Effect of annealing temperature on nanocrystalline TiO2 thin films prepared by sol–gel dip coating method

Nanocrystalline TiO₂ thin films have been prepared by sol–gel dip coating method. X-ray diffraction results showed the formation of anatase phase TiO₂ with grain size in the range of 18–26 nm. The HRTEM studies show that the average particle size of TiO₂ is 24 nm. The EDX analysis confirmed that Ti and O elements are present in the samples. The optical absorption spectra reveal that the absorption edge shifts towards longer wavelength side with increase in annealing temperature.     

Electroluminescence properties of In-doped Zn2SiO4 thin films prepared by sol–gel process

The effect of In doping on the electroluminescence (EL) properties of Zn₂SiO₄:In thin films was investigated. In-doped Zn₂SiO₄ thin films were deposited on BaTiO₃ substrates and their EL properties were characterized in this study. X-ray powder diffraction patterns of In-doped Zn₂SiO₄ powders revealed a single phase of Zn₂SiO₄ for In concentrations up to approximately 1.5 mol%, whereas a secondary phase of In₂O₃ was observed for In concentrations in the range of 2–10 mol%. The maximum luminance of thin film electroluminescent (TFEL) devices varied significantly with the amount of In doping. The highest luminance with blue emission was obtained when 2 mol% In was doped. The blue emission of In-doped Zn₂SiO₄ thin film may be related to the In substitution for Zn. The 2 mol% In-doped Zn₂SiO₄ thin film exhibited blue emission with CIE color coordinates of x=0.208 and y=0.086.     

Effect of annealing temperature on the structural and optical properties of ZnO thin films prepared by sol–gel method

In this work, ZnO thin films were synthesized by sol–gel method on glass substrates followed by calcinations on different temperatures. The effect of annealing temperature on the structure and optical properties of the films was studied. The structural characteristics of the samples were analyzed by X-ray diffraction and atomic force microscope. The optical properties were studied by a UV-visible spectrophotometer. The results show that all the prepared ZnO thin films have a high preferential oriented c-axis orientation with compact hexagonal wurtzite structure. With the increasing annealing temperature (mse.ufl.edu), the intensity of (002) peak, particle size, surface RMS roughness, and absorbance of the ZnO thin films were increased as well. On the contrary, the transmittance and optical band gaps were decreased.     

Effect of calcination atmosphere on photoluminescence properties of nanocrystalline ZrO2 thin films prepared by sol–gel dip coating method

Highly transparent and homogeneous nanocrystalline ZrO₂ thin films were prepared by the sol–gel dip coating method. The X-ray diffraction (XRD) pattern of ZrO₂ thin films calcined in air, O₂ or N₂ shows the formation of tetragonal phase with varying crystallite size. X-ray photoelectron spectroscopy (XPS) gives Zr 3d and O 1s spectra of thin film annealed in air, which reveal zirconium suboxide component (ZrO_x, 0<x<2), Zr–O bond and surface defects. An average transmittance greater than 85% (in UV–vis region) is observed in all calcined samples. Photoluminescence (PL) reveals an intense emission peak at 379 nm and weak peaks at 294, 586 and 754 nm for ZrO₂ film calcined in air. An enhancement of PL intensity and red-shift is observed in films calcined in O₂ and N₂ atmosphere. This is due to the reconstruction of zirconium nanocrystal interfaces and vacancies, which help passivate the non-radiative defects. The oxygen deficient defect, which is due to the distorted Zr–O bond, is suggested to be responsible for photoluminescence. The defect states in the nanocrystalline zirconia thin films play an important role in the energy transfer process. The luminescence defects in the film make it suitable for gas sensors development and tunable lasers.     

Nanostructures and luminescence properties of porous ZnO thin films prepared by sol–gel process

ZnO thin films containing nano-sized pores were synthesized on solid substrates through a sol–gel process by accommodating cetyl-trimethyl-ammonium bromide (CTAB) as an organic template in the precursor solution. By X-ray diffraction the resultant ZnO films were found to possess ordered pore arrays forming lamellar structure with the spacing between two adjacent pores being ∼3.0 nm. Photoluminescence measurements indicated that the surfactants effectively passivated the surface defects of the ZnO films responsible for the green emission. Al doping was found to improve not only the lamellar structure of the pore arrays but also the near-band-gap emission intensity while the suppression effect of CTAB on the green emission remained undisturbed. With a proper control of doping level, the optical property as well as the structural integrity can be tailored to augment the potential of ZnO films for the optoelectronics and sensor applications.     

Sol–gel derived ferroelectric Bi3.15Nd0.85Ti3O12 thin films of predominant 100/010/119 orientation deposited both on Nb-doped (011)SrTiO3 and on (011)SrRuO3/(011)SrTiO3

Ferroelectric Bi_3.15Nd_0.85Ti₃O₁₂ (BNdT) thin films of predominant 100/010/119 orientation were grown through a cheap and simple sol–gel process both on Nb-doped (011)SrTiO₃ and on (011)SrRuO₃/(011)SrTiO₃. Using rapid heating rates during crystallization, films containing 28% (100)/(010)-oriented grains plus 19% (119)-oriented grains were obtained on SrRuO₃/SrTiO₃, while 30% (100)/(010)- and 18% (119)-oriented grains were obtained on Nb:SrTiO₃. The films consist of columnar grains and 90° a–b domains exist in large BNdT grains. The BNdT thin films exhibit excellent ferroelectric and dielectric properties with a remanent polarization 2P_r=39.2 μC/cm² and a dielectric constant ε_r=184.5. PACS 77.80.Fm; 77.80.Dj; 68.60.Wm; 68.55.Jk; 68.37.Lp     

Electrical and optical properties of Sb-doped ZnO thin films synthesized by sol–gel method

Sb-doped ZnO thin films with different values of Sb content （from 0 to 1.1 at.%） are deposited by the sol-gel dip- coating method under different sol concentrations. The effects of Sb-doping content, sol concentration, and annealing ambient on the structural, optical, and electrical properties of ZnO films are investigated. The results of the X-ray diffraction and ultraviolet-visible spectroscopy （UV-VIS） spectrophotometer indicate that each of all the films retains the wurtzite ZnO structure and possesses a preferred orientation along the c axis, with high transmittance （〉 90%） in the visible range. The Hall effect measurements show that the vacuum annealed thin films synthesized in the sol concentration of 0.75 mol/L each have an adjustable n-type electrical conductivity by varying Sb-doping density, and the photoluminescence （PL） spectra revealed that the defect emission （around 450 nm） is predominant. However, the thin films prepared by the sol with a concentration of 0.25 mol/L, despite their poor conductivity, have priority in ultraviolet emission, and the PL peak position shows first a blue-shift and then a red-shift with the increase of the Sb doping content.     

Structures and local ferroelectric polarization switching properties of orthorhombic YFeO_3 thin film prepared by a sol–gel method

Orthorhombic YFeO_3 thin film was prepared on La_(0.67)Sr_(0.33)MnO_3/LaAlO_3 substrate by a sol-gel spin-coating method. The structures of the YFeO_3/La_(0.67)Sr_(0.33)MnO_3/LaAlO_3(YFO/LSMO/LAO) sample were detected by x-ray diffraction pattern, Raman spectrometer, scanning electron microscopy, and atomic force microscope. The local ferroelectric polarization switching properties of the orthorhombic YFO film were confirmed by piezoresponse force microscopy(PFM) for the first time. The results show that the YFO film deposited on LSMO/LAO possesses orthorhombic structure,with ultra-fine crystal grains and flat surface. The leakage current of the YFO film is 8.39 × 10~(-4) A·cm~(-2) at 2 V,with its leakage mechanism found to be an ohmic behavior. PFM measurements indicate that the YFO film reveals weak ferroelectricity at room temperature and the local switching behavior of ferroelectric domains has been identified. By local poling experiment, polarization reversal in the orthorhombic YFO film at room temperature was further observed.     

Study of NiCuZn ferrite powders and films prepared by sol gel method

This paper reports that a series of NiCuZn ferrite powders and films are prepared by using sol-gel method.The effects of raw material composition and the calcinate temperature on magnetic properties of them are investigated.The NiCuZn ferrite powders are prepared by the self-propagating high-temperature synthesis method and subsequently heated at 700 C～1000 C.The results show that NiCuZn ferrite powders with single spinel phase can be formed after heat-treating at 750 C.Powders obtained from Ni 0.4 Cu 0.2 Zn 0.4 Fe 1.9 O 4 gel have better magnetic properties than those from gels with other composition.After heat-treating at 900 C for 3 h,coercivity H c and saturation magnetization M s are 9.7 Oe (1 Oe=80 A/m) and 72.4 emu/g,respectively.Different from the powders,NiCuZn films produced on Si (100) from the Ni 0.4 Cu 0.2 Zn 0.4 Fe 2 O 4 gel formed at room temperature possess high properties.When heat-treating condition is around 600 C for 6 min,samples with low H c and high M s will be obtained.The minimal H c is 16.7 Oe and M s is about 300 emu/cm 3.In comparison with the films prepared through long-time heat treating,the films prepared through short heat-treating time exhibits better soft magnetic properties.     

Influence of post-deposition annealing on the structural and optical properties of ZnO thin films prepared by sol–gel and spin-coating method

Thin films of zinc oxide have been deposited onto (0001) sapphire substrate by sol–gel and spin-coating methods. The XRD pattern showed that the crystallinity of the annealed ZnO films had improved in comparison with that of the as-grown films. Photoluminescence spectra revealed a two-line structure, which is identified in terms of UV emission and defect-related emission. The emission intensity was found to be greatly dependent on heat treatment. Host phonons of ZnO and a shift of the _E2$E_2$ (high) peak from its position have been observed from Raman spectra. The surface morphologies of the film had been improved after annealing was observed from AFM images.     

Si基铁电Bi3.15Nd0.85Ti3O12多层薄膜的一致取向生长和性能的研究

采用脉冲激光沉积(PLD)技术，利用LSCO/CeO₂/YSZ多异质缓冲层，在Si(100)基 片上成功地制备了c轴一致取向的Bi_3.15Nd_0.85Ti₃O12(BNT)铁电薄膜.利用X射线衍射(XRD)和扫描电镜(SEM)分析测定了薄膜的相结构 、取向和形貌特征，考察了沉积温度和氧分压对BNT薄膜微结构、取向和形貌的影响，确定 了BNT薄膜的最佳沉积条件.对在优化的条件下制备得到的BNT薄膜的C-V曲线测试得到了典型 的蝴蝶形曲线，表明该薄膜具有较好的电极化反转存储特性.最后讨论了BNT薄膜铁电性能与 薄膜取向的相关性. 关键词： 3.15Nd_0.85Ti₃O₁₂')" href="#">Bi_3.15Nd_0.85Ti₃O₁₂ 铁电薄 膜 多层异质结 脉冲激光沉积     

Physical properties of NxTiO2 prepared by sol–gel route

The compounds N_xTiO₂(x=0, 0.05, 0.1, 0.2) with the anatase structure have been synthesized by Sol–Gel method using Tri-ethyl Amine as nitrogen source and their optical, electrical and electrochemical properties are investigated. The electrical conductivity and thermoelectric power are measured in the temperature rang 300–600 K. The samples exhibit p-type behavior in contrast to TiO₂. The doped-samples exhibit two optical transitions (2.35≤E_h−Vis(eV)≤2.55; 1.97≤E_l−Vis (eV)≤2.06) directly allowed in the visible region, while only one transition is observed in UV region (E_UV∼3.00 eV). Pure TiO₂ shows direct band gap transition of 3.17 eV. The results confirm experimentally the calculations of Di. Valentin et al. [42]. The transitions E_h−Vis and E_l−Vis are attributed respectively to the promotion of electrons from the localized N 2p and π^? N–O bond to the conduction band. In all cases, E_UV is associated to the forbidden band energy. Though that the conductivity is generally improved by doping process, only N_0.05TiO₂ and N_0.1TiO₂ shows an enhanced mobility. The mechanism of conduction takes place by small polaron hopping. The band edge positions of N_xTiO₂ (x=0, 0.05, 0.1, 0.2) at room temperature is predicted from the obtained physical properties. This study proves experimentally the principal role of nitrogen in doping process and permits the electronic states localization associated with N-impurities in TiO₂ anatase.     

Bi3.15Eu0.85Ti3O12铁电薄膜的结构与光学性能

采用化学溶液沉积法在石英衬底上制备了Bi_3.15Eu_0.85Ti₃O₁₂ (BEuT) 铁电薄膜,研究了 BEuT薄膜的结构和光学性能。XRD结果表明,不同温度退火的BEuT皆形成铋层状钙钛矿型结构,其晶粒尺寸随着退火温度的升高而增大,与SEM观察结果一致。对BEuT薄膜的拉曼光谱研究表明,Eu³⁺主要取代钙钛矿层中的Bi³⁺位。光学透过率曲线显示,在大于500 nm的波段,各BEuT薄膜的透过率均比较高,其禁带宽度约为 3.69 eV。BEuT薄膜的发光随着退火温度的升高而增强,这可归因于其结晶状况的改善。     

Phase transformation of nanostructured titanium dioxide thin films grown by sol–gel method

Nanostructured TiO₂ thin films were deposited on quartz glass at room temperature by sol–gel dip coating method. The effects of annealing temperature between 200^∘C to 1100^∘C were investigated on the structural, morphological, and optical properties of these films. The X-ray diffraction results showed that nanostructured TiO₂ thin film annealed at between 200^∘C to 600^∘C was amorphous transformed into the anatase phase at 700^∘C, and further into rutile phase at 1000^∘C. The crystallite size of TiO₂ thin films was increased with increasing annealing temperature. From atomic force microscopy images it was confirmed that the microstructure of annealed thin films changed from column to nubbly. Besides, surface roughness of the thin films increases from 1.82 to 5.20 nm, and at the same time, average grain size as well grows up from about 39 to 313 nm with increase of the annealing temperature. The transmittance of the thin films annealed at 1000 and 1100^∘C was reduced significantly in the wavelength range of about 300–700 nm due to the change of crystallite phase. Refractive index and optical high dielectric constant of the n-TiO₂ thin films were increased with increasing annealing temperature, and the film thickness and the optical band gap of nanostructured TiO₂ thin films were decreased.     

Effect of preheating temperatures on microstructure and optical properties of Na-doped ZnO thin films by sol–gel process

The chemical composition, crystalline structure, surface morphology and photoluminescence spectra of Na-doped ZnO thin films with different heat treatment process were investigated by X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy and a fluorescence spectrometer. The results show that preferred orientation, residual stress, average crystal size and surface morphology of the thin films are strongly determined by the preheating temperature. The effects of preheating temperature on microstructure and surface morphology have been discussed in detail. The photoluminescence spectra show that there are strong violet & UV emission, blue emission and green emission bands. The violet & UV emission is ascribed to the electron transition from the localized level below the conduction band to the valence band. The blue emission is attributed to the electron transition from the shallow donor level of oxygen vacancies to the valence band, and the electron transition from the shallow donor level of interstitial zinc to the valence band. The green emission is assigned to the electron transition from the level of ionized oxygen vacancies to the valence band.     

Structure and properties of DLC–MoS2 thin films synthesized by BTIBD method

Diamond-like carbon (DLC)–MoS₂ composite thin films were synthesized using a biased target ion beam deposition (BTIBD) technique in which MoS₂ was produced by sputtering a MoS₂ target using Ar ion beams while DLC was deposited by ion beam deposition with CH₄ gas as carbon source. The structure and properties of the synthesized films were characterized by X-ray diffraction, X-ray absorption near edge structure (XANES), Raman spectroscopy, nanoindentation, ball-on-disk testing, and corrosion testing. The effect of MoS₂ target bias voltage, ranging from −200 to −800 V, on the structure and properties of the DLC–MoS₂ films was further investigated. The results showed that the hardness decreases from 9.1 GPa to 7 GPa, the Young?s modulus decreases from 100 GPa to 78 GPa, the coefficient of friction (COF) increases from 0.02 to 0.17, and the specific wear rate coefficient (k) increases from 5×10⁻⁷ to 5×10⁻⁶ mm³ N⁻¹ m⁻¹, with increasing the biasing voltage from 200 V to 800 V. Also, the corrosion resistance of the DLC–MoS₂ films decreased with the raise of biasing voltage. Comparing with the pure DLC and pure MoS₂ films, the DLC–MoS₂ films deposited at low biasing voltages showed better tribological properties including lower COF and k in ambient air environment.     

Synthesis and characterization of nanostructured strontium hexaferrite thin films by the sol–gel method

Nanostructured single phase strontium hexaferrite, SrFe₁₂O₁₉, thin films have been synthesized on the (100) silicon substrate using a spin coating sol–gel process. The thin films with various Fe/Sr molar ratios of 8–12 were calcined at different temperatures from 500 to 900 °C. The composition, microstructure and magnetic properties of the SrFe₁₂O₁₉ thin films were characterized using Fourier transform infrared spectroscopy, differential thermal analysis, thermogravimetry, X-ray diffraction, electron microscopy and vibrating sample magnetometer. The results showed that the optimum molar ratio for Fe/Sr was 10 at which the lowest calcination temperature to obtain the single phase strontium hexaferrite thin film was 800 °C. The magnetic measurements revealed that the sample with Fe/Sr molar ratio of 10, exhibited higher saturation magnetization (267.5 emu/cm³) and coercivity (4290 Oe) in comparison with those synthesized under other Fe/Sr molar ratios.     

Photoconductivity studies on nanoporous TiO2/dopamine films prepared by sol–gel method

Dopamine was encapsulated into nanoporous amorphous TiO₂ matrix by sol–gel method under atmospheric conditions. A second sample was obtained by the addition of the crown-ether 15C5 in this previous sample. Thin films were spin-coated on glass wafers. No heat treatment was employed in both films. All films were characterized using infrared spectroscopy, high resolution transmission electronic microscopy, X-ray diffraction, optical absorption and scanning electronic microscopy. Despite the films prepared with 15C5 were no calcined, a partial crystallization was identified. Anatase and rutile nanoparticles with sizes of 4–5 nm were obtained. Photoconductivity technique was used to determine the charge transport mechanism on these films. Experimental data were fitted with straight lines at darkness and under illumination wavelengths at 320, 400, and 515 nm. It indicates an ohmic behavior. Photovoltaic and photoconductivity parameters were determined from the current density vs. the applied-electrical-field results. Amorphous film has bigger photovoltaic and photoconductive parameters than the partially crystalline film. Results observed in the present investigation prove that the nanoporous TiO₂ matrix can protect the dopamine inhibiting its chemical instability. This fact modifies the optical, physical and electrical properties of the film, and is intensified when 15C5 is added.     

A comparative study on the nanocrystalline ZnO thin films prepared by ultrasonic spray and sol⿿gel method

Nanocrystalline ZnO thin films are deposited through two different chemical methods: (i) the films prepared by ultrasonic spray with 0.1 M and (ii) dip-coating from zinc acetate complex solutions with 0.5 M, the films obtained at different temperatures. The XRD analyses indicated that ZnO films have nanocrystalline hexagonal structure with (0 0 2) preferential orientation and the maximum crystallite size value of 103 nm measured from the films prepared by dip-coating. UV?vis measurement indicated that all films are transparency in the visible region. The optical band gap increased with decreasing of the Urbach tail energy indicating that the increase in the transition tail width and decrease of the defects, respectively.     

Optical, electrical and morphological properties of p-type Mn-doped SnO2 nanostructured thin films prepared by sol–gel process

SnO₂ thin films doped with various manganese concentrations were prepared on glass substrates by sol–gel dip coating method. The decomposition procedure of compounds produced by alcoholysis reactions of tin and manganese chlorides was studied by thermogravimetric analysis (TGA). The effects of Mn doping on structural, morphological, electrical and optical properties of prepared films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Hall effect measurement, Fourier Transform Infrared (FTIR) spectral analysis, UV–Vis spectrophotometry, and photoluminescence (PL) spectroscopy. The results of the X-ray diffraction show that the samples are crystalline with a tetragonal rutile structure and the grain size decreases with increasing the doping concentration. The SEM and AFM images demonstrate that the surface morphology of the films was affected from the manganese incorporation. The Sn_1?x Mn _x O₂ thin films exhibited electrically p-type behavior in doping level above x=0.035 and electrical resistivity increases with increase in Mn doping. The optical transmission spectra show a shift in the position of absorption edge towards higher wavelength (lower energy). The optical constants (refractive index and extinction coefficient) and the film thickness were determined by spectral transmittance and using a numerical approximation method. The oscillator and dispersion energies were calculated using the Wemple–DiDomenico dispersion model. The estimated optical band gap is found to decrease with higher manganese doping. The room-temperature PL measurements illustrate the decrease in intensity of the emission lines when content of Mn is increased in Mn-doped SnO₂ thin films.