Bilayer

Molybdenum disulfide

Epitaxy

Voltage

Engineering

Chemical physics

Materials science

Layer (electronics)

Biochemistry

Sapphire

Laser

Transistor

Physics

Nanotechnology

Organic chemistry

Membrane

Electron mobility

Optics

Composite material

Field-effect transistor

Monolayer

Chemistry

Nucleation

Optoelectronics

Electrical engineering

Nature

Two-dimensional transition-metal dichalcogenides (TMDs) are of interest for beyond-silicon electronics1,2. It has been suggested that bilayer TMDs, which combine good electrostatic control, smaller bandgap and higher mobility than monolayers, could potentially provide improvements in the energy-delay product of transistors3–5. However, despite advances in the growth of monolayer TMDs6–14, the controlled epitaxial growth of multilayers remains a challenge15. Here we report the uniform nucleation (&gt;99%) of bilayer molybdenum disulfide (MoS2) on c-plane sapphire. In particular, we engineer the atomic terrace height on c-plane sapphire to enable an edge-nucleation mechanism and the coalescence of MoS2 domains into continuous, centimetre-scale films. Fabricated field-effect transistor (FET) devices based on bilayer MoS2 channels show substantial improvements in mobility (up to 122.6 cm2 V−1 s−1) and variation compared with FETs based on monolayer films. Furthermore, short-channel FETs exhibit an on-state current of 1.27 mA μm−1, which exceeds the 2028 roadmap target for high-performance FETs16. The epitaxial growth of bilayer molybdenum disulfide on sapphire enables the fabrication of field-effect transistor devices with improved performance in carrier mobility and on-state current over traditional monolayer films.

Uniform nucleation and epitaxy of bilayer molybdenum disulfide on sapphire