We have investigated the formation of Schottky barriers on diamond employing metal systems coupled with a shallow Si implant that would form low resistivity, high temperature stable metal silicide contact layer. We find that the barrier height of metals such as Pt, Ti and Mo were reduced when deposited on shallow Si implants and given a heat treatment at 500 degree(s)C. The barrier height of Pt on diamond was reduced from 1.89 eV to 0.97 eV by annealing of a sputtered Pt contact on a Si implanted dose of 1015 cm-2 that peaks at approximately 120 angstroms into the diamond surface. Using the same approach, the barrier height of Ti on diamond was reduced from 2.00 eV to 1.29 eV, while the barrier height of Mo remained essentially unchanged. Although we have no direct evidence for silicide formation at this time, the reduction of the barrier height scaled inversely to the temperature of formation of the metal silicide. This is an extremely interesting observation and points to the possibility of achieving very low resistance contacts. We also re-examine the interpretation of barrier height measurements using internal photoemission and attempt to explain the appearance of two barriers and resolve the wide range of reported barrier heights of metals on diamond.
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