High-mobility 2D layered semiconducting transistors based on large-area and highly crystalline CVD-grown MoSe2 for flexible electronics

Layered semiconductor materials of molecular thickness, in particular transition metal dichacholgenides (TMDs), possess desirable characteristics including the existence of bandgap, low-power switching behavior, and high carrier mobility that afford them promising as active components of future high speed and low-power electronics. Reliable large-volume production of 2D layered semiconductors is an essential step for translating their intriguing properties into applications. Although atomically thin flakes of 2D layered TMD such as MoS
₂
can be peeled from bulk crystals by micromechanical exfoliation, this method is not integrated in large-volume and does not allow systematic control of thickness and size of 2D layered semiconductors. Hence, the growth of large-area MoSe
₂
is one of the critical challenges to realize its promising potential.potential. Many groups are currently developing various methods to synthesize TMDs materials. However, the growth of highly crystalline TMDC materials over large areas is still a major hurdle to achieve commercially viable integrated circuits. In this work the direct growth of large-area multilayer films is demonstrated by chemical vapour transport (CYT) on SiO
₂
insulator, with a well-defined crystal structure (2H phase) and large grains reaching several hundred micrometers. As-grown MoSe
₂
films are characterized by high-resolution scanning/transmission electron microscopy, X-ray diffraction, and high-resolution X-ray photoelectron spectroscopy, which reveal that each grain consists of a single crystal free of structural defects. Multilayer field-effect transistors grown on SiO
₂
insulator exhibit high mobility up to 121 cm
²
V
^-1
s
^-1
, high on/off current ratio (>10
⁴
), robust current saturation at large drain voltages, and excellent mechanical flexibility on polyimide substrates with a bending radius as small as 5 mm. All together, the results predict that high mobility materials will be indispensable for various future applications such as high-resolution displays, flexible large-area integrated circuits, and human-centric soft electronics.