Tailoring the Interfacial Band Offset by the Molecular Dipole Orientation for a Molecular Heterojunction Selector

Understanding and designing interfacial band alignment in a molecular heterojunction provides a foundation for realizing its desirable electronic functionality. In this study, a tailored molecular heterojunction selector is implemented by controlling its interfacial band offset between the molecular self-assembled monolayer with opposite dipole orientations and the 2D semiconductor (1_L-MoS₂ or 1_L-WSe₂). The molecular dipole moment direction determines the direction of the band bending of the 2D semiconductors, affecting the dominant transport pathways upon voltage application. Notably, in the molecular heterostructure with 1_L-WSe₂, the opposite rectification direction is observed depending on the molecular dipole moment direction, which does not hold for the case with 1_L-MoS₂. In addition, the nonlinearity of the molecular heterojunction selector can be significantly affected by the molecular dipole moment direction, type of 2D semiconductor, and metal work function. According to the choice of these heterojunction constituents, the nonlinearity is widely tuned from 1.0 × 10¹ to 3.6 × 10⁴ for the read voltage scheme and from 0.4 × 10¹ to 2.0 × 10⁵ for the half-read voltage scheme, which can be scaled up to an ≈482 Gbit crossbar array.