthesized with the combined effect from a copper film seed layer and a passivation layer to further improve FE properties with an Eon of 1.65 V μm(-1) and a β of 8351. The mechanism of the patterned CuS nanoflake preferred edge growth is reported and discussed for the first time.