Imprint Behavior Research Articles

Role of charge injection/de-trapping in imprint behavior of ferroelectric Hf0.5Zr0.5O2 thin film

Ferroelectric HfO2-based thin films have attracted increasing interest due to their potential applications in nonvolatile memory areas. However, their unique properties, such as imprint, lead to serious reliability issues. In this study, the origin of imprint behavior is investigated by using TiN/Hf0.5Zr0.5O2 (10 nm)/TiN MFM capacitors. By modulating the internal electric field during imprint, we discover that charge injection/de-trapping in metal–ferroelectric interfaces plays an essential role in imprint behavior rather than charge movement inside the FE layer. The asymmetric shift of the coercive field is also discussed, which is attributed to nonlinear interaction between polarization's bound charges and the electrode's screening charges. This suggests that controlling interface quality should effectively suppress imprint in HfO2-based thin films.

Wake-Up and Imprint Effects in Hafnium Oxide-Based Ferroelectric Capacitors during Cycling with Different Interval Times

This work experimentally investigated the wake-up behaviors of hafnium oxide-based ferroelectric capacitors by manipulating the interval time between each characterization cycle. Both Positive-Up–Negative-Down (PUND) and Negative-Down–Positive-Up (NDPU) waveforms were used as the stress and measurement waveforms in the experiments. It was found that the imprint occurs as the total interval time increases to a several-seconds level. However, this only affects the remnant polarization (PR) of ferroelectric capacitors when stressed by NDPU waveforms, since the voltage amplitude saturates under the PUND stress conditions and does not influence the PR. The wake-up behavior has been proved to be caused by the defects redistribution during electrical cycling. Notably, when using PUND waveforms, the change in the interval time can result in different increase rates of PR, indicating the possibility of recovery during the intervals. This recovery leads to a slower wake-up when cycling with a longer interval time. Moreover, it is observed that this PR recovery could reach saturation after several seconds of the interval time. This comprehensive investigation of wake-up and imprint behaviors can provide new insights to evaluate and enhance the reliability of ferroelectric memories.

A Study on Imprint Behavior of Ferroelectric Hafnium Oxide Caused by High‐Temperature Annealing

Hafnium oxide is found to be a favorable material for ferroelectric nonvolatile memory devices. Its compatibility with complementary metal–oxide–semiconductor processes, the relatively low crystallization temperature when zirconium‐doped, and the thickness scaling are among the advantageous properties of hafnium oxide. Different requirements must be fulfilled for different applications of hafnium oxide. Herein, high‐temperature annealing and operation conditions are analyzed in order to investigate nonvolatile memories for automotive applications. A strong imprint behavior (shift in coercive voltages) is observed after annealing hafnium–zirconium–oxide thin films at temperatures varied between 100 and 200 °C. The imprint behavior is a significant challenge in many applications. Therefore, to reduce/recover the undesirable imprint behavior caused by high‐temperature treatment, two different ways are successfully examined and delineated here: endurance cycling and applying high electric fields.

THz Thin Film Varactor Based on Integrated Ferroelectric HfZrO2.

In this paper, we present a broadband microwave characterization of ferroelectric hafnium zirconium oxide (Hf0.5Zr0.5O2) metal-ferroelectric-metal (MFM) thin film varactor from 1 kHz up to 0.11 THz. The varactor is integrated into the back-end-of-line (BEoL) of 180 nm CMOS technology as a shunting capacitor for the coplanar waveguide (CPW) transmission line. At low frequencies, the varactor shows a slight imprint behavior, with a maximum tunability of 15% after the wake-up. In the radio- and mmWave frequency range, the varactor's maximum tunability decreases slightly from 13% at 30 MHz to 10% at 110 GHz. Ferroelectric varactors were known for their frequency-independent, linear tunability as well as low loss. However, this potential was never fully realized due to limitations in integration. Here, we show that ferroelectric HfO2 thin films with good back-end-of-line compatibility support very large scale integration. This opens up a broad range of possible applications in the mmWave and THz frequency range such as 6G communications, imaging radar, or THz imaging.

Preisach modeling of imprint on hafnium zirconium oxide ferroelectric capacitors

Imprint, the preferential orientation of the polarization of a ferroelectric device subjected to elevated temperatures, is a primary reliability concern afflicting data retention in ferroelectric RAM. In this paper, we demonstrate Preisach-based hysteresis modeling, which can be used to predict imprint behavior in ferroelectric thin films. A method was developed for capturing imprint in the context of a Preisach model and a numerical approach for evaluating the Preisach distribution was expanded upon. Interpolation and curve fitting were used to make predictions of the Preisach distributions of imprinted ferroelectric hafnium zirconium oxide devices after short-duration bakes at 23–260 °C and long-term bakes at 85 and 125 °C. In the case of long-term bakes, imprint-induced coercive shifts were modeled as shifts in the derivative of the top and bottom hysteretic polarization curves. The shift in the curves is modeled by fitting experimental data to a commonly used empirically logarithmic relationship reported in the literature. Simulations give remanent polarizations and coercive fields within <5.0 μC/cm2 and 0.1 V, respectively, of the raw data average.

Alteration of Metabolic Conditions Impacts the Regulation of IGF-II/H19 Imprinting Status in Prostate Cancer.

Simple SummaryInsulin-like growth factor II (IGF-II) is a potent growth factor implicated in several cancer types. The IGF-II gene shares its locus with the long non-coding RNA, H19. IGF-II/H19 is an imprinted gene—a phenomenon where only the maternal copy is expressed. The silencing of the paternal copy is lost in many cancer types—including prostate. Our in vitro findings show it is possible to disrupt imprinting through the alteration of metabolic conditions, with changes occurring at the molecular level only. Comparing with prostate tissue samples we additionally found a positive correlation to exist between IGF-II and H19 mRNA expression, which was further confirmed by in silico data from the Cancer Genome Atlas.Prostate cancer is the second major cause of male cancer deaths. Obesity, type 2 diabetes, and cancer risk are linked. Insulin-like growth factor II (IGF-II) is involved in numerous cellular events, including proliferation and survival. The IGF-II gene shares its locus with the lncRNA, H19. IGF-II/H19 was the first gene to be identified as being “imprinted”—where the paternal copy is not transcribed—a silencing phenomenon lost in many cancer types. We disrupted imprinting behaviour in vitro by altering metabolic conditions and quantified it using RFLP, qPCR and pyrosequencing; changes to peptide were measured using RIA. Prostate tissue samples were analysed using ddPCR, pyrosequencing and IHC. We compared with in silico data, provided by TGCA on the cBIO Portal. We observed disruption of imprinting behaviour, in vitro, with a significant increase in IGF-II and a reciprocal decrease in H19 mRNA; the increased mRNA was not translated into peptides. In vivo, most specimens retained imprinting status apart from a small subset which showed reduced imprinting. A positive correlation was seen between IGF-II and H19 mRNA expression, which concurred with findings of larger Cancer Genome Atlas (TGCA) cohorts. This positive correlation did not affect IGF-II peptide. Our findings show that type 2 diabetes and/or obesity, can directly affect regulation growth factors involved in carcinogenesis, indirectly suggesting a modification of lifestyle habits may reduce cancer risk.

Development of a soft UV-NIL step&repeat and lift-off process chain for high speed metal nanomesh fabrication

In this work, we present a fabrication procedure of metal nanomesh arrays with the newly developed nanoimprint resist mr-NIL212FC used in a bi-layer resist system for a lift-off process. We comparatively analyzed and evaluated nanomeshes fabricated with a freshly prepared h-PDMS/PDMS stamp and a stamp used 501 times. Therefore, we first performed a step&repeat imprint test run in a self-built low cost step&repeat UV-NIL setup. We inspected the imprint behavior of the stamp, the UV-transmission through the stamp as well as stamp lifetime and stamp degradation with regard to the possible changes of its surface roughness.The nanomesh fabrication process is characterized by a good lift-off performance, leading to a low defect density of <1.26 defects 100 µm−2. Even after 501 imprints, only a negligible stamp degradation occurred without effecting the imprint performance. Likewise, the same holds true for the nanomeshes, which showed comparable low defect densities and feature sheet resistances of 3.54 ± 0.14 Ω/□ for the first and 3.48 ± 0.23 Ω/□ for the 501st nanomesh, respectively. AFM analyses further revealed that the maximum height of the roughness Rt changed over the course of the 501 imprints from 6.3 nm to 13.3 nm, representing <5% of the overall imprint height.In general, the mr-NIL212FC resist shows a good wettability and compatibility with standard h-PDMS/PDMS stamps, a fast curing behavior, a high replication fidelity, easy separation characteristics, and a very low diffusion of resist components into the stamp. The mr-NIL212FC resist allows exposure times as short as 2 s in the applied tool setup, enabling high throughput production. Moreover, all performed measurements indicate that a much higher number of imprints with one stamp seem possible.

A study of imprint and etching behavior on fused silica of a new tailored resist mr-NIL213FC for soft UV-NIL

Abstract A new type of a specifically tailored resist for Soft Nanoimprint Lithography (Soft UV-NIL) namely mr-NIL213FC has been developed. It aims for a significant improvement of its etch-resistance with regard to underlying oxide substrates such as glass. This work demonstrates the first study of its imprint performance and etching behavior against fused silica wafers. First of all, the resist shows full compatibility with automated Soft UV-NIL using PDMS-based soft stamps and at ambient (oxygen containing) conditions for both step-and-repeat and full-wafer approaches. Moreover, the selectivity of the resist to the underlying fused silica substrate, in a high power and high etch rate condition, has reached to over 0.6, which is a significant step-up among most products in this context. The improved resistance of the resist facilitates direct etching processes for high resolution and high structure fidelity.

A multi-scale model linking microstructure and macro electric behaviors of ferroelectric field effect transistor

A multi-scale model linking microstructure and macro electric properties of ferroelectric field effect transistor (FeFET) is established based on the phase field method and Maxwell's total current law. The simulation results confirm that the channel current of FeFET is modulated by local interface ferroelectric domains which are easily affected by the microstructure. Using the developed transistor model, we investigate the effects of location of dislocation sites on hysteresis behavior of ferroelectric film and electric behavior of FeFET. Interfacial dislocations have strong effects on hysteresis behavior than internal dislocations since the former can induce imprint behavior while the latter only reduce the coercive field. However, due to the c-domains at the interface, the effects of interfacial and internal dislocations on FeFET electrical properties are the exact opposite. The interfacial dislocations just increase the voltage required to toggle the channel while the internal dislocations can induce disappearance of the FeFET memory window.

Research status of common processing technology of traditional Chinese medicine "maintaining medicinal properties after carbonisatus" and supramolecular "imprinting template" characterization technology

Based on the characteristics of biological supramolecules and the law of " imprinting template",the research status and common problems in " maintaining medicinal properties after carbonisatus" in traditional Chinese medicine( TCM) were analyzed,and the further countermeasures were put forward. According to the historical evolution of " maintaining medicinal properties after carbonisatus" in TCM processing,the origin of its common problems was clarified by using the theory of biosupramolecular chemistry. TCM is a megacomplex biological supramolecular system,so TCM processing is just the processing of megacomplex biological supramolecular system,and its essence is a TCM pharmaceutical technology with chemical changes in host and guest of biological supramolecular system with or without adjuvant material under high temperature and humidity. In this study on pharmaceutical technology,host molecule was destructed in the process of carbonizing,but guest molecule was retained. The changing law of the host and guest molecule was controlled by the " imprinting template",which was reflected in the degree of change in the drug properties and efficacy of the decoction pieces. Supramolecular chemistry ran through the whole process,and the " imprinting template" of charcoal medicine was characterized by the supramolecular topological structure characteristics and imprinting behavior. After being combined with the quantitative mathematical model of heating degree in processing,it can realize the accurate processing of " maintaining medicinal properties after carbonisatus" from the source,quantitatively control the quality of carbonic herbs,and formulate stable and controllable quality standards.

Effects of dislocations with different locations, orientations and density on domain evolution of ferroelectric thin film: A phase field study

The effects of dislocations on polarization distribution and switching in ferroelectric thin films are discussed based on a modified multi-field coupling theoretical framework that combining the flexoelectric effect and the strain field caused by dislocations. First, the correctness of the model is verified through a study about the effects of different flexocoupling types on domain structures around the dislocations. Then, effects of dislocations with different locations, orientations and density are systematically studied. Dislocations in the film will induce the appearance of a-domain. And the size of the new a-domain depends on the orientations and locations of dislocations. Among [001¯], [101¯] and [100] oriented single dislocations, the size of the new a-domain near the [101¯] oriented dislocation is the largest. It is essential to avoid generating [100] and [101¯] oriented dislocations since the [101¯] oriented dislocations can cause imprint failure and [100] oriented dislocations bring intense pinning effects. As the density of dislocations increases, the pinning effect and imprint behavior becomes stronger. The hysteresis loop of the film with [100] oriented multi-dislocations shows no ferroelectricity once the density reaches a certain limit. These dislocations induced imprint behavior and pinning effect can be eliminated by a larger applied electric field when the dislocation density is low. But when the dislocation density gets higher, the situation is different.

Preparation of Monodisperse Enrofloxacin Molecularly Imprinted Polymer Microspheres and Their Recognition Characteristics.

This study presents a new strategy for the detection of enrofloxacin (ENR) in food samples by the use of monodisperse ENR molecularly imprinted polymers (MIPs). Using enrofloxacin as template molecule, methacrylic acid as functional monomer, and ethylene diglycidyl ether as cross-linker, surface molecularly imprinted polymers (MIPs) were prepared on the surface of polymeric glycidyl methacrylate-ethylene glycol dimethacrylate (PGMA-EDMA) microspheres. The surface morphology and imprinting behavior of PGMA-EDMA@MIPs were investigated and optimized. Synthesized PGMA-EDMA@MIPs showed good physical and chemical stability and specific recognition toward fluoroquinolones. The introduction of PGMA-EDMA microspheres greatly increased the adsorption area of PGMA-EDMA@MIPs and increased the adsorption capacity of target molecules. The core shell structure increased the adsorption rate, and adsorption equilibrium was achieved within 6 min, much higher than that of MIPs synthesized by traditional methods. Enrofloxacin in milk samples was detected by molecular imprinting solid phase extraction (MISPE) combined with high performance liquid chromatography (HPLC). Implementing this method resulted in a recovery rate of 94.6~109.6% with a relative standard deviation (RSD) of less than 3.2%. The limit of detection (LOD) of this method was identified as three times the signal-to-noise ratio (10 μg/L). In summary, this work proposed a sensitive, rapid, and convenient method for the determination of trace ENR in food samples.

A restricted access molecularly imprinted polymer coating on metal-organic frameworks for solid-phase extraction of ofloxacin and enrofloxacin from bovine serum.

A restricted access molecularly imprinted polymer (RAMIP) crosslinked with bovine serum albumin (BSA) was prepared on the surface of the mesoporous UiO-66-NH2 metal–organic framework (MOF). The surface morphology, imprinting behavior, and protein exclusion properties of UiO-66-NH2@RAMIP@BSA were investigated. The maximum adsorption capacity was 50.55 mg g−1 for ofloxacin, with a 99.4% protein exclusion rate. Adsorption equilibrium was reached in 9 min. Combined with RP-HPLC, a solid-phase extraction column filled with UiO-66-NH2@RAMIP@BSA was used to selectively enrich and analyze ofloxacin and enrofloxacin antibiotics from bovine serum with recoveries of 93.7–104.2% with relative standard deviations of 2.0–4.5% (n = 3). The linear range and the limit of detection were 0.1–100 μg mL−1 and 15.6 ng mL−1, respectively. These results suggest that UiO-66-NH2@RAMIP@BSA is an efficient pretreatment adsorbent for biological sample analysis.

Internal-field-dependent low-frequency piezoelectric energy harvesting characteristics of in situ processed Nb-doped Pb(Zr,Ti)O3 thin-film cantilevers

Piezoelectric thin-film-based cantilevers have been investigated for higher energy-harvesting performance with simplified processing steps. Here, a simple in situ film deposition process of heavily Nb-doped lead zirconate titanate (PZT) films, which does not require annealing and poling, has been demonstrated to verify the possibility of use of the resultant films as energy-harvesters specifically for low frequency vibrating sources. The in situ domain formation of the films during the deposition was demonstrated from the apparent shifts of the capacitance-electric field curves, indicating the presence of internal electric fields. The so-called imprint behavior was found to be directly related to the performance of piezoelectric energy harvesting. As an optimal example, 12 mol% Nb-doped cantilever harvesters that showed the largest imprint behavior exhibited the best values of ∼19.1 GPa figure-of-merit and ∼1436 μWcm−3g−2 power density, which are competitive compared to other reported values.

Characteristic expressions of the natriuretic peptide family in the telencephalon of juvenile chick

Elucidation of the genes regulating the critical (sensitive) period of imprinting behavior may shed light on the mechanism underlying neural plasticity in early childhood learning. We focused on the family of natriuretic peptides (NPs) as candidates involved in the regulation of the critical period. In avians, several structurally related molecules comprised the NP family, including renal NP (RNP), B-type NP (BNP) and C-type NP (CNP1, CNP3 and CNPP). To understand the functional roles of NPs in neural plastic changes, we aimed to characterize NPs and their receptors in chick brain. We found that CNP3 mRNA was expressed in several regions in the telencephalon, including the visual Wulst (VW, considered as mammalian visual cortex) and amygdala. CNP1 mRNA was expressed throughout the telencephalon. Using real-time PCR, the gene expression levels of NPs and their receptors (NPR1 and NPR2) were studied during and after the critical period of imprinting (post-hatching day [P]1 and P7). CNP3 mRNA was found to show higher expression in the VW of P1 chicks than in VW of P7 chicks. Moreover, the ability of these peptides to stimulate chicken NPR1 or NPR2 was tested in HEK293 cells expressing either of the receptors. The activation of NPR1 was stronger with CNP3 than with other subtypes of CNP. In the VW, CNP3-expressing cells were negative for NPR1, but they resided in the vicinity of NPR1-expressing cells. These results suggest that CNP3 and its receptor NPR1 in the VW may have functional roles in the early learning.

Imprint behavior and polarization relaxation of PLZT thin films

Thickness dependence of imprint and polarization dynamics of Pb1-xLax(Zr1-yTiy)1-x/4O3 (PLZT) thin films is reported in this work. Asymmetries in the histograms of the local piezoresponse reveal an imprint effect in the studied films whose origin could be associated to Schottky barriers near the film-substrate interface. Time-resolved spectroscopic measurements shows that the local polarization relaxation follows the exponential dependence . A maximum relaxation time τ ≈ 2.18 s was observed for the 350 nm thick film. A similar thickness dependence between grain size, correlation length (ξ) and relaxation time (τ) suggest an intrinsic relationship between them.

Effect of thermal annealing on crystal structures and electrical properties in BaTiO3 ceramics

Mechanical damage and stress caused by polishing and cutting of ferroelectric materials could deteriorate their dielectric, ferroelectric, and piezoelectric properties. BaTiO3 piezoelectric ceramics were polished and cut, and thermally annealed at 600, 800, 1000, and 1200 °C for recovery. The electrical measurements revealed a reduction in the coercive field, elimination of imprint behavior, and an increase in saturation polarization in the thermally annealed ceramics. Furthermore, the electromechanical properties measured by the resonance method, prior to thermal annealing were d33 = 184 pC/N, k33 = 0.36, and s33E = 10.9 × 10−12 m2/N, while the values after 1200 °C-4 h thermal annealing were d33 = 287 pC/N, k33 = 0.54, and s33E = 12.1 × 10−12 m2/N. The in situ crystal structure evaluation and Williamson-Hall analysis suggested the decrement of microstrain from 6.38 × 10−4 to 5.20 × 10−4, indicating the retrieval of the residual stress imposed. The enhancement of piezoelectricity by 56% was ascribed to the effective annealing out of the surface mechanical damaged layers.

Coarse-Grained Simulation of Protein-Imprinted Hydrogels.

The MARTINI force-field is adapted for acrylic functional monomers and used to simulate protein-imprinted polymers, including complexation in solution, cross-linking reaction, washing, and rebinding of the protein. A globally controlled grand canonical Monte Carlo simulation combined with molecular dynamics is used to achieve proper hydration and swelling of the gel. Two gel formulations are compared, one with only polar functional monomers and one with additional small number of charged monomers. Imprinted hydrogels are evaluated for two proteins, lysozyme, and cytochrome c and chosen due to their similarity in size and isoelectric point, though it is known that their imprinting behavior is very different. Analysis of diffusion of the proteins within the gel shows that their interaction with functional monomers and their diffusion mechanism differ substantially and hence affect their specific and nonspecific interactions with the gel.

Enhanced piezoelectric and imprint characteristics of in situ sputtered Ta-doped Pb(Zr,Ti)O3 thin films on Ir/TiW/SiO2/Si substrates

High quality piezoelectric thin films have been pursued with simpler processing steps without subsequent annealing and poling procedure. Here, the in situ domain formation process of Ta-doped Pb(Zr0.52Ti0.48)O3 thin films was experimentally verified when the sputtering deposition proceeded with nonconventional buffer electrodes of Ir/TiW. The 2 mol% Ta-doped thin films with ∼2 μm thickness showed promising transverse piezoelectric coefficient e31 of −8.66 C/m2 and enhanced imprint behavior with a coercive field shift Ec,shift of ∼24 kV/cm. These improvements, which are ideally useful for mobile sensor applications, are attributed to the increase in crystallinity and the preferred domain orientation induced by the in situ polarization upon deposition. The incorporation of Ta into the perovskite lattices as a donor seems to help in inducing stronger internal field in the film by forming defects-driven dipoles. Therefore, this internal field might cause a clamping of domain walls, leading to the strong imprint behavior.

Origin of in Situ Domain Formation of Heavily Nb-Doped Pb(Zr,Ti)O3 Thin Films Sputtered on Ir/TiW/SiO2/Si Substrates for Mobile Sensor Applications.

High-quality piezoelectric thin films have recently been in demand for mobile sensor applications. An investigation was conducted to understand the improvements in the piezoelectric and imprint characteristics of heavily Nb-doped lead zirconate titanate thin films with an extensive range of Nb content (up to 14 mol %) beyond the typical solid solubility limit of Nb. The positive effects produced by the unusual doping of Nb were realized by utilizing an in situ sputtering process that did not require a subsequent annealing and poling procedure. An enhanced piezoelectric coefficient, -e31, of -12.87 C/m2 and a stronger shift in the coercive field, Ec,shift, of ∼20 kV/cm, which are ideally useful for mobile sensor applications, were obtained for the 12 mol % Nb-doped films deposited on nonconventional buffer electrodes of Ir/TiW. The reduced oxygen vacancy concentration and preferred domain orientation with a stronger piezoresponse induced by the Nb donor doping contributed to the enhancement of the piezoelectric properties. Potential defect dipoles aligned by a residual stress gradient along columnar structures seemed to induce an internal electric field in the Nb-doped films, leading to the preferred domain orientation, as well as the strong imprint behavior due to a clamping of domain walls.