An anisotropic van der Waals dielectric for symmetry engineering in functionalized heterointerfaces

Abstract

Van der Waals dielectrics are fundamental materials for condensed matter physics and advanced electronic applications. Most dielectrics host isotropic structures in crystalline or amorphous forms, and only a few studies have considered the role of anisotropic crystal symmetry in dielectrics as a delicate way to tune electronic properties of channel materials. Here, we demonstrate a layered anisotropic dielectric, SiP2, with non-symmorphic twofold-rotational C2 symmetry as a gate medium which can break the original threefold-rotational C3 symmetry of MoS2 to achieve unexpected linearly-polarized photoluminescence and anisotropic second harmonic generation at SiP2/MoS2 interfaces. In contrast to the isotropic behavior of pristine MoS2, a large conductance anisotropy with an anisotropy index up to 1000 can be achieved and modulated in SiP2-gated MoS2 transistors. Theoretical calculations reveal that the anisotropic moiré potential at such interfaces is responsible for the giant anisotropic conductance and optical response. Our results provide a strategy for generating exotic functionalities at dielectric/semiconductor interfaces via symmetry engineering.

Unraveling High Thermal Conductivity with In-Plane Anisotropy Observed in Suspended SiP2

“…Normally, the thermal conductivity contributes from both electrons and lattices. 5 While, by considering the low electrical conductivity of SiP 2 , 23 the electronic contribution to total thermal conductivity can be ignored in suspended SiP 2 flakes, and thus the phonon component dominates the thermal conduction. Hence, one can deduce that the in-plane thermal conductivity decreases monotonically as the temperature increases due to stronger phonon scattering at higher temperatures.…”

“…Since the layered semiconductor SiP 2 exhibits typical in-plane anisotropy embedded quasi-one-dimensional (1D) P−P chains along the b-axis direction of the crystal lattice, 19 its low-symmetric lattice and the corresponding anisotropic properties have been demonstrated 19−21 in polarized optoelectronic applications 22 and as a dielectric for novel nanodevices. 23 With these promising characteristics, heat dissipation in SiP 2 -based nanodevices has attracted much attention. However, the experimental investigation of the anisotropic thermal transport properties of SiP 2 remains elusive.…”

“…By this means, heat generation and dissipation can thus be properly regulated to prevent devices from heat-induced performance degradation. , Therefore, exploring emerging anisotropic 2D materials with high thermal conductivity would be helpful for addressing heat-related challenges and enhancing device performance. Since the layered semiconductor SiP 2 exhibits typical in-plane anisotropy embedded quasi-one-dimensional (1D) P–P chains along the b -axis direction of the crystal lattice, its low-symmetric lattice and the corresponding anisotropic properties have been demonstrated − in polarized optoelectronic applications and as a dielectric for novel nanodevices . With these promising characteristics, heat dissipation in SiP 2 -based nanodevices has attracted much attention.…”

Controllable Synthesis of Transferable Ultrathin Bi2Ge(Si)O5 Dielectric Alloys with Composition-Tunable High-κ Properties

“…The observed composition-varied dielectric constants and breakdown field strength are consistent with the fact that Bi 2 SiO 5 has a larger band gap but lower dielectric constant than Bi 2 GeO 5 . To illustrate the superior high-κ characteristic of the BiGe­(Si)­O 5 dielectric alloy, we benchmark the value with the reported representative vdW dielectrics. ,,− ,− As shown in Figure f, the ε r of >40 in Bi 2 GeO 5 is almost the highest value among CVD-grown 2D single-crystalline insulators (exemplified by ε r = 3.3 for h -BN and ε r = 10.8 for LaOCl) and is apparently higher than the commercial atomic-layer-deposited (ALD) high-κ dielectrics, such as HfO 2 (ε r ≈ 16) and Al 2 O 3 (ε r ≈ 9).…”

Recent developments in the state-of-the-art optoelectronic synaptic devices based on 2D materials: a review

“…The trapping of a few electrons at the interface of sodium alginate and MoS 2 resulted from the low conductance of the MoS 2 channel. 66 The interface-induced charge trapping can be achieved by combining various TMDCs with Ta 2 O 5 –TiO 2 (TTO), 123 van der Waals dielectrics such as hBN, 124 SiP 2 , 125 SiO 2 , 126 polymers, 103,127,128 etc. , as reported in the literature.…”