(Invited) Nanoelectronics Based on Silicene
In the past decade, two-dimensional (2D) materials have evolved into a big family with emerging new members beyond graphene, such as hexagonal boron nitride (hBN), transition metal dichalcogenides (TMDs), and elemental monolayers (e.g. silicene, phosphorene). Silicene, the group IV elemental cousin of graphene, has a buckled honeycomb lattice1 with predicted Dirac band structure2, 3. It has the potential to be a widely tuneable 2D monolayer, where external fields and surface interactions can influence fundamental properties like the band gap4, for future innovative nanoelectronics5. For instance, several interesting phenomena in silicene has been predicted such as quantum spin Hall effect3, piezo-magnetism6 and strain-related thermal conductivity7. Despite the aforementioned exciting theoretical studies and the developing epitaxial synthesis of silicene8, air-stability is still a central issue9 for experimental material and device studies.
Here, we report our recent progress addressing the air-stability issue by a unique growth-transfer-fabrication process named silicene encapsulated delamination with native electrodes (SEDNE). SEDNE process preserves silicene during transfer and device fabrication, and enables a short time window for Ag-removed silicene device studies. As a result, we demonstrated the first silicene field-effect transistors (FETs), corroborating theoretical expectations on ambipolar Dirac charge transport. Monolayer silicene FETs exhibit ON/OFF ratio over one order of magnitude with extracted mobility ~100 cm2/V-s. Our preliminary data suggest that bilayer silicene FETs also comply to ambipolar transport but with lower ON/OFF ratio and reduced mobility. The mobilities are currently limited by acoustic phonon scattering, and phase and grain boundary scattering. This work suggests a promising route to minimizing the risk of degradation during transfer and device fabrication for air-sensitive elemental 2D materials such as phosphorene and germanene. Importantly, the allotropic affinity of silicene with crystalline bulk silicon and its relatively low synthesis temperature suggest a more direct path for silicene integration with ubiquitous semiconductor technology.
This work is supported in part by the Army Research Office under contract W911NF-13-1-0364 and the Future and Emerging Technologies (FET) program # 270749 within the Seventh Framework Program for Research of the European Commission.
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