Dissertation Defense

2D Atomic Layer Crystals for Nanoelectronics and Applications

Zhe Liu

Two-dimensional (2D) atomic layer crystals, such as graphene and transitional metal dichalcogenides (TMDCs), are emerging materiaccurateals with unique physical and electrical properties promising for nanoelectronics and device applications. For example, the ultra-high surface-to-volume ratio makes them ideal candidates for sensor applications. Fascinatingly, the Fermi level tunability of graphene, which originates from its unique linear gapless band structure, can add an extra dimension to device control, providing a broader platform for invention and innovation.

This thesis focuses on 2D crystal growth and nanoelectronic device applications. Chemical vapor deposition (CVD) growth of monolayer MoS2 is first presented for both monocrystalline flake and large area continuous film growth, followed by various characterization methods to examine growth quality. For the application part, an electrically tunable lateral structured graphene-silicon-graphene bipolar junction transistor (BJT) has been developed, with its direct current gain simply controlled by a gate electrode. Moreover, a true label-free nanoelectronic sensing platform is also pioneered by combining the electrical gate tunability of graphene sensor responsivity (or gate spectra) with principal component analysis (PCA) technique. In contrast to conventional electronic sensor or electronic nose technology, surface functionalization is no longer needed for this single graphene sensor to achieve chemical sensing and discrimination, which lays the groundwork toward true label-free electronic sensor with high sensitivity and selectivity, and a novel electronic nose technology with better simplicity and higher accuracy.

Chair: Professor Zhaohui Zhong