Unveiling the piezoelectric nature of polar α-phase P(VDF-TrFE) at quasi-two-dimensional limit

Abstract

Piezoelectric response of P(VDF-TrFE), which is modulated by the dipole density due to the polarization switching on applying an electric field, allows it act as the fundamental components for electromechanical systems. As proposed since the 1970s, its polar α-phase is supposed to yield an enhanced piezoelectric activity. However, its experimental verification has never been reported, hampered by a substantial challenge for the achievement of a smooth, neat α-phase film. Here, we prepare ultrathin crystalline α-phase P(VDF-TrFE) films on the AlOx/Al-coated SiO2/Si substrates via a solution-based approach at room temperature. Thus, we unveil the piezoelectric nature of the polar α-phase P(VDF-TrFE) at a quasi-two-dimensional limit. The obtained values of the relative morphological deformation, the local effective piezoelectric coefficient, and the electric field-induced strain reach up to 37 pm, −46.4 pm V−1, and 4.1%, respectively. Such a robust piezoelectric response is even higher than that of the β-phase. Besides, the evolution of piezoelectricity, which is related to the piezoelectric properties of two polarization states, is also studied. Our work can enable the exploration of the prospective applications of polar α-phase P(VDF-TrFE) films.

Temperature dependence of piezo- and ferroelectricity in ultrathin P(VDF–TrFE) films

“…3g and h). It is in good agreement with our previous study, manifesting that the ato b-phase transformation is complete at 60 C. 32 As stated above, a thermally-induced ato b-phase transformation behavior accompanying the change of the lamellar morphology is obtained in quasi-2D ultrathin crystalline P(VDF-TrFE) lms. During thermal crystallization, lamellae structure of crystallites changes from a spherulitic to a brillar, and the metastable a-chain reorganizes to form the most thermodynamically stable b-chain.…”

“…This electromechanical activity has been proven to root from the polar a-P(VDF-TrFE) in our previous work. 32 In addition, the ferroelectric features can be veried by the PFM phase images (Fig. 4e-h), which indicate that a reliable ferroelectricity with the homogeneous polarization can be sustained down to a few nanometers scale in P(VDF-TrFE).…”

“…[44][45][46] These results are consistent well with that of our previous report. 32 To further illustrate the temperature dependence of local polarization nature for both regions, we thus estimated the value of the polarization relaxation time as the period of which before the upward polarization relaxed switch to the downward polarization. Table 1 summarized the polarization relaxation time for both the grain and intergrain regions at four different temperatures.…”

“…17,31 Recently, our work has revealed that the ultrathin crystalline P(VDF-TrFE) lms with highly morphological uniformity can be prepared via a solution-based technique. 32 Consequently, it is of key importance to study the piezo-and ferroelectric properties of ultrathin crystalline P(VDF-TrFE) lms upon the thermal annealing treatment.…”

Solution‐Processed 2D Molecular Crystals: Fabrication Techniques, Transistor Applications, and Physics

“…More recently, ultrathin polar α‐phase P(VDF‐TrFE) films with a film thickness of ≈4.0 nm were fabricated at room temperature on AlO x /Al‐coated SiO 2 /Si substrates by utilizing an antisolvent‐assisted‐crystallization technique . We unveiled the ferroelectric and piezoelectric properties of the polar α‐P(VDF‐TrFE) at a quasi‐2D limit.…”