Direct observation of Schottky to Ohmic transition in Al-diamond contacts using real-time photoelectron spectroscopy

Real-time photoelectron spectroscopy and in situ electrical measurements have been applied to the formation of Al contacts on p-type diamond. At 294 K, an initially uniform Al film induces band bending in the diamond consistent with the measured (current-voltage) barrier height of 1.05 V. The temperature-induced transition to an Ohmic contact has been monitored in real time revealing a direct correlation between the onset of surface bonding at 755 K and an abrupt change in surface band bending. The reaction temperature is lower than previously believed, and there is a second transition point at 1020 K where the rates of change of both reaction and band bending increase sharply.