Two-dimensional ferroelectrics

Different approaches to adjusting band offsets at intermolecular interfaces

“…By biasing the diode by ±15 V, hysteresis is seen in the current versus voltage traces at low bias, as seen in Figure 6. Application of bias voltages up to ±15 V is more than sufficient to polarize the ferroelectric P(VDF-TrFE) [11], and/or flip the dipole direction of P(VDF-TrFE) (or both P(VDF-TrFE) and CuPc) thin films of this thickness, so this is not entirely unexpected. The dipole interaction could affect the diode properties in several ways.…”

“…The thin films thickness was dictated by a need to ensure layers free of pin-holes while still as thin as possible to diminish contributions of final state photoemission effects. Throughout, the P(VDF-TrFE) thin films were made on Al, Au and graphite substrates using the Langmuir-Blodgett (LB) technique, as described elsewhere [11,12], and are seen to be highly crystalline on graphite substrates [32][33][34].…”

“…Organic ferroelectrics are among the best candidates for such studies as with such systems band bending is minimized and one can ensure compositional control of the interface. Organic ferroelectrics have been exploited as components in heterojunction devices, in particular using the better known [11] copolymers of the ferroelectric copolymer poly(vinylidene fluoride with trifluoroethylene) (P(VDF-TrFE)). Organic heterojunction diodes [12,13] and transistors [14,15] have been fabricated with the crystalline ferroelectric P(VDFTrFE).…”

Electromagnetically induced switching of ferroelectric thin films

“…Ferroelectrics can also be used to create memory devices and optically controlled switches [13,16,17,18]. Many recent results are collected in the review on two dimensional ferroelectrics and thin polymer ferroelectric films represents in [19].…”

“…Using the phenomenological LandauKhalatnikov model [20,21,22,23] describing a uniaxial ferroelectric and the Maxwell equation for an electromagnetic wave, we consider the reflections and refractions of a short electromagnetic spike (i.e., a pulse without a carrier wave) through a ferroelectric thin film. We assumed that the film width is less than the spatial size of the spike, but is greater then the critical length L c below which no ferroelectricity exists [17,23,19]. According to theoretical estimations and [23,13] L c = 0.5nm for BaT iO 3 , L c = 20nm for P bT iO 3 .…”