6 research outputs found
Exciton-Sensitized Second-Harmonic Generation in 2D Heterostructures
The efficient optical second-harmonic generation (SHG) of two-dimensional
(2D) crystals, coupled with their atomic thickness that circumvents the
phase-match problem, has garnered considerable attention. While various 2D
heterostructures have shown promising applications in photodetectors, switching
electronics, and photovoltaics, the modulation of nonlinear optical properties
in such hetero-systems remains unexplored. In this study, we investigate
exciton sensitized SHG in heterobilayers of transition metal dichalcogenides
(TMDs), where photoexcitation of one donor layer enhances the SHG response of
the other as an acceptor. We utilize polarization-resolved interferometry to
detect the SHG intensity and phase of each individual layer, revealing the
energetic match between the excitonic resonances of donors and the SHG
enhancement of acceptors for four TMD combinations. Our results also uncover
the dynamic nature of interlayer coupling, as evidenced by the dependence of
sensitization on interlayer gap spacing and the average power of the
fundamental beam. This work provides insights into how interlayer coupling of
two different layers can modify nonlinear optical phenomena in 2D
heterostructures
Real-Time Determination of Twist Angle in Hetero-Bilayer TMDs with Phase-Resolved Second-Harmonic Generation
1
Exciton-Sensitized Second-Harmonic Generation in 2D Heterostructures
The
efficient optical second-harmonic generation (SHG) of two-dimensional
(2D) crystals, coupled with their atomic thickness, which circumvents
the phase-match problem, has garnered considerable attention. While
various 2D heterostructures have shown promising applications in photodetectors,
switching electronics, and photovoltaics, the modulation of nonlinear
optical properties in such heterosystems remains unexplored. In this
study, we investigate exciton-sensitized SHG in heterobilayers of
transition metal dichalcogenides (TMDs), where photoexcitation of
one donor layer enhances the SHG response of the other as an acceptor.
We utilize polarization-resolved interferometry to detect the SHG
intensity and phase of each individual layer, revealing the energetic
match between the excitonic resonances of donors and the SHG enhancement
of acceptors for four TMD combinations. Our results also uncover the
dynamic nature of interlayer coupling, as made evident by the dependence
of sensitization on interlayer gap spacing and the average power of
the fundamental beam. This work provides insights into how the interlayer
coupling of two different layers can modify nonlinear optical phenomena
in 2D heterostructures
Epitaxial single-crystal hexagonal boron nitride multilayers on Ni (111).
Large-area single-crystal monolayers of two-dimensional (2D) materials such as graphene1-3, hexagonal boron nitride (hBN)4-6 and transition metal dichalcogenides7,8 have been grown. hBN is considered to be the 'ideal' dielectric for 2D-materials-based field-effect transistors (FETs), offering the potential for extending Moore's law9,10. Although hBN thicker than a monolayer is more desirable as substrate for 2D semiconductors11,12, highly uniform and single-crystal multilayer hBN growth has yet to be demonstrated. Here we report the epitaxial growth of wafer-scale single-crystal trilayer hBN by a chemical vapour deposition (CVD) method. Uniformly aligned hBN islands are found to grow on single-crystal Ni (111) at early stage and finally to coalesce into a single-crystal film. Cross-sectional transmission electron microscopy (TEM) results show that a Ni23B6 interlayer is formed (during cooling) between the single-crystal hBN film and Ni substrate by boron dissolution in Ni. There are epitaxial relationships between hBN and Ni23B6 and between Ni23B6 and Ni. We also find that the hBN film acts as a protective layer that remains intact during catalytic evolution of hydrogen, suggesting continuous single-crystal hBN. This hBN transferred onto the SiO2 (300 nm)/Si wafer acts as a dielectric layer to reduce electron doping from the SiO2 substrate in MoS2 FETs. Our results demonstrate high-quality single-crystal multilayered hBN over large areas, which should open up new pathways for making it a ubiquitous substrate for 2D semiconductors