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It is of great significance to understand the role of carrier in piezocatalysis of composites by studying the separation mode of carriers under dynamic polarization field. Herein, the separation and migration pathways of carriers under piezoelectric field are investigated by synthesizing heterojunctions with Bi2WO6 (BWO) nanosheets grown vertically on g-C3N4 (CN) coated ZnO nanorods and directly on ZnO. Compared with the photocatalysis, the piezocatalytic efficiency of Rhodamine B (RhB) by BWO/ZnO is significantly increased to 0.121 min−1, which indicated the polarization field promotes band tilt and Z-scheme formation. After introducing the CN interlayer, the piezocatalytic efficiency of BWO/CN/ZnO is further improved (0.217 min−1), which can be attributed to the unique core–shell structure with Z-scheme heterojunctions. This unique structure provides more active sites and excited carrier concentration, the intermediate layer CN also reduces the direct contact and recombination of electrons and holes controlled by polarization potential at the interface between BWO and ZnO. This work deeply analyzes the influence of carrier concentration, separation efficiency and transport process on piezocatalysis, which provides a reference for the design of efficient catalysts.

Antiferroelectric Sm-doped PbZrO3 (PSZO) thin films were prepared on Pt(111)/Ti/SiO2/Si substrates using a chemical solution deposition method. The effects of Sm doping concentration on structural, morphology, dielectric, antiferroelectric, and energy storage characteristics of PSZO thin films were investigated. With Sm doping, all the thin films were crystallized in perovskite phase along with a strong (111)- preferential orientation. It is found that Sm doping significantly altered the Curie temperature (Tc) and electric field-induced phase switching of the films. The PSZO film with Sm = 0.01 exhibited a maximum polarization of 53.7 μC/cm2, an energy storage density of 17.1 J/cm3 at ~444 kV/cm, and a dielectric constant of 175 at 1 kHz. The improved energy storage performance was attributed to high (111) degree of preferred orientation and site occupation of Sm ions.

Orthorhombic Bi2SiO5 thin films were fabricated on Pt/Ti/SiO2/Si substrates by incorporating a NiO thin layer between Bi2SiO5 and bottom electrode. Compared with those bare Pt/Bi2SiO5/Pt devices, a remarkably improved uniformity of resistive switching parameters such as electroforming voltages, reset voltages, and a resistance ratio of low/high states was demonstrated in the Bi2SiO5 devices with an embedded NiO layer. This improvement was attributed to the formation of the partial conductive filaments resulted from sufficient oxygen vacancies at the interface. Our results provide a method for the optimization of the operation voltage control toward forefront applications in nonvolatile memory.

Structure, dielectric, ferroelectric, fatigue, and photoluminescent properties of Bi3.86−kSm0.14LakTi3O12 (BSLT) thin films synthesized by sol–gel method were investigated. The XRD analysis indicated that the BSLT thin films formed single phase orthorhombic structure, and orthorhombic distortion was found to increase with increasing lanthanum doping content. Raman spectra revealed that BSLT thin films have significantly structure distorted because of La3+ doping, which is consistent with XRD results. Increasing La substitution results in improvement in dielectric and ferroelectric properties of BSLT thin films due to distorted structure and defects reduction. The films show almost fatigue-free ferroelectric polarization behavior at room temperature. Besides, the BSLT thin films show orange-red color emission at 604 nm and long florescence lifetime (about 0.75 ms). This study indicates that the thin films with an appropriate doping concentration of Sm3+, La3+ ions may have potential applications in multifunctional optoelectronic devices.

Sol-gel method was used to prepare the Pr3+ ions-doped (1-x)Na0.5Bi0.5TiO3-xCaTiO3 (Pr-NBT-xCTO) (x = 0, 0.04, 0.06, 0.08, 0.1, 0.12, and 0.16) thin films on Pt/Ti/SiO2/Si and fused silicon substrates. The structure phase of thin films was evolving from rhombohedral (R3c) to orthorhombic (Pnma) with increasing CTO content. Owing to the morphotropic phase boundary (MPB), the improved ferroelectric and dielectric properties were obtained at x = 0.06–0.1. The MPB was formed from the concomitant phase of rhombohedral (R3c) and orthorhombic (Pnma). The Pr-NBT-0.08CTO thin film showed the best ferroelectric and dielectric properties, as well as strong relaxor behavior (the diffusion factor is γ = 1.79). In addition, all the films exhibited strong red emission as excited by UV light, and wide optical band-gap (3.44–3.47 eV), which might be influenced by grain size and structural variation. Our results indicate that Pr-NBT-xCTO thin films may have potential applications in ferroelectric-luminescence multifunctional optoelectronic devices.

We report on the structure, dielectric, ferroelectric, and photoluminescent properties of Sm3+-doped Bi4Ti3O12 thin films which were prepared on fused silica and Pt/Ti/SiO2/Si substrates by sol-gel method. The X-ray diffraction analysis confirmed that the Bi4-xSmxTi3O12 (BSmT) thin films were well crystallized in layered perovskite structure without any secondary phase. Raman spectra indicated that the structure of BSmT thin films was significantly distorted because of the Sm3+ doping. An appropriate doping amount of Sm3+ ions leads to obvious enhancement in ferroelectric and dielectric properties of BSmT thin films due to structure distortion and reduction in defects. In addition, the BSmT thin films also show orange-red color emission at 601 nm and long florescence lifetime (> 0.6 ms). This study indicated that lead-free BSmT thin films, which are featuring good electrical and photoluminescent properties, may have potential applications in integrated optoelectronic devices.

In this work, we have fabricated the MgZnO thin films directly on low resistive silicon substrates by using a chemical solution deposition route. Besides the investigation of the structures, morphologies, chemical states, and photoluminescence properties of MgZnO thin films, the bipolar resistive switching behaviours have been evaluated in the simple Ag/MgZnO/Si structures. The self-compliance resistive switching characteristics simplify the device configuration and circuit design for practical applications. In addition, the multilevel storage capabilities have also been investigated by regulating different operation voltages or compliance currents, respectively. The four level storage capabilities show long retention time and good cycling performance. The resistive switching mechanism has been explicated by the formation and rupture of Ag filament based on the electrochemical metallization model. This work suggests that the Ag/MgZnO/Si structures have potential non-volatile multilevel memory applications.

This work examined carefully the electrical performance of Pt/InGaZnO/W memory device and found the co-existence of volatile and non-volatile resistive switching effects dependent on the electroforming process. The Pt/InGaZnO/W device exhibited stable and volatile switches without electroforming process, which were originated from electron trapping and detrapping in intrinsic defects of InGaZnO thin films. However, after electroforming process, the device showed non-volatile bipolar resistive switching properties with high reliability including long retention, good endurance and concentrated switching voltages. On the basis of the resistance temperature dependence and the change of chemical states, the non-volatile resistive switching effects were explained by the formation and rupture of oxygen vacancies related filament. This study provides new insights into the effects of electroforming process and defect types on resistive switching behaviours.

Pr-doped ZnO hexagonal structure thin films with c-axis preferred orientation were deposited on Pt/Ti/SiO 2 /Si substrates by chemical solution deposition technique. The effects of Pr doping amount on the resistive switching behavior of Pt/Zn 1−x Pr x O/Pt (x = 0, 0.01, 0.03, and 0.05) memory cells were investigated. The results showed that Pr-doping lowered the c-axis orientation degree of the ZnO thin films, but improved the resistive switching properties of Pt/Zn 1−x Pr x O/Pt devices. The resistive switching devices exhibited good endurance, long retention, and uniform switching voltages. I-V characteristics and their temperature dependence analysis indicated that the conduction mechanism of LRS was Ohmic behavior, and that of HRS at relatively higher voltage is trap-controlled space charge limited current. The physical origin of the resistive switching can be referred to the formation and rupture of the oxygen vacancies related filaments.

Ce-doping NiFe2O4 spinel ferrite thin films were prepared on Pt / Ti / SiO2 / Si substrates using a chemical solution deposition method. It has been observed that Ce-doping induced enhancement of unipolar resistive switching properties, such as uniform switching voltages, enlarged ON / OFF ratio, and long retention in Pt / NiFe2O4 / Pt memory devices. The dominant conduction mechanisms in the thin film devices were Ohmic conduction at low resistance state and lower voltage region of high resistance state, while Schottky emission dominated at higher voltage region in high resistance state. The physical mechanism of resistive switching is related to the formation and rupture of conducting filament. The improved stability of the switching parameters for the devices can be attributed to Ce-doping minimizing random formation and rupture of conductive filament. This study indicates that doping rare earth ions in ferrite thin films would be an effective approach for obtaining stable resistance switching memory devices.

c-Axis oriented Tm3+-Dy3+-Eu3+ tri-codoped Bi2VO5.5 ferroelectric thin films were prepared on fused silica and Pt(111)/Ti/SiO2/Si substrates by using chemical solution deposition method, and charac...

Nanoscale photodetectors are highly attractive for their potential applications in integrated optoelectronic devices. One-dimensional flexible nanowire-based photodetectors are especially important because low-dimensional nanostructures are fascinating platforms for manipulating electrons and photons at the subwavelength scale. Herein, we report an ultraviolet–visible photodetector based on a single crossed heterojunction assembled with quantum-dot-embedded polyaniline nanowires. The quantum-dot-embedded polyaniline nanowires are fabricated by a direct drawing method. Based on these inorganic–organic hybrid nanowires, room-temperature, high-performance, high-speed photodetectors are constructed. The fabricated photodetectors show an excellent light response in the wavelength region of 365 to 550 nm, with an external quantum efficiency of 105 %, a responsivity of 103 A/W, an on–off switching ratio of 10, and a short response/recovery time of 9 ms. These excellent performance characteristics are attributed ...

Plasmons of gold nanostructures provide a powerful tool to enhance exciton–exciton coupling and energy transfer at spherical geometry, while quantum dots have confined excitons with strong optical oscillator strength and gain. Here, we report a plasmon-mediated whispering-gallery-mode emission from CdSe-ZnS quantum dot-coated gold nanosphere at room temperature. The whispering-gallery-mode emissions with different gold nanosphere sizes have been studied. Polarization-dependent emission is observed and explained. The decay dynamics of radiative emission is investigated by analyzing the photoluminescence decay spectrum. The underlying physical mechanism of the measured interference rings is further investigated by spatial distribution of photoluminescence intensity.

In this work, large-area ferrite thin films of ferromagnetic yttrium iron garnet (Y3Fe5O12, YIG) were synthesized on Pt/Ti/SiO2/Si (Pt) substrates by a sol-gel method to investigate the resistive and magnetization switching properties. The synthesized YIG thin films acquire a single garnet structure. The Pt/YIG/Pt stack illustrates unipolar resistive switching behavior with excellent switching uniformity, large memory window (102), stable cycle-to-cycle endurance, and good data storage retention (104 s). The ~46% saturation magnetization variation could be realized via the conversion between high and low resistance states by manipulating the electric field. Schottky emission is governed in the high-field region for the high resistance state. Temperature dependence of resistance and magnetization variation confirms that oxygen vacancies conductive filament model and valence state change (Fe2+ and Fe3+) are responsible for the resistive and magnetization switching mechanisms. These results indicate that YIG ferrite based stack is suitable to design the electro-magnetic coupling multifunctional nonvolatile memory devices.

Oxygen vacancies derived resistive and magnetic switching, was demonstrated in facile solution-processed Au-Co3O4 nanocomposite thin films, in terms of optimum Au content. The metal element introduced is a unique way to create the optimum amount of oxygen vacancies in the dielectric films even in the absence of electrochemically active electrodes. Compared with pure Co3O4 based device, the RRAM device with Au additives showed bipolar switching behavior with uniform Set/Reset voltages, enhanced endurance of >103 cycles, and stable time-dependent resistances up to 104 s. The introduction of Au nanoparticles caused the oxygen vacancies based confined filament growth for optimum switching uniformity and stability. Results showed that Ohmic conduction was dominant at LRS and Schottky emission was dominated at HRS of the devices. Temperature dependence and magnetization change of various resistance states revealed that resistive and magnetic switching was due to the formation and rupture of conductive filaments of Au atoms confined oxygen vacancies with the conversion of cation valence states (Co2+ and Co3+). The present study suggests that Au-Co3O4 nanocomposite thin films have a potential for future multifunctional electromagnetic integrated device applications.

The photoluminescent and dielectric properties of Eu3+/Gd3+ co-doped Bi2Ti2O7 ((Bi1.5-xGdxEu0.5)Ti2O7, BGET) pyrochlore thin films, with Gd content varying in the full range of 0 ≤ x ≤ 1.5, have been investigated. The thin films were synthesized by a conventional chemical solution deposition method. The typical intra-4f transitions of Eu3+ ions can be excited by UV radiation. The close correlation between the excitation spectra and the optical band-gap energy of the BGET thin films indicates the essential role of host sensitization in the excitation of Eu3+ luminescence. The host sensitization mechanism can be explained by a resonant energy transfer between host fundamental emission and Eu–O bond absorption. A two-step charge transfer (CT) process is proposed based on the energy band structure determined by XPS technique and spectral analysis. The maximum PLE efficiency can be obtained when the greatest overlap between host emission and Eu→O CT absorption spectra is achieved. The essential role of the host energy-band structure is confirmed by these results.

Au nanoparticles loaded c-axis oriented Bi2VO5.5 (BVO) porous thin films were prepared by using a simple spin-coating technique. The porous structures were formed through the hydrolysis of bismuth nitrate, Bi(NO3)3, one of the raw materials for synthesizing the BVO precursor solutions. The optimal photocatalytic rate of the porous thin film is three times more than that of pure BVO thin film. The enhancement of photocatalytic activity can be attributed to the Schottky barrier in the intimate interface between Au nanoparticles and BVO grains and the increase of absorption of light caused by surface plasmon resonance effect of gold nanoparticles. The possible degradation mechanism of Au–BVO-Methylene Blue system has been discussed based on the energy band structure and further trapping experiments. This study provides a simple method to prepare bismuth-containing oxide porous thin films without any pore-forming reagents, and the results suggest that the Au nanoparticles loaded BVO thin film is a promising candidate material for water or air treatment.

Eu 3+ -doped Bi 12 TiO 20 thin films were prepared on Pt/Ti/SiO 2 /Si and fused silica substrates by a chemical solution deposition method. The thin films annealed at 600 °C crystallized in a sillenite structure with a uniform thickness. After an electroforming process, the resistive switching properties were observed in the thin films sandwiched with top and bottom Pt electrodes. The dominant conduction mechanisms in Pt/Bi 10.8 Eu 1.2 TiO 20 /Pt devices were Ohmic conduction at low resistance state and lower-voltage region of high resistance state, and Schottky emission at higher-voltage region in high resistance state. The dielectric and photoluminescent properties of the thin films have also been investigated. With increasing Eu 3+ content, the dielectric constant increased and dielectric loss decreased due to improved crystallization of the thin films. Under 350 nm excitation, the thin films on fused silica substrates exhibited the visible emissions assigned to the transitions 5 D 0 → 7 F 1,2 of Eu 3+ ions. The results indicate that Eu 3+ -doped Bi 12 TiO 20 thin films are potential multifunctional materials which could be applied to optoelectronic thin film devices.

Eu-doped Ba1−xSrxTiO3 (x = 0, 0.2, 0.3, and 0.4) thin films with Eu-doping content of 1 mol% have been prepared on fused silica substrates by a chemical solution deposition method and characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), optical and photoluminescence measurements. XRD analysis showed that the films were well crystallized with a pure perovskite structure in the annealing temperature range from 650 to 750 °C. AFM observation indicated that the films were dense and smooth. The band-gap energies of the thin films were also investigated. The more the Sr content in the thin films, the narrower the energy gap of the thin films. Photoluminescence spectra of the thin films showed two prominent transitions of Eu3+ ions at 594 nm (5D0 → 7F1) and 618 nm (5D0 → 7F2) upon excitation at 395 nm (7F0 → 5L6). The observed changes of luminescence spectra by the decrease of the intensity ratio R, which was defined as the ratio of the integrated emission intensity of 5D0 → 7F2 transition to that of 5D0 → 7F1 transition, were associated with the increase of the inversion symmetry of Eu3+ sites when Sr content increased. Lifetime study of photoluminescence indicated that the average lifetime of the thin films was approximately 0.7 ms.

(200)-oriented Eu-doped cerium oxide thin films were fabricated, on fused silica substrates by a chemical solution deposition method. The thin films obtained were characterized by X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and photoluminescence measurements. Ce with valence state 4 + is confirmed to be predominant in Eu-doped CeO2 thin films. All the thin films were dense and crack-free, and showed bright orange-red emissions under ultraviolet light excitation, originated from the 5D0 → 7F1 and 5D0 → 7F2 transitions of Eu3 + ions. Structure distortions induced by Eu-doping affected the light emission of electric dipole transition 5D0 → 7F2. The strongest photoluminescent intensity was observed in the thin films with a Eu-doping content x of 0.08, indicating the existence of concentration quenching effect of photoluminescence. Lifetime study of photoluminescence indicated that the decrease of lifetime was originated from augmented pathway for deactivating excited Eu3 + ions. Our study suggests that Eu3 +-doped CeO2 thin films have potential applications in optoelectronic devices.

We report on an effective combination of good dielectric properties with bright red emission in Y 3+ /Eu 3+ -codoped ZrO 2 thin films. The thin films were deposited on fused silica and Pt/TiO 2 /SiO 2 /Si substrates using a chemical solution deposition method. The crystal structure, surface morphology, electrical and optical properties of the thin films were investigated in terms of annealing temperature, and Y 3+ /Eu 3+ doping content. The 5%Eu 2 O 3 –3%Y 2 O 3 –92%ZrO 2 thin film with 400 nm thickness annealed at 700 °C exhibits optimal photoluminescent properties and excellent electrical properties. Under excitation by 396 nm light, the thin film on fused silica substrate shows bright red emission bands centered at 593 nm and 609 nm, which can be attributed to the transitions of Eu 3+ ions. Dielectric constant and dissipation factor of the thin films at 1 kHz are 30 and 0.01, respectively, and the capacitance density is about 65.5 nf/cm 2 when the bias electric field is less than 500 kV/cm. The thin films also exhibit a low leakage current density and a high optical transmittance with a large band gap.

High-sensitive visible-light photodetectors based on α-Fe2O3 thin films on p-Si substrates with a responsivity as high as 2 × 103 A/W have been fabricated and characterized. The solution-processed devices exhibit a rapid rise/decay time (

We reported the effects of Mn doping on the structure and dielectric properties of (Ba0.835Ca0.165)(Zr0.09Ti0.91)O3 (BCZT) thin films prepared by sol–gel method. The (Ba0.835Ca0.165)Mnx(Zr0.09Ti0.91)1 − xO3 (x = 0, 0.002, 0.005, and 0.01) thin films exhibited a pure pseudo-cubic perovskite structure with random orientation. Scanning electron microscopy and atomic force microscopy observation showed that increasing Mn-doping amount caused a decrease in particle size and a cluster of the particles, while the film surface remained smooth and crack-free. Compared with the undoped film, Mn doped BCZT thin films exhibited smaller dielectric constant and lower dielectric loss. The figure of merit reached the maximum value of 16.7 with a tunability of 53.6% for the film with 0.5 mol % Mn doping, when a bias electric field of 400 kV/cm was applied at 100 kHz. The results indicated that the Mn doped BCZT thin films are suitable for tunable microwave device applications.

Bi4-xEuxTi3O12 (BEuT) ferroelectric thin films were prepared on fused silica substrates by using chemical solution deposition technique. The attained samples had a polycrystalline bismuth-layered perovskite structure, and their optical properties were composition dependent. The thin film samples had good optical transmittance above 500 nm wavelength. A blue shift of the optical absorption edge was observed in the BEuT thin films with increasing Eu3+ concentration. The optical band gaps of BEuT thin films were estimated to be about 3.57, 3.60, 3.61, 3.63, and 3.69 eV for the samples with x = 0.25, 0.40, 0.55, 0.70, and 0.85, respectively. Photoluminescence measurements showed that two emission peaks of BEuT thin films originated from two transitions of 5 D 0 → 7 F 1 (594 nm) and 5 D 0 → 7 F 2 (617 nm) had maximum intensities when Eu3+ concentration was x = 0.40. The relatively high quenching concentration of Eu3+ content was thought to be related to the layered structure of BEuT thin films. These results suggested that multifunctional BEuT thin film materials could have promising applications in optoelectronic devices.

We report high dielectric tunabilities of (1 − x)Ba(Zr 0.2 Ti 0.8 )O 3 − x(Ba 0.7 Ca 0.3 )TiO 3 (BZT–xBCT) (x = 0.15, 0.30, 0.40, 0.45, 0.50, and 0.55) thin films prepared by a sol–gel method. The films show a pure perovskite structure with random orientation. They have moderate dielectric constant ranging from 350 to 500 and low dielectric loss near 3.0% at 1 kHz with 0 V bias at room temperature. The dielectric tunability of the BZT–0.55BCT thin films is up to 65% at 400 kV/cm and 100 kHz. The films exhibit a high optical transmission in the range of 420 nm–1500 nm. Their optical band gap energies are about 3.90 eV.

Highly c-axis oriented \( {\text{M}}{{\text{g}}_{\text{x}}}{\text{Z}}{{\text{n}}_{{1 - {\text{x}}}}}{\text{O}}\left( {x = 0 \sim 0.2} \right) \) thin films with pure hexagonal phase were prepared on Pt/TiO2/SiO2/Si substrates by chemical solution deposition method, and their structure, photoluminescence, and lattice vibrational properties were studied. For the thin films with Mg contents ranging 0 ≤ x ≤ 0.20, the room-temperature near-band-edge emission exhibited blueshift up to about 0.35 eV, indicating that the band-gaps of thin films could be tailored by Mg incorporation, meanwhile, the green emission of the thin films enhanced with increasing Mg content. Raman spectra analysis indicated that the decreasing high frequency E2 Raman modes showed composition-dependent asymmetrically broadening. The difference of electronegativity between Mg2+ for Zn2+ as well as the potential fluctuation were discussed. Furthermore, longtitudial optical modes exhibited one-mode behavior with observed ~25.8 cm−1 blueshift. X-ray photoelectron spectroscopy measurements clearly confirmed the Mg incorporation.

Bi4-xPrxTi3O12 thin films were prepared by a chemical solution deposition method and their photoluminescence properties are investigated. The layered perovskite structure of the films is not destroyed by substituting Bi with Pr. The emission lines at 493, 533 and 612 nm are observed, and they can be assigned to the transitions of 3P0→3H4, 3P0→3H5 and 1D2→3H4 of Pr3+ ions. The quenching concentrations are identified to be x = 0.09 and 0.03 for the emissions at 493 and 612 nm. The crystal field plays a crucial role in the luminescence properties of Bi4-xPrxTi3O12 thin films.

Pb0.5Sr0.5TiO3 (PST50) thin films with different Cr doping amounts were prepared on LaNiO3 coated silicon substrates by a chemical solution deposition method. Their dielectric and ferroelectric properties were studied at room temperature. The dielectric constant decreased from 417 to 207 (at 1 kHz), as the Cr content increased from 0 to 8%. When the content of Cr was 3%, the tunability and the figure of merit factor reached maximal values of 61.3% and 21.4, respectively. The remnant polarization of the Cr-doped PST thin films decreased from 7.4 μC/cm2 to 2.0 μC/cm2, as the Cr content increased from 0 to 5%.

Pb0.5Sr0.5TiO3 thin films were prepared on Pt/TiO2/SiO2/Si and LaNiO3 (LNO)/Si substrates by using chemical solution deposition technique, and a layer-by-layer annealing method was used in an attempt to improve the dielectric properties of the thin films. The structure, dielectric, and ferroelectric properties of the thin films were investigated. Improved dielectric properties of the thin films were clearly confirmed: the dielectric constant and dielectric loss for the films on Pt/TiO2/SiO2/Si substrates annealed at 650 °C were 1064 and 0.027, respectively, at 1 kHz, with a dielectric tunability of more than 50%; similarly, the films prepared on LNO/Si substrates, showed a high dielectric constant of 1280 and a low dielectric loss of 0.023, at 1 kHz. P–E hysteresis loop measurements indicated that the remanent polarization and coercive field for the films on Pt/TiO2/SiO2/Si substrates annealed at 650 °C were 15.7 μC/cm2 and 51 kV/cm, respectively.

Neodymium-doped lanthanum nickelate (La 1 − x Nd x NiO 3 , LNNO) thin films have been prepared on Si substrates by chemical solution deposition method. The effects of annealing temperature and the neodymium concentration on the structural and electrical properties of the thin films have been investigated. X-ray diffraction analysis showed that the LNNO thin films exhibited perovskite structure with (100) preferential orientation. The (100) orientation degree of the thin films changed with neodymium content; however, the resistivity of the thin films was not related to the degree of orientation. Field emission scanning electron microscopy observations confirmed that the films had a smooth surface and uniform thickness. The resistivity of the thin films annealed at 700 °C increased from 1.97 mΩ·cm to 5.35 mΩ·cm, with increasing neodymium doping amount from LaNiO 3 to La 0.6 Nd 0.4 NiO 3 .

Pb(Zr0.25Ti0.75)O3 (PZT25) thin films were prepared on LaNiO3-coated thermally oxidized silicon substrates by chemical solution deposition method, where LaNiO3 electrodes were also prepared by a chemical solution deposition technique. The dielectric constant and dielectric loss of the PZT25 thin films were 570 and 0.057, respectively. The remanent polarization and coercive field were 20.11 μC/cm2 and 60.7 kV/cm, respectively. The PZT25 thin films on LaNiO3-coated thermally oxidized silicon substrates showed improved fatigue characteristics compared with their counterparts on plantium-coated silicon substrates.

All-epitaxial multilayered ferroelectric thin films of (Bi,La)4Ti3O12(BLT)/ Pb(Zr,Ti)O3(PZT) were prepared on SrTiO3 substrates by pulsed laser deposition. X-ray pole-figure and electron diffraction analyses showed that the epitaxial relationships between BLT, PZT, and STO were BLT(001)//PZT (001)4//STO (001), and BLT[110]//PZT [100]//STO [100] for the multilayered thin films on (001)-oriented STO substrates, whereas for the multilayered thin films on (011)-oriented STO substrates, the epitaxial relationships between BLT, PZT, and STO were identified to be BLT(118)//PZT(011)//STO(011), and BLT[ 0]//PZT[100]//SrTiO3[100]. Clear interfaces between different film layers were confirmed by cross-sectional transmission electron microscopy observation. Tri-layered films of the same composition showed well-defined hysteresis loops as well as a high fatigue resistance up to 1 × 1010 switching cycles.

PbTiO3 (PT) thin films were prepared on ZrO2, SrTiO3, thermally oxidized silicon, and fused silica substrates by a simple sol–gel technique. The crystallization and optical properties of the thin films were investigated. The PT films on ZrO2 and SrTiO3 substrates have a c-axis preferential orientation, whereas the films on thermally oxidized silicon and fused silica substrates are slightly a-axis oriented. The thin films exhibited good optical transmittivity, and had optical direct transitions. The band gap energy of the film annealed at 650°C was 3.60 eV, which is comparable to those of PT polycrystalline ceramic bulk and films. The thin films on Pt/Ti/SiO2/Si substrates exhibited a ferroelectric hysteresis loop with a remanent polarization of 17.1 μC cm−2 and a coercive field of 132.1 kV cm−1.

Well-crystallized LaNiO3 (LNO) thin films were grown on thermally oxidized silicon (SiO2/Si) and SrTiO3 substrates by a simple chemical solution deposition (CSD) technique. The LNO thin films obtained had pseudocubic phase without the existence of impurity phase. The LNO films on SiO2/Si substrates were polycrystalline, dense, and randomly oriented with a uniform surface and cross-section, whereas those on SrTiO3 substrates were (100) highly oriented with uniform grain size. The room temperature resistivity of the films on SiO2/Si substrates annealed at 750°C was about 0.54 mΩ cm, which is much lower than that of the films derived by the water-based solution technique. The subsequent deposition and electrical measurements of PbTiO3, (Pb,La)TiO3, Pb(Zr,Ti)O3 thin films on the CSD derived LNO/SiO2/Si confirmed the LNO films to be promising electrode materials for ferroelectric thin films.

Sandwich structured (Bi, La)4Ti3O12/Pb(Zr, Ti)O3/(Bi, La)4Ti3O12 thin films were fabricated on Pt/Ti/SiO2/Si substrates, with the intention of simultaneously utilizing the advantages of both (Bi, La)4Ti3O12 (BLT) and Pb(Zr, Ti)O3 (PZT) thin films such as non-fatigue behaviours of BLT and good ferroelectric properties of PZT. Both BLT and PZT layers were prepared by a chemical solution deposition technique. The experiments demonstrated that the sandwich structure showed fatigue-free characteristics at least up to 1010 switching bipolar pulse cycles under 8 V and excellent retention properties. The sandwich structured thin films also exhibited well-defined hysteresis loops with a remanent polarization (2Pr) of 8.8 µC cm-2 and a coercive field (Ec) of 47 kV cm-1. The room-temperature dielectric constant and dissipation factor were 210 and 0.031, respectively, at a frequency of 100 kHz. These results suggest that this sandwich structure is a promising material combination for ferroelectric memory applications.

A forming-free resistive switching effect was obtained in Pt/Eu2O3/Pt devices in which the Eu2O3 thin films were fabricated by a chemical solution deposition method. The devices show unipolar resistive switching with excellent switching parameters, such as high resistance ratio (107), stable resistance values (read at 0.2 V), low reset voltage, good endurance, and long retention time (up to 104 s). On the basis of the analysis of the current–voltage (I–V) curves and the resistance-temperature dependence, it can be concluded that the dominant conducting mechanisms were ohmic behavior and Schottky emission at low resistance state and high resistance state, respectively. The resistive switching behavior could be explained by the formation and rupture of conductive filament, which is related to the abundant oxygen vacancies generated in the deposition process. This work demonstrates the great potential opportunities of Eu2O3 thin film in resistive switching memory applications, which might possess distinguished properties.

Calcium modified lead titanate sol was synthesized using lead acetate trihydrate, calcium nitrate tetrahydrate and titanium tetra-n-butoxide as starting materials, methanol and ethanolamine were selected as solvent and stabilizing or complexing agent, respectively. (Pb0.76Ca0.24)TiO3 thin films were prepared on platinum-coated silicon and fused silica substrates with the solution using the spinning method. The surface morphology and crystal structure, surface compositions and chemical states, electrical and optical properties of the thin films were investigated. The films have good composition homogeneity and thickness uniformity. The dielectric constant and dissipation factor of 1 kHz at room temperature were found to be 280 and 0.027, respectively, for thin films with 0.5 μm thickness annealed at 600°C for 1 h. The remanent polarization and coervive field were 15 μC/cm2 and 64 kV/cm, respectively. The thin films exhibited good optical transmissitivity, and had optical direct transitions. The dispersion relation of refractive index and wavelength followed the single electron oscillation model. The band gap of the film which annealed at 650°C was 3.68 eV. The results also confirmed that ethanolamine was very effective in preparing uniform and dense oxide films, owing to the superior stability of the sols during hydrolytic polycondensation.

Transparent and crack-free SrTiO 3 thin films were prepared on fused silica substrates by a sol-gel technique. Strontium acetate and titanium tetra-n-butoxide were used as starting materials. The structural properties of the thin films were studied by X-ray diffraction. The films annealed at 700 °C have good crystallinity. The optical transmission properties of the thin films were measured in the wavelength range 200 to 1100 nm. The thin films possess high optical transmission. By using an approximate formula, the refractive index and the band gap were evaluated. The dispersion relation follows the single electron oscillation model. The band gap of well-crystallized film is comparable to that of single crystal reported. However, for poor-crystallized films, their band gap values are much larger than of single crystal. The larger gap shift is believed to be mainly due to both quantum size effect and amorphous phase effect.

Growth of well(111)-oriented Pt and Pt/Ti films on SiO2/Si(111) substrates and crystallinity of PZT films grown on the Pt(111)/SiO2/Si(111) and Pt(111)/Ti/SiO2Si(111) substrates have been investigated. It was found by X-ray diffraction analysis that well (111)-oriented Pt film with a best full-width at half maximum (FWHM) of 0.28° was grown by the DC sputtering method. PZT films were prepared by metallo-organic decomposition (MOD) on Pt(111)-coated SiO2Si(111) substrates. The crystallinity of the PZT films improved as the FWHM of the Pt(111) diffraction peak decreased. The best FWHM obtained for a PZT film grown on a Pt(111)/Ti/SiO2/Si(111) substrate was 0.33°.

Potassium tantalate-niobate thin films were prepared from metal-organic compounds by sol-gel processing. Effects of substrates and processing parameters on K(Ta, Nb)O 3 thin film growth were studied. The results showed that perovskite phase of K(Ta, Nb)O 3 was formed through the reactions of pyrochlore phases, and K(Ta, Nb)O 3 thin films with pure perovskite phase can be obtained. The formation mechanism of the perovskite phase of K(Ta, Nb)O 3 on SrTiO 3 and MgO single crystal substrates was discussed, and the causes that K(Ta, Nb)O 3 thin films with pure perovskite structure on single crystal silicon and quartz glass substrates cannot be obtained was detailed.

Piezoelectric ignition voltage and energy formula is derived from piezoelectric equations, the correlations of energy and piezoelectric material parameters are analysed by electromechanical coupling relation, and general conclusions about comprehensive selection of piezoelectric ignition material parameters are given, also

Expitaxial and highly oriented K(Ta0.65Nb0.35)O3 thin films were prepared on (100) SrTiO3 and (100) Mgo single crystal plates by sol-gel processing, using a multilayer sprinning method. The preparation process and the thin film characterization were studied by x-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED). The mechanism of orientation of K(Ta0.65Nb0.35)O3 films was discussed in detail. The substrate strongly influenced on the film orientation, and the concentration of the precursor solution and heat-treatment conditions were also found to affect the orientation of the thin films.

Zinc oxide thin films were prepared from metallo-organic compounds through the sol-gel process. The crystal structure of ZnO films was investigated by XRD and SEM. Optical properties of the thin films were analyzed by using UV/visible spectroscopy. Strongly c-axis oriented ZnO thin films were obtained on fused quartz substrates; the surface of the thin films was smooth, homogeneous, crack-free, and dense. The growth of the thin films depends strongly on the heat-treatment conditions. The Crystal lattice constant of the thin films is a little larger than that of the ZnO crystal, the band gap is 3. 444 eV, and the absorption limit shifts to shorter wavelengths.

The surface state of a topological insulator always has a weak antilocalization (WAL), and the bulk state would theoretically have a weak localization (WL). Although the WAL topological surface state has been observed, the WL bulk state has never been demonstrated by experiments. Using the Sn-doping Bi${}_{2}$Te${}_{3}$ polycrystalline topological insulator films and the magnetotransport characteristic analysis, we directly observed the WL effect from the bulk state. The experimental data suggested that an inflection from WAL to WL indeed takes place in the parallel magnetoresistance (MR) curve of the low-doped film with increasing the magnetic field, and the inversion phenomenon from a positive to a negative MR cusp at low fields driven by the temperature was observed in the parallel MR trace of the high-doped sample. Observations of the WL bulk state actually open a path toward magnetic device application of a topological insulator, and the polycrystalline topological insulator films provide an attractive material platform to explore the novel effects of topological insulators.

c-Axis oriented zinc oxide thin films were prepared by sol-gel process on fused quartz substrates. The structure, optical and electrical properties of ZnO films were investigated. Growth of the thin films strongly depends on heat-treatment conditions. The c-axis lattice constants of the thin films and the band gap are a little bigger than that of ZnO crystal. The differences between the thin film and crystal might be attributable to the grain boundaries and imperfections in thin films.