Controllable Polarization and Doping in Ferroelectric In₂Se₃ Monolayers and Heterobilayers via Intrinsic Defect Engineering

Abstract

ferroelectric In 2 Se 3 with rarely discovered out-of-plane polarization has great potentials in advanced electronic and electromechanical applications. Considering that point defects are ineluctable in practical applications and may greatly influence the electronic properties, we systematically investigate the stability, induced conductive type, and electric polarization of defects in 2D In 2 Se 3 (D-In 2 Se 3 ) monolayers and In 2 Se 3 -graphene heterobilayers through first principles calculations. Among the 40 kinds of considered vacancies, the decentralized vacancy possesses relatively high stability. In addition, the difficulty in migration of these vacancies leads to the localized electronic effect. The n-and p-doped conditions are, respectively, achieved by single In and surface Se vacancies in the D-In 2 Se 3 monolayers. Their out-of-plane polarity can also be regulated by the types and concentrations of vacancies due to the induced charge redistribution. More interestingly, different from the perfect In 2 Se 3 −graphene heterobilayer, where only n-type graphene can be achieved, the existence of surface Se vacancies in the D-In 2 Se 3 layer can toggle the conductive type of the graphene layer between p-and n-doped conditions by reversing its electric polarization, suggesting the applications in the electric-controlled p−n junction. This work establishes the theoretical foundation for the influence of intrinsic vacancies on electronic and ferroelectric properties in the D-In 2 Se 3 monolayer and heterobilayer, providing the application guides on 2D ferroelectrics by defect engineering.

Modulated Ferromagnetism and Electric Polarization Induced by Surface Vacancy in MX2 Monolayers

“…By calculating the position of both positive and negative charge centers, we were able to calculate the dipole moment of MX 2 monolayers. Former research ,, confirmed the validity of such an approach, and our calculation result of In 2 Se 3 is 0.0952 eÅ, which is considerably close to experimental data, further validating the results. The results of the calculated dipole moment showed great consistence with simulation results (Section II in SI for details).…”

“…Such a strategy was applied in CrX 3 (X = F, Cl, Br, I) and successfully induced switchable polarization, demonstrating its feasibility of detecting possible multiferroic candidates . However, more subtle modulation effects on ferromagnetism and the feasibility on other magnetic monolayers remain unexplored . Before all explorations, the stability of ferromagnetic order in multiferroic monolayers fabricated with such a mechanism is supposed to be examined first.…”

Thermally Tunable Analog Memristive Behaviors in Sulfurized In2Se3 Nanoflakes for Bio-Plausible Synaptic Devices

“…Therefore, to unveil the underlying mechanisms of analog and thermal tunable memristive behaviors, we performed first-principal calculations of formation energy and migration barrier of vacancies for pristine and sulfurized In 2 Se 3 . For easy visualization, here, we only investigate single selenium and sulfur vacancy formation, although more types of defects may be induced in reality . The selenium and sulfur atoms indicated by a circle in Figure a,b are deleted to raise a single vacancy.…”

“…For easy visualization, here, we only investigate single selenium and sulfur vacancy formation, although more types of defects may be induced in reality. 47 The selenium and sulfur atoms indicated by a circle in Figure 4a and chemical potential of selenium/sulfur element, respectively. We use the calculated energies of Se6 and S6 rings to estimate the chemical potential of selenium and sulfur, respectively.…”

Thermoelectric Properties of Si-Doped In2Se3 Polycrystalline Alloys

“…At this stage, the clear reason for this abnormal behavior is unknown, but it can be speculated that the various intrinsic defects, including vacancies, interstitials, and antisite defects, in In 2 Se 3 , seem to play complex roles as doping increases. Various intrinsic defects exist for this complex structure of α(2H)-In 2 Se 3 [24]. The complex phase change in In2Se3 may imply larger possibility of the intrinsic defects [19][20][21][22][23].…”