Sol-gel Spin-coating Technique Research Articles

Bipolar resistive switching characteristics of PbZrO3/LaNiO3 heterostructure thin films prepared by a sol–gel process

Herein, PbZrO3 (PZO) films with good density and homogeneity were grown on a LaNiO3 (LNO)-buffered Si(100) substrate by a conventional and low-cost sol–gel spin-coating technique. The results indicated that the PZO films prepared on the LNO/Si substrate can be fabricated into a Au/PZO/LNO/Si heterojunction device via annealing at 650 °C under an air atmosphere. The device exhibited excellent and repeatable bipolar resistance switching (RS) behavior at room temperature. Its high/low resistance ratio reached 102 at +0.2 and -0.2 V bias voltages, and the RS characteristics of the device did not significantly deteriorate after 100 consecutive cycles of testing. Weibull distribution results show that the proposed device has a uniform and stable high/low-resistance state. Furthermore, we demonstrated that the conduction mechanisms of the device are Ohmic conduction and Schottky emission. The modulation of a Schottky-like barrier owing to the migration of oxygen vacancies in the PZO films is considered to be responsible for the RS phenomenon of the Au/PZO/LNO/Si device.

Optical, electrical and electronic properties of SnS thin films deposited by sol gel spin coating technique for photovoltaic applications

In the current study, thin films of tin sulfide (SnS) were grown by sol–gel spin-coating technique deposited on glass substrates. The obtained thin films were characterized using X-ray diffraction (XRD), photoluminescence (PL) and UV–Vis spectrometer and the four point technique, respectively. The effect of annealing temperature on the SnS properties has been studied. The XRD results reveal that the films annealed at 500 °C have good crystalline quality with orthorhombic phase. Fourier-transform infrared spectroscopy (FTIR) spectra shows the Sn–S bond. The photoluminescence spectra showed two categories of band emission. The optical parameters (α, e, n, k, Eg, and σop) were determined using UV–Vis spectroscopy. Moreover, the obtained results were compared to the theatricals results obtained with density functional theory (DFT) method using ab-initio approach. The optical and the electrical properties of the SnS Layers annealed at 400 °C and 500 °C offer the best possibility for their utilization in photovoltaic applications.

Visible-light induced photosplitting of water using solution-processed [formula omitted] photoelectrodes and a tandem approach for development of Pt-free photoelectrochemical cell

In this present work, investigation on the physical and chemical properties of the quaternary Copper–barium–thiostannate (Cu2BaSnS4) compound was carried out. Cu2BaSnS4(CBTS) thin films were synthesized by using the cost-effective, sol-gel spin-coating technique without further sulfurization. The light-sensitive nature of CBTS was investigated by illuminating the thin films directly under AM 1.5G condition, resulting in an enhancement of 47% in terms of photocurrent density. The p-type nature was confirmed from the Mott Schottky analysis carried out in 0.5 M Na2Ssolution without illumination. A flat band potential value of 2.354 ±0.003 V vs. RHE along with a carrier density of 9.314 ×1019cm−3and Debye length of 0.288 nm were also obtained for the CBTS thin films. From Bode plots, the carrier lifetime of CBTS films was estimated to be 88 m s. Further Pt-free photoelectrochemical cells were fabricated by using ZnO nanorods as counter electrodes. From linear sweep voltammetry results, photocurrent density of −6.805 and −2.112 mA/cm2 at 0 V (vs. RHE) under illumination in the presence of Pt electrodes and ZnO Nanorods, respectively. Photoconversion efficiency of ∼10% and ∼4% were estimated for the CBTS thin film in the presence of Pt and ZnO counter electrodes. Thus the physical properties observed here indicate the suitability of solution-processed CBTS thin films in its further use for harvesting solar energy.

Colossal photosensitive boost in Schottky diode behaviour with Ce-V2O5 interfaced layer of MIS structure

In the present work, we have fabricated a highly photo responsive Schottky barrier diode based on cerium infused vanadium pentoxide thin film (Ce-V2O5) as a interfacial layer. It was coated on a glass slide by low-cost sol-gel spin-coating technique and annealed at 500 °C. Structure, surface morphology, optical and electrical characteristic of Ce infused V2O5 films with different Ce concentrations viz 0, 2, 4 and 6 wt% were investigated. X-ray diffraction (XRD) pattern exposed that all coated films are tetragonal structure. And a peak shift was recorded after doping Ce ion into the V2O5 system. FE-SEM images showed a smooth nanorods and nanoplate-like structures in nano-scale region. Topology view by AFM showed a significant decrease in surface roughness of the film at different wt.% of Ce. The incorporation of Ce concentration based on the optical absorbance and band gap energy were studied, using UV–vis spectroscopy. Current-voltage (I–V), characteristics, photo-diode parameters of the Cu/Ce-V2O5/n-Si diodes were evaluated under dark and light exposed conditions. A maximum quantum efficiency of 25.54 % was achieved for the MIS diode fabricated with 6 % of Ce. The photosensitivity of the Cu/Ce-V2O5/n-Si diode 100 times higher than pure diode. Photodiode parameters and I–V analysis revealed that Ce with 6 wt.% is appropriate for the development of high quality photodiode and photo detector applications based to its electrical-performance.

Structural, Optical and Surface Properties of Multilayer Anatase-TiO2 Films Grown by Sol–Gel Spin Coating Technique

TiO2 films are widely used in such technological applications as solar cells, photocatalysts and gas sensors due to their interesting physical, chemical and optical properties. In the present work, multilayer anatase-TiO2 films were produced by the sol–gel spin coating technique. The effects of the number of coating layers (4, 5, 6 and 7) on the structural, optical and surface properties of TiO2 films are reported in detail. The optimal number of spinning cycles was determined as 6–7 to produce anatase-TiO2 films having improved structural properties, as obtained by x-ray diffraction analysis. Spectroscopic ellipsometry was used to determine the thickness, refractive index and extinction coefficient values. Transmittance spectra showed that TiO2 films produced after 4, 5 and 7 spinning cycles were highly transparent in the visible region. In addition, the direct band gaps of the TiO2 films were calculated as 3.47–3.69 eV by using optical measurements. The possible deep trap levels, which act as recombination centers, were investigated by photoluminescence spectra analysis. The atomic force microscopy images showed that sixfold spin coating resulted in improved surface homogeneity and reduced roughness values. This study indicates that TiO2 film having 6 layers may be a potential candidate in photocatalytic applications due to its desired structural, optical and surface properties.

Synthesis of SnO2 Thin Coatings by Indium and Aluminum Mixed Doping using the Sol-Gel Spin-Coating Technique

This research succeeded in creating a thin layer of SnO2 and SnO2: In+Al through a synthesis process with the sol-gel spin-coating technique on a glass substrate. The manufacture of this thin layer uses the basic material SnCl2.2H2O, and the doping material InCl3.4H2O and AlCl3. This thin layer is made with variations in doping concentration, number of layers, and heating temperature. The results of the synthesis of SnO2: In+Al films show that the thin film formed is more transparent when the doping concentration and the number of layers is increased. Meanwhile, the thin layer that forms is increasingly not transparent when heated at higher temperatures

Sn–Ga co-doping in sol-gel derived ZnO thin films: Studies of their microstructural, optical, luminescence and electrical properties

Sn–Ga co-doped ZnO films with different proportions synthesized by the sol-gel spin-coating technique have been investigated for their microstructural, optical, luminescence, and electrical properties using a variety of characterization techniques. All the films exhibit c-axis orientation along the (0 0 2) plane having a hexagonal wurtzite structure of zinc oxide. The crystallinity of the films improves upon doping and co-doping. Morphological images reveal that the films possess the granular morphologies with varying features. The co-doped films have a higher root mean square (RMS) roughness in comparison to the undoped and doped ZnO films. In general, relative to the undoped film, the transmittance of the film improves upon doping and co-doping. The direct energy band-gap has a maximum value of 3.26 eV for the undoped ZnO film, which decreases upon doping and co-doping. In the visible region, the refractive index exhibits a minimum value of 2.12 for the 1T3GZO film at the wavelength of 600 nm. The photoluminescence spectra of the films consist of one near-band edge (NBE) emission peak related to the recombination of free excitons, and a few broad emission peaks linked to the native defects in the films. Among the co-doped ZnO films, the 1 at% Sn–Ga co-doped film (1T1GZO) has the optimum transmittance and electrical conductivity.

Molybdenum Disulfide Film Saturable Absorber Based on Sol-Gel Glass and Spin-Coating Used in High-Power Q-Switched Nd:YAG Laser.

In recent years, many different kinds of nonlinear optical materials have been applied to passively Q-switched solid-state lasers. However, the average output powers of these lasers are typically limited to 1 W due to the low damage threshold of the materials. In this study, a molybdenum-disulfide-doped glass-composite absorber was synthesized using the sol-gel method and spin-coating technique. The optical damage threshold of the absorber reached 3.17 J/cm2. Saturation intensity, modulation depth, and nonsaturable loss are 9.35 MW/cm2, 8.41%, and 9.14%, respectively. After inserting the absorber into a linear Nd:YAG laser cavity, the maximum average output power (3.22 W) and stable Q-switched laser pulses duration (132 ns) were obtained.

Structural and optical characterization of aluminum zinc co-doped tin oxide grown by sol-gel spin coating techniques

Aluminum Zinc co-doped Tin Oxide (AZSO) thin film was grown by sol-gel spin coating techniques onto a glass substrate using various doping concentrations (0, 2, 4, 6, and 8 wt%) and the effect of doping on each sample were studied using structural analysis; X-ray Diffraction (XRD) pattern, gravimetric method; thin film thickness and UV photo-spectrometer; optical properties. The results of the XRD were revealed that all the peaks have a tetragonal phase of SnO2, which were oriented at the 110, 101, and 211 planes. The film thickness was observed to vary with doping concentration. In the visible region, all the film samples were exhibited at average transmittance. The coefficient of absorption was gradually increased with an increase in photon energy at a certain level with a decrease in the absorption coefficient as the photon energy increases further. At 550-800 nm range of wavelength, a high extinction coefficient (k) was recorded and the refractive index curves show regular dispersion behavior. The optical conductivity of the films followed a similar pattern, which showed that conductivity increased to a peak at 3.60 eV. The energy bandgap of the film samples (AZSO1 - AZSO5) is 4.095 eV, 4.103 eV, 4.087 eV, 4.114 eV, and 4.106 eV, respectively. The studies show that the properties of Al-Zn co-doped SnO2 films can be explored for optoelectronic applications.

Cu2ZnSnS4 (CZTS) thin films prepared by sol–gel spin-coating technique

The [Formula: see text] (CZTS) thin film is a photovoltaics material with excellent photoelectric properties and has good potential applications. The CZTS thin films with different spin-coated layers and sulfurized temperatures were successfully prepared by a sol–gel spin-coating technique. The relationships of microstructure, surface morphology and processing parameters were studied using XRD, SEM and EDS. The results indicate that the grain size of the sample sulfurized at [Formula: see text]C was larger than that of the sample sulfurized at [Formula: see text]C. With increasing layers of spin, coatings, the films showed better crystalline structure. The sulfureted CZTS thin films prepared by six spin-coating possess uniform elemental distribution.

The Effect of Indium Doped SnO2 Thin Films on Optical Properties Prepared by Sol-Gel Spin Coating Technique

This study aims to investigate the optical properties of SnO2 thin films doped with Indium synthesized using the sol-gel spin coating technique. The optical properties of thin films were measured using Thermo Scientific GENESYS UV-Vis Spectrophotometer. The results of characterization of optical properties showed that the thin films of Indium doped SnO2 experienced an increase in transmittance from 75 - 96.6% at wavelengths 300 - 350 nm and increased maximum absorbance at a wavelength of 300 nm from 3.19 - 4.32 with an increase in doping percentage. This shows that thin films absorbance the maximum wave at a wavelength of 300 nm. Increasing the percentage of doping causes the thin films of SnO2 to experience a decrease in energy gap both in the direct energy gap of 3.64 - 3.57 eV and indirect energy gap i.e from 3.92 - 3.87 eV. The optical activation energy of the SnO2 thin films decreased with increasing doping percentage from 2.91 - 2.35 eV. The results of this study indicate that SnO2: In thin films is high-quality because it has high transmittance and low energy gap.

Solution growth of highly crystalline and dense-packed ZnO nanorods on a TiO2 seed layer with enhanced absorbance properties

Titanium dioxide:zinc oxide (TiO2:ZnO) nanorod thin films were deposited on glass substrates via a sol-gel spin-coating technique for deposition of a TiO2 seed layer and solution-immersion method for growth of ZnO nanorods. ZnO nanorods were grown at different molar concentrations (0.002–0.060 M) on a TiO2 seed layer annealed at 450 °C for 1 h. The surface topography of the TiO2 seed layer and structural properties of the TiO2:ZnO nanorods were characterized using atomic force microscopy, field emission scanning electron microscopy and X-ray diffraction (XRD). The absorbance performance has been observed by a UV–vis spectrophotometer. The seed layer improved the structures of ZnO nanorods by reducing the diameter size of the nanorods. The denser distribution of nanorods with improved crystallinity was observed at higher concentrations. At 0.060 M, the XRD peak was slightly shifted to a higher angle, attributed to decrease in tensile stress between the TiO2 seed layer and nanorods. Meanwhile, UV–vis spectra of the films displayed high absorption in the UV region and high transparency in the visible region.

Structural and optical studies of aluminosilicate films doped with (Tb3+, Er3+)/Yb3+ by ion implantation

Harvesting solar energy demands efficient solar cells working over the largest region of the solar spectrum possible. The extension of the wavelength region is viable through the use of frequency converting phosphors. Rare earth (RE) pairs fulfill this criterion and in particular the Erbium/Ytterbium pair allows a good coverage from the near-infrared (NIR) to visible by up conversion (UC) at room temperature.In this study we report the structural and optical properties of aluminosilicate glass films grown by sol-gel (SG) spin-coating deposition technique and co-doped with (Er, Tb)/Yb by ion implantation with different fluences and energy. After implantation, the films were annealed at 1000 °C for 20 min and characterized by scanning electron microscopy (SEM), Rutherford Backscattering (RBS), X-ray diffraction (XRD) and Photoluminescence (PL). The annealing induces a significant redistribution of the RE ions in the films. In particular, the samples implanted with Tb + Yb show a tendency to form a homogeneous distribution over the entire film. In both cases PL shows the cooperative up conversion process.

Effect of Pt doping on the preferred orientation enhancement in FeCo/SiO2 nanocomposite films

We prepared FeCoPt/SiO2 thin films by sol-gel spin-coating technique. As-prepared composite films were reduced in hydrogen to induce texture growth. Structural, magnetic property and surface morphology of the films were characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and scanning electron microscope (SEM). These experimental data indicate that integrated intensity ratio I(200)/I(110) of diffraction peaks (200) and (110) of FeCo firstly increases and then decreases, while the coercivity first decreases and then increases with increasing Pt doping content. The specimen with less Pt doping content has a large I(200)/I(110) value and small coervicity value, which is closely related with strong (200) texture in FeCo thin film. These results indicate that fcc-Pt is also in favor of promoting (200) FeCo texture like Al or Cu elements, and this similar trends of Pt and Al originate from their similar atomic radius and crystal cell volume.

Simultaneous improvement of piezoelectric and magnetic properties in diamagnetic ion modified BiFeO3 film

Multiferroic BiFeO3 (BFO) and Bi0.97Y0.03Fe0.95Sc0.05O3 (BYFSO) films were fabricated on FTO coated glass substrate using sol-gel spin-coating technique. Y–Sc co-doping induces the structural distortion without changing the crystal structure (rhombohedral: R3c) of BFO. The electrical and magnetic properties of co-doped film may tuned due to increase in grain and particles size. The high dielectric constant (εr=290) and low loss (tanδ=0.084) indicates the improved insulating properties in BYFSO film. Increase in oxygen vacancy concentration in BYFSO film is explained with leakage current density, which follows Ohmic-SCLC conduction mechanism. Switching of 1800 domains into non-1800 (maximum 710 and 1090 type) ensures improved ferrolectric and piezoelectric properties in BYFSO film. The magnetic properties enhance significantly with saturation magnetization (Ms), remanent magnetization (Mr) are 9.45 emu/cm3, 6.154 emu/cm3 respectively at coercive (Hc) field of 0.822 kOe. Room temperature multiferroic BYFSO film with improved insulating and magnetic properties may be useful for non-volatile RRAM memory application.

Effect of film thickness on electrochromic performance of sol-gel deposited tungsten oxide (WO3)

In recent year, considerable interest has been addressed towards the high energy usage in buildings for indoor comfort due to the less energy efficient windows. Electrochromic (EC) smart window is a new technology that is capable of changing from transparent to opaque and has the potential in energy saving applications. Tungsten oxide (WO3) is a transition metal oxide with a wide range of applications which include electrochromic (EC) smart windows, displays and rear-view mirrors. In EC smart windows, WO3 is the key element where it is responsible for the colouring and bleaching of the device. Therefore the properties of WO3 will affect the EC performance. In this work, WO3 films were deposited on tin doped indium oxide (ITO) coated glasses via the sol-gel spin-coating technique. The WO3 film thicknesses were varied by means of number of deposited layers. The film thickness, morphological, structural, optical and EC properties were characterised by using step profilometer, scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, ultraviolet-visible (UV-Vis) spectrophotometer and cyclic voltammetry (CV) and chronoamperometry (CA) measurements, respectively.

Effect of doping concentration and annealing temperature on nitrogen-doped ZnO thin films: an investigation through spectroscopic techniques

Undoped and nitrogen-doped ZnO (NZO) thin films were deposited by sol–gel spin-coating technique on glass substrates. The thin film preparation was accomplished using zinc acetate dihydrate, monoethanolamine and 2-methoxyethanol as the precursors. Ammonium acetate was used as the source of nitrogen for doping. The effect of dopants and the post-heating temperature on the various physical properties of the deposited films was explored. The X-ray diffraction studies reveal the polycrystalline nature of the films which possess a preferred c-axis orientation. Raman characterizations of the films show a clear indication of nitrogen incorporation in the films. The carrier concentration of the thin films was of the order of 1017/cm3 and resistivity as minimum as 0.371 Ω cm was observed for 1 at.% NZO thin films post-heated at 500 °C. The 1 at.% and 2 at.% doped NZO films post-heated at 300 °C and 1 at.%, 2 at.% and 3 at.% doped NZO films with post-heat treatment at 500 °C exhibited p-type conductivity. In the aging study, 500 °C annealed films retained p-type conductivity for 5 days.

Efficiency Enhancement in Dye-Sensitized Solar Cells with ZnO and TiO2 Blocking Layers

Dye-sensitized solar cells (DSSCs) have great potential for solar generation owing to their low cost and ease of fabrication compared with silicon-based photovoltaic devices. One of the major issues with TiO2-based DSSCs is the recombination loss at the substrate–electrolyte interface due to the mesoporous nature of the TiO2 film. It was proposed earlier that introduction of a blocking layer at the substrate–TiO2 interface could reduce this recombination loss by preventing direct contact of the substrate and electrolyte. In this study, ZnO blocking layers (ZBLs) with different thicknesses were spin-coated onto fluorine-doped tin oxide (FTO) glass and the influence studied in comparison with a conventional TiO2 blocking layer (TBL) prepared using the same technique. The ZBL functions as an energy barrier at the FTO–electrolyte interface to prevent backtransfer of electrons to the electrolyte from the FTO. The blocking effect of the ZBL was verified by an enhancement of the fill factor (FF) and open-circuit photovoltage (Voc) of the DSSC, leading to an improvement in the power conversion efficiency (PCE) from 3.86% to 4.34% for the ZBL with optimum thickness of 120 nm. The suppression of the dark current density revealed a reduction of charge recombination with increasing ZBL thickness. Further increase in the ZBL thickness resulted in reduced cell performance due to a drastic decrease of the short-circuit current density (Jsc). The PCE was slightly improved to 4.36% by replacing the ZBL with a 100-nm TBL. These results suggest that the facile and low-cost sol–gel spin-coating technique is a feasible method for formation of a ZBL or TBL to reduce the recombination loss in DSSCs.

Effect of molar concentration on structural, magnetic domain and optical properties of BiFeO3 thin films

Pure crystalline bismuth ferrite BiFeO3 (BFO) thin films have been deposited on the cleaned glass substrate by sol–gel spin-coating technique with different molar concentrations (from 0.1 to 0.5 M) of the precursor solution. The influence of molar concentrations on the structural, magnetic and optical properties has been investigated by different advanced techniques. The X-ray diffraction patterns of BFO films revealed that the increase of the molar concentration from 0.1 to 0.5 M induced the structural transformation from distorted orthorhombic to single orthorhombic phase. The average crystallite size of BFO thin films was calculated using Scherrer formula and found to be in the range of 15–28 nm. The elemental composition of Bi, Fe and O was confirmed using energy-dispersive spectroscopy of X-rays. The atomic force microscopic images revealed that shape of particles are changing from ellipsoid to nanorods with increasing the molar concentration from 0.3 to 0.5 M. The root means square roughness of BFO films was also varying from 6.34 to 29.88 nm. The stripe-like structure of domain was explored through magnetic force microscopy. The films prepared from the precursor of molar concentration of 0.5 M revealed the microscopic remnant magnetization of 0.19 emu/cm3 and coercivity of 443.06 Oe from the M–H measurements. This enhancement of ferromagnetic properties may be due to the formation of nanorods resulted by destroying the cycloid spin structure. The optical bandgaps were also tuned from 2.58 to 2.49 eV due to increase of the crystallite size from 15 to 28 nm.

Aluminum Nitride Thin Films Grown by Sol-Gel Spin Coating Technique

In this study, aluminum nitride (AlN) thin films were grown on p-type silicon (100) substrate by sol-gel spin coating method. Two types of ethanol-based precursors were prepared, namely, precursors with and without the aid of diethanolamine (DEA). The objective of this work is to investigate the effects of the DEA on the surface morphology, structural and optical properties of the deposited thin films. The coating films were undergone nitridation process under ammonia ambient at 1100 °C for 60 min. The surface morphology and structural properties of the deposited AlN thin films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). XRD results revealed that both samples have AlN (100) preferred orientation. In addition, the crystallinity of sample without the aid of DEA is higher compared to the sample prepared with DEA. While, the AFM results showed that both samples have uniform and smooth surface. The optical properties of AlN thin films was investigated by Raman spectroscopy. For sample without DEA, Raman results showed the present of wurtzite AlN characteristics phonon modes of E2(high) and A1(LO) at 660 cm-1 and 892 cm-1, respectively. Whereas only E2(high) is observed for sample with the aid of DEA. Finally, all the results revealed that the present of DEA has a strong influence on the properties of deposited AlN thin films and film prepared without DEA have better quality.