Comprehensive summary of the progress including crystal structures, fabrication methods, applications (especially for electronics) and functionalization of 2D-hBN from its discovery.

Electronic bipolar resistance switching (eBRS) in an Al/TiOx/Al structure, where the TiOx layer was reactively sputter-deposited, was examined in conjunction with a structural analysis using transmission electron microscopy. A thin (3-5 nm) insulating Al(Ti)Ox layer was formed at the bottom Al electrode interface, which provided the necessary asymmetric potential barrier for the eBRS to emerge, whereas the top Al electrode interface appeared to have provided the fluent carrier (electron) injection. The set and reset switching were related to the trapping and detrapping of the carriers at the trap centers, the characteristic energy of which was ∼0.86 eV, across the entire electrode area. The general features of this material system as the feasible RS memory were insufficient: endurance cycle, <∼8000, and retention time at 85 °C, 10(6) s. However, the detailed analysis of the switching behavior based on the space-charge limited current conduction mechanism, and its variation with the switching cycles, provided useful information on the general features of the eBRS, which could also be applicable to other binary (or even ternary) metal-oxide RS systems based on the electronic switching mechanism.

Two-dimensional (2D) materials play more and more important roles these days, due to their broad applications in many areas. Herein, we propose an optically-pumped terahertz (THz) modulator, based on Si-grown MoS2 nanosheets. The broadband modulation effect has been proved by THz time domain spectroscopy and numerical simulation. The modulation depth of this Si-grown MoS2 nanosheet can reach over 75% under the low pumping power of 0.24 W cm(-2), much deeper than that of bare silicon. By theoretical models and simulation, it is proved that the broadband modulation effect can be described as a free carrier absorption for THz waves in the Drude form. Importantly, by a catalyst mechanism in the Si-grown MoS2, it is concluded that the MoS2-Si heterostructure enables the MoS2 to catalyze more carriers generated on the Si surface. This novel 2D material has a high effective modulation on THz waves under a low pumping power density, which affords it a promising potential in THz applications.

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