Computing

Graphene Nanoribbon Transistors Beyond Silicon

Silicon transistors have carried computing for over fifty years, but they are approaching fundamental physical limits just as artificial intelligence is pushing the demand for computation and energy efficiency higher than ever. We study atomically precise graphene nanoribbons (GNRs), quasi-one-dimensional strips of carbon about a nanometer wide, as a channel material for post-silicon transistor technology. GNRs are synthesized bottom-up from designed molecular precursors, so their width and edge structure are defined with atomic precision, and their band structure follows directly from that geometry through quantum confinement. A ribbon can be engineered to be semiconducting, with a band gap and carrier mobility suited to high-performance logic, simply by choosing the right precursor molecule. In effect, the electronic structure is programmed through chemistry.

We cover the entire pipeline in-house, from on-surface synthesis and wafer-scale transfer to nanofabrication and cryogenic-to-room-temperature electrical characterization. We have demonstrated high-performance short-channel GNR transistors, established how metal-nanoribbon interfaces govern charge injection, solved a long-term stability problem through atomic-layer-deposited dielectric encapsulation, and developed an etch-free transfer method that operates at 100-mm wafer scale. This device work connects to a broader effort on two-dimensional quantum materials and dielectrics, including the integration of GNRs onto single-crystalline 2D dielectrics and nanoscale metrology of gate stacks. Our current work aims at ballistic transport, a long-predicted regime in which electrons traverse the channel without scattering, and at the first integrated circuits built entirely from atomically precise carbon.

Communication

Topological Acoustic Wave Devices for Next-Generation Wireless

Every wireless device depends on components that filter and route radio-frequency signals. Many of these are surface acoustic wave (SAW) devices, which process information as coherent acoustic phonons propagating on a chip surface. As wireless technology moves toward 6G and beyond, these components must operate at higher frequencies with lower insertion loss, and conventional designs become increasingly sensitive to nanoscale fabrication disorder.

We design acoustic devices using concepts from topological physics, in which the band topology of an engineered phononic lattice protects the wave from backscattering off defects. On piezoelectric lithium niobate, we pattern interdigitated electrodes and phononic crystal structures that confine and guide acoustic waves along topologically protected paths, so device performance survives fabrication imperfections by design. We are also making these platforms reconfigurable, using phase-change materials to rewrite the acoustic band structure on demand, a capability suited to adaptive communication systems and to sensing hardware designed together with the AI-based signal processing that interprets its output. In this effort, we build and measure the devices that turn theoretical predictions into working hardware, in close collaboration with theory groups.

Sensing

Chip-Scale Quantum Sensors from Extreme Environments to Single Molecules

In a channel one nanometer wide, every atom sits at the surface and every perturbation leaves an electronic fingerprint. This extreme sensitivity, a challenge for logic devices, becomes the operating principle for a family of chip-scale quantum sensors built on the same platform. We pursue it along two lines.

Sensing in Extreme Environments

In a recent study, we exposed GNR transistors to gamma radiation and measured an electrical response orders of magnitude stronger than in conventional semiconductors, an effect rooted in quantum localization of charge carriers in a one-dimensional channel. We are developing this into solid-state detectors for gamma and neutron monitoring in settings where conventional electronics degrade, including space systems, nuclear facilities, and the diagnostic environments of future fusion energy reactors. Because the active element is a single layer of carbon atoms, these devices are also compact and low-power enough to be placed where larger detectors cannot go.

Quantum Sensors for Emerging Applications

The second line treats the quantum states of the nanostructure itself as the sensing element. Atomically precise ribbons host topological and confined electronic states whose energies shift in response to nearby charge and field, and those shifts can be read out electrically on the same chip. We are working toward detection at the single-molecule limit, with long-term applications in trace chemical detection, field and radiation metrology, and other settings where sensitivity, size, and power consumption all matter at once.

Exploratory Research Directions

Side Experiments and Early-Stage Ideas

Alongside our three main areas, we keep room for questions that fall outside them, whether they apply our expertise in semiconductor characterization and nanofabrication to an unfamiliar domain or start from an unexpected measurement or a question that sits between two fields. They begin as short side experiments on platforms we already run, carried out by one student with a few weeks of instrument time, which is usually enough to tell whether an idea is worth following further. One current example treats copper ore as a semiconductor problem, using Hall effect measurements on chalcopyrite from different geological sources to link its electronic structure to how readily it dissolves during extraction. Most of these stay small, and we expect them to. A few grow into new collaborations and become part of ANNLab’s main research, and a few have led to patent filings and new device concepts. Small experiments are where the surprises tend to come from, so we protect the time for them.