Engineering the Dipole Orientation and Symmetry Breaking with Mixed‐Dimensional Heterostructures

Abstract

Engineering of the dipole and the symmetry of materials plays an important role in fundamental research and technical applications. Here, a novel morphological manipulation strategy to engineer the dipole orientation and symmetry of 2D layered materials by integrating them with 1D nanowires (NWs) is reported. This 2D InSe -1D AlGaAs NW heterostructure example shows that the in-plane dipole moments in InSe can be engineered in the mixed-dimensional heterostructure to significantly enhance linear and nonlinear optical responses (e.g., photoluminescence, Raman, and second harmonic generation) with an enhancement factor of up to ≈12. Further, the 1D NW can break the threefold rotational symmetry of 2D InSe, leading to a strong optical anisotropy of up to ≈65%. These results of engineering dipole orientation and symmetry breaking with the mixed-dimensional heterostructures open a new path for photonic and optoelectronic applications.

Raman Investigation, Second Harmonic Generation, and Ultrasensitive Photoresponse of Low Symmetry Transition Metal Halide PdBr2

“…The power exponent between the SHG intensity and excitation power was fitted as 1.97, nearly a quadratic dependence (Figure d). These results confirm the second-order NLO process and are in line with the prediction of the electric-dipole theory. − As discussed above, PdBr 2 belongs to the centrosymmetric point group C 2 h . Due to the presence of central inversion symmetry between adjacent layers, it is expected that PdBr 2 would exhibit a negligible second-order susceptibility, resulting in the inhibition of SHG signals.…”

Second Harmonic Generation Control in 2D Layered Materials: Status and Outlook

“…[62,87,170,[234][235][236] Apart from the above-mentioned homostructures, recent works have also revealed their tunability and enhancement of SHG properties in vdW heterostructures. [82,88,221,224,[240][241][242][243][244] By stacking two different 2D crystals on top of each other or twisting them with designed angles without the constrain of lattice matching, various heterostructures have been studied during the latest decade, such as GaSe-InSe, [88] MoTe 2 -WSe 2 , [240] MoS 2 -graphene, [221] ReS 2 -graphene, [244] etc. Zhang et al observed emergent SHG in vdW stacking of centrosymmetric bilayer MoS 2 and monolayer graphene (Figure 3d).…”

Inducing Strong Light–Matter Coupling and Optical Anisotropy in Monolayer MoS2 with High Refractive Index Nanowire

“…Since the exfoliation of graphene, the unique electrical, optical, magnetic, and topological properties of two-dimensional (2D) van der Waals (vdW) materials have attracted significant interest and largely transformed the landscape of fundamental research and technological advances in physics, material sciences, and chemistry. − Remarkably, the dangling-bond-free nature of 2D materials enables them to be integrated with non-2D materials (e.g., 0-, 1-, or 3-dimensional materials) through noncovalent interactions to form emerging mixed-dimensional vdW heterostructures. − These heterostructures can combine the synergistic advantages of different dimensional materials, thus providing a more favorable platform than bare 2D materials for numerous advanced applications ranging from on-chip photodetectors to nanolasers. − …”