Interfacial ferroelectricity in marginally twisted 2D semiconductors

Abstract

Twisted heterostructures of two-dimensional crystals offer almost unlimited scope for the design of novel metamaterials. Here we demonstrate a room-temperature ferroelectric semiconductor that is assembled using mono- or few- layer MoS2. These van der Waals heterostructures feature broken inversion symmetry, which, together with the asymmetry of atomic arrangement at the interface of two 2D crystals, enables ferroelectric domains with alternating out-of-plane polarisation arranged into a twist-controlled network. The latter can be moved by applying out-of-plane electrical fields, as visualized in situ using channelling contrast electron microscopy. The interfacial charge transfer for the observed ferroelectric domains is quantified using Kelvin probe force microscopy and agrees well with theoretical calculations. The movement of domain walls and their bending rigidity also agrees well with our modelling results. Furthermore, we demonstrate proof-of-principle field-effect transistors, where the channel resistance exhibits a pronounced hysteresis governed by pinning of ferroelectric domain walls. Our results show a potential venue towards room temperature electronic and optoelectronic semiconductor devices with built-in ferroelectric memory functions.

Moiré band structures of twisted phosphorene bilayers

“…α = 0 suggests the absence of an out-of-plane ferroelectric effect, such as that observed in transition-metal dichalcogenide homo-and heterobilayers [57], in agreement with recent ab initio results [58].…”

Self-organised quantum dots in marginally twisted MoSe$_2$/WSe$_2$ and MoS$_2$/WS$_2$ bilayers

“…For APbilayers we expect a single line of circularly polarised iX emission. For P-bilayers iX energies and polarisations are different for Mo t X b and X t W b domains, with the energy splitting determined by the interlayer charge transfer [30,40,41] and circular (in Mo t X b ) vs linear (in X t W b ) polarization, established in Ref. [42].…”

Inkjet printing of two-dimensional van der Waals materials: a new route towards emerging electronic device applications

“…65 Additionally, even the stacking angles of a heterostructure were found to possibly act as a key factor in modulating the band structure since they can introduce an additional periodic potential to the system by forming a moiré lattice. 66–68 Additional functionalities, e.g. , superconductivity of Gr 68 or ferroelectricity of twisted h-BN, 66 can also be delivered by introducing the vdW transfer technique.…”

“…65 Additionally, even the stacking angles of a heterostructure were found to possibly act as a key factor in modulating the band structure since they can introduce an additional periodic potential to the system by forming a moire ´lattice. [66][67][68] Additional functionalities, e.g., superconductivity of Gr 68 or ferroelectricity of twisted h-BN, 66 can also be delivered by introducing the vdW transfer technique. The absence of dangling bonds on the surface of 2D vdW materials and their weak vdW interactions between layers provide promising opportunities to fabricate heterostructures with atomically clean interfaces with different neighbouring 2D layers.…”

“…As a result, superconducting 1.11 twisted bilayer Gr has become the most well-known twisted homobilayer system, also called ''magic-angle'' Gr. 67 These 2D vdW heterostructures have been widely studied in a variety of research fields, not only limited to electronics but also including thermoelectrics, magnetism, spintronics, and topology. 9,12,50,[70][71][72][73][74][75][76][77] From the 2D vdW material perspective, much effort has been dedicated to synthesizing and discovering new vdW materials exhibiting various electrical properties, as shown in Fig.…”