Bi3.15Nd0.85Ti3O12 Films Research Articles

High-performance self-powered ultraviolet photodetector based on bismuth layered perovskite Bi3.15Nd0.85Ti3O12 ferroelectric thin films

The photovoltaic effect of ferroelectric materials has been widely concerned. With the development of wearable technology and the requirements of device miniaturization, self-powered devices have been studying by more and more researchers. The photovoltaic effect of ferroelectric materials provides a possibility for self-powered photodetectors. Here, we have investigated the photovoltaic effect and the self-powered ultraviolet photodetecting properties in Pt/Bi3.15Nd0.85Ti3O12 (BNT)/Pt heterostructure. The Bi3.15Nd0.85Ti3O12 (BNT) thin films were prepared by sol–gel method on Pt/Ti/SiO2/Si substrate. XRD pattern and P-E loops shows that BNT films are polycrystalline with typical ferroelectric hysteresis. The BNT films shows obvious photovoltaic characteristics, with an open-circuit voltage VOC of 0.67 ± 0.04 V and a short-circuit current density JSC of 2.27 ± 0.08 μA/cm2 at the wavelength of 365 nm of a power of 77.50 mW/cm2. The zero bias transient photocurrent response under light ON and OFF states confirms the photodetecting ability of the heterolayered structure. The responsivity and the detection rate of the self-powered ultraviolet photodetector were calculated to be 0.047 ± 0.003 mA/W and (1.47 ± 0.04) × 109 Jones, respectively. The reversal photocurrent response mechanism of the Pt/BNT/Pt heterostructure has been clarified based on the driving internal electric field for the separation and transport of the photo-excited electron-hole pairs. The JSC dependance on the polarization direction reveals the electrical manipulation nature of the BNT based self-powered photodetectors, providing a novel route for the design of photodetectors based on ferroelectric oxides.

Retracted] Application and Equipment of Preparation Technology of Ferroelectric Thin Film Materials in Sports Industry

With the rapid development of the integrated circuit industry, ferroelectric thin film materials and technologies have become increasingly important. Ferroelectric materials have been widely used in aerospace, information storage, artificial intelligence, microelectromechanical, wearable devices, and other fields. Traditional sports is an important carrier of traditional culture. It contains the sports cultural resources created and precipitated by the Chinese nation for thousands of years, and all sectors of society are also paying great attention to this. Under the background of the market economy system and the major premise of the vigorous development of the cultural industry and sports industry, industrialization is obviously the inevitable choice for traditional sports to break through the difficulties and seek development, and it will also promote the further inheritance and promotion of traditional sports. The complex combination causes its performance to decrease or even fail. Therefore, it cannot cause foresee losses and disasters. It has important application value and significance to master the performance changes and mechanisms of ferrous film materials under different adding environments. This paper takes ferroelectric Pb (Zr0.52Ti0.48)O3(PZT)Bi3.15Nd0.85Ti3O12(BNT) as the research object, proposes the preparation of sol coating for thin film materials, and studies the preparation parameters PZT of the sol electric ferroelectric method. Electrical method and BNT electrical film properties affect iron and physical experiments on the properties of iron. The influence of the best sol‐iron coating method on the electrical properties of PZT and BNT films is the ferroelectric properties of the 700°C layer of high‐temperature gas, 10‐layer PZT films, and 8‐layer BNT films. The elasticity and elastic moduli of PZT and BNT films are 66.8 MPa and 99.6 MPa and 159.3 GPa and 189GPa, respectively; the elastic coefficients of PZT and BNT films are15.4 × 1010 N/m2 and18.4 × 1010 N/m2, and their elastic coefficients|e31|decrease with accompanying increase in swallowing. And with the disease of reading and writing field strength, as the speed becomes faster and slower, the carriers have more time to move to the brain wall, so the intensity is also intuitive. It has strong practicability and feasibility to popularize the material and manufacture the equipment of the current sports equipment club.

Photovoltaic effect of ITO/Bi3.15Nd0.85Ti3O12/Pt heterojunction structure

ITO/BNT/Pt heterojunction structure has been prepared by sol-gel method combined with dc magnetron sputtering. The BNT (Bi3.15Nd0.85Ti3O12) films were polycrystalline with typical ferroelectric hysteresis. The ITO/BNT/Pt structure displayed photovoltaic properties with a Voc of about 0.28 V and a photocurrent of 2.4 nA. After being polarized by a + 4 V pulse, at the voltage of 0.1 V, the current was 3 × 10−8 A, while it was −1 × 10−9 A after being polarized by a −4 V pulse. This demonstrated the depolarization field of the BNT films played a significant role in the I–V properties of the ITO/BNT/Pt structure. Therefore, we speculated the depolarization field had influenced the photovoltaic properties.

Flexible ferroelectric capacitors based on Bi3.15Nd0.85Ti3O12/muscovite structure

Inorganic ferroelectrics which have low tensile strength and poor ductility are difficult to be bent. In this paper, in order to realize great toughness, the inorganic ferroelectric film was deposited on flexible muscovite (Mica) substrate. For efficiency and convenience, sol-gel method is adopted to fabricate the Bi3.15Nd0.85Ti3O12 (BNT) thin-film capacitor on flexible Mica substrate with SrRuO3 (SRO) electrode layer. The remnant polarization of the Pt/BNT/SRO/CFO/Mica capacitor achieves ∼38 μC cm−2, which is larger than most BNT films prepared on hard substrates. No obvious fatigue phenomenon is observed for the BNT capacitor with 1010 switching cycles. The most important is that the Pt/BNT/SRO/CFO/Mica capacitor still owns relatively stable electrical properties when it is bent to 5 mm radius, showing an excellent bending performance for this structure. The flexible, anti-fatigue ferroelectric capacitor prepared in this paper is expected to get a wide range of application in flexible logic and elements for information storage, data processing and communication.

Effects of deposition temperatures of Nd-doped Bi4Ti3O12 thin films prepared by pulsed laser deposition

Recently the deleterious environmental impact of the lead used in many ferroelectric and piezoelectric devices has stimulated research into lead-free alternatives with comparable properties. Bismuth titanate-based materials are considered to be candidates for use as lead-free piezoelectrics. In this study, we prepared the Bi3.15Nd0.85Ti3O12 (BNdT) thin films by using Pulsed Laser Deposition (PLD), which is a relatively easy method for the fabrication of thin films. The samples were grown on Pt/Ti/SiO2/Si substrates using a KrF laser (248 nm). To find an optimal fabrication condition of this sample, we varied the PLD deposition conditions, including the substrate temperature, oxygen gas pressure, repetition frequency, target-substrate distance and pulse energy density. We found that the deposition temperature is an important parameter which should be optimized to get high-quality BNdT films. The BNdT thin films were studied by X-ray diffraction (XRD), atomic force microscopy (AFM) surface images, measurements of frequency-dependent dielectric constant and dielectric loss, polarization–electric field (P–E) curves, and fatigue tests. With increasing the deposition temperature the (117) peak of XRD increased, and the intensity ratio of (117)/{(117) + (006) + (200)} peak increased and its value was 68.3% at 650 °C and 44.3% at 700 °C. We note that the phase formation was strongly dependent on the deposition temperature in our BNdT films.

Effect of chromium doping on the structure and band gap of Bi3.15Nd0.85Ti3O12 thin films

The Bi3.15Nd0.85Ti3O12 (BNdT) and Cr-doped BNdT films on quartz substrates were prepared by a sol-gel process and the effects of Cr doping on the structure and band gap of BNdT were examined. Cr-doping does not change the three-layered perovskite structure of BNdT but transforms the grain morphology from equiaxed grains to rectangular grains. The utilization of visible light is increased by Cr doping and the large band gap reduction (∼1.1 eV) was obtained, which is analyzed from the electronegativity and the distortion caused by substitution. The present work provides an available way to make ferroelectric (FE) BNdT getting more extensively applied in the new photovoltaic cells and other novel optoelectronic devices.

Ethanol sensing properties of Bi3.15Nd0.85Ti3O12 films at low operating temperatures

Bi3.15Nd0.85Ti3O12 (BNdT) films were deposited on Pt/Ti/SiO2/Si(100) substrates by a metal organic decomposition (MOD) method, and annealed by a rapid thermal annealing process in oxygen atmosphere and in air, respectively. The crystalline structures and morphologies of BNdT films were characterized by X-ray diffraction and field-emission scanning electron microscopy, and the gas sensing properties were measured by monitoring its resistance at different gas concentrations. The results indicate that the BNdT films annealed in air are of porous microstructure and rough surface, and the annealing atmosphere has great influence on gas sensing properties. At an operating temperature of 100 °C, the BNdT films annealed in air are of high response value to 1×10−6 gaseous ethanol, and the detecting limit is as low as 0.1×10−6. The corresponding response and recovery time is about 10 and 6 s, respectively. The results can offer useful guidelines for fabricating high performance ethanol sensors.

Mixed grains and orientation-dependent piezoelectricity of polycrystalline Nd-substituted Bi4Ti3O12 thin films

Polycrystalline Bi3.15Nd0.85Ti3O12 (BNT) thin films were prepared on Pt/Ta/glass substrates by a pulsed laser deposition method. X-ray diffraction measurements revealed that the BNT thin films were preferentially oriented along the (117) direction although they possessed a polycrystalline structure. Good ferroelectric properties of the BNT thin film were observed with a remnant polarization of 13 μC/cm2 (2Pr ~26μC/cm2). The fatigue resistance test exhibited that the ferroelectric polarization of the BNT thin film degraded significantly after around 109 switching cycles, which can be attributed to its crystal structure. We investigated the surface morphology and ferroelectric domain structure by atomic force microscopy (AFM) and piezoresponse force microscopy (PFM), respectively. Interestingly, mixed grains consisting of long and circular shapes were observed on the BNT film surface, which corresponded to a- and c-axes orientations of crystal growth, respectively. The PFM study revealed that the piezoelectric coefficient (d33) of the long grains was much larger than that of the circular grains.

Nonlinear optical absorption tuning in Bi3.15Nd0.85Ti3O12 ferroelectric thin films by thickness

The tunability of nonlinear optical (NLO) absorption in Bi3.15Nd0.85Ti3O12 (BNT) ferroelectric thin films was investigated through the open aperture Z-scan method with femtosecond laser pulses at the wavelength of 800 nm. NLO absorption responses of the BNT films were observed to be highly sensitive to the film thickness. As the film thickness increases from 106.8 to 139.7 nm, the NLO absorption changes from saturable absorption (SA) to reverse saturable absorption (RSA). When the film thickness further increases to 312.9 nm, the RSA effect is enhanced. A band-gap-related competition between the ground-state excitation and the two-photon absorption is responsible for the absorption switching behavior. Such a tunable NLO absorption can widen the photonic application of the BNT thin films.

Tuning the Physical Properties of BNT Ferroelectric Film by Miscut Si Substrate

The electrical and domain switching properties of Bi3.15Nd0.85Ti3O12 (BNT) thin films have been studied, which were prepared by pulse laser deposition (PLD) on exact and miscut (2°) Si substrates. The films have a bismuth-layered perovskite structure, and the leakage current of BNT film on miscut substrate is smaller than that on exact one. The domain structure, domain switching and hysteresis loops of BNT film on miscut substrate were studied, multidirectional domain structure, complete domain switching and strong piezoresponse are found in it. The phase-voltage hysteresis and butterfly loops were very saturated with a coercive voltage (Vc) about 3.75 V. The film also exhibited excellent piezoelectric property with a high piezoelectric coefficient d33~20 pm/V.

Size effect on the ultrathin ferroelectric film directly grown on silicon for electronic devices

We demonstrate that the size effects impact on the electrical properties of the ultrathin Bi3.15Nd0.85Ti3O12 (BNT) film grown directly on silicon. The remnant polarization is observed for the 2 nm thick BNT film by direct quantitative P–V measurements and the corresponding obvious contrast images are confirmed by scanning probe microscopy. We address the physical mechanism of the ferroelectric behavior of the ultrathin films deposited on Si substrates which is different from those grown on the metal and oxide substrates. Moreover, the results also reveal low leakage current, good fatigue and retention characteristics. This opens the way for the ultrathin ferroelectric films directly grown on Si substrates for Si-based integrated microelectronics while they still retain excellent electrical properties. In addition, we also discuss the possible microcosmic mechanism of the performance of the ultrathin film integrated with current Si technology in electronic miniaturization devices.

Piezoresponse force microscopy observation of domain switching in Bi3.15Nd0.85Ti3O12 thin film prepared by pulsed laser deposition

Bi3.15Nd0.85Ti3O12 (BNT) ferroelectric thin film was fabricated on Pt(111)/Ti/SiO2/Si substrate using pulsed laser deposition. Domain structure, domain switching and hysteresis loops of the BNT film were investigated via piezoresponse force microscopy (PFM). Clear domain structure, complete domain switching and strong piezoresponse are found in BNT film. The PFM images before and after poling illustrate that domain structure and domain switching are restricted by grain boundaries. The shifted P-V hysteresis loops and butterfly loops indicate that internal field exists in the prepared BNT film. Both grain boundaries and internal field affect domain switching of the polycrystalline BNT film.

Temperature dependence of polarization switching properties of Bi3.15Nd0.85Ti3O12 ferroelectric thin film

The temperature dependences of the polarization switching properties of Bi3.15Nd0.85Ti3O12 (BNT) ferroelectric thin film in the range from 25 to 150°C have been investigated. With increasing temperature, the switchable polarization and switching time decrease. Meanwhile, the depolarization field due to the interfacial layer between the electrode and the BNT film increases with increasing temperature, which induces more domain back-switching. In addition, the local switching properties of BNT film have been studied using piezoresponse force microscopy, and it is found that the prepared BNT film has good local switching behaviors.

Effects of Film Thickness on Microstructure and Ferroelectric Properties of Bi<sub>3.15</sub>Nd<sub>0.85</sub>Ti<sub>3</sub>O<sub>12</sub> Thin Films Prepared by Sol-Gel Method

Bi3.15Nd0.85Ti3O12 (BNT) thin films with different thicknesses (200, 270, 360, 450 and 540 nm) were prepared on Pt/Ti/SiO2/Si substrates by sol–gel method. The effect of film thickness on the microstructure and ferroelectric properties of BNT thin films was investigated. All BNT thin films were consisted of a single phase of bismuth-layered perovskite structure. With increasing film thickness, grains gradually became larger, the remanent polarization (2Pr) firstly increased and then decreased, and the leakage current density showed opposite trend. The 360 nm-thick BNT film exhibited better electrical properties with 2Pr 26 µC/cm2, coercive field (2Ec) 220 kV/cm, dielectric constant 345 (at 1 MHz) and low leakage current density.

The electrical and switching properties of a metal-ferroelectric (Bi3.15Nd0.85Ti3O12)-insulator (Y2O3-stabilized ZrO2)-silicon diode

Metal-ferroelectric-insulator-silicon diodes with Bi3.15Nd0.85Ti3O12 (BNT) as the ferroelectric layer and Y2O3-stabilized ZrO2 (YSZ) as the insulating buffer layer have been fabricated. Measurements revealed that the memory window of the fabricated diode reduces with increasing operating temperature, which is due to the decrease of coercive field and polarization of the BNT film. The diode demonstrates excellent retention and fatigue characteristics because of the good interface and high barrier height of YSZ/Si. In addition, the switching of the diode corresponds to an approximate constant-current process, and the complete switching time displays an obvious decrease as the gate voltage increases.

Nanoscale Observation of Poling Behaviors in Nd-Substituted Bi4Ti3O12 Ferroelectric Thin Films

In this study, the effects of oxygen vacancies on the local poling properties of Bi-layered ferroelectric thin films were examined. Bi3.15Nd0.85Ti3O12 (BNT) thin films were coated on Pt(111)/Ti/SiO2/Si substrates using a sol–gel method. An oxygen vacancy of 2.4±0.5% was observed mainly at the Bi2O22+ layers in the film that annealed in an oxygen-deficient atmosphere. The film containing oxygen vacancies showed a shift in the polarization–electric field hysteresis loop. Contact-mode electrostatic force microscopy revealed a domain pinning behavior in the BNT film with oxygen vacancies. The unpolarized domains were explained by the built-in field formed by the oxygen vacancies in the Bi2O22+ layers.

THE EFFECT OF A-SITE La AND Nd SUBSTITUTION ON THE RESIDUAL STRESS OF Bi4Ti3O12 THIN FILMS FABRICATED BY SOL-GEL METHOD

ABSTRACT In this paper, thin films of Bi4Ti3O12 (BTO), Bi3.25La0.75Ti3O12 (BLT) and Bi3.15Nd0.85Ti3O12 (BNT) were fabricated on Pt/Ti/SiO2/Si substrates by sol-gel method. The structures and ferroelectric properties of the polycrystalline films are studied and the correlation between substitution and residual stress are discussed in detail. The results show that, the ferroelectric and fatigue properties of the BLT and BNT films are improved greatly, compared with those of the BTO thin film. The Pr values of BLT and BNT are 13.14 and 21.23 μC/cm2, respectively. X-ray diffraction result shows that the measured residual stress is tensile stress for all films. After A-site substitution, the value of tensile stress for the BTO films has increased and the stress value is maximal for the BNT film. The calculated intrinsic residual stress values are 288.4, 418.4 and 608.2 MPa for BTO, BLT and BNT, respectively.

Characterization of Pt/Bi3.15Nd0.85Ti3O12/HfO2/Si structure using a hafnium oxide as buffer layer for ferroelectric-gate field effect transistors

We have investigated the structural and electrical properties of metal-ferroelectric-insulator-semiconductor (MFIS) capacitors with Bi3.15Nd0.85Ti3O12 (BNdT) thin film deposited on Si and hafnium oxide (HfO2)/Si substrates. Microstructural analysis reveals the formation of well-crystallized BNdT perovskite film and good interface between BNdT film and HfO2 buffer layer. Pt/BNdT/HfO2/Si structure exhibits a memory window of 1.12 V at an operation voltage of 3.5 V. The width of memory window for the MFIS structure varies with increasing thickness of HfO2 layer, and 4-nm-thickness is optimum. The results from the fatigue test indicate a slight degradation of the memory window after 1010 switching cycles. These properties are encouraging for the development of ferroelectric memory transistors.

The ferroelectric properties and residual stress analysis of Bi3.15Nd0.85Ti3O12 thin films with a LaNiO3 buffer layer

Bi3.15Nd0.85Ti3O12 (BNT) thin film with a thin LaNiO3 film as buffer layer was fabricated by sol–gel method on Pt/TiO2/SiO2/Si substrate. The BNT thin films have a perovskite phase with a dense microstructure. The P r and V c value are 25.5 μc/cm2 and 3.7 V, respectively under the applied voltage of 15 V. After the switching of 2 × 109 cycles, the P r value decreases to 86% of its pre-fatigue value. The leakage current density of the BNT thin films with LaNiO3 buffer layer were generally in the order of 10−8 to 10−6 A/cm2. The fatigue and leakage current properties were improved dramatically compared with the BNT film without a LaNiO3 buffer layer that we prepared before. The measured residual stress was tensile stress and its value was 176 MPa.

Electrical characteristics of (0 0 1)- and random-oriented Bi3.15Nd0.85Ti3O12 thin films: a comparative study

Highly (0 0 1)-oriented Bi3.15Nd0.85Ti3O12 (BNdT) films were deposited directly on single-crystalline Nb-doped SrTiO3 (STON) conductive substrates by chemical solution deposition. The electrical characteristics of BNdT films were studied and compared with random-oriented BNdT films on Pt/TiO2/SiO2/Si substrates. BNdT films on STON substrates show much smaller remanent polarization and ϵr values. This indicates that dominant polarization of BNdT is not along the (0 0 1)-axis. However, (0 0 1)-oriented BNdT films exhibit better retention characteristics, which can be ascribed to the better film/electrode interface between BNdT and STON.