Phenothiazine (PTZ) crystals are grown by a physical vapor transport method in a horizontal tube furnace. The resulting disk-type PTZ single crystals have a layered structure, which can be mechanically exfoliated into stacked individual layers to exhibit various colors depending on the thickness. The PTZ single-crystal field-effect transistor (FET) devices exhibit a p-type semiconducting property with 3.03 x 10(-6) S/cm electrical conductivity, 1.15 x 10(-4) cm(2)/(V s) carrier mobility, and a 10(4) on/off ratio.