Sol-gel Spin-coating Technique Research Articles

Effect of ytterbium doping concentration on structural, optical and photocatalytic properties of TiO2 thin films

Abstract Ytterbium (Yb) doped TiO 2 thin films have been synthesized by sol-gel spin-coating technique. Films with different Yb concentrations such as 0.5, 1, 2, 4 wt% were deposited and the impact of the dopant concentration on their physicochemical properties was evaluated. The films were characterized by X-Ray diffraction, transmission electron microscopy, Raman spectroscopy, UV–Vis transmittance spectroscopy and photoresponse. The results showed that the incorporation of ytterbium modified the properties of TiO 2 films. The photocatalytic efficiency of TiO 2 :Yb films was determined using methylene blue (MB) as the generic pollutant. Compared to undoped TiO 2 , 1 wt% Yb doped films exhibited higher photocatalytic activity toward MB degradation under UV light. When the amount of Yb dopant concentration was increased, there was a negative effect on the photosensitivity and photocatalysis.

Investigation of microstructural, optical and dc electrical properties of spin coated Al:WO3 thin films for n-Al:WO3/p-Si heterojunction diodes

Tungsten trioxide (WO3) thin films have been prepared via sol-gel spin-coating technique for different concentrations of Al (0, 3, 6, 9 and 12wt.%) and investigated them by structural, optical, dc electrical and Al:WO3/p-Si heterojunction diodes. The XRD analysis reveals that the trivalent impurity of Al effectively influences the WO3. The UV–vis analysis shows an increase in the Al dopant that caused the band gap energy (Eg) to decrease. The SEM analysis shows that the size of the plate-like grains has reduced the Al:WO3 thin films. The composition ratio of W, O and Al elements has been confirmed by EDX spectrum. The dc electrical conductivity analysis has identified that Mott’s 3D variable hopping (VRH) mechanism influences the Al:WO3 thin films. The Al:WO3/p-Si p-n heterojunction diode parameters of ideality factor (n), barrier height (ΦB) and series resistance (Rs) have been calculated using the J-V method. From the current density-voltage-temperature (J-V-T) analysis, the inhomogeneity of barrier heights was extracted using the thermionic emission mechanism with Gaussian distribution (GD) function. As a result, the 9wt.% of Al:WO3/p-Si diode gives better results compared to the other Al:WO3/p-Si diodes.

Sodium and potassium doped P-type ZnO films by sol-gel spin-coating technique

Zinc oxide (ZnO) is a promising material in a variety of applications including sensors, transistors and solar cells. Many researchers studied N-type ZnO films and reported enhanced properties. On the other hand, P-type ZnO films were rarely attempted due to the self-compensation effect. Success in achieving P-type ZnO films is important as it will pave the way for more advanced complementary devices. In this work, P-type sodium and potassium doped ZnO films were fabricated on glass substrates with doping concentration between 0 and 25 at.%. The influences of doping concentration on surface morphology, structural, optical and electrical properties were investigated using atomic force microscopy, X-ray diffraction spectroscopy, energy-dispersive X-ray spectroscopy, ultraviolet–visible (UV–Vis) spectrophotometer, photoluminescence spectroscopy and Hall-effect electrical transport measurement system. The distinctive behavior of P-type ZnO films with different doping concentrations will be discussed.

Structural, optical, and electrical properties of cadmium oxide thin films prepared by sol–gel spin-coating method

Cadmium oxide thin films were prepared on glass substrates by the sol–gel spin-coating technique. The effects of the annealing temperature and Cd2+ concentration at the initial solution on the physical properties of the thin films are studied. It was found that 450 °C is the optimum annealing temperature for the preparation of cadmium oxide thin films with high transparency in visible and near infrared spectral regions, as well as high electrical conductivity. Then, by using this optimum annealing temperature, cadmium oxide thin films of various molar concentrations were deposited at the same experimental conditions. X-ray diffraction patterns show that the obtained films are polycrystalline. The structural analysis shows that all the samples have a cubic structure. The crystallite size and the preferred orientation were calculated from the X-ray diffraction data. Optical measurements have shown that an increase in the molar concentrations results in a reduction in the optical transmission of the layer. The films are highly absorbing in the visible region lower than 600 nm and their absorption is strongly influenced by the film thickness, with an average value above 60% for the current growth conditions. At the same time, the optical band gap decreases from 2.35 to 2.15 eV when the molar concentration of precursor solutions increases. The electrical measurements show that the resistivity of the films varies slightly from 2.7 × 10−3 to 7.5 × 10−3 Ω cm with the molar concentration. The cadmium oxide film, with the minimum resistivity of 2.7 × 10−3 Ω cm, was prepared by an initial concentration of Cd2+ of 0.1 M, with carrier concentration and mobility 1.16 × 1019 cm−3 and 199 cm2/Vs, respectively. The dependence of the band gap and the electrical properties of CdO thin films elaborated at different annealing temperature and molar concentrations.

Fabrication of ZnO Thin Films by Sol–Gel Spin Coating and Their UV and White-Light Emission Properties

ZnO thin films have been fabricated by the sol–gel spin-coating technique and annealed under different conditions, and their ultraviolet (UV) and white-light emission properties investigated. Different ambient conditions including oxygen, nitrogen, zinc-rich nitrogen, and vacuum were used to tune the main properties of the ZnO thin films. The resistivity varied from the conductive to semi-insulating regime, and the luminescence emission from fairly intense UV to polychromatic. The emission intensity was also found to be a function of the annealing conditions. Possible routes to compensate the loss of emission characteristics are discussed. X-ray photoelectron spectroscopy (XPS) analysis was carried out to detect the chemical states of the zinc/oxygen species. The changes in the electrical and emission properties are explained based on annihilation/formation of inherent donor/acceptor-type defects. Such ZnO thin films could have potential applications in solid-state lighting.

Impact of Sr-doping on structural and electrical properties of Pb(Zr0.52Ti0.48)O3 thin films on RuO2 electrodes

Abstract In this paper, we investigated the impact of Sr-doping on the structural properties and electrical characteristics of lead zirconate titanate [Pb(Zr 0.52 Ti 0.48 )O 3 , PZT] thin films deposited on RuO 2 electrodes by a sol-gel process and spin-coating technique. We used X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, and field-emission transmission electron microscopy to explore the structural, morphological, chemical, and microstructural features, respectively, of these films as a function of the growth condition (strontium doping concentrations varied from 1, 3, and 5 mol%). The PZT thin film processed at the 3 mol% Sr exhibited the best electrical characteristics, including a low leakage current of 2.27×10 −7 A/cm 2 at an electric field of 50 kV/cm, a large capacitance value of 2.74 μF/cm 2 at a frequency of 10 kHz, and a high remanent polarization of 37.95 μC/cm 2 at a frequency of 5 kHz. We attribute this behavior to the optimal amount of strontium in the PZT film forming a perovskite structure and a thicker interfacial layer at the PSZT film-RuO 2 electrode interface.

Effect of aging heat time and annealing temperature on the properties of nanocrystalline tin dioxide thin films

Nanocrystalline tin dioxide (SnO2) thin films have been successfully prepared by sol–gel spin-coating technique on p-type Si (100) substrates. A stable solution was prepared by mixing tin(II) chloride dihydrate, pure ethanol, and glycerin. Temperature affects the properties of SnO2 thin films, particularly the crystallite size where the crystallization of SnO2 with tetragonal rutile structure is achieved when thin films that prepared under different aging heat times are annealed at 400[Formula: see text]C. By increasing aging heat time in the presence of annealing temperatures the FESEM images indicated that the thickness of the fabricated film was directly proportional to solution viscosity, increasing from approximately 380 nm to 744 nm, as well as the crystallization of the thin films improved and reduced defects.

Characterization of Doped and Undoped Tin Oxide Thin Films Prepared by Sol Gel Spin Coating Technique

Characterization of Doped and Undoped Tin Oxide Thin Films Prepared by Sol Gel Spin Coating Technique

Preparation and Characterization of Ni Added ZnO Thin Film by Sol-Gel Spin Coating Techniques

Preparation and Characterization of Ni Added ZnO Thin Film by Sol-Gel Spin Coating Techniques

Comparative Study on the Structural, Morphological, Linear and Nonlinear Optical Properties of CZTS Thin Films Prepared by Spin-Coating and Spray Pyrolysis

This work describes some results concerning the fabrication of quaternary semiconductor Cu2ZnSnS4 deposited on glass substrates by spray pyrolysis using a perfume atomizer and sol-gel spin-coating techniques. Structural, morphological and optical properties of deposited films were examined. An original study was conducted to determine the third order nonlinear susceptibility via the Third Harmonic Generation technique. The results showed that the morphology of the films elaborated by spin-coating is more improved than the one by the spray method. However the value of the third order nonlinear susceptibility of CZTS thin film obtained by spray Pyrolysis is higher than the spin-coated one.

Spin-coated nickel doped cadmium sulfide thin films for third harmonic generation applications

In the current study, different percentages of Nickel (0%, 2%, 4% and 6%) doped CdS thin films have been deposited on glass substrates by the sol-gel spin-coating technique. Before performing the nonlinear optical studies, the structural, morphological and optical properties were examined as a function of Ni doping concentration through the XRD, SEM, AFM and UV–vis spectrometry, respectively. According to the XRD patterns, all films are polycrystalline and the incorporation of Ni does not change qualitatively the crystalline phase of CdS. The Ni doping affects the surface morphology of the CdS thin films which is indicated by scanning electron microscopy and atomic force microscopy images. The band gap was determined via the equation related to the absorption coefficient. It's deduced that the optical band-gap values increased from 2.35 eV to 2.41 eV depending on Ni content. Though, the nonlinear optical properties were determined based on the measurements of the third harmonic generation (THG) using the rotational Maker fringe technique. The results showed that the third order nonlinear optical susceptibilities oscillate between 5.40 × 10−21 m2/V2 for CdS:Ni (2%) and 4.98 × 10−21 m2/V2 for CdS:Ni (6%) while the pure CdS one falls inward, with a value of 5.09 × 10−21 m2/V2.

A Comparative Investigation of Optical and Structural Properties of Cu-Doped CdO-Derived Nanostructures

In this report, we studied various structural and optical properties of pure and copper-doped cadmium oxide (CdO) thin films. Nanostructured Cu-doped CdO films were deposited using sol–gel spin-coating technique. The structural and morphological changes have been observed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM) studies. The optical and electrical properties of the pure and Cu-doped CdO thin films were studied by UV–vis spectroscopy and four-point probe method, respectively. The XRD peaks show the formation of nanocrystalline CdO with cubic face-centered crystal structure. The band gaps of the as deposited films were found in the range of 2.32–2.73 eV, while after doping, it decreases due to structural deformation. The electrical resitivity was found to decrease approximately ∼10 in Cu-doped CdO thin films.

Structural and optical properties of Cr-doped ZnO thin films

In the present work, chromium (Cr)-doped zinc oxide (ZnO) thin films were prepared on silicon and glass substrates by using the sol–gel spin-coating technique. The influence of chromium doping on the structural and optical properties of zinc oxide films was investigated. The X-ray diffraction results reveal that the films are polycrystalline in nature with hexagonal wurtzite structure. The absence of secondary diffraction peaks other than those for zinc oxide suggests that the chromium ions successfully replaced zinc (Zn) ions and were incorporated into the crystal-lattice positions. The average grain size and the strain arising due to the introduction of chromium ions in the lattice were obtained by using Williamson–Hall analysis. The surface morphology of the films was observed by field emission scanning electron microscopy. The Raman spectra of the films show a peak at 434 cm−1 corresponding to E2 (high) mode of crystalline zinc oxide wurtzite structure, and the intensity of this mode decreases with increase in chromium doping. The films are highly transparent (∼90%) in the visible region, which reduces with chromium doping.

Tunable dielectric properties of TiO2 thin film based MOS systems for application in microelectronics

Post-deposition annealing (PDA) is an inherent part of a sol-gel fabrication process to achieve the optimum device performance, especially in CMOS applications. Annealing removes the oxygen vacancies and improves the structural order of the dielectric films. The process also reduces the interface related defects and improves the interfacial properties. Here, we applied a sol-gel spin-coating technique to prepare high-k TiO2 films on the p-Si substrate. These films were fired at 400 °C for the duration of 20, 40, 60 and 80 min to know the effects of annealing time on the device characteristics. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of annealed TiO2 films were examined in Al/TiO2/p-Si device configuration at room temperature. The 60 min annealed film gives the optimum performance and contained 69.5% anatase and 39.5% rutile phase with refractive index 2.40 at 550 nm. The C-V and I-V characteristic showed a significant dependence on annealing time such as variation in dielectric constant and leakage current. This allows us to tune the various electrical properties of MOS systems. The accumulation capacitance (Cox), dielectric constant (κ) and the equivalent oxide thickness (EOT) of the film fired for 60 min were found to be 458 pF, 33, and 4.25 nm, respectively with a low leakage current density (3.13 × 10−7 A/cm2) fired for 80 min at −1 V. The current conduction mechanisms at high bias voltage were dominated by trap-charge limited current (TCLC), while at small voltages, space charge limited current (SCLC) was more prominent.

Effect of Heat Treatment on the Structural Properties of TiO2 Films Produced by Sol-Gel Spin Coating Technique

Due to have superior properties as fotocatalyst and have wide band gap, TiO2 thin films often investigated by researchers and used by technological applications widely. In this study TiO2 films were deposited on glass substrate by Sol-Gel Spin Coating Technic. TiO2 films were deposited at different number of layer and then annealed at 400o C, 500o C, and 600o C in air. Effect of anneal temperature to structural properties were investigated by XRD analysis. It was observed by the light of XRD results that the structural properties of films had changed by anneal temperature.

Influence of Film Thickness and Annealing Temperature on Optical Properties of Nanostructured-TiO2 Thin Films Prepared by Sol–Gel Spin Coating Technique

TiO2 powder was found to be polycrystalline with rutile system. TiO2 films were deposited on quartz substrates by a sol–gel spin coating technique. X-ray diffraction and transmission electron microscope results have confirmed that the TiO2 films have nanostructure nature. It is found the crystallite size increased with annealing temperature. The optical constants of nanostructured TiO2 films were found to be independent of film thickness in the range from 100[Formula: see text]nm to 500[Formula: see text]nm. It is found that the optical constants and the dielectric constant of the thin films were all affected by annealing temperature. The existing allowed optical transitions in the as-deposited and annealed films were found to be direct and indirect transitions. Finally, the bandgaps of the as-deposited film were found to decrease with the annealing temperature.

Effect of Preheating Temperature on Microstructure and Optical Properties of ZnO Thin Films Prepared by Sol-Gel Spin Coating Technique

of the preheating temperature on the microstructure and the optical properties of the films were in particular investigated. The mechanisms for the preheating in the formation of the films and for the reactions involved in the sol solution prepared by the two-step method were also proposed in terms of the experimental results. The preheating not only enhances the volatilization of the solvent 2-methoxyethanol and the decomposition of the residual organic species, but also results into the formation of small number of ZnO particles. The preheating temperature of 300 C is most favorable for the highly-oriented ZnO thin film. Increasing the preheating temperature results into the blue shift of the absorption edges of the films. This can be explained by using the quantum-size eect. The photoluminescence spectra of the films show an UV emission at the near-band edge and a broad green-yellow emission at 470‐620 nm. The former is closely related to the excitons, while the latter is to the intrinsic defect species in the film.

Tuning the photovoltaic effect of multiferroic CoFe2O4/Pb(Zr, Ti)O3 composite films by magnetic fields

The 0–3 type CoFe2O4-Pb(Zr,Ti)O3 (CFO-PZT) multiferroic composite films have been prepared by a sol-gel process and spin-coating technique. A confirmable photovoltaic effect is observed under ultraviolet light irradiation. Moreover, this photovoltaic effect can be tuned by external magnetic fields. The maximum magnetic modulation ratios of short-circuit current density and open-circuit voltage can reach as high as 13.7% and 12.8% upon the application of 6 kOe DC magnetic field. Through remnant polarization measurements under various magnetic fields and detailed analysis of the energy band structures, we elucidate the mechanism of tuning photovoltaic effect by magnetic fields and attribute it to the combination of two factors. One is the decreased ferroelectric-polarization-induced depolarization electric field and another is the band structure reconstruction at CFO-PZT interfaces, both of which are dominated by the magnetoelectric coupling via interfacial stress transferring at nanoscale. This work makes some attempts of coupling photo-induced effects with magnetoelectric effect in multiferroic materials and will widen the practical ranges of multiferroic-based applications.

Annealing-induced modifications in sol–gel spin-coated Ga:ZnO thin films

Transparent conductive gallium-doped zinc oxide (Ga:ZnO) thin films were prepared by the optimized sol–gel spin-coating technique on glass substrate. After deposition, the films were annealed at temperatures ranging from 200 to 500 °C in the air. The effect of post-annealing temperature on structural, optical and electrical behaviors of Ga:ZnO (GZO) thin films was investigated. Experimental results showed the polycrystalline nature of the films with a hexagonal (wurtzite) crystal structure and a preferred orientation with c-axis, perpendicular to the substrate. The average optical transmittance of all the annealed films is over 89 %. The grain size and optical transmittance of the GZO films increased with increasing annealing temperatures. The photoluminescence spectra of GZO films showed the near-band-edge (NBE) emissions at 390 nm and blue emissions at 456 nm. The NBE emissions might originate from excitonic recombination, and the blue emission peak can be attributed to the zinc interstitial and oxygen vacancies in the ZnO lattice. The lowest resistivity of 2.23 × 10−3 Ω cm and the highest figure of merit are achieved for a GZO film annealed at 500 °C. The new results obtained from this study indicate that the structural, optical and electrical properties of GZO thin films can all be improved through an appropriate post-annealing operation. The obtained results confirm that the thermal annealing has considerable effects on the properties of GZO thin films deposited by sol–gel spin-coating method and can be used as a promising TCO for optoelectronic applications. AFM surface morphology of GZO thin films annealed at (a) 200 °C, (b) 300 °C, (c) 400 °C, (d) 500 °C

Influence of praseodymium content and postdeposition annealing on the structural and sensing characteristics of PrTixOysensing films using the sol–gel spin-coating method

In this paper, we developed a low-cost, simple and rapid fabrication method for a PrTixOyelectrolyte–insulator–semiconductor (EIS) sensor using the sol–gel spin-coating technique.