Several proposed beyond-CMOS devices based on two-dimensional (2D) heterostructures require the deposition of thin dielectrics between 2D semiconductor layers as an interlayer, or on the 2D semiconductor as a gate. However the direct deposition of dielectrics on 2D materials is challenging due to their inert surface chemistry. To deposit subnanometer EOT dielectrics on 2D semiconductors, a flat lying titanyl phthalocyanine (TiOPc) monolayer was employed to functionalize the 2D materials via non-bonding interaction for atomic layer deposition (ALD), and the initial stage of growth was probed using in-situ STM. ALD pulses of trimethyl aluminum and H₂O resulted in the uniform deposition of AlO_x on the TiOPc/HOPG via dissociative chemisorption onto TiOPc reactive sites. The uniformity of the dielectric is consistent with DFT calculations showing multiple reaction sites on each TiOPc molecule for reaction with TMA.

In order to deposit dielectrics with low leakage and low equivalent oxide thickness (EOT) on WSe₂, a flat-lying titanyl phthalocyanine (TiOPc) monolayer (ML), deposited via molecular beam epitaxy (MBE), was integrated to create a seed layer for atomic layer deposition (ALD) on WSe₂ surfaces. TiOPc molecules formed a flat lying monolayer on WSe₂ ML, with four fold crystal structure in scanning tunneling microscopy. ALD pulses of trimethyl aluminum and H₂O resulted in the uniform deposition of Al₂O₃ on TiOPc/WSe₂, confirmed by AFM and cross sectional TEM. After deposition of 50 cycles of the Al₂O₃ onto the TiOPc/multilayer WSe₂, top gated FETs were fabricated. The top gated leakage current was measured 0.046 pA/µm² at 1 V gate bias with 2.4 nm EOT, which is lower leakage current than previous results. A subthreshold swing of 80 mV/dec was measured in n-branch of dual gated device.