Ferroelectric Switching at Symmetry‐Broken Interfaces by Local Control of Dislocations Networks

Abstract

Semiconducting ferroelectric materials with low energy polarization switching offer a platform for next‐generation electronics such as ferroelectric field‐effect transistors. Recently discovered interfacial ferroelectricity in bilayers of transition metal dichalcogenide films provides an opportunity to combine the potential of semiconducting ferroelectrics with the design flexibility of 2D material devices. Here, local control of ferroelectric domains in a marginally twisted WS2 bilayer is demonstrated with a scanning tunneling microscope at room temperature, and their observed reversible evolution is understood using a string‐like model of the domain wall network (DWN). Two characteristic regimes of DWN evolution are identified: (i) elastic bending of partial screw dislocations separating smaller domains with twin stackings due to mutual sliding of monolayers at domain boundaries and (ii) merging of primary domain walls into perfect screw dislocations, which become the seeds for the recovery of the initial domain structure upon reversing electric field. These results open the possibility to achieve full control over atomically thin semiconducting ferroelectric domains using local electric fields, which is a critical step towards their technological use.

Tunnel junctions based on interfacial two dimensional ferroelectrics

“…experience some changes due to expansion/contraction of Mo t S b / S t Mo b areas, complete switching cannot be achieved, since both types of polarisation are present in the tunnelling area at all times. This complies with the earlier observed transformations of domains/ domain wall networks in marginally twisted MoS 2 bilayers, where it was noted that the networks of domain walls separating areas with opposite FE polarisation have a higher rigidity in bilayers with shorter moiré periods, and nodes of such networks are essentially pinned 40,41 due to C 3 symmetry of the acting forces. Also, we note that the period of the network of partial dislocationsdomain walls is set by the local twist angle, imprinted in the device by the transfer, encapsulation, and contact deposition.…”

Ferroelectricity in twisted double bilayer graphene

“…Interfacial ferroelectricity is a generalized concept to construct novel 2D ferroelectrics [13,16,20,23,28,30,63]. Creating moiré superlattices can establish arrays of ferroelectric domains with switchable polarity.…”

Pseudomagnetic fields in fully relaxed twisted bilayer and trilayer graphene

“…The interaction between the two twisted layers in tBLG leads to lattice relaxation [16][17][18][19][20][21][22][23][24][25], which shrinks the highly unstable AA regions while enlarging the more energetically favorable AB regions effectively reducing the twist angle in the AB regions while increasing the local twist angle in the AAstacking zones. Lattice relaxation has been shown to play a pivotal role in the piezoelectric, ferroelectric and electronic properties of twisted TMDs [26][27][28][29][30][31][32][33][34][35][36][37][38][39] as well as in the charge density wave phases of twisted NbSe 2 [40,41]. In graphitic systems [42], atomic relaxation has been shown to determine the outof-plane polarization of twin boundaries [43] while in supermoiré systems such as the non-symmetric twisted trilayer graphene, lattice relaxation leads to a clear separation between the flat band and the highly dispersive Dirac cone [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58]<...…”