MoS2 Field-Effect Transistor with Sub-10 nm Channel Length.

Atomically thin molybdenum disulfide (MoS2) is an ideal semiconductor material for field-effect transistors (FETs) with sub-10 nm channel lengths. The high effective mass and large bandgap of MoS2 minimize direct source-drain tunneling, while its atomically thin body maximizes the gate modulation efficiency in ultrashort-channel transistors. However, no experimental study to date has approached the sub-10 nm scale due to the multiple challenges related to nanofabrication at this length scale and the high contact resistance traditionally observed in MoS2 transistors. Here, using the semiconducting-to-metallic phase transition of MoS2, we demonstrate sub-10 nm channel-length transistor fabrication by directed self-assembly patterning of mono- and trilayer MoS2. This is done in a 7.5 nm half-pitch periodic chain of transistors where semiconducting (2H) MoS2 channel regions are seamlessly connected to metallic-phase (1T') MoS2 access and contact regions. The resulting 7.5 nm channel-length MoS2 FET has a low off-current of 10 pA/µm, an on/off current ratio of >107, and a subthreshold swing of 120 mV/dec. The experimental results presented in this work, combined with device transport modeling, reveal the remarkable potential of 2D MoS2 for future sub-10 nm technology nodes.

Multilayer block copolymer meshes by orthogonal self-assembly.

Continued scaling-down of lithographic-pattern feature sizes has brought templated self-assembly of block copolymers (BCPs) into the forefront of nanofabrication research. Technologies now exist that facilitate significant control over otherwise unorganized assembly of BCP microdomains to form both long-range and locally complex monolayer patterns. In contrast, the extension of this control into multilayers or 3D structures of BCP microdomains remains limited, despite the possible technological applications in next-generation devices. Here, we develop and analyse an orthogonal self-assembly method in which multiple layers of distinct-molecular-weight BCPs naturally produce nanomesh structures of cylindrical microdomains without requiring layer-by-layer alignment or high-resolution lithographic templating. The mechanisms for orthogonal self-assembly are investigated with both experiment and simulation, and we determine that the control over height and chemical preference of templates are critical process parameters. The method is employed to produce nanomeshes with the shapes of circles and Y-intersections, and is extended to produce three layers of orthogonally oriented cylinders.

Rectangular symmetry morphologies in a topographically templated block copolymer.

Using an array of majority-block-functionalized posts makes it possible to locally control the self-assembly of a block copolymer and achieve several morphologies on a single substrate. A template consisting of a square symmetry array of posts produces a square-symmetry lattice of microdomains, which doubles the areal density of features.