Coal-derived carbon nanodots advance 2D electronics

Coal-derived carbon nanodots are emerging as a promising solution for advancing two-dimensional (2D) electronics. Researchers at the University of Illinois Urbana-Champaign, led by Professor Qing Cao, in collaboration with the U.S. Department of Energy National Energy Technology Laboratory (NETL), have identified these graphene-like particles as effective interfacial binders. These carbon nanodots, derived from bituminous coal, facilitate the integration of 2D materials such as graphene and molybdenum disulfide with dielectric layers, without hybridizing with the 2D channels. This clean interface supports the growth of ultrathin, thermally stable dielectrics, crucial for manufacturing transistors.

The study, published in Nature Communications, reports that the dielectric layers achieved exceed industry targets set by IEEE, with an equivalent oxide thickness of 0.6 nanometers and a leakage current density below 0.1 milliamperes per square centimeter. Field effect transistors and integrated logic gates fabricated using this method operate at around 0.5 volts, significantly lower than the typical 0.6- to 0.8-volt range of advanced silicon technologies, thus reducing energy consumption.

Two-dimensional materials like molybdenum disulfide are attractive for semiconductor devices due to their atomic thinness and lack of dangling bonds, which often scatter electrons in silicon. However, this feature also presents challenges in fabricating devices. Cao's research addresses this by using coal-derived carbon nanodots as nucleation centers for dielectric layer growth. These nanodots exert van der Waals forces on 2D materials, allowing oxide insulators to bond without altering the semiconductor's structure.

The research team employed a Langmuir-Schaefer assembly to create a tightly packed monolayer of carbon nanodots, which seeds the growth of high dielectric constant oxides using atomic layer deposition. This method ensures the chemical purity necessary for semiconductor manufacturing, overcoming the perception of coal as a 'dirty' material.

Supported by Illinois Grainger Engineering's Center for Advanced Semiconductor Chips with Accelerated Performance, the project also involves collaboration with semiconductor industry partners such as IBM, Intel, and the Taiwan Semiconductor Manufacturing Company. The study's contributors include researchers from both the University of Illinois Urbana-Champaign and NETL.

The findings present a practical pathway for integrating high-quality dielectric layers with 2D semiconductors, potentially advancing future electronic technologies. The study, "Integration of high-κ oxide on 2D semiconductors with carbon-dot monolayer assembly as van der Waals interfacial layer," is available online.