Synergetic Behavior in 2D Layered Material/Complex Oxide Heterostructures

Abstract

Most heterostructures are realized using materials within the same structural families, such as compound semiconductors, perovskite oxides, and more recently van der Waals heterostructures. [1][2][3][4] These conventional heterostructures have their advantages in the epitaxial matching of lattices with minimized structural defects. [5,6] They are also easy to apply and control the homogeneous epitaxial strain. Nevertheless, heterostructures with structurally distinct layers can also be conceived. If the interface between the dissimilar layers can be well defined, the heterostructure is equally feasible as the conventional heterostructures composed of the same structural families. This vastly expands the possibilities and potential of the heterostructures vastly as the combination of the materials is now multidimensional. Since the discovery of 2D layered materials (2DLM), including graphene, numerous studies have focused on their behavior on different substrates. Ideally, freestanding 2DLM is theoretically plausible, but they are rather difficult to achieve experimentally. In particular, homogeneous control of strain is rather challenging for freestanding 2D layers. Therefore, the choice of the substrate materials for the 2DLMs is of prime importance in discovering, studying, and utilizing novel properties. While Si-based semiconductor materials or simple metals such as Cu or Au have predominantly been utilized as the substrates for 2DLMs, [7,8] design of more exciting properties is achieved by adopting functional materials. When a 2DLM is fabricated on top of a substrate material, a heterostructure composed of two distinct materials is naturally achieved.Complex transition metal oxides (TMOs), or so-called functional oxides, foster a variety of exotic electrical and magnetic behaviors, including superconductivity, colossal magnetoresistance, 2D electron liquid, and multiferroicity. [9][10][11][12][13] The strongly correlated electronic nature originates from the strong polarizability of O ions in the interatomic scale, resulting in the versatile properties depending on the kind of transition metal element. With the recent advancement of atomic-scale epitaxy, an atomistic layer design of the physical properties of the TMOs is plausible, extending their potential with regard to "oxide electronics."In terms of the heterostructures, oxides have long served as the "gate dielectric layer" within conventional semiconductor technology. Considerable effort is directed toward the The marriage between a 2D layered material (2DLM) and a complex transition metal oxide (TMO) results in a variety of physical and chemical phenomena that cannot be achieved in either material alone. Interesting recent discoveries in systems such as graphene/SrTiO 3 , graphene/LaAlO 3 /SrTiO 3 , graphene/ferroelectric oxide, MoS 2 /SrTiO 3 , and FeSe/SrTiO 3 heterostructures include voltage scaling in field-effect transistors, charge state coupling across an interface, quantum conductance probing of the electrochemical activity, novel memory funct...

Emerging Opportunities for 2D Semiconductor/Ferroelectric Transistor‐Structure Devices

“…), ambient environment, etc. [18,21,96,117] While for P(VDF-TrFE) based structures, the solution spin-coating approach followed by a low-temperature annealing process could contribute to clean interface and improved device stability due to the fully surround dielectric layer preventing any adsorbates on 2D layer surface. [118] An early work by McGuire et al achieved an encouraging SS value as low as 11.7 mV dec −1 in a P(VDF-TrFE)/internal metal/Al 2 O 3 /MoS 2 NC-FET.…”

“…[76] Unfortunately, their high crystallization temperature (>500 °C) and oxygen atmosphere required for film growth along with strict limits to lattice-matched substrates lead to poor compatibility with CMOS process. [18,[126][127][128][129] Recently emerged fluorite-structure binary oxides (fluorites), i.e., doped-HfO 2 have shown robust ferroelectricity at reduced thickness (<10 nm) and conformal low-temperature growth on silicon. This offers a plausible solution to bridge the gap between thickness scaling ferroelectric oxides and CMOS technology.…”

“…In parallel with efforts on adopting 2D semiconductors for performance enhancement of existing semiconductor devices, active research in synergistic combination of these atomic sheets with other functional materials to provide new working principles has recently gained increasing interest. [17][18][19] The new functions in 2D semiconductor/functional material hybrids can be employed to enhance the overall system performance, [12] and/or provide means to actively modulate optical, electrical, mechanical and magnetic properties of 2D semiconductor sheets. [20,21] A unique heterostructure that is both technology relevant and of great academic interest is the combination of 2D semiconductors with ferroelectrics.…”

Room‐Temperature Colossal Magnetoresistance in Terraced Single‐Layer Graphene

“…Hybrid 2D material/complex oxide interface, combining the layered 2D materials and complex oxides, provides various opportunities to study the intriguing physics and develop multifunctional devices, due to the rich properties of both 2D materials and complex oxides, such as 2D electron gas, ferromagnetism, ferroelectricity, and superconductivity. [ 1,2 ] The interface coupling between 2D materials and complex oxides will alter the lattice structure and induce the entanglement of the charge, spin and orbital degrees of freedom in 2D materials. This gives rise to a variety of unexpected phenomena, for example, the high dielectric constant SrTiO 3 (STO) can efficiently screen the long‐range Coulomb potential and restore the dominant role of the spin polarization, consequently, resulting in a ferromagnetic phase at the edge states.…”

Optically Controllable 2D Material/Complex Oxide Heterointerface

“…Complex transition metal oxides (TMO), exhibiting exotic electrical and magnetic properties either in the crystalline or amorphous phase, have been considered as a promising candidate for the nonconventional heterostructure with 2D materials. [10] Strontium titanate (SrTiO 3 , STO), one of the typical TMO materials, has been integrated with 2D materials as a gate dielectric in the field-effect-transistor (FET) geometry, giving rise to a range of extraordinary phenomena. [11,12] The correlation between graphene and STO has been extensively investigated, revealing virtually noninteracting Dirac electrons in graphene by screening the long-range electron-electron interactions and the potential fluctuations.…”