Spin-coating Deposition Technique Research Articles

Tailoring of the Structural, Optical, and Electrical Characteristics of Sol-Gel-Derived Magnesium-Zinc-Oxide Wide-Bandgap Semiconductor Thin Films via Gallium Doping.

The Ga-doped Mg0.2Zn0.8O (GMZO) transparent semiconductor thin films were prepared using the sol-gel and spin-coating deposition technique. Changes in the microstructural features, optical parameters, and electrical characteristics of sol-gel-synthesized Mg0.2Zn0.8O (MZO) thin films affected by the amount of Ga dopants (0-5 at%) were studied. The results of grazing incidence X-ray diffraction (GIXRD) examination showed that all as-prepared MZO-based thin films had a wurtzite-type structure and hexagonal phase, and the incorporation of Ga ions into the MZO nanocrystals refined the microstructure and reduced the average crystallite size and flatness of surface roughness. Each glass/oxide thin film sample exhibited a higher average transmittance than 91.5% and a lower average reflectance than 9.1% in the visible range spectrum. Experimental results revealed that the optical bandgap energy of the GMZO thin films was slightly higher than that of the MZO thin film; the Urbach energy became wider with increasing Ga doping level. It was found that the 2 at% and 3 at% Ga-doped MZO thin films had better electrical properties than the undoped and 5 at% Ga-doped MZO thin films.

Effective photoabsorption of two-way spin-coated metal oxides interfacial layers: Surface microstructural and optical studies

In this study, Molybdenum oxide (MoO3) and Vanadium oxide (V2O5) thin films were grown separately on pre-deposited cobalt oxide (Co3O4) thin film to form two different bilayer structures. The films were synthesized by spin-coating deposition technique. The precursors were prepared from common chemical reagents. Sample's surface microstructure, elemental composition and optical properties were investigated. The microstructural studies of the deposited bilayers show that the Co3O4 underlayer comprises crystalline grains with some overgrown clusters. Nanorod arrays of MoO3 adhering to the underlying Co3O4 layer with no chemical interaction are observed. In the second sample, the V2O5 top layer completely laminated the proximate Co3O4 film. Optical properties of the samples were examined from the UV/Vis spectra data. Energy band gap and band tail width changed with the adherence of top layer. Optical skin depths were also analyzed to reaffirm the suitability of the structures as potential window in thin film photovoltaics. The study demonstrated cheap process of developing interfacial layers of some transition metal oxide materials with high photoresponse. It also showed that the layers can offer the advantage of enhancing light harvesting, charge transport and storage.

A Novel Ethanol-Based Non-Particulate Ink for Spin-Coating Cu2ZnSnS4Thin Film

The Cu2ZnSnS4(CZTS) thin films were fabricated by the direct solution coating method using a novel non-particulate ink. The ink was formulated using ethanol as the solvent and 1,2-diaminopropane as the complex-ing agent. The pure phase kesterite films with good crystallinity, large-sized crystals and excellent electrical properties were prepared by the spin-coating deposition technique using the homogeneous and air-stable ink. It was found that the subsequent pre-treatment temperature had an influence on the film crystallinity and electrical properties. The best film was obtained by pre-treating the spin-coated film at 250 °C, and then post-annealing at 560 °C. The film shows a narrow bandgap of 1.52 eV and excellent electrical properties, with a resistivity of 0.07 Ocm, carrier concentration of 3.0 x 1017cm-3, and mobility of 4.15 cm2V-1s-1. The novel non-particulate ink is promising for printing high quality CZTS thin films as absorber layers of thin film solar cells.

Nanoparticles of CuO thin films for room temperature NO2 gas detection: Annealing time effect

In this work, the effect of annealing time on sensing properties of cupric oxide nanoparticles deposited on black silicon (CuO/BSi) as a gas sensor device was studied. CuO nanoparticles were prepared using pulsed laser ablation (PLA) beyond which, the prepared precursor was deposition using the spin coating deposition technique. The deposited CuO thin films were annealed in air for 1, 2, and 3 h at 400 °C. The influence of annealing time on the structural, morphological, and sensing performance at room temperature of prepared CuO/BSi was investigated in details. XRD patterns revealed nanocrystal of CuO with the crystallite size increased from 17 to 25 nm when that annealing time increased from 1 h to 3 h. The FESEM images revealed a nanostructured stone-like structure of different sizes. The average diameter increased with 1 h annealing time. The appearance of the porous surface of the annealed sample for two hours, while the porosity on the surface of the annealed sample for three hours decreased. A strong, sharp emission in the Visible-region was observed in the spectrum of CuO nanostructures, revealed by PL measurements at room temperature. The PL spectrum also showed a shift towards a shorter wavelength in the visible region that refers to the decreasing of energy gap from 1.73 eV to 1.71 eV. The prepared films were exposed to NO2 to detect the sensitivity of the nanostructured CuO/BSi thin films. It was found that the annealing time had a major role in increased sensitivity. The sensitivity of the annealed sample increased from 77% to 90% when the annealing time increased from one to two hours, while the sensitivity of the third model decreased to 4% at a three-hour annealing time. The reason for this behavior has been also discussed.

A comparative study of two-step and three-step methods for coating organometallic lead halide perovskite thin films

Two-step sequential spin coating deposition technique provides a cost-effective and high performance route for the synthesis of the organometallic lead halide perovskite materials. In this method, initially the metal halide film is coated, over which the MAI with a particular concentration is again spin-coated. However, it is difficult to obtain complete conversion of PbI2 in CH3NH3PbI3 perovskite. In this work, we show that good quality perovskite films can be coated by a three-step method to obtain improved conversion to perovskite and with improved materials properties. We have coated the perovskite films by two-step as well as three-step methods and presented a comparison of obtained film properties. Our results show that at lower concentration of MAI, complete conversion of PbI2 does not take place. With increase in MAI concentration, in addition to the perovskite phase an intercalated MAI into PbI2 phase is formed. In three-step coating, good phase of perovskite and improved morphology is obtained at comparatively lower MAI concentration. At higher concentrations of MAI in three-step method, leads to removal of already existing perovskite material and therefore leads to lower absorption.

Synthesis and characterization of organic-inorganic lead halide perovskite ([formula omitted]) thin films for photovoltaic applications

Solar cells based on hybrid perovskite have marked the world of photovoltaics as a promising photo-absorber material for solar cells, and using inexpensive deposition methods. CH3NH3PbI3 have gained significant notice in photovoltaic application as a result of their low fabrication cost and high efficiency that stepped from 3.8% in 2009 to up to 22% in 2018. In the present paper, thin films perovskites were synthesized using low cost method which is the spin coating deposition technique. To obtain the structural characteristic of CH3NH3PbI3, X-ray diffraction was employed. The UV–Visible spectroscopy shows the variation of the absorbance in CH3NH3PbI3 between wavelengths 300–800 nm.

Effect of graphene oxide on microstructure and optical properties of TiO2 thin film

GO/TiO2 thin films have been synthesized from titanium (IV) isopropoxide (TTIP) by a sol-gel method. The films were deposited onto a glass substrate using spin coating deposition technique then were subjected to annealed process at 350 °C. The different amount of graphene oxide (GO) was added into the parent solution of sol in order to investigate the microstructure, topography, optical band gap and photocatalytic activity of the thin films. The prepared thin films were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), UV-VIS spectrophotometry and degradation of methylene blue (MB). AFM images reveal a rougher surface of GO/TiO2 thin film than bare TiO2 thin film due to GO particles. Moreover, the SEM images showed the formation of semispherical microstructure of bare TiO2 changes to some larger combined molecules with GO addition. The UV–Vis spectrophotometer results show that with optical direct energy gap decreases from 3.30 to 3.18 eV after GO addition due to the effect of high surface roughness and bigger grain size. Furthermore, the optical results also indicated that GO improved the optical properties of TiO2 in the visible range region.

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.

Development of Cu2NiSnS4 based thin film solar cells without a sulfurization step

Copper nickel tin sulfide thin films were prepared by a low-cost and facile route, using spin-coating deposition technique without a sulfurization step. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy dispersive analysis, and Hall-effect measurements were used to analyze the influence of the annealing temperature on the structural, morphological, compositional, optical and electrical properties of the deposited thin films. After annealing at 300 °C in a nitrogen atmosphere for 1 h, the prepared thin films exhibit a pure cubic structure, good morphology without any cracks, and are nearly stoichiometric. The films showed a p-type conductivity with a sheet carrier concentration of 4.5 1017cm−3, a sheet resistivity of ~ 0.4 Ω cm and a Hall mobility of ~ 3 cm2/V.s. On the other hand, optical transmittance measurements of the annealed films revealed an optical gap of 1.35 eV and an absorption coefficient greater than 104 cm−1. These results suggest that the annealed copper nickel tin sulfide thin films at these relatively low temperatures (300 °C) in a nitrogen atmosphere for 1 h are very suitable for low-cost photovoltaic applications.

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.

Structural, morphological and opto-nonlinear studies of Cu:NiO: glass thin films facilely designed by spin coater for electro-optics

Fabrications of pure and Cu (1, 5, 10 and 15 wt%) doped NiO (Cu–NiO) films was attained using spin-coating deposition technique onto the glass substrates. Influences of Cu on pure NiO were studied regarding structure, morphological, linear and nonlinear optical traits by XRD, EDXs, AFM, UV–vis-NIR, Z-scan, respectively. XRD studies confirm the single phase of Cu doped NiO and EDX mapping confirms the interaction Cu atoms with pure NiO matrix. AFM studies confirm the formation spherical shaped nanostructures after addition of Cu this nanostructure formation increased with increased size. The transmittance, reflectance and absorption of all the samples were showing the same movement with decreasing band gap from 3.87 to 3.80 eV. Various nonlinear constants were estimated from Z-scan studies. The values noticed for χ1, χ2, χ3, and n2 were in range of 7.5 to 0.5, 8.0 × 10−8 to 0.5 × 10−8 esu and 0.5 × 10−8 to 8.5 × 10−8 esu, respectively. Moreover, the values of n2 and β are varying between 8.36 × 10−9 to 1.18 × 10−9 cm2 W−1 and 9.01 to 9.81 for all films.

Non-Isothermal Sublimation Kinetics of 2,4,6-Trinitrotoluene (TNT) Nanofilms.

Non-isothermal sublimation kinetics of low-volatile materials is more favorable over isothermal data when time is a crucial factor to be considered, especially in the subject of detecting explosives. In this article, we report on the in-situ measurements of the sublimation activation energy for 2,4,6-trinitrotoluene (TNT) continuous nanofilms in air using rising-temperature UV-Vis absorbance spectroscopy at different heating rates. The TNT films were prepared by the spin coating deposition technique. For the first time, the most widely used procedure to determine sublimation rates using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) was followed in this work using UV-Vis absorbance spectroscopy. The sublimation kinetics were analyzed using three well-established calculating techniques. The non-isothermal based activation energy values using the Ozawa, Flynn–Wall, and Kissinger models were 105.9 ± 1.4 kJ mol−1, 102.1 ± 2.7 kJ mol−1, and 105.8 ± 1.6 kJ mol−1, respectively. The calculated activation energy agreed well with our previously reported isothermally-measured value for TNT nanofilms using UV-Vis absorbance spectroscopy. The results show that the well-established non-isothermal analytical techniques can be successfully applied at a nanoscale to determine sublimation kinetics using absorbance spectroscopy.

A facile route for synthesis of cadmium sulfide thin films

This study describes a facile spin-coating deposition technique for cadmium sulfide thin film. The structural analysis revealed the formation of a pure hexagonal cadmium sulfide phase. The lattice constant, the crystallite size, dislocation density and micro strain were calculated. Energy dispersive x-ray analysis confirmed that these as-prepared CdS thin films are stoichiometric. The surface morphology studies showed homogenous and uniform films without any cracks with a low surface roughness of value 9 nm. The optical analysis indicated a relatively high transmission, optical band gap of 2.4 eV and Urbach energy value of 0.48 eV. All these properties indicate that cadmium sulfide thin films prepared by this simple route can be used as a window in heterojunction photovoltaic solar cells.

Synthesis and Characterization of Al-Doped ZnO Nano-Wires on the ITO/Glass by Sol–Gel Spin Coating and Chemical Bath Deposition Technique

Synthesis and Characterization of Al-Doped ZnO Nano-Wires on the ITO/Glass by Sol–Gel Spin Coating and Chemical Bath Deposition Technique

Fabrication of p-type Organic Field Effect Transistor using PMMA:TiO2 as Nanocomposite Dielectric Layer

This paper report on the fabrication of p-type organic field effects transistor (OFET) using low temperature spin coating deposition technique. The p-type OFETs were fabricated using poly (3-hexylthiophene-2,5-diyl) (P3HT) and poly (methyl methacrylate):titanium dioxide (PMMA:TiO2) nanocomposite material were used as semiconductor and the gate dielectric, respectively. The electrical and structural properties of OFETs were analysed using current-voltage (I-V), atomic force microscopy (AFM) and RAMAN spectroscopy. Results from I-V show that the fabricated p-type OFET has moderate performance with threshold voltage, VTH is -3V and mobility, μ is 2.01 cm2 V-1s.

Up-conversion emission of aluminosilicate and titania films doped with Er3+/Yb3+ by ion implantation and sol-gel solution doping

A key challenge in second generation solar cell development is to overcome major energy losses and to obtain high efficiency homogeneous films. In order to take advantage of the major portion of the solar spectrum, minimizing transparency losses, the use of frequency converting phosphors is a promising solution. From this viewpoint, the development of up-conversion (UC) materials for improving the light harvesting efficiency is a demanding task. Here, we report a low cost sol-gel (SG) spin-coating deposition technique which allows scalability to deposit SiO2 – Al2O3 and TiO2 films doped with the Erbium/Ytterbium lanthanide pair to obtain functional coatings with efficient near-infrared (NIR) to visible UC photoluminescence (PL) at room temperature. An alternative direct incorporation of the lanthanide ions into the solar cell material was also achieved by ion implantation. Comparison of both methods indicates that, although ion implantation is an accurate and controllable doping method, UC emission is superior at present from the films obtained by solution doping. However, this is the first time, to the best of the authors' knowledge, that UC properties have been studied for the Er/Yb pair in this system by this route. Therefore, the results reported here provide an additional approach for better understanding the doping parameters needed to obtain high PL performance.

A strategy toward air-stable and high-performance ZnO-based perovskite solar cells fabricated under ambient conditions

Despite the recently reported efficiency over 20%, the long-term stability of perovskite solar cells (PSCs) under ambient conditions remains a great challenge. For most of the highly efficient PSCs, fabrication processes are usually carried out in glovebox to guarantee their performance and stability. Herein, a new manufacturing strategy is introduced to optimize the device performance under ambient conditions. We skillfully merge both of ultrasonic assisted method and a two-step sequential spin-coating deposition technique to prepare a more compact and pinhole-free ZnO and perovskite films in air. As a result, the ZnO-based PSC with a conventional structure of glass/FTO/ZnO/CH3NH3PbI3/Spiro-OMeTAD/Au demonstrate an efficiency of up to 14.25%. Notably, the efficiency can be maintained at 86.25% of its initial value even though it is exposed to air for 45 days. Most importantly, all processes including fabrication, measurement as well as storage are performed in ambient air. We believe the proposed synergetic strategy can open up a new pathway for boosting the commercial applications of PSCs.

Large-area and high-performance CH3NH3PbI3 perovskite photodetectors fabricated via doctor blading in ambient condition

Abstract Organic-inorganic hybrid halide perovskites have attracted much research interest in optoelectronic field due to their excellent photoelectric properties. Herein, we report large-area and high-performance perovskite CH3NH3PbI3 photodetectors fabricated via in-situ thermal-treatment doctor blading technique in ambient condition (humidity ∼45%). As compared with spin-coating deposition technique, the doctor-bladed CH3NH3PbI3 films have larger grain size, as well as good reliability and reproducibility in large area. The doctor-bladed CH3NH3PbI3 photodetectors exhibited high detectivity (D*) of 2.9 × 1012 Jones and high responsivity (R) of 8.95 A/W, as well as the fast response time of less than 7.7 ms. The results indicate that doctor-bladed CH3NH3PbI3 film is a very promising candidate for fabricating large-scale and high-performance optoelectronic devices.

Conduction Mechanisms in Multiferroic Multilayer BaTiO3/NiFe2O4/BaTiO3 Memristors

Memristive devices and materials are extensively studied as they offer diverse properties and applications in digital, analog and bio-inspired circuits. In this paper, we present an important class of memristors, multiferroic memristors, which are composed of multiferroic multilayer BaTiO3/NiFe2O4/BaTiO3 thin films, fabricated by a spin-coating deposition technique on platinized Si wafers. This cost-effective device shows symmetric and reproducible current–voltage characteristics for the actuating voltage amplitude of ±10 V. The origin of the conduction mechanism was investigated by measuring the electrical response in different voltage and temperature conditions. The results indicate the existence of two mechanisms: thermionic emission and Fowler–Nordheim tunnelling, which alternate with actuating voltage amplitude and operating temperature.

Conductivity Comparison of Calix[8]arene-MWCNTs Through Spin Coating Technique

In this study, we investigated the conductivity enhancement of calix[8]arene-multi-walled CNTs (MWCNTs) thin film. Two types of calix[8]arenes were used, which were 5,11,17,23,29,35,41,47-p-tert-butyl-49,50,51,52,53,54,55,56-oktakis[(carboxy)-pentoxy] -calix[8]arene (C[8]1) and 49,50,51,52,53,54,55,56 -octahydroxycalix[8]arene (C[8]2). The monolayer properties of these two types of calix[8]arene on water subphase were examined. Later, the thin films were fabricated by combining different ratios of each types of calix[8]arene with MWCNTs using spin coating deposition technique. Then, the developed thin films were characterized using surface potential meter and four point probe. Thin films of C[8]2 with hydroxyl groups at lower rims demonstrated higher surface potential and conductivity as compared to the thin films of C[8]1 with upper rims of tert-butyl groups and lower rims of carboxyl groups. These results indicated that the conductivity of calixarene thin films can be enhanced by MWCNTs through simple spin coating technique.