Silicon-based transistors are approaching their physical limits and thus new high-mobility semiconductors are sought to replace silicon in the microelectronics industry. Both bulk materials (such as silicon-germanium and III–V semiconductors) and low-dimensional nanomaterials (such as one-dimensional carbon nanotubes and two-dimensional transition metal dichalcogenides) have been explored, but, unlike silicon, which uses silicon dioxide (SiO2) as its gate dielectric, these materials suffer from the absence of a high-quality native oxide as a dielectric counterpart. This can lead to compatibility problems in practical devices. Here, we show that an atomically thin gate dielectric of bismuth selenite (Bi2SeO5) can be conformally formed via layer-by-layer oxidization of an underlying high-mobility two-dimensional semiconductor, Bi2O2Se. Using this native oxide dielectric, high-performance Bi2O2Se field-effect transistors can be created, as well as inverter circuits that exhibit a large voltage gain (as high as 150). The high dielectric constant (~21) of Bi2SeO5 allows its equivalent oxide thickness to be reduced to 0.9 nm while maintaining a gate leakage lower than thermal SiO2. The Bi2SeO5 can also be selectively etched away by a wet chemical method that leaves the mobility of the underlying Bi2O2Se semiconductor almost unchanged. Nature Electronics 2020, in press.
High-resolution electron microscopy requires robust and noise-free substrates to support the specimens. The peng research group presents a polymer- and transfer-free direct-etching method for scalable fabrication of robust graphene grids with ultraclean surfaces and demonstrate cryo-EM at record high resolution. (Liming Zheng, et al. Robust ultraclean atomically thin membranes for atomic-resolution electron microscopy. Nature Communications 2020, 11, 541.）
Ultrafast and highly-sensitive infrared photodetectors based on two-dimensional oxyselenide crystals
The Peng research group and collaborators have demonstrated high-performing flexible infrared photodetectors based on an air-stable 2D oxyselenide crystals at room temperature. 2D Bi2O2Se devices demonstrate a very high sensitivity of 65 A/W at 1200 nm and an ultrafast photoresponse ~1ps, implying an ultrahigh material-limited photodetection bandwidth up to 500 GHz. (Jianbo Yin, et al. Ultrafast and highly sensitive infrared photodetectors based on two-dimensional oxyselenide crystals. Nature Communications 2018, 9, 3311).
The Peng research group realized the controlled syntheses of high-mobility semiconducting 2D crystals--- layered bismuth oxychalcogenides (BOX, Bi2O2X: X = S, Se, Te), and are vigorously exploring their vistas in electronics and optoelectronics. (Jinxiong Wu, et al. High electron mobility and quantum oscillations in non-encapsulated ultrathin semiconducting Bi2O2Se. Nature Nanotechnology 2017, 12, 530)
The Peng research group has several innovative contributions to the ultrafast growth of large-area graphene single crystals in a controlled manner and achieved its growth rate with world record (Nature Nanotech. 2016; Adv. Mater. 2017; ACS Nano 2016).
The Peng research group has successfully grown wrinkle-free single-crystal graphene wafer on a 4-inch-sized twin-boundary-free single-crystal Cu(111)/sapphire substrate through interfacial strain engineering (ACS Nano 2017; Small 2018).
The Peng research group has achieved the mass production of graphene film via continuous roll-to-roll chemical vapor deposition and non-destructive lamination transfer process (Nano Lett. 2015; Adv. Mater. 2015; Adv. Mater. 2018).
The Peng research group has demonstrated that twisted bilayer graphene (tBLG) with twist-angle dependent van Hove singularities exhibits strong and peculiar light-matter interactions and selectively enhanced photocurrent generation (Nature Commun. 2016; ACS Nano 2016; Nano Lett. 2015).