In SituObservation of Initial Stagein Dielectric Growth and Deposition of Ultrahigh Nucleation DensityDielectric on Two-Dimensional Surfaces.

Severalproposed beyond-CMOS devices based on two-dimensional (2D) heterostructuresrequire the deposition of thin dielectrics between 2D layers. However,the direct deposition of dielectrics on 2D materials is challengingdue to their inert surface chemistry. To deposit high-quality, thindielectrics on 2D materials, a flat lying titanyl phthalocyanine (TiOPc)monolayer, deposited via the molecular beam epitaxy, was employedto create a seed layer for atomic layer deposition (ALD) on 2D materials,and the initial stage of growth was probed using in situSTM. ALD pulses of trimethyl aluminum (TMA) and H2O resultedin the uniform deposition of AlOxon theTiOPc/HOPG. The uniformity of the dielectric is consistent with DFTcalculations showing multiple reaction sites are available on theTiOPc molecule for reaction with TMA. Capacitors prepared with 50cycles of AlOxon TiOPc/graphene displaya capacitance greater than 1000 nF/cm2, and dual-gateddevices have current densities of 10–7A/cm2with 40 cycles. [ABSTRACT FROM AUTHOR]