Two-Dimensional Ferroelectric Tunnel Junction: The Case of Monolayer In:SnSe/SnSe/Sb:SnSe Homostructure

Abstract

Ferroelectric tunnel junctions, in which ferroelectric polarization and quantum tunneling are closely coupled to induce the tunneling electroresistance (TER) effect, have attracted considerable interest due to their potential in non-volatile and low-power consumption memory devices.The ferroelectric size effect, however, has hindered ferroelectric tunnel junctions from exhibiting robust TER effect. Here, our study proposes doping engineering in a two-dimensional in-plane ferroelectric semiconductor as an effective strategy to design a two-dimensional ferroelectric tunnel junction composed of homostructural p-type semiconductor/ferroelectric/n-type semiconductor.Since the in-plane polarization persists in the monolayer ferroelectric barrier, the vertical thickness of two-dimensional ferroelectric tunnel junction can be as thin as monolayer. We show that the monolayer In:SnSe/SnSe/Sb:SnSe junction provides an embodiment of this strategy. Combining density functional theory calculations with non-equilibrium Green's function formalism, we investigate the electron transport properties of In:SnSe/SnSe/Sb:SnSe and reveal a giant TER effect of 1460%. The dynamical modulation of both barrier width and barrier height during the ferroelectric switching are responsible for this giant TER effect. These findings provide an important insight towards the understanding of the quantum behaviors of electrons in materials at the twodimensional limit, and enable new possibilities for next-generation non-volatile memory devices based on flexible two-dimensional lateral ferroelectric tunnel junctions. * Electronic address:

Recent Progress in Two‐Dimensional Ferroelectric Materials

“…This is the first demonstration of the 2D FTJ based on homostructures that promise future ultralow-power, high-speed, and nonvolatile nanoscale applications. [183] Experimentally, although only few 2D materials have been proven to be ferroelectrics, they perform well in electric transformation and could potentially be used as light sensors, energy Figure 15. a) Ferroelectric field-effect transistors based on MoS 2 and CuInP 2 S 6 2D van der Waals heterostructure.…”

Microscopic Manipulation of Ferroelectric Domains in SnSe Monolayers at Room Temperature

“…The discovery that highly oriented SnSe MLs on graphene are 2D ferroelectrics whose ferroelectric domains can be controllably manipulated at room temperature brings predicted effects and device concepts based on group-IV monochalcogenide MLs, such as linearly polarized-light-controlled valley selective excitations, 24 , 43 , 37 shift current photovoltaics, 32 intrinsic valley Hall effects, 37 in-plane ferroelectric tunneling junctions, 30 , 31 and nonlinear photocurrent switching devices, 33 one step closer to reality. Additionally, we envision that the coupling between existing 2D ferromagnets and 2D ferroelectrics via vertical or horizontal heterojunctions may lead to an eventual deployment of layered artificial multiferroics.…”

Design of a multifunctional polar metal via first-principles high-throughput structure screening

“…The role of lone-pair electrons. A local structural instability arising from lone-pair electrons has been reported in ferroelectric insulators and degenerately doped ferroelectrics 10,[29][30][31][32][33][34][35] . However, lone-pair electrons alone are not sufficient to stabilize a polar state in metals nor a ferroelectric state in insulators.…”

“…À1 ), implying that the structural transition temperature of BPTO is higher than that of LiOsO 3 40 . We note that the above second-order structural phase transition is a key property to distinguish instrinsic polar metals from degenerately doped ferroelectrics [32][33][34][35]41,42 , because realistic dopants (cation substitution or oxygen vacancies) make the crystal symmetry of doped ferroelectrics ill-defined and correspondingly there is no well-defined continuous structural phase transition at finite temperatures.…”