Research

Semiconductor electronics and photonics have been the key driving force of the information technology revolution, but are facing substantial challenge for future growth. We are using synthetic chemistry to produce a wide variety of low-dimensional nanostructures, and further assembling them into functional electronic and photonic systems.

• Nanostructured Graphene. Graphene posses many attractive electronic properties and unique optical properties and has been identified as one of the most promoising materials for future generations of electronic and optoelectronic devices. However, graphene cannot be used for logic transistors with sufficient on/off ratio because of its zero band semimetal nature. Our group invest efforts in exploring unique nanostructures and integrations of graphene for practical device applications. To this end, we have made significant efforts to create conduction bandgap in graphene. We have created sub-10 nm graphene nanostructures including nanoribbons and nanomeshes wherein the lateral confines leads to a sizable bandgap to enable room temperature, digital transistors.
• High Frequency Transistors. Our team of collaborators has continued to make significant contributions to the area of graphene materials and devices, demonstrating fast switching speeds in graphene transistors with a record high cutoff frequency of over 400 GHz. Other layered materials such as molybdenum disulfide have also been utilized for high frequency signal proccessing and communicaitons.
• Optoelectronics and Photonics. A new type of highly sensitive ultras-fast multi-color photodetectors by integrating plasmonic nanostructures with graphene offers many advantages over conventional optoelectronics.
• Vertically Stacked Nanoelectronics. In addition, we have recently explored a vertical device structure as an alternative way to logic transistors from graphene without damaging the gaphene lattice. We used the vertically stacked multi-heterostructures of layered materials such as graphene, molybdenum disulfide, boron nitride, and cobaltites (Bi2Sr2Co2O8) to obtain both n- and p-channel vertical field-effect transistors with high on-off ratio as well as complementary inverters.
• Chemical and Bio Sensors. Combining the specific binding capability of selected molecules and the single atomic thickness of graphene, we create highly selective and sensitive molecular sensors. By functionalizing hemin on a graphene transistor, a highly sensitive molecular sensor enables real-time detection of NO in physiological solutions and in living cells with a direct electrical-readout.