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: In this article, the authors explore diisopropylammonium iodide (DPI) for its ferroelectric properties and phase transitions and identify two phase transitions which were identified by differential scanning calorimetry and dielectric and nonlinear optical measurements.
Abstract: In this manuscript, we explore diisopropylammonium iodide (DPI) for its ferroelectric properties and phase transitions. DPI showed two phase transitions which were identified by differential scanning calorimetry and dielectric and nonlinear optical measurements. From detailed structural studies it was found that the first transition at 369 K is from orthorhombic P212121 to monoclinic P21. The polar P21 phase is ferroelectric as evidenced by the pyroelectric data and has a very high value of spontaneous polarization (Ps = 33 μC cm−2), which is probably the highest among other reported bulk organic ferroelectrics. The second transition at 415 K is identified as polar monoclinic P21 space group to non-polar monoclinic P21/m. Thus, DPI has a high Curie temperature of 415 K. The large spontaneous polarization and high Curie temperature make DPI technologically important.
20 citations
TL;DR: In this article, a novel all-organic composite comprising polyvinylidene fluoride (PVDF) and diisopropylammonium bromide (DIPAB) crystal particles with significant dielectric properties has been synthesized via coating method.
Abstract: A novel all-organic composite comprising polyvinylidene fluoride (PVDF) and diisopropylammonium bromide (DIPAB) crystal particles (0–20 mass%) with significant dielectric properties has been synthesized via coating method. The DIPAB crystal nano-particles were prepared in the PVDF matrix by in situ growth method, which were found effective in transforming structure and enhancing the dielectric properties of the composites. X-ray diffraction pattern and Fourier transform infrared spectroscopy confirmed that the DIPAB in situ particles can improve the content of the electroactive β phase nucleation in PVDF matrix, whereas the PVDF matrix could induce the (00l) preferred orientation of the DIPAB nano-crystal. And the dielectric performance of the DIPAB/PVDF composite was significant influenced by the enhanced electroactive β phase and (00l) textured DIPAB. Relative dielectric constants as high as 94 was obtained at 40 Hz with 5 mass% DIPAB filler, which is 11-fold higher than that of the pure PVDF matrix (~8.5). The breakdown strength decreased as the mass fraction of DIPAB increased but still stayed more than 38.9 kV/mm.
13 citations
TL;DR: In this paper, the dielectric properties of Al2O3 oxide films with a pore size of 330 and 60 nm with particles of an organic ferroelectric diisopropylammonium bromide (C6H16BrN, DIPAB) introduced into the pores, aimed at determining the size dependences of phase transition parameters.
Abstract: We present the results of studies of the dielectric properties of nanocomposites based on Al2O3 oxide films with a pore size of 330 and 60 nm with particles of an organic ferroelectric diisopropylammonium bromide (C6H16BrN, DIPAB) introduced into the pores, aimed at determining the size dependences of phase transition parameters. A shift in the phase transition to low temperatures and diffusion of the transition are found, which become more significant for smaller pores. A broadening of the temperature hysteresis of the dielectric constant of nanocomposites during the phase transition was also observed. The decrease in the phase transition temperature in nanocomposites with DIPAB nanoparticles is consistent with theoretical models of the size effects on the structural phase transition.
10 citations
TL;DR: In this paper, the results of a computational first-principles study of the structural and electrical properties of three ferroelectric diisopropylammonium halides containing chlorine, bromine, and iodine were reported.
Abstract: We report the results of a computational first-principles study of the structural and electrical properties of three ferroelectric diisopropylammonium halides containing chlorine, bromine, and iodine. Calculations were carried out using density-functional theory with maximally-localized Wannier functions utilized for computing electrical polarization within the Modern Theory of Polarization formalism. For each of the crystals, the polar properties for all of the relevant polymorphs were evaluated and decomposed into contributions from individual positive diisopropylammonium and negative halogen-ion charge centers. The calculations show that each diisopropylammonium-halide unit in the crystal possesses a substantial dipole moment with magnitude of 10 to 15 Debye, but that these dipoles are arranged in a mutually opposing manner, leading to full cancellation in the paraelectric phase. In the ferroelectric phase, the dipoles cant along a common polar axis, inducing a small net dipole moment in the crystallographic unit cell, with spontaneous polarization ranging from 5 μC cm−2 for the iodide to 6 μC cm−2 for the bromide and 7 μC cm−2 for the chloride, suggesting no strong dependence of the polarization on the chemical identity of the halide counter ion. We propose that structural modifications of the diisopropylammonium-halide system aimed at stabilization of large unit-dipole cantings could produce molecular crystals with greatly increased spontaneous polarization.
8 citations
TL;DR: The study presents experimental results for investigating linear and nonlinear dielectric properties of nanocomposites based on bromide diisopropylammonium and aluminum oxide films and indicated that the phase transition was blurred and shifted toward lower temperatures.
Abstract: The study presents experimental results for investigating linear and nonlinear dielectric properties of nanocomposites based on bromide diisopropylammonium (C6H16NBr, DIPAB) and aluminum oxide films (Al2O3) with pore diameter of 330, 100 and 60 nm. It was indicated that the phase transition was blurred and shifted toward lower temperatures. This anomaly became more significant with decreasing pore size. The reduction of phase transition temperature in the nanocomposites, containing DIPAB, was consistent with theoretical models for the influence of size effects on the structural phase transition.
7 citations
References
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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