High Carrier Mobility p- and n-Type WSe2 Monolayers for Advanced Electronics

The monolayers of transition metal dichalcogenides (TMDCs), such as WSe2, have gained significant interest in the field of post-silicon electronics and photonics due to their unique properties, including high carrier mobility, tunable bandgap, and atom-thick 2D structure. However, in order to fully utilize these materials for various device applications, such as complementary metal-oxide-semiconductor (CMOS) circuits and photovoltaics, it is crucial to be able to control the electrical polarity of the TMDCs.

In this study, the researchers successfully demonstrated the ability to chemically tune the electrical polarity of monolayer WSe2. They achieved this by using two different molecules, 4-nitrobenzenediazonium tetrafluoroborate and diethylenetriamine, to convert ambipolar WSe2 field-effect transistors (FETs) into p- and n-type semiconductors, respectively.

Furthermore, the chemically-doped WSe2 monolayers showed significantly increased effective carrier mobilities compared to the pristine WSe2. The effective carrier mobilities for holes and electrons were measured to be 82 and 25 cm2 Vls-1, respectively, which are much higher than those of the pristine WSe2.

The researchers used various characterization techniques, including photoluminescence, Raman spectroscopy, X-ray photoelectron spectroscopy, and density functional theory, to study and understand the doping effects. They also integrated the chemically-tuned WSe2 FETs into CMOS inverters, which exhibited extremely low power consumption of only 0.17 nW.

Additionally, the researchers were able to achieve a p-n junction within a single WSe2 grain by spatially controlling the chemical doping. This demonstrates the potential of the chemical doping method for controlling the transport properties of WSe2 and its applicability in the development of advanced TMDC-based electronics.

Overall, this study highlights the importance of chemically tuning the electrical polarity of TMDCs for advanced electronics and photonics applications, and provides a promising approach for achieving high carrier mobility in these materials.