(Invited) Mechanism of Low Temperature ALD of Al₂O₃ on Graphene Terraces

Abstract

Uniform and defect-free Al 2 O 3 films were grown on highly oriented pyrolytic graphite (HOPG) terraces by thermal atomic layer deposition (ALD) at low temperature (50 o C) without any functionalization of the surface. Controlling the pulse times of trimethylaluminum (TMA) and H 2 O while using short Ar purge times, 1-2 nanometer size Al 2 O 3 particles were formed on the HOPG terraces. The particles provided a layer of nanoscale nucleation centers on the HOPG terraces. Capacitance-voltage measurements of Al 2 O 3 films grown at 50 o C using 50 ALD cycles showed an areal capacitance 1.17 mF/cm 2 with very small frequency dispersion, consistent with the absence of induction cycles and formation of a high quality interface. The leakage current of the Al 2 O 3 was ~10 -5 A/cm 2 in large area devices (1900 mm 2 ) which is comparable with results from devices prepared using an identical ALD process for Al 2 O 3 on Si 0.7 Ge 0.3 (001) substrates, and is consistent with the absence of pinholes.