Since the discovery of graphene in 2004, many 2D layered materials emerge as promising candidates for next generation information processing devices. In our lab, innovations on material synthesis, engineering and device integration are constantly developed. Below are several examples of our current research projects.
1.High performance MoS? field-effect transistors
MoS? is considered as one of the most promising 2D semiconductors for electronic and optoelectronic device applications. Due to its atomic thickness, the projected monolayer MoS? field-effect transistor performance is better than Si MOSFET at the scaling limit, making it a promising candidate for CMOS extension. In our lab, we study the charge transport in MoS? and develop new strategies to engineer the sample quality towards high-performance transistors.
Reference: H. Qiu et al. Hopping transport through defect-induced localized states in molybdenum disulphide. Nature Communications 4, 2642 (2013). H. Qiu et al. Electrical characterization of back-gated bi-layer MoS? field-effect transistors and the effect of ambient on their performances. Applied Physics Letters 100, 123104 (2012).
2.Graphene electronics Graphene has many attractive properties such as ultrahigh carrier mobility, wide band optical absorption and strong mechanical strength. Due to its 2D nature, graphene can be integrated into layered heterostructures that's not possible in bulk materials. Many devices including field-effect transistors, barristors, logic inverters and photovoltaic devices are demonstrated with heterostructures. We integrate graphene/oxide heterostructures to realize ultralow power resistive memory, which is one of the most promising candidates for next generation non-volatile memory. Compared to conventional metal/oxide/metal structures, graphene based devices show significant reduction of switching power up to ~10? times.
Reference: M. Qian et al. Tunable, Ultralow‐Power Switching in Memristive Devices Enabled by a Heterogeneous Graphene–Oxide Interface. Advanced Materials 26, 3275 (2014).
3.Two-dimensional organic crystals
Organic molecular crystals represent an important class of materials for electronic and photonic applications with light weight and low cost. However, achieving high-quality 2D organic crystals is still very challenging. For the first time, we realize the epitaxial growth of 2D organic crystals down to monolayer. Surprisingly, these few-layer organic crystals exhibit pristine quality that afford high-performance organic field-effect transistors. Our work unveils an exciting new class of two-dimensional molecular materials.
Reference: D. He et al. Two-Dimensional Monolayer Quasi-Freestanding Molecular Crystals for High-Performance Organic Field-Effect Transistors. Nature Communication 5, 5162 (2014).