Study of ferroelectric characteristics of diisopropylammonium bromide films
TL;DR: In this article, a thick film of diisopropylammonium bromide organic molecular ferroelectric is fabricated on the ITO/glass substrate and a butterfly loop in amplitude and hysteretic character of the phase is revealed, which are the expected characteristics features of ferroelectrics.
Abstract: Organic molecular ferroelectrics are highly desirable due to their numerous advantages. In the present work, a thick film of diisopropylammonium bromide organic molecular ferroelectric is fabricated on the ITO/glass substrate. The grown film shows preferential orientation along the c-axis with a ferroelectric transition at 419 K. The piezoresponse force microscopic measurements are done in a dual ac resonance tracking mode for its switching characteristics. The amplitude and phase images of the oppositely written domain patterns exhibit a clear contrast with 180° phase difference. The dynamical spectroscopic studies reveal a butterfly loop in amplitude and hysteretic character of the phase which are the expected characteristics features of ferroelectrics. In addition, the macroscopic polarization versus electric field hysteresis gives an additional proof for ferroelectric character of the film with the maximum polarization of 3.5 μC/cm2. Overall, we have successfully fabricated diisopropylammonium bromide...
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TL;DR: The reconstructive phase transition from the initial orthorhombic P212121 structure of DIPAB to the monoclinic ferroelectric P21 structure leads to an abrupt alteration in the 13C spectrum, which evidence its first order.
Abstract: The diisopropylammonium chloride (C6H16ClN, DIPAC) and diisopropylammonium bromide (C6H16BrN, DIPAB) molecular crystals are recently discovered ferroelectrics with sufficiently high spontaneous polarization and Curie temperature. We performed first studies of these crystals by 13C NMR. CP MAS spectra were collected within large temperature ranges covering the Curie points. The reconstructive phase transition from the initial orthorhombic P212121 structure of DIPAB to the monoclinic ferroelectric P21 structure leads to an abrupt alteration in the 13C spectrum. The 13C spectra for DIPAC and DIPAB in the ferroelectric P21 phase are quite similar with four lines at lower frequencies, which correspond to the CH3 groups, and two lines with close chemical shifts, which correspond to two CH groups. The transition into the paraphase leads to gradual reduction of the interline distances in the low-frequency quadruplet and in the doublet. The step-like changes in the interline frequency shifts at this transition indicating its first order. The analysis of the spectrum evolution in the paraphase shows that only a CH group lays in the reflection plane above the P21 → P21/m transition, while the second CH group only moves closer to the reflection plane upon further heating.
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TL;DR: In this article, the authors used a solution growth technique to synthesize organic molecular ferroelectrics and demonstrated its temperature-dependent dielectric relaxation in polycrystalline powder.
Abstract: An interest in organic molecular ferroelectrics is increasing due to their numerous advantages such as eco-friendly, lightweight, cost-effective, scalable and low processing temperatures In the present work, the organic molecular ferroelectric diisopropylammonium bromide (DIPAB) and 50% fluorine-doped diisopropylammonium bromide (DIPABF) are synthesized in the form of polycrystalline powder using solution growth technique The X-ray diffraction measurements done on as prepared DIPAB and DIPABF samples confirmed the room temperature orthorhombic phase (P212121) The temperature-dependent dielectric studies are carried out on DIPAB confirmed its phase transitions nearly at 416 K and 429 K But, DIPABF has shown a frequency-dependent transition near 429 K and the transition at 416 K is suppressed It is also observed from the temperature-dependent dielectric constant and dielectric loss curves that the ferroelectric to paraelectric transition at 429 K is broad in DIPABF and it is frequency dependent This confirms the presence of dielectric relaxation in DIPABF The origin of such dielectric relaxation is explained with respect to temperature-dependent dipole rotation and electronegativity Overall, DIPAB and DIPABF organic polycrystalline ferroelectric materials have been successfully synthesized and demonstrated its temperature-dependent dielectric relaxation in DIPABF
TL;DR: In this paper , a set of characteristic molecular ferroelectrics are simulated by molecular dynamics with polarized crystal charge (PCC), and their switching mechanisms are elucidated, with their ferroelectric hysteresis loops.
Abstract: Molecular ferroelectrics are a promising class of ferro-electrics, with environmental friendliness, flexibility and low cost. In this work, a set of characteristic molecular ferroelectrics are simulated by molecular dynamics (MD) with polarized crystal charge (PCC). From the simulated results, their ferroelectric switching mechanisms are elucidated, with their ferroelectric hysteresis loops. The PCC charge model, recently developed by our group, containing the quantum electric polarization effect, is suitable in nature for studying molecular ferroelectrics. The simulated systems include the typical molecular ionic ferroelectrics, di-isopropyl-ammonium halide (DIPAX, X=C (Cl), B (Br), and I), as well as a pair of newly validated organic molecular ferroelectrics, salicylideneaniline and (-)-camphanic acid. In total, there are five systems under investigation. Results demonstrate that the PCC MD method is efficient and reliable. It not only elucidates the ferroelectric switching mechanism of the studied molecular ferroelectrics, but also extends the application range of the PCC MD. In conclusion, PCC MD provides an efficient protocol for extensive computer simulations of molecular ferroelectrics, with reliable ferroelectric properties and associated mechanisms, and would promote further exploration of novel molecular ferroelectrics.
TL;DR: In this article, the linear and nonlinear dielectric properties of nanocomposites based on diisopropylammonium bromide (C6H16NBr, DIPAB) and porous Al2O3 oxide films with pore diameters of 330, 100, and 60 nm were studied.
Abstract: Results are presented from studying the linear and nonlinear dielectric properties of nanocomposites based on diisopropylammonium bromide (C6H16NBr, DIPAB) and porous Al2O3 oxide films with pore diameters of 330, 100, and 60 nm. A shift of the phase transition to low temperatures and a blurring of the transition are detected and grow for smaller pores.
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TL;DR: In this paper, the authors show that lanthanum-substituted bismuth titanate (SBT) thin films provide a promising alternative for FRAM applications, since they are fatigue-free on metal electrodes, they can be deposited at temperatures of ∼650°C and their values of Pr are larger than those of the SBT films.
Abstract: Non-volatile memory devices are so named because they retain information when power is interrupted; thus they are important computer components. In this context, there has been considerable recent interest1,2 in developing non-volatile memories that use ferroelectric thin films—‘ferroelectric random access memories’, or FRAMs—in which information is stored in the polarization state of the ferroelectric material. To realize a practical FRAM, the thin films should satisfy the following criteria: compatibility with existing dynamic random access memory technologies, large remnant polarization (Pr) and reliable polarization-cycling characteristics. Early work focused on lead zirconate titanate (PZT) but, when films of this material were grown on metal electrodes, they generally suffered from a reduction of Pr (‘fatigue’) with polarity switching. Strontium bismuth tantalate (SBT) and related oxides have been proposed to overcome the fatigue problem3, but such materials have other shortcomings, such as a high deposition temperature. Here we show that lanthanum-substituted bismuth titanate thin films provide a promising alternative for FRAM applications. The films are fatigue-free on metal electrodes, they can be deposited at temperatures of ∼650 °C and their values of Pr are larger than those of the SBT films.
2,008 citations
TL;DR: It is shown that a large piezoelectric response can be driven by polarization rotation induced by an external electric field, and the computations suggest how to design materials with better performance, and may stimulate further interest in the fundamental theory of dielectric systems in finite electric fields.
Abstract: Piezoelectric materials, which convert mechanical to electrical energy (and vice versa), are crucial in medical imaging, telecommunication and ultrasonic devices. A new generation of single-crystal materials, such as Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) and Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT), exhibit a piezoelectric effect that is ten times larger than conventional ceramics, and may revolutionize these applications. However, the mechanism underlying the ultrahigh performance of these new materials-and consequently the possibilities for further improvements-are not at present clear. Here we report a first-principles study of the ferroelectric perovskite, BaTiO3, which is similar to single-crystal PZN-PT but is a simpler system to analyse. We show that a large piezoelectric response can be driven by polarization rotation induced by an external electric field. Our computations suggest how to design materials with better performance, and may stimulate further interest in the fundamental theory of dielectric systems in finite electric fields.
1,789 citations
TL;DR: DIPAB is a molecular alternative to perovskite ferroelectrics and ferroelectric polymers in sensing, actuation, data storage, electro-optics, and molecular or flexible electronics and exhibits good piezoelectric response and well-defined ferro electric domains.
Abstract: Molecular ferroelectrics are highly desirable for their easy and environmentally friendly processing, light weight, and mechanical flexibility. We found that diisopropylammonium bromide (DIPAB), a molecular crystal processed from aqueous solution, is a ferroelectric with a spontaneous polarization of 23 microcoulombs per square centimeter [close to that of barium titanate (BTO)], high Curie temperature of 426 kelvin (above that of BTO), large dielectric constant, and low dielectric loss. DIPAB exhibits good piezoelectric response and well-defined ferroelectric domains. These attributes make it a molecular alternative to perovskite ferroelectrics and ferroelectric polymers in sensing, actuation, data storage, electro-optics, and molecular or flexible electronics.
641 citations
TL;DR: In this article, the authors summarize the recent progress in applications of piezoresponse force microscopy (PFM) for imaging, manipulation and spectroscopy of ferroelectric switching processes.
Abstract: Ferroelectrics and multiferroics have recently emerged as perspective materials for information technology and data storage applications. The combination of extremely narrow domain wall width and the capability to manipulate polarization by electric field opens the pathway toward ultrahigh (>10 TBit inch−2) storage densities and small (sub-10 nm) feature sizes. The coupling between polarization and chemical and transport properties enables applications in ferroelectric lithography and electroresistive devices. The progress in these applications, as well as fundamental studies of polarization dynamics and the role of defects and disorder on domain nucleation and wall motion, requires the capability to probe these effects on the nanometer scale. In this review, we summarize the recent progress in applications of piezoresponse force microscopy (PFM) for imaging, manipulation and spectroscopy of ferroelectric switching processes. We briefly introduce the principles and relevant instrumental aspects of PFM, with special emphasis on resolution and information limits. The local imaging studies of domain dynamics, including local switching and relaxation accessed through imaging experiments and spectroscopic studies of polarization switching, are discussed in detail. Finally, we review the recent progress on understanding and exploiting photochemical processes on ferroelectric surfaces, the role of surface adsorbates, and imaging and switching in liquids. Beyond classical applications, probing local bias-induced transition dynamics by PFM opens the pathway to studies of the influence of a single defect on electrochemical and solid state processes, thus providing model systems for batteries, fuel cells and supercapacitor applications.
405 citations
TL;DR: A simple organic salt, diisopropylammonium chloride, shows the highest ferroelectric phase transition temperature among molecule-based ferroelectrics with a large spontaneous polarization, making it a candidate for practical technological applications.
Abstract: A simple organic salt, diisopropylammonium chloride, shows the highest ferroelectric phase transition temperature among molecule-based ferroelectrics with a large spontaneous polarization, making it a candidate for practical technological applications.
292 citations