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In this study, the Mg doping effects on the nanostructural dependence of photoluminescence and the photosensing properties in Zn1−xMgxO (x = 0.01, 0.03, and 0.05) nanorod arrays were systematically examined. The vertical-aligned nanorod arrays were separately grown on ZnO-seeded n-Si substrates via a low-temperature hydrothermal process. X-ray diffraction analysis revealed that all Zn1−xMgxO nanorod arrays exhibited the same preferentially c-oriented wurtzite structure. Images of all the Zn1−xMgxO nanorod arrays provided by field emission scanning electron microscope showed that both the length and diameter of the Zn1−xMgxO nanorod arrays increased with increasing Mg doping concentration. Also, an enhanced blue-shifted ultraviolet (UV) emission and a reduced visible emission were observed from the photoluminescence spectra of the Zn1−xMgxO nanorod arrays. The former indicated the decrease of defects and the latter indicated the enhancement of the crystallinity and the increase in optical bandgap. Current–voltage curves were separately measured in the dark and under UV illumination. Finally, the mechanism of the Mg doping effects on the corresponding defects, bandgap, and UV photosensing characteristics of the Zn1−xMgxO nanorod arrays was investigated in detail.

Electrical conduction mechanism and bipolar resistive switching properties of the manganese oxide thin films resistive random access memory (RRAM) devices for high resistive status and low resistive status (HRS/LRS) were investigated and discussed. The electrical and physical properties of post-treatment manganese oxide thin films for different oxygen concentration parameters were measured by x-ray diffraction (XRD) and operation current versus applied voltage ( I-V ) measurement. For I-V curves in different temperature, the ohmic conduction, space charge limited conduction (SCLC), schottky emission conduction, and hopping conduction mechanism of manganese oxide RRAM devices were discussed and verified in initial metallic filament path forming process. Finally, the excess oxygen ions, vacancy, and defect factor resulting in bipolar and unipolar resistive switching behavior of thin films RRAM devices will be explained and investigated by metallic filament path forming model.

Pr-doped ZnO thin films (Zn1−xPrxO) (x = 0.00, 0.01, 0.02, 0.04) were prepared on fluorine-doped tin oxide substrates by means of the sol–gel method and spin coating technology, followed by rapid thermal annealing treatment at 800 °C. The influence of Pr content on the structural and optical properties of the Zn1−xPrxO thin film was examined and discussed. The wurtzite hexagonal structural characteristics were investigated by X-ray diffraction analysis, and Pr3+ substitution for Zn2+ ions was indicated. Finally, the typical bipolar current-voltage switching curves and electrical conduction model of Zn1−xPrxO film resistive random access memory devices were discussed and investigated for low resistance state/high resistance state in the initial forming process.

Indium tin oxide (ITO; Indium oxide with tin doping) nanowires were first prepared via the electrochemical deposition and an oxidization method based on an AAO template. FE-SEM results show the synthesized ITO nanowires to have an approximate length of 8–10 μm with an aspect ratio close to 167. ITO nanowires with an In/Sn weight ratio of 8.8 (∼9:1) were observed from EDS. The crystal structure of ITO nanowires showed that all the peaks within the spectra can be indexed to In2O3 with a cubic structure. The ITO nanowire is single-crystalline determined from selected area electron diffraction (SAED) patterns. An optical energy gap (Eg) of the ITO nanowire is 3.8 eV.

Bi0.9Gd0.1FeO3 (BGFO) thin films were fabricated on Pt(111)/Ti/SiO2/Si(100) substrates by using the sol–gel technology. The effects of annealing temperature (400–700 °C) on microstructure and multiferroic properties of thin films were investigated. The X-ray diffraction analysis showed that the BGFO thin films had an orthorhombic structure. The thin films showed ferroelectric and ferromagnetic properties with remanent polarization (2Pr) of 10 μC/cm2, remnant magnetization (2Mr) of 2.4 emu/g and saturation magnetization (Ms) of 5.3 emu/g. A small leakage current density (J) was 4.64×10−8 A/cm2 under applied field 100 kV/cm. It was found that more than one conduction mechanism is involved in the electric field range used in these experiments. The leakage current mechanisms were controlled by Poole–Frenkel emission in the low electric field region and by Schottky emission from the Pt electrode in the high field region.

Praseodymium and niobium-substituted bismuth titanate (Bi 3.96 Pr 0.04 Ti 2.95 Nb 0.05 O 12 , BPTNO) thin films were deposited on Pt(111)/Ti/SiO 2 /Si(100) substrates by a sol–gel technology. The effects of annealing temperature (500 ~ 800 °C) on microstructure and electric properties of thin films were investigated. X-ray diffraction analysis shows that the BPTNO thin films have a bismuth-layered perovskite structure with preferred (117) orientation. The intensities of (117) peak increases with increasing annealing temperature. With the increase of annealing temperature from 500 °C to 800 °C, the grain size of BPTNO thin films increases. The highly (117)-oriented BPTNO thin films exhibits a high remnant polarization (2 P r ) of 48 μC/cm 2 and a low coercive field (2 E c ) of 110 kV/cm, fatigue free characteristics up to > 10 8 switching cycles. A small leakage current density ( J ) was 6.23 × 10 − 8 A/cm 2 at 200 kV/cm. The leakage current mechanisms were controlled by Poole–Frenkel emission in the low electric field region and by Schottky emission in the high field region.

The transparent ZnO and Zn0.96Fe0.04O nanocrystalline films were deposited on the glass substrates by sol–gel method followed by repaid thermal annealing treatment. The grain size of the ZnO films was decreased by the doping of Fe. X-ray diffraction measurements of the films showed the same wurtzite hexagonal structure and preferential orientation along the c-axis. Temperature dependence resistivity showed a semiconductor transport behavior for both compositions. At high temperature region, the transport mechanism can be fitted with semiconductor behavior by Arrhenius equation, σ(T) = σ0 exp[−(Ea/kT)m] with m = 1. The activation energy Ea is increased from 0.47 meV for pure ZnO film to 0.69 meV for Zn0.96Fe0.04O film obtained from equation. At low temperature region, the resistivity can be fitted well with the behavior of Mott variable range hopping, σ(T) = σh0 exp[−(T0/T)n] with n = 1/4. The results demonstrate that the crystallization and the corresponding carrier transport behavior of the Zn1 − xFexO films are affected by the doping of Fe in the Zn1 − xFexO films.

Sm–Ta co-doped Bi 4 Ti 3 O 12 (Bi 3.96 Sm 0.04 Ti 2.92 Ta 0.08 O 12 , BSTTO) thin films were fabricated on Pt(111)/Ti/SiO 2 /Si(100) substrates by sol–gel technology, and the microstructure, dielectric, ferroelectric and leakage current properties of the thin films were investigated. BSTTO thin film exhibits a high remanent polarization (2 P r ) of 46.2 μC/cm 2 and a low coercive field (2 E c ) of 102 kV/cm, fatigue-free characteristics up to ≧ 10 8 switching cycles. The 2 P r of the BSTTO thin film is larger than that of the Bi 4 Ti 3 O 12 thin film (2 P r = 26 μC/cm 2 ). In addition, the leakage current density of Sm–Ta co-doped Bi 4 Ti 3 O 12 thin film is 2.56 × 10 − 8 A/cm 2 , which is lower than that of the Bi 4 Ti 3 O 12 thin film (1.0 × 10 − 5 A/cm 2 ). These improvements in the ferroelectric and leakage current properties can be attributed to the enhanced stability of the oxygen in the Ti–O octahedron layer by the substitution with Sm and Ta for Bi 3 + and Ti 4 + in A-site and B-site of the BTO thin film, respectively.

Herein one-dimensional Sm-doped ZnO nanostructures have been successfully fabricated by a simple hydrothermal method at a low temperature of 90 � C. The effect of Sm doping on the microstructure, photoluminescence and magnetism of ZnO nanorods is also investigated. FE-SEM images show that the average diameter of the Sm-doped ZnO nanorods is obviously smaller than that of ZnO nanorods. Photoluminescence spectrum of Sm-doped ZnO nanorods shows a slightly red-shifted decrease of UV emission and an enhancement of photoluminescence performance of visible emission. Raman spectrum of Sm-doped ZnO nanorods reveals that the peak intensity corresponding to the E2 high mode decreases significantly compared with that of the pure ZnO nanorods, indicating the restraint of crystallization. Room temperature ferromagnetism is observed from magnetization curves of both ZnO and Sm-doped ZnO nanorods. The increase of the saturation magnetization induced by the Sm doping in the ZnO nanorods reveals an association with the increase of oxygen vacancies and oxygen interstitials.

Tantalum-substituted Bi4Ti3O12 (Bi4Ti3-x/5Tax/5O12, BTTO) thin films were fabricated on Pt(111)/Ti/SiO2/Si(100) substrates by sol–gel technology. The effects of various processing parameters, including Ta content (x=0∼0.08) and annealing temperature (500∼800 °C), on the growth and properties of thin films were investigated. X-ray diffraction analysis shows that the BTTO thin films have a bismuth-layered perovskite structure with preferred (117) orientation. With the increase of Ta content, the grain size of film decreased slightly, and highly (117)-oriented BTTO films were obtained in the composition of x=0.06. Ta doping on the B-site of Bi4Ti3O12 could induce the distortion of oxygen octahedral and decrease the oxygen vacancy concentration by a compensating effect. The highly (117)-oriented BTTO thin films with x=0.06 exhibits the maximum remanent polarization (2Pr) of 50 μC/cm2 and a low coercive field (2Ec) of 104 kV/cm, fatigue free characteristics up to ≧ 108 switching cycles.

Titanium oxide (TiO 2 ) thin films are prepared by the sol–gel method and annealed at 600 °C by conventional (CTA) and rapid thermal annealing (RTA) processes on fluorine-doped tin oxide -coated glass substrates for application as the work electrode for the dye-sensitized solar cells (DSSC). TiO 2 thin films are crystallized using a conventional furnace and the proposed RTA process at annealing rates of 5 °Cmin −1 and 600 °Cmin −1 , respectively. The TiO 2 thin films are characterized by X-ray diffraction, scanning electron microscopy and Brunauer–Emmett–Teller analysis. Based on the results, the TiO 2 films crystallized by RTA show better crystallization, higher porosity and larger surface area than those of CTA. The short-circuit photocurrent and open-circuit voltage values increased from 5.2 mAcm −2 and 0.6 V for the DSSC with the CTA-derived TiO 2 films to 8.3 mAcm −2 and 0.68 V, respectively, for the DSSC containing RTA-derived TiO 2 films.

Praseodymium-substituted bismuth titanate (Bi 3.2 Pr 0.8 Ti 3 O 12 , BPTO) thin films were successfully deposited on Pt(111)/Ti/SiO 2 /Si(100) substrates by spin coating with a sol-gel technology and rapid thermal annealing. The effects of annealing atmospheres (vacuum, ambient atmosphere and oxygen) on the growth and properties of thin films were investigated. The results show that the intensity of the (117) diffraction peak of Bi 3.2 Pr 0.8 Ti 3 O 12 film annealed in oxygen is stronger than those annealed in ambient atmosphere and vacuum. The XRD spectra demonstrated that a highly (117) orientation could be obtained when the Bi 3.2 Pr 0.8 Ti 3 O 12 thin film was annealed in an oxygen-sufficient environment. The BPTO thin films annealed in oxygen atmosphere exhibits the maximum remanent polarization (2P r ) of 49 μC/cm 2 and a low coercive field (2E c ) of 130 kV/cm, fatigue free characteristics up to ≥10 11 switching cycles. These results indicate that the BPTO thin film is useful in nonvolatile ferroelectric random access memory applications.

Nanocrystalline anatase TiO 2 thin films with different thicknesses (0.5-2.0 μm) have been deposited on ITO-coated glass substrates by a sol-gel method and rapid thermal annealing for application as the work electrode for dye-sensitized solar cells (DSSC). From the results, the increases in thickness of TiO 2 films can increase adsorption of the N3 dye through TiO 2 layers to improve the short-circuit photocurrent (J sc ) and open-circuit voltage (V oc ), respectively. However, the J sc and V oc of DSSC with a TiO 2 film thickness of 2.0 μm (8.5 mA/cm 2 and 0.61 V) are smaller than those of DSSC with a TiO 2 film thickness of 1.5 μm (9.2 mA/cm 2 and 0.62 V). It could be due to the fact that the increased thickness of Ti0 2 thin films also resulted in a decrease in the transmittance of TiO 2 thin films thus reducing the incident light intensity on the N3 dye. An optimum power conversion efficiency (η) of 2.9% was obtained in a DSSC with the TiO 2 film thickness of 1.5 μm.

High-performance pyroelectric infrared (IR) detectors have been fabricated using tantalate-doped lithium niobate LiNb 1 -x Ta x 0 3 (abbreviated as LNT, with x= 0-1.0) thin films deposited on Pt(1 1 11)/TilSiO 2 /Si(100) substrates by diol-based sol-gel processing, in which, tantalate (Ta) is adopted as dopant in lithium niobate. The randomly oriented LNT thin film exhibits a relatively small dielectric constant and a large pyroelectric coefficient. The pyroelectric characteristics of detectors with various tantalate contents, as a function of modulation frequency, were investigated. It was found that LiNb 0,8 Tau 0.2 O 3 had the largest voltage responsivity of 7020 (V/W) at 70 Hz, and a specific detectivity (D*) of 7.76 x 10 7 cm Hz 1/2 /W at 200 Hz. These results indicate that the LNT thin film with x=0.20 is most suitable for application as high-performance pyroelectric thin-film detectors.

Yttrium-substituted bismuth titanate (Bi 3.2 Y 0.8 Ti 3 O 12 , BYT) thin films were successfully deposited on Pt(1 1 1)/Ti/SiO 2 /Si(1 0 0) substrates by spin coating with a sol–gel technology and rapid thermal annealing. The effects of annealing temperature (500–800 °C) on microstructure and electrical properties of thin films were investigated. X-ray diffraction analysis shows that the BYT thin films have a bismuth-layered perovskite structure with preferred (1 1 7) orientation. The intensities of (1 1 7) peaks increases with increasing annealing temperature. With the increase of annealing temperature from 500 to 800 °C, the grain size of BYT thin films increases. The highly (1 1 7)-oriented BYT thin films exhibit a high-remnant polarization (2 P r ) of 58 μC/cm 2 and a low-coercive field (2 E c ) of 116 kV/cm, fatigue free characteristics up to >10 8 switching cycles. The leakage current density ( J ) were 4.38×10 −8 A/cm 2 at 200 kV/cm. These results indicate that the highly (1 1 7)-oriented BYT thin film is useful in nonvolatile ferroelectric random access memory applications.

The influence of La substitution by rare-earth elements on the magnetization behaviors of perovskite oxides, La0.7−x Lnx Pb0.3 MnO3 ( Ln = Pr , Nd, Gd, Dy, Sm and Y), is investigated. The replacement of La ion by Pr, Nd, Gd, Dy, Sm or Y results in a considerable decrease in the ferromagnetic ordering temperature T C and clearly irreversible behavior in the FC–ZFC curves showing a short-range spin order phase. The fact is in agreement with the smaller ionic radii of Pr, Nd, Gd, Dy, Sm and Y ions in contrast to La ion and the corresponding larger distortion of perovskite structures. The saturation magnetization M S increases as Pr or Nd content increases while M S decreases as Sm or Y content increases. Moreover, the saturation magnetization M S increases and then decreases as Gd or Dy content increases. These results can be explained in terms of the competition between the increase of ferromagnetically interacting spins due to the introduction of magnetic ions with f-shell electrons and suppression of ferromagnetism due to structure tuning induced by the small ionic radius of the interpolated cation into the La-site.

The transport properties in La0.7−xYxPb0.3MnO3 (0.0 ⩽ x ⩽ 0.2) is investigated. The substitution of La3+ ions by smaller nonmagnetic Y3+ leads to greater spin disorder and induces variations in the magnetotransport behavior. From resistivity versus temperature curves a metal–insulator transition phenomenon is observed at the transition temperature, TP, decreases as the Y content increases. The resistivity is well fitted using the equation ρ(T) = ρnexp[(T∗/T)n] with n = 1/4 and n = 1/2 at high and intermediate temperatures, respectively. The characteristic temperature T∗ varies with Y content in a manner consistent with the localization model of variable range hopping. Below TP, resistivity varies as a function of power law contributions, ρ = ρ0 + ρ2T2 + ρ5/2T5/2, corresponding to the electron scattering processes in the ferromagnetic phase.

Lithium tantalite (LiTaO3) thin films (∼0.5 μm ) have been successfully deposited on Pt (111)/ SiO 2 / Si (1 0 0) substrates by means of sol–gel spin-coating technology. Figures of merit for infrared detector were studied for the LiTaO3 thin films. There exists high figures of merit Fv of 2.1×10 −10 C cm/J and Fm of 2.4×10 −8 C cm/J because of the relative low dielectric constant (er) of 35 and high pyroelectric coefficient (γ) of 4.0×10 −8 C/cm 2 K of the films. The pyroelectric infrared detector fabricated by the LiTaO3 thin film exhibits a voltage reponsivity Rv of 4584 V/W at 20 Hz and a high specific detectivity D ∗ of 4.23×10 7 cm Hz 1/2 / W at 100 Hz .