Optical and structural properties of TiO2 films as a function of Nb doping concentration

Ti_1?Cx Nb _x O₂ (x?=?0?C0.06) films were prepared on quartz substrates by sol?Cgel spin coating and characterized by a variety techniques. The effect of Nb doping on the structural and optical properties of Ti_1?Cx Nb _x O₂ films were mainly investigated by X-Ray diffraction (XRD), Raman spectroscopy, Field-emission scanning electron microscopy and UV?Cvis transmittance spectroscopy. XRD and Raman study showed that the Nb doping inhibited the grain growth. The grain size decreased from 39.4 to 23.4?nm as the doping concentration increased from 0 to 0.06 in atomic percent. The UV?Cvis transmittance spectroscopy analysis revealed that the films exhibited 55?C65% transmittance in the visible region and the band gap of films became wider with increasing Nb doping concentration.     

Effect of platinum doping on the structural and electrical properties of SnO2 thin films

The investigation of Pt doping effect on the structural and electrical properties of SnO₂ thin films was aimed in this study. For this purpose, the polycrystalline pure and Pt-doped SnO₂ thin films were deposited onto n-type silicon substrate and the Pt sputter power was varied as 0 (un-doped), 2, 5 and 7 W by using radio frequency confocal sputtering system. The structural properties of the samples were analysed by X-ray diffraction measurements. The structural results show that the 5 W Pt-doped SnO₂ sample has better crystallinity than the other samples. The results of the electrical measurements as current–voltage, capacitance–voltage and conductance–voltage were also obtained and discussed in detail for fabricated diodes. The analysis of electrical characteristics shows that the use of different Pt doping has significant effect on electrical properties of such devices. The study also provides an improved supplemental understanding to the related technologies which use Pt-doped SnO₂ materials.     

The effects of oxygen partial pressure on local structural properties for Ga-doped ZnO thin films

We report on Raman scattering studies of Ga-doped ZnO thin films that were grown by intentionally changing oxygen partial pressure in order to study the influences of oxygen partial pressure on local structural properties of this material. Raman spectra of ZnO:Ga (3 wt.% Ga-doped) films revealed vibrational modes at 575 and 630–660 cm^− 1 in addition to the host phonons of ZnO. These additional modes correspond to local vibrational modes associated with oxygen vacancy (V_O) and Ga impurity (Ga_Zn), respectively. With increasing oxygen partial pressure (oxygen flow rate up to ∼ 10 sccm), the 575-cm^− 1 mode decreases in its intensity, indicating the reduced V_O concentration. Further increasing oxygen partial pressure (> 10 sccm), we find a substantial disorder apparent in host ZnO phonons and some additional modes. These results suggest that the oxygen-rich condition may cause the formation of compensating-defects such as oxygen interstitials (O_i), Zn vacancy (V_Zn) and their complexes (Ga_Zn–O_i, Ga_Zn–V_Zn), strongly reducing carrier concentration in this system.     

溅射功率和氧分压对ITO薄膜光电性能的影响研究

采用直流反应磁控溅射法制备了氧化铟锡(ITO)透明导电薄膜,通过四探针、紫外可见分光光度计、X射线衍射(XRD)、霍尔效应仪、扫描电镜(SEM)等对薄膜样品进行了表征,研究了溅射功率和氧分压对ITO薄膜微观结构和光电性能的影响,结果表明:溅射功率对ITO的光电性能影响较小,沉积速率随着溅射功率的增大而加快;随着氧分压的升高,载流子浓度降低,霍尔迁移率先增大后减小,电阻率逐渐增大。在优化的工艺条件下,制备了在可见光区平均透过率达85%、电阻率为1×10-4Ω.cm的光电性能优良的ITO薄膜。     

氧分压对氧化镍薄膜表面形貌和光电性能的影响

采用射频溅射法在SnO2衬底上生长了NiOx薄膜,制备的薄膜是非理想化学计量的微晶薄膜.研究了氧分压对NiOx薄膜的溅射速率、表面形貌和光学电学特性的影响.研究结果显示,O2分压在1∶10时,可得到最快的沉积速率;低的氧分压沉积的薄膜表面比较疏松;随着氧含量的增加,方块电阻呈上升趋势,当氧分压达到一定值时,膜电阻又开始下降;随着氧分压的升高,颜色会逐渐加深,透射率降低.     

Effect of oxygen partial pressure on the structural and optical properties of sputter deposited ZnO nanocrystalline thin films

We report the influence of deposition parameters such as oxygen partial pressure and overall sputtering pressure on the structural and optical properties of the as-grown ZnO nanocrystalline thin films. The films were prepared by dc magnetron sputtering using Zn metal target under two different argon and oxygen ratios at various sputtering pressures. Microstructure of the films was investigated using X-ray diffraction and scanning electron microscopy. Optical properties of the films were examined using UV-Visible spectrophotometer. The results show that the films deposited at low oxygen partial pressure (10%) contain mixed phase (Zn and ZnO) and are randomly oriented while the films deposited at higher oxygen partial pressure (30%) are single phase (ZnO) and highly oriented along the c-axis. We found that the oxygen partial pressure and the sputtering pressure are complementary to each other. The optical band gap calculated from Tauc's relation and the particle size calculation were in agreement with each other.     

Influence of oxygen partial pressure and substrate temperature during vapour deposition on the structural properties of CdSe films

CdSe films prepared in vacuum by sublimation from the compound at oxygen partial pressures in the residual atmosphere from 2.8 × 10^?5 to 3.2 × 10^?4 Torr and at substrate temperatures of 295 and 523 K were subjected to X-ray structural analysis. The results obtained are analysed and discussed in terms of some structures different from those of CdSe, e.g. CdSeO₃ and CdSeO₃.SeO₂.     

Substitution of Nb doping on the structural, microstructural and electrical properties in PZT films

Undoped and niobium (Nb) doped Pb_1−y(Zr_0.54Ti_0.46)_1−yNb_yO₃ have been deposited by sputtering on Pt metallized silicon substrates. The niobium concentration, y, was varied from 1 to 7 at.% by 1 at.%. The Zr/Ti ratio was fixed to 54/46 corresponding to the Morphotropic Phase Boundary. Structural, microstructural, and electrical properties were evaluated depending on Nb content. The films (doped and undoped) present a (1 1 1)-preferred orientation. The Nb doping induces an increase of the grain size and as it was observed in bulk materials the dielectric constant (ε_r) and the piezoelectric coefficients (e₃₁ and d₃₃) reach their maximum for low Nb concentration (2 at.%). The remnant and the maximum polarizations increase as the coercive field decreased slightly with the Nb concentration. The internal electric field increases with Nb content; as a result, the ‘self-polarization’ of the films (polarization measured without poling treatment) is enhanced with niobium substitution. In term of fatigue behavior, it was found that switching endurance characteristics are maximum for low Nb doping level.     

Ti/TiO2多层膜的光电性能研究

用真空蒸发和自然氧化法在玻璃基底上制备了Ti／TiO2多层膜，并检测了薄膜的光电性能。电性能检测表明Ti／TiO2多层膜存在类负阻效应，多层膜的层间的类负阻效应比表面的更明显，薄膜的层间电阻率高于表面电阻率；用分光光度计测得试样退火前后的透射谱；用X射线衍射仪和扫描电镜检测了Ti／TiO2多层膜的晶体结构和表面形貌。     

不同氧分压下电子束蒸发氧化锆薄膜的特性

在不同的氧分压下用电子束热蒸发的方法制备了氧化锆薄膜。用扫描探针显微镜、X射线衍射仪和分光光度计分别对薄膜的表面粗糙度、微结构和透射谱等特性进行了表征。实验发现,薄膜沉积中氧分压与薄膜性质及微结构有密切的关系。当氧分压由3.0×10-3Pa升高到11×10-3Pa,薄膜的表面粗糙度由3.012nm降低到1.562nm,而薄膜的折射率由2.06降低到2.01。此外,X射线的衍射还发现,薄膜是以四方相为主多相共存的,随着氧分压的增加,特征衍射峰强度逐渐减弱,最后完全变成非晶。     

Influence of fluorine doping on structural, electrical and optical properties of spray pyrolysis ZnS films

ZnS films were deposited by spray pyrolysis on glass at 500 °C substrate temperature. In order to study the influence of fluorine on the properties of ZnS film, undoped and F-doped films were investigated using X-ray diffraction, scanning electron microscopy and optical transmittance spectroscopy. The absorption coefficient was measured and correlated with the photon energy to estimate the energy gap, which rises from 3.20 to 3.35 eV with increased F content. Carrier concentrations of our samples were determined from Hall effect measurements. It was found that the carrier concentration increases from 7.0 × 10¹² cm^− 3 to 8.0 × 10¹³ cm^− 3 with increasing F content from 0 to 6 wt.% in ZnS films.     

Effect of alumina doping on structural, electrical, and optical properties of sputtered ZnO thin films

A systematic study of the influence of alumina (Al₂O₃) doping on the optical, electrical, and structural characteristics of sputtered ZnO thin films is reported in this study. The ZnO thin films were prepared on 1737F Corning glass substrates by R.F. magnetron sputtering from a ZnO target mixed with Al₂O₃ of 0-4 wt.%. X-ray diffraction (XRD) analysis demonstrates that the ZnO thin films with Al₂O₃ of 0-4 wt.% have a highly (002) preferred orientation with only one intense diffraction peak with a full width at half maximum (FWHM) less than 0.5°. The electrical properties of the Al₂O₃-doped ZnO thin films appear to be strongly dependent on the Al₂O₃ concentration. The resistivity of the films decreases from 74 Ω·cm to 2.2 × 10^− 3 Ω·cm as the Al₂O₃ content increases from 0 to 4 wt.%. The optical transmittance of the Al₂O₃-doped ZnO thin films is studied as a function of wavelength in the range 200-800 nm. It exhibits high transparency in the visible-NIR wavelength region with some interference fringes and sharp ultraviolet absorption edges. The optical bandgap of the Al₂O₃-doped ZnO thin films show a short-wavelength shift with increasing of Al₂O₃ content.     

Preparation of sprayed tin oxide transparent conducting films and their structural and electrical properties

The aim of the present work was to prepare fairly uniform transparent and conductive tin oxide films using an inexpensive and easily controllable method. The technique adopted was spray deposition. The design of the spray deposition apparatus takes into consideration its reliability in controlling the different parameters affecting the formation of deposited layers, as well as its adaptability for large-area applications. The growth rate was independent of substrate type but increased with increasing substrate temperature. The crystalline structure of the films was found to be a function of substrate temperature and film thickness. The X-ray diffraction patterns showed that the preferred orientation was (110) and the grain size was in the range of a few tens of nanometres. The variation of sheet resistance with deposition parameters was studied and an empirical formula relating the sheet resistance to the film thickness was obtained. The prepared tin oxide layers of thicknesses up to 200 nm were found to have a transparency of about 80% to 85%, which makes them suitable for application as a single antireflecting coating of silicon solar cells.     

不同结构稀土掺杂铝酸锶的合成与发光性能研究

采用燃烧法成功合成了稀土掺杂铝酸锶长余辉发光材料.XRD结果表明,当铝锶n(Al)∶n(Sr)=2时,发光基质中只存在SrAl2O4相结构.随着Al∶Sr比值的增大,出现新相Sr4Al14O25.当Al∶Sr比值增大到4时, SrAl12O19相开始形成.而Al∶Sr比值增大到12时,全部为SrAl12O19相.光致发光测量结果表明,发光样品SrAl2O4∶Eu2 ,Dy3 发射谱峰值位于519nm,而发光样品SrAl12O19∶Eu2 ,Dy3 的发射峰位于512nm.余辉检测结果表明,不同结构铝酸锶发光样品的衰减都是由初始的快衰减过程和其后的慢衰减过程组成,但是不同结构铝酸锶发光样品的初始亮度和发光衰减快慢不同.     

Effect of Ag doping on structural, electrical and dielectric properties of TiO2 nanoparticles synthesized by a low temperature hydrothermal method

Silver (Ag) doped thermally stable TiO₂ nanoparticles in the anatase phase have been synthesized by a low temperature hydrothermal method. The formation of anatase phase has been investigated by X-ray diffraction. Thermogravimetry and differential scanning calorimetry have been used for thermal studies. Scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy have been used for the morphology and composition studies. Surface areas were studied by the Brunauer-Emmett-Teller method. Dielectric properties were studied for dopant levels of 0.25, 0.5 and 1.0?wt% at 300?K in the frequency range of 42?Hz–5?MHz. The crystallite size, alternating current (AC) conductivity and dielectric properties of undoped TiO₂ nanoparticles were greatly affected by doping with Ag. At high frequencies, the materials showed high AC Conductivity and low dielectric constant.     

Correlation between the structural and electrical transport properties of SnO2 films

Transparent and conducting thin films of tin oxide have been deposited by spray pyrolysis on Corning 7059 substrates. The films were investigated by X-ray diffraction and Seebeck measurements to study the structural and electrical transport properties. The films were polycrystalline and the oxide phase observed was SnO₂ in cassiterite structure. The films were preferentially oriented along [200]. Trap densities along [310] and [101] have been calculated for the first time. Assigning the traps mainly to the grain boundaries, the grain-boundary barrier height was calculated and compared with that obtained from the Seebeck measurements. A good agreement between these values was observed. The agreement was the best for films deposited under optimum deposition conditions.     

Synthesis and structural, optical and electrical properties of TiO2/SiO2 nanocomposites

Sole components of titania (TiO₂), silica (SiO₂) nanoparticles, and binary TiO₂–SiO₂ nanocomposites with various molar ratios of silica contents were prepared by modified sol–gel method. The samples were calcined at 500 °C for 5 h and characterized by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, Brunauett–Emmett–Teller (BET), and photoconductivity. The crystallite size for TiO₂/SiO₂ nanocomposites was calculated using Scherrer’s formula and found to be 5 nm for TiO₂ nanoparticles. The binary oxide shows the anatase type of TiO₂ at the mole ratio up to 80 mol% of TiO₂ added. The band gap for as-synthesized nanocomposites was calculated and it was found that the band gap decreases with increase of SiO₂ content and then decreases with excess SiO₂ content. FTIR confirms that both TiO₂ and SiO₂ phases have been formed. The BET surface area for TiO₂/SiO₂ nanocomposite is found to be 303 m²/g, and pore size distribution has an average pore diameter about 10 nm for 40 mol% of TiO₂ added. It also confirms the absence of macropores and the presence of micro and mesopores. The field-dependent dark and photoconductivity studies reveal that the dark and photocurrent increase linearly with applied field confirming the ohmic nature of the electric contacts. The dark and photocurrent increase slightly with increase of SiO₂ content and decrease with excess amount of SiO₂.     

Effect of fluorine doping and SiO2 under-layer on the optical properties of TiO2 thin films

Fluorine-doped TiO₂ thin films were prepared via sol–gel method. Optical constants were obtained by fitting theoretical UV–Vis transmittance spectra to experimental ones within Forouhi–Bloomer dispersion model. The results show that doping with fluorine does not affect the absorption edge of TiO₂ films. The linear part of the absorption edge for the films on SiO₂/soda lime substrate is red shifted in comparison with that on bare soda lime and a broadened ‘tail’ up to ∼ 2.7 eV is observed. It is attributed to additional localized states within the TiO₂ band gap introduced by structural defects in titania lattice originated from TiO₂/SiO₂ interface.