High Performance Field-Effect Transistors Based on Partially Suspended 2D Materials via Block Copolymer Lithography.

Although various two-dimensional (2D) materials hold great promise in next generation electronic devices, there are many challenges to overcome to be used in practical applications. One of them is the substrate effect, which directly affects the device performance. The large interfacial area and interaction between 2D materials and substrate significantly deteriorate the device performance. Several top-down approaches have been suggested to solve the problem. Unfortunately, however, they have some drawbacks such as a complicated fabrication process, a high production cost, or a poor mechanical property. Here, we suggest the partially suspended 2D materials-based field-effect transistors (FETs) by introducing block copolymer (BCP) lithography to fabricate the substrate effect-free 2D electronic devices. A wide range of nanometer size holes (diameter = 31~43 nm) is successfully realized with a BCP self-assembly nanopatterning process. With this approach, the interaction mechanism between active 2D materials and substrate is elucidated by precisely measuring the device performance at varied feature size. Our strategy can be widely applied to fabricate 2D materials-based high performance electronic, optoelectronic, and energy devices using a versatile self-assembly nanopatterning process.

Neutral-layer-free directed self-assembly of block copolymer in trench using capillary force-induced meniscus.

We propose trench-directed self-assembly (TDSA) of a block copolymer (BCP) driven by a capillary force-induced meniscus as a facile scalable nanolithography method. Unlike conventional directed self-assembly methods, TDSA enables the achievement of neutral surface-free vertical orientations of the BCP nanopatterns irrespective of the polarizability of the substrate, which may be, for example, a ceramic (SiO2) on Semiconductor (Si). In our demonstration of the proposed method, we generated various morphologies of the BCP nanopatterns by varying the trench width, and molecular weight of the BCP. The proposed TDSA method is potentially advantageous for the design of a process/device layout required for the development of an effective manufacturing process.