Transfer of Electric Charges through Rutile Single Crystals

Electron transfer and onset of field emission has been investigated in Ti${\mathrm{O}}_2$ single crystals with dc currenttime characteristics parallel and perpendicular to the optic axis as function of voltage, temperature, electrode material, and light absorption. The currents are much larger and field emission sets in at lower voltage when the field is parallel to the optic axis. Higher temperature favors the current transfer by increasing the carrier mobility. The effect of different electrode materials proved minor, except in the case of Ti, which as cathode raised the current by about one order of magnitude. Photoelectric measurements showed that, in the critical voltage region of incipient field emission, light absorption can apparently force the current reversibly into the field-emitting stage.