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Bi1-xMgxFeO3 (BMFO, x = 0, 0.02, 0.04, 0.06 and 0.08) multiferroic films were directly synthesized on flexible stainless steel (FSS), save the bottom electrode process, by means of sol&ndash, gel spin-coating technology. The effects of different bending conditions on ferroelectric, dielectric and leakage-current properties of BMFO films were investigated. The leakage-current densities of BiFeO3 (BFO, x = 0) and BMFO (x = 0.06) films were 5.86 &times, 10&minus, 4 and 3.73 &times, 7 A/cm2, which shows that the BMFO (x = 0.06) has more than three orders of magnitude lower than that of BFO film. The residual polarization (2 Pr) can be enhanced from 120 to 140 &mu, C/cm2. The proper doping of Mg in BiFeO3 film could provide an effective method for reducing the leakage-current values as well as boosting the ferroelectric properties. In this study, the leakage-current mechanism of low electric field and high electric field of BMFO film is analyzed and established. In addition, the flexible BMFO film maintains practical ferroelectric and leakage-current properties at retention time of 106 s under different symmetry bending conditions. These results indicate that the BFMO film will be very practical in opto-electronic and storage device applications.

Zn1&minus, xMgxO (x = 0, 0.03, 0.05, and 0.07) nanocrystalline films were grown on silicon substrates using the sol&ndash, gel method. Furthermore, Zn1&minus, xMgxO vertically aligned hexagonal symmetrical nanorods with six reflection symmetries were fabricated on pure ZnO-seeded layer n-type silicon substrates via a low-temperature hydrothermal method to enhance the ultraviolet (UV) light response. The crystal microstructures and surface morphologies of nanocrystalline films and nanorod arrays were determined by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Transmission spectra showed that the increasing Mg content will increase the band gap energy from 3.28 to 3.46 eV. However, the current&ndash, voltage curves in the dark and under UV illumination showed that the UV response did not improve by the incorporation of magnesium. We changed the flat surface of films into symmetrical nanorod arrays and demonstrated they can significantly enhance the normalized photo-to-dark-current ratio up to ten times.

By a sol–gel method, a BiFeO3 (BFO) capacitor is fabricated and connected with the control thin film transistor (TFT). Compared with a control thin-film transistor, the proposed BFO TFT achieves 56% drive current enhancement and 7–28% subthreshold swing (SS) reduction. Moreover, the effect of the proposed BiFeO3 capacitor on IDS-VGS hysteresis in the BFO TFT is 0.1–0.2 V. Because dVint/dVGS > 1 is obtained at a wide range of VGS, it reveals that the incomplete dipole flipping is a major mechanism to obtain improved SS and a small hysteresis effect in the BFO TFT. Experimental results indicate that sol-gel BFO TFT is a potential candidate for digital application.

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.

GaAs p-i-n solar cells are studied using electroreflectance (ER) spectroscopy, light beam induced current (LBIC) mapping and photovoltaic characterization. Using ER measurements, the electric field across the pn junction of a wafer can be evaluated, showing 167 kV/cm and 275 kV/cm in the built-in condition and at &minus, 3 V reverse bias, respectively. In order to understand the effect of the interval between metal grids on the device&rsquo, s solar performance, we performed LBIC mapping and solar illumination on samples of different grid spacings. We found that the integrated photocurrent intensity of LBIC mapping shows a consistent trend with the solar performance of the devices with various metal grid spacings. For the wafer used in this study, the optimal grid spacing was found to be around 300 &mu, m. Our results clearly show the importance of the metal grid pattern in achieving high-efficiency solar cells.

The bipolar switching properties and electrical conduction mechanism of vanadium oxide thin-film resistive random-access memory (RRAM) devices obtained using a rapid thermal annealing (RTA) process have been investigated in high-resistive status/low-resistive status (HRS/LRS) and are discussed herein. In addition, the resistance switching properties and quality improvement of the vanadium oxide thin-film RRAM devices were measured by x-ray diffraction (XRD) analysis, x-ray photoelectron spectrometry (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and current–voltage (I–V) measurements. The activation energy of the hopping conduction mechanism in the devices was investigated based on Arrhenius plots in HRS and LRS. The hopping conduction distance and activation energy barrier were obtained as 12 nm and 45 meV, respectively. The thermal annealing process is recognized as a candidate method for fabrication of thin-film RRAM devices, being compatible with integrated circuit technology for nonvolatile memory devices.

Bipolar resistive switching properties and endurance switching behavior of the neodymium oxide (Nd2O3) thin films resistive random access memory (RRAM) devices for a high resistive status/low resistive status (HRS/LRS) using a low temperature supercritical carbon dioxide fluid (SCF) improvement post-treatment process were investigated. Electrical and physical properties improvement of Nd2O3 thin films were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and current versus voltage (I-V) measurement. The metal-like behavior of ohmic conduction mechanism and metallic cluster reaction of hopping conduction mechanism in initial metallic filament path forming process of the SCF-treated thin films RRAM devices was assumed and discussed. Finally, the electrical conduction mechanism of the thin films RRAM derives for set/reset was also discussed and verified in filament path physical model.

Bi0.8Pr0.2Fe0.95Mn0.05O3/Bi3.96Gd0.04Ti2.95W0.05O12 (BPFMO/BGTWO) bilayer thin films with Multiferroic/Ferroelectric (MF/FE) structures were deposited onto Pt(111)/Ti/SiO2/Si(100) substrates by using the sol-gel method with rapid thermal annealing. The BPFMO/BGTWO thin films exhibited well-saturated ferromagnetic and ferroelectric hysteresis loops because of the electro-magnetic coupling induced by the MF/FE structure. The remnant magnetization (2Mr) and remnant polarization (2Pr) were 4.6 emu/cm3 and 62 μC/cm2, respectively. Moreover, the bipolar I-V switching curves of BPFMO/BGTWO bilayer thin films resistive random access memory (RRAM) devices were discussed, and investigated for LRS/HRS.

The Bi0.85 Eu0.15 FeO3 /Bi3.2 Y0.8 Ti3 O12 bilayer thin films were prepared on Pt(111)/Ti/SiO 2/Si(100) substrates using the sol-gel process and annealed by rapid thermal annealing in various annealing environments (ambient atmosphere and oxygen). The multiferroic/ferroelectric bilayer thin films were composed of 0.8-μ m thickness Bi0.85 Eu0.15 FeO3 and 0.2-μ m thickness of Bi3.2 Y0.8 Ti3 O12 thin film. The effects of annealing atmospheres (ambient atmosphere and oxygen) on the growth and properties of thin films were investigated. The results show that the intensities of the (117) diffraction peak of Bi3.2Y0.8Ti3O 12 film and (110) diffraction peak of Bi0.85Eu0.15FeO3 annealed in oxygen is stronger than those annealed in an ambient atmosphere. The Bi0.85Eu0.15FeO3/Bi3.2Y0.8Ti3O12 bilayer thin films annealed in the oxygen atmosphere exhibit the maximum remanent polarization (2\mbi Pr) and remnant magnetization (2Mr) of 26 μ C/cm2 and 3.44 emu/g, respectively. The improved magnetic and ferroelectric properties can be attributed to the elimination of defects, such as oxygen vacancy and vacancy complexes.

Bi0.9Eu0.1FeO3 (BEFO) thin films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates using the sol-gel method and rapid thermal annealing in an oxygen atmosphere. 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 BEFO thin films had an orthorhombic structure. The thin films showed ferroelectric and ferromagnetic properties with remanent polarization (2Pr) of 15 μC/cm2 and remnant magnetization (2Mr) of 4.2 emu/g. The leakage current density (J) of the BEFO thin film annealed at 700 °C was 4.25t10-8& A/cm2 at 150 kV/cm. The leakage current was affected not only by the microstructure but also by the interface between the Pt electrode and the BEFO thin films. Moreover, it was found that more than one conduction mechanism was involved in the electric field range used in these experiments. In the low electric field region, the leakage current was controlled by Poole-Frenkel emission. However, the mechanism could be explained by Schottky emission from the Pt electrode in the high electric field region.

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.

TransparentZn1-xMgxO(x=0.01, 0.03, and 0.05) nanocrystalline films were prepared by sol-gel method followed by thermal annealing treatment of 700°C. Mg doping effect on the microstructural and optical properties of theZn1-xMgxOfilms is investigated. From SEM images of all films, mean sizes of uniform spherical grains increase progressively. Pure wurtzite structure is obtained from the results of XRD. Grain sizes increase from 34.7 nm forx=0.01and 37.9 nm forx=0.03to 42.1 nm forx=0.05deduced from the XRD patterns. The photoluminescence spectra of the films show a strong ultraviolet emission and a weak visible light emission peak. The enhancement of ultraviolet emission and reduction of visible emission are observed due to the increase of Mg doping concentration and the corresponding decrease of oxygen vacancy defects. Besides, the characteristics of the dark/photo currents withn-Zn1-xMgxO/n-Siheterojunction are studied for photodetector application.

Aligned ZnO nanowires with different lengths (1 to approximately 4 μm) have been deposited on indium titanium oxide-coated glass substrates by using the solution phase deposition method for application as a work electrode in dye-sensitized solar cells (DSSC). From the results, the increases in length of zinc oxide (ZnO) nanowires can increase adsorption of the N3 dye through ZnO nanowires to improve the short-circuit photocurrent (Jsc) and open-circuit voltage (Voc), respectively. However, the Jsc and Voc values of DSSC with ZnO nanowires length of 4.0 μm (4.8 mA/cm2 and 0.58 V) are smaller than those of DSSC with ZnO nanowires length of 3.0 μm (5.6 mA/cm2 and 0.62 V). It could be due to the increased length of ZnO nanowires also resulted in a decrease in the transmittance of ZnO nanowires thus reducing the incident light intensity on the N3 dye. Optimum power conversion efficiency (η) of 1.49% was obtained in a DSSC with the ZnO nanowires length of 3 μm.

One-dimensional pure zinc oxide (ZnO) and Y-doped ZnO nanorod arrays have been successfully fabricated on the silicon substrate for comparison by a simple hydrothermal process at the low temperature of 90°C. The Y-doped nanorods exhibit the same c-axis-oriented wurtzite hexagonal structure as pure ZnO nanorods. Based on the results of photoluminescence, an enhancement of defect-induced green-yellow visible emission is observed for the Y-doped ZnO nanorods. The decrease of E2(H) mode intensity and increase of E1(LO) mode intensity examined by the Raman spectrum also indicate the increase of defects for the Y-doped ZnO nanorods. As compared to pure ZnO nanorods, Y-doped ZnO nanorods show a remarked increase of saturation magnetization. The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods.