Fig. 3: Observation of incipient ferroelectricity in STO-gated MoS₂ FET.

a Dual sweep transfer characteristics of a representative STO-gated MoS₂ FET measured at T = 300 K. b Schematic showing polarization switching in STO film can lead to low/high threshold voltage in MoS₂ FETs. c Optical characterization of the freestanding STO nanomembrane at T = 300 K using second harmonic generation (SHG) at normal incidence as a function of the incident fundamental laser power. d Non-volatile retention of memory states for STO-gated MoS₂ FET at T = 300 K. e Dual sweep transfer characteristics and (f) memory retention for STO-gated MoS₂ FET measured at different temperatures, \(\it T\) = 225, 200, 150, and 100 K. Counterclockwise hysteresis is retained at all temperatures. However, memory retention improves significantly at lower temperatures. g Temperature-dependent SHG measurements show that the SHG intensity is maximum at 77 K and decreases with increasing temperature up to ~150 K, followed by a gradual increase until 300 K. The enhanced SHG intensity at lower temperatures agrees with memory retention results. h Schematic showing the possible origin of ferroelectricity in STO nanomembrane. i Atomic resolution HAADF STEM image of the STO film under the contact electrode. Corresponding maps of (j) the projected polar displacement vector on the (100) plane, and its (k) magnitude and (l) direction.