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

Abstract

Uniform and defect-free Al2O3 films were grown on highly oriented pyrolytic graphite (HOPG) terraces by thermal atomic layer deposition (ALD) at low temperature (50 oC) without any functionalization of the surface. Controlling the pulse times of trimethylaluminum (TMA) and H2O while using short Ar purge times, 1-2 nanometer size Al2O3 particles were formed on the HOPG terraces. The particles provided a layer of nanoscale nucleation centers on the HOPG terraces. Capacitance-voltage measurements of Al2O3 films grown at 50 oC using 50 ALD cycles showed an areal capacitance 1.17 mF/cm2 with very small frequency dispersion, consistent with the absence of induction cycles and formation of a high quality interface. The leakage current of the Al2O3 was ~10-5 A/cm2 in large area devices (1900 mm2) which is comparable with results from devices prepared using an identical ALD process for Al2O3 on Si0.7Ge0.3(001) substrates, and is consistent with the absence of pinholes.