Microstructure and electrical properties of (Zr, Sn)TiO4 thin film deposited on Si(1 0 0) using a sol-gel process

Polycrystalline zirconium tin titanate (Zr_0.8Sn_0.2TiO₄, ZST) thin films with thickness of 81 nm were deposited successfully along the (1 0 0) on a p-type Si substrate by an improved sol-gel method. The deposited films were crystallized when annealing temperature was up to 450 °C. The thickness and compositions of the interface layer between the ZST films and Si substrate were identified by high-resolution transmission electron microscope (HRTEM). The electrical properties such as leakage current density, flat-band voltage and capacitance of the films were measured and discussed. Furthermore, the mechanism of the leakage current was also investigated.     

Synthesis and electrical conductivity of various melilite-type electrolytes Ln1 + xSr1 − xGa3O7 + x/2

Melilite type ceramics ABC₃O₇ such as La_1.54Sr_0.46Ga₃O_7.27 are a new class of oxide conductors where the conductivity is carried out through interstitial oxygen ions. This work presents the attempt to replace the A-site element La with the other lanthanide elements and Y, resulting in various Ln_1 + xSr_1 − xGa₃O_7 + x/2 ceramics, in which Ln = La, Pr, Nd, Sm, Eu, Gd, Dy, Yb, Y, and 0.1 < x < 0.54. X-ray diffraction analysis shows that the melilite structure could be formed when the replacement is conducted with most lanthanides but not Yb and Y. Impedance spectroscopy demonstrates that the conductivity decreases dramatically with the decreasing of Ln³⁺ size and the charge-carrier concentration. These results suggest that, as an interstitial oxide ion electrolyte, La_1.54Sr_0.46Ga₃O_7.27 is the most promising ceramic in the Ln_1 + xSr_1 − xGa₃O_7+x/2 melilite family since La³⁺ has the largest ionic radius of the lanthanide elements.     

Electrical and electrochemical properties of glass-ceramic electrolytes in the systems Li2S-P2S5-P2S3 and Li2S-P2S5-P2O5

Electrical and electrochemical properties of the 70Li₂S·(30 − x)P₂S₅·xP₂S₃ and the 70Li₂S·(30 − x)P₂S₅·xP₂O₅ (mol%) glass-ceramics prepared by the mechanical milling technique were investigated. Glass-ceramics with 1 mol% P₂S₃ and 3 mol% P₂O₅ showed the highest conductivity of 5.4 × 10^− 3 S cm^− 1 and 4.6 × 10^− 3 S cm^− 1, respectively. Moreover, these glass-ceramics showed higher electrochemical stability than the 70Li₂S·30P₂S₅ (mol%) glass-ceramic. From the XRD patterns of the obtained glass-ceramics, trivalent phosphorus and oxygen were incorporated into the Li₇P₃S₁₁ crystal. We therefore presume that the Li₇P₃S₁₁ analogous crystals, which were formed by incorporating trivalent phosphorus and oxygen into the Li₇P₃S₁₁ crystal, improve the electrical and electrochemical properties of the glass-ceramics. An all-solid-state cell using the 70Li₂S·29P₂S₅·1P₂S₃ (mol%) glass-ceramic as solid electrolyte operated under the high current density of 12.7 mA cm^− 2 at the high temperature of 100 °C. The cell showed an excellent cyclability of over 700 cycles without capacity loss.     

Molecular simulation of C60 adsorption onto a TiO2 rutile (1 1 0) surface

A Monte Carlo molecular simulation study is presented on the adsorption and growth of C₆₀ films on the surface of the (1 1 0) face of rutile. Simulations are performed for a temperature of 600 K using atomistic models both for the fullerene molecules and the TiO₂ surface. It is found in this work that C₆₀ is adsorbed preferably in an ordered arrangement along the surface depressions over the exposed undercoordinated Ti cations. At low densities adsorption occurs preferably at alternate rows, with locations in consecutive rows being occupied appreciably only at higher C₆₀ densities. At low densities, the fullerene molecules tend to aggregate into islands in the surface plane. Additional layers of C₆₀ form only as the density increases, and do so before a monolayer is completed in all consecutive rows. Full monolayer capacity obtained at the highest densities is about 0.9 C₆₀ molecules per nm², but this is only achieved by completing the packing of molecules in interstices at a slightly upper level. The fraction of the molecules that lie closest to the surface only amounts to 0.6 molecules per nm².     

Molten salt synthesis of Li1 + x (Ni0.5Mn0.5)1 − xO2 as cathode material for Li-ion batteries

Li_1 + x(Ni_0.5Mn_0.5)_1 − xO₂ cathode material for Li-ion batteries has been prepared by a molten salt method using Li₂CO₃ salt. The influences of synthetic temperature and time have been intensively investigated. It is easy to obtain materials with a hexagonal α-NaFeO₂ structure except broad peaks between 20° and 25°. Nickel in Li_1 + x(Ni_0.5Mn_0.5)_1 − xO₂ is oxidized to a trivalent state while manganese maintained a tetravalent state. It is found that the discharge capacities of all samples increase with cycling. The sample prepared at 850 °C for 5 h has a discharge capacity of 130 mAh g^− 1 between 2.5 and 4.5 V versus V_Li+/Li at a specific current of 0.13 mA cm^− 2 after 50 cycles at 25 °C.     

Preparation of LiMn2O4 thin films by a sol–gel method

LiMn₂O₄ thin films were prepared by a sol–gel method using spin-coating and annealing processes. Anhydrous Mn(CH₃COCHCOCH₃)₃ (manganese acetylacetonate) and LiCH₃COCHCO–CH₃ (lithium acetylacetonate) were chosen as source materials. The film electrochemical properties depended on the drying temperature even when subjected to the same annealing conditions. The discharge capacity of annealed film increased as the drying temperature was increased. However, the rate of capacity fading during cycling increased as the drying temperature was increased.     

The epitaxial sexiphenyl (0 0 1) monolayer on TiO2(1 1 0): A grazing incidence X-ray diffraction study

A para-sexiphenyl monolayer of near up-right standing molecules (nominal thickness of 30 Å) is investigated in-situ by X-ray diffraction using synchrotron radiation and ex-situ by atomic force microscopy. A terrace like morphology is observed, the step height between the terraces is approximately one molecular length. The monolayer terraces, larger than 20 μm in size, are extended along the [0 0 1] direction of the TiO₂(1 1 0) substrate i.e. along the Ti-O rows of the reconstructed substrate surface. The structure of the monolayer and its epitaxial relationship to the substrate is determined by grazing incidence X-ray diffraction. Extremely sharp diffraction peaks reveal high crystalline order within the monolayer, which was found to have the bulk structure of sexiphenyl. The monolayer terraces are epitaxially oriented with the (0 0 1) plane parallel to the substrate surface (out-of-plane order). Four epitaxial relationships are observed. This in-plane alignment is determined by the arrangement of the terminal phenyl rings of the sexiphenyl molecules parallel to the oxygen rows of the substrate.     

Impacts of compressive strain on phase diagram of epitaxial Pr0.5Sr0.5MnO3 films grown on LaAlO3 (0 0 1)

Series Pr_0.5Sr_0.5MnO₃ (PSMO) films of thickness ranging from 20 to 400 nm were epitaxially grown on (0 0 1)-oriented LaAlO₃ using pulsed laser deposition method. The biaxial compressive strain effect on phase transition of the films was systematically investigated by both electrical and magnetic measurements. The 60 nm film shows a ferromagnetic metal to antiferromagnetic insulator (FMM-AFI) transition at a temperature of ∼190 K. Such a FMM-AFI transition is depressed as the films become thicker, and finally disappears in the strain-relaxed situation. On the other hand, the Curie temperature is remarkably enhanced (∼50 °C) when the film thickness increases from 60 to 400 nm. These results may yield the possibility to modulate the phase transitions by varying the structural strain.     

Solid-state synthesis and magnetic properties of epitaxial FePd3(0 0 1) films

The solid-state synthesis of magnetically soft phase FePd₃ in epitaxial Pd(0 0 1)/Fe(0 0 1)/MgO(0 0 1) film systems was studied experimentally. The system had a Fe to Pd ratio of 1:3. An increase to 450 °C leads to the formation of three variants of ordered L1₀-FePd crystallites. At 500 °C, the solid-state reaction of unreacted Pd with L1₀-FePd crystallites initiates the growth of an ordered epitaxial L1₂-FePd₃(0 0 1) layer. When annealing at 650 °С, a gradual disordering is observed. The magnetic anisotropy (K₁=−2.0×10³ erg/cm³) and the saturation magnetization (M_S=650 emu/cm³) of the disordered FePd₃ phase were determined.     

(Mo + N) codoped TiO2 for enhanced visible-light photoactivity

A series of Ti_1−xMo_xO_2−yN_y samples were prepared by using sol-gel method and characterized by X-ray diffraction, transmission electron microscopy and UV-vis absorption spectroscopy. All Ti_1−xMo_xO_2−yN_y samples are anatase phase. It is found that Mo, N mono-doping can increase visible light absorption, while (Mo + N) co-doping can greatly enhance absorption in whole visible region. Results of our first-principles band structure calculations reveal that (Mo + N)-doping, especially passivated co-doping can increase the up-limit of dopant concentration and create more impurity bands in the band gap of TiO₂, which leads to a greatly increase of its visible-light absorption without a decrease of its redox potential. It reveals that (Mo + N) co-doped TiO₂ is promising for a photocatalyst with high photocalystic activity under visible light.     

X-ray multiple diffraction in the characterization of TiNO and TiO2 thin films grown on Si(0 0 1)

TiO₂ and TiN_xO_y thin films grown by low pressure metal-organic chemical vapor deposition (LP-MOCVD) on top of Si(0 0 1) substrate were characterized by X-ray multiple diffraction. X-ray reflectivity analysis of TiO₂[1 1 0] and TiNO[1 0 0] polycrystalline layers allowed to determine the growth rate (−80 Å/min) of TiO₂ and (−40 Å/min) of TiNO films. X-ray multiple diffraction through the Renninger scans, i.e., ?-scans for (0 0 2)Si substrate primary reflection is used as a non-conventional method to obtain the substrate lattice parameter distortion due to the thin film conventional deposition, from where the information on film strain type is obtained.     

Li1+xGe2-xAlxP3O12系统的相关系和电导

本文研究了Li_1+xGe_2-xAl_xP₃O₁₂系统的相组成和电导的关系。发现用LiGe₂P₃O₁₂作为基体化合物,通过离子置换可以得到好的锂离子导体。用Al³⁺置换LiGe₂P₃O₁₂中的Ge⁴⁺,在0关键词：     

Optical and hydrophilic properties of Cr doped TiO2-SiO2 nanostructure thin film

Cr doped TiO₂-SiO₂ nanostructure thin film on glass substrates was prepared by a sol-gel dip coating process. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the structural and chemical properties of the films. A UV-vis spectrophotometer was used to measure the transmittance spectra of the thin film. The hydrophilicity of the thin film during irradiation and storage in a dark place was measured by a contact angle analyzer. The results indicated that Cr doping has a significant effect on the transmittance and super-hydrophilicity of TiO₂-SiO₂ thin film.     

Influence of MgO and ZrO2 buffer layers on dielectric properties of Ba(Zr0.20Ti0.80)O3 thin films prepared by sol-gel processing

Ba(Zr_0.20Ti_0.80)O₃ (BZT) thin films are deposited on Pt(1 1 1)/Ti/SiO₂/Si, MgO and ZrO₂ buffered Pt(1 1 1)/Ti/SiO₂/Si substrates by a sol-gel process. The BZT thin films directly grown on Pt(1 1 1)/Ti/SiO₂/Si substrates exhibit highly (1 1 1) preferred orientation, while the films deposited on Pt(1 1 1)/Ti/SiO₂/Si substrates with MgO and ZrO₂ buffer layers show highly (1 1 0) preferred orientation. At 100 kHz, dielectric constants are 417, 311 and 321 for the BZT thin films grown on Pt(1 1 1)/Ti/SiO₂/Si, MgO and ZrO₂ buffered Pt(1 1 1)/Ti/SiO₂/Si substrates, respectively. The difference in dielectric properties of three BZT films can be attributed to the series capacitance effect, interface conditions and their orientations.     

NMR study on an Li+-ion diffusion in the solid solution Li4−x(PO4)x(SiO4)1−x with the Li4SiO4-type structure

Diffusive motion of an Li⁺ion in the solid solution Li_4?x(PO₄)_x(SiO₄)_1?x (0 ≦ x ≦ 0.35) was studied by ⁷Li pulsed nmr between ? 70 and 440°C. Activation energies for an Li⁺ ion diffusion decreased monotonically with increasing x in the composition. These values are smaller than those reported from the measurement of ionic conductivity. Discrepency seems to result from the local nature of an Li⁺ diffusion observed by nmr contrary to the long-range one in the ionic conduction.     

Scanning tunneling microscopy study on a BC3 covered NbB2(0 0 0 1) surface

We have investigated a BC₃ covered NbB₂(0 0 0 1) surface using scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and low energy electron diffraction (LEED). The STM images reveal characteristic features of a Moiré pattern reflecting an incommensurate relation of the BC₃ sheet with the substrate: bright protrusions with the periodicity of the substrate lattice are modulated in intensity with the periodicity of the BC₃ lattice. As a result, the surface exhibits nm-scale patchy regions with either the √3 × √3 or the 1 × 1 structure of the substrate. The two-dimensional Fourier transformation pattern of the STM image is consistent with the LEED pattern proving the epitaxial and incommensurate relationship between BC₃ surface sheet and substrate. No feature of a predicted superconducting gap was found in STS spectra measured at 5 K.     

Electrical and optical properties of thermally-evaporated thin films from A2[TiO(C2O4)2] (A = K, PPh4) and 1,8-dihydroxyanthraquinone

In this work, the synthesis of molecular materials formed from A₂[TiO(C₂O₄)₂] (A = K, PPh4) and 1,8 dihydroxyanthraquinone is reported. The synthesized materials were characterized by atomic force microscopy (AFM), infrared (IR) and ultraviolet-visible (UV-vis) spectroscopy. IR spectroscopy showed that the molecular-material thin-films, deposited by vacuum thermal evaporation, exhibit the same intra-molecular vibration modes as the starting powders, which suggests that the thermal evaporation process does not alter the initial chemical structures. Electrical transport properties were studied by dc conductivity measurements. The electrical activation energies of the complexes, which were in the range of 0.003-1.16 eV, were calculated from Arrhenius plots. Optical absorption studies in the wavelength range of 190-1090 nm at room temperature showed that the optical band gaps of the thin films were around 1.9-2.3 eV for direct transitions Eg_d. The cubic NLO effects were substantially enhanced for materials synthesized from K₂[TiO(C₂O₄)₂], where χ⁽³⁾ (−3ω; ω, ω, ω) values in the promising range of 10⁻¹² esu have been evaluated.     

Structural and luminescence characterization of synthetic Cr-doped Ni3(PO4)2

Ni_3–xCr_2x/3(PO₄)₂ (x=0 and 0.02) microcrystalline powders were obtained as single phases via a modified sol–gel Pechini-type in situ polymerizable complex method. The samples were characterized using scanning electron microscopy, X-ray diffraction, cathodoluminescence (CL), and thermoluminescence (TL) techniques. We found that Cr³⁺ doping modified the average particle and distribution. The mean particle size was 0.441 μm for Ni₃(PO₄)₂ and 0.267 μm for Ni_2.98Cr_0.013(PO₄)₂. The results also reveal that Cr³⁺ doping notably enhanced the CL and TL UV-blue emission.     

Structural and optical properties of low temperature synthesized Nanostructured BiFeO3 thin films

Nanostructured bismuth ferrite (BiFeO₃) thin films were deposited on glass substrate by the sol-gel process. The as-fired film at 250 °C was found to be amorphous crystallizing to pure rhombohedral phase after annealing at 450 °C for 2 h in air. The XRD pattern shows that the sample is polycrystalline in nature. The average grain size of the film calculated from the XRD data was found to be 16 nm. The as-fired film show high transmittance that decreases after crystallization. The absorption edge of the films was found to be sharper and shifting towards the lower energy as the annealing temperature increases. The optical energy band gaps of the amorphous and crystalline films were found to be 2.63 and 2.31 eV, respectively. The refractive indices of the amorphous and crystalline films were 2.05 and 2.26, respectively.     

Structural and magnetic properties of sol-gel Co2xNi0.5−x Zn0.5−xFe2O4 thin films

Nanocrystalline Co_2xNi_0.5−xZn_0.5−xFe₂O₄ (x=0−0.5) thin films have been synthesized with various grain sizes by a sol-gel method on polycrystalline silicon substrates. The morphology as well as magnetic and microwave absorption properties of the films calcined at 1073 K were studied using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. All films were uniform without microcracks. The Co content in the Co-Ni-Zn films resulted in a grain size ranging from 15 to 32 nm while it ranged from 33 to 49 nm in the corresponding powders. Saturation and remnant magnetization increased with increase in grain size, while coercivity demonstrated a drop due to multidomain behavior of crystallites for a given value of x. Saturation magnetization increased and remnant magnetization had a maximum as a function of grain size independent of x. In turn, coercivity increased with x independent of grain size. Complex permittivity of the Co-Ni-Zn ferrite films was measured in the frequency range 2-15 GHz. The highest hysteretic heating rate in the temperature range 315-355 K was observed in CoFe₂O₄. The maximum absorption band shifted from 13 to 11 GHz as cobalt content increased from x=0.1 to 0.2.