Two-dimensional materials have shown exceptional optoelectronic properties that can be further enhanced through formation of junctions. This thesis demonstrates a new approach to fabricate the gaps at nanometer-sized scale within a 2D material device. By exploiting the enhanced reactivity of 2D materials' edges, edge trimming of graphene was achieved with nanometer precision. The charge carrier transport mechanism inside the nanogap is found to be direct tunneling which is expected to be suitable for high-frequency applications. Moreover, the fabrication process of nanogap was proven to be robust and scalable and 70% of nanogap junctions were within a 0.5 nm window and 97% were within a 3nm window. The formation of precise lateral junctions opens a new way to produce MIM diodes consisting of graphene/nanogap/titanium. Simulations indicate the high cutoff frequency of such a lateral device which make it promising as an optical rectennas which extracts energy from the light field through a wave rectification process. We demonstrate the experimental realization of such an optical 2D rectenna and show rectification behaviors at wavelengths around 500 nm and explicit polarization control. Furthermore, the experimental data shows good agreement with semi-classical Photon-Assisted Tunneling (PAT) model and a tenfold increase in photon-electron coupling over previous rectennas was observed. The unprecedented conversion efficiency of 7x10-4 % demonstrates the potential of 2D nanogap junctions for future optoelectronic devices in areas such as optical quantum computing.

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