Fig. 4: 3D force field simulation results.
From: Domain wall enabled steep slope switching in MoS2 transistors towards hysteresis-free operation
a Schematic double-well Gibbs free energy profile of a ferroelectric material showing the negative capacitance regime (circled). b 2D charge density Q vs. \(\psi _{{{\mathrm{s}}}}\) curve for MoS2. For a ferroelectric gate, the continuity of electric displacement yields Q ≈ P. The red arrow indicates the change of \(\psi _s\) during a polarization flipping (from \(Q = - 0.5\;{{{\mathrm{C}}}}\;{{{\mathrm{m}}}}^{ - 2},\;\psi _s = - 0.53\;{{{\mathrm{V}}}}\) to \(Q = + 0.5\;{{{\mathrm{C}}}}\;{{{\mathrm{m}}}}^{ - 2},\psi _s = 1.01\;{{{\mathrm{V}}}}\)). The blue arrow indicates the change of \(\psi _{{{\mathrm{s}}}}\) during a polarization increase (from \(Q = 0\;{{{\mathrm{C}}}}\;{{{\mathrm{m}}}}^{ - 2},\psi _{{{\mathrm{s}}}} = 0\;{{{\mathrm{V}}}}\) to \(Q = + 0.0043\;{{{\mathrm{C}}}}\;{{{\mathrm{m}}}}^{ - 2},\psi _{{{\mathrm{s}}}} = 0.76\;{{{\mathrm{V}}}}\)). c Simulated multi-domain structure in PZT with two inequivalent DWs. The left DW hosts a polar vortex, and the right one hosts an anti-vortex. d Simulated change of polarization upon the Id jump around Vg ≈ −0.25 V. e Simulated Id vs. Vg curves without (red) and with (blue) an extrinsic current contribution I0 taken into account, and the corresponding SS vs. Id (inset). The dashed line depicts the thermal limit for SS at 300 K.
