Papers by Keyword: SILAR

Abstract: Highly conducting Ag₂S thin films were synthesized on FTO substrates at room temperature using simple and versatile successive ionic layer adsorption and reaction (SILAR) method. SILAR method was used to deposit silver sulfide (Ag₂S) thin films of about 299 nm thickness, under optimized deposition conditions viz. SILAR cycles (50), immersion time (25 s), and rinsing time (15 s). X-ray diffraction (XRD) study indicates the formation of polycrystalline Ag₂S with preferential orientation along (1 0 0) plane. Field emmission scanning electron microscopy (FESEM) will be used for study of the surface morphology of materials synthesized in thin film form. FESEM images showed that the deposited Ag₂S thin films were homogenous, without cracks and with dense surface morphology covering entire substrate surface area. Compositional analysis showed that the Ag₂S thin film becomes sulphur deficient and silver richer. Electrical studies showed that the deposited Ag₂S films are highly conducting and can be used in photosensor and/or optoelectronic devices.

Abstract: Zinc oxide (ZnO) thin films are synthesized by using modified successive ionic layer adsorption and reaction techniques (SILAR) on glass substrate at room temperature. These as deposited thin films are characterized for structural, compositional, surface morphology and optical characterizations using X-ray diffraction (XRD), energy dispersive X-ray absorption spectra analysis (EDAX), atomic force microscopy (AFM) and Uv-vis absorption spectroscopy. From XRD pattern; the low intensity peaks indicate that the films consist coarsely fine grains and/or amorphous in nature. The diffraction peaks observed at 2θ = 31.71 ̊, 36.27 ̊and 56.29 ̊ are attributed to (100), (101) and (110) planes having hexagonal phase while EDAX shows elemental traces for Zn and O. Surface morphology observed from the AFM corresponds granular shape evenly distributed over substrate surface.

Abstract: This study aims to investigate the impact of mesoporous and compact layers, like TiO₂ and TiO_x on the photovoltaic performance of bismuth oxyiodide (BiOI) films. BiOI thin films were prepared using the spin-coating method for 10 cycles onto FTO glass, FTO/TiO_x, FTO/TiO₂, and a combination of FTO/TiO_x-TiO₂ layer. Then, the resulted films were characterized on their optical, structural, and photovoltaic properties. By adding the TiO_x or TiO₂ layer into the cell, it resulted in the shifting of UV-Visible absorbance to a longer wavelength. On the structural property analysis, Raman spectra showed an overlapping peak among TiO_x, TiO_2, and BiOI films. Moreover, the solar cell was successfully developed using iodine electrolyte and Pt-counter electrode. By the photovoltaic analysis, it was known that the combination of those layers of metal oxide nanomaterials could give a slight improvement on the short-current density and open-circuit voltage of BiOI thin films. Therefore, the overall BiOI photovoltaic parameter was enhanced.

Abstract: Ternary metal vanadates have recently emerged as promising photoelectrode materials for sunlight-driven water splitting. Here, we show that highly active nanostructured BiVO₄ films can be deposited onto fluorine-doped tin oxide (FTO) substrates by a facile sequential dipping method known as successive ionic layer adsorption and reaction (SILAR). After annealing and deposition of a cobalt phosphate (Co-Pi) co-catalyst, the photoelectrodes produce anodic photocurrents (under 100 mW cm^-2 broadband illumination, 1.23 V vs. RHE) in pH 7 phosphate buffer that are on par with the highest reported in the literature for similar materials. To gain insight into the reason for the good performance of the deposited films, and to identify factors limiting their performance, incident photon-to-electron conversion efficiency spectra have been analyzed using a simple diffusion–reaction model to quantify the electron diffusion length (L_n; the average distance travelled before recombination) and charge separation efficiency (η_sep) in the films. The results indicate that η_sep approaches unity at sufficiently positive applied potential but the photocurrent is limited by significant charge collection losses due to a short L_n relative to the film thickness. The Co-Pi catalyst is found to improve η_sep at low potentials as well as increase L_n at all potentials studied. These findings help to clarify the role of the Co-Pi co-catalyst and show that there could be room for improvement of BiVO₄ photoanodes deposited by SILAR if L_n can be increased.

Abstract: Cotton fabric was coated with polyaniline molecules using Successive Ionic Layer Adsorption and Reaction (SILAR) technique. This method provides layer by layer deposition of polyaniline molecules. Infrared spectrum showed the vibrational peaks attributed with the presence of polyaniline molecules on the samples. Four-point probe measurements were done to obtain the surface conductivity of the samples. Upon increasing the dipping cycles, the conductivity of cotton fabric significantly increases. The optimum number of dipping cycle is found to be at 130. Beyond the optimum dipping cycle, the conductivity starts to decrease.

Abstract: This study aimed to determine the ammonia (NH₃) gas sensing ability of zinc oxide (ZnO) films deposited on glass tube substrates via successive ionic layer adsorption and reaction (SILAR) technique. The fabricated films were annealed at different temperatures. The sensor films were exposed to different volumes of ammonium hydroxide (NH₄OH), converted to parts per million (ppm). The change in voltage from concentrations 595ppm up to 1189ppm exhibited a linear trend. However, no trend was revealed in concentrations 2378ppm and 3964ppm due to film saturation. Results showed that the films annealed at 250 °C, 300 °C, 350 °C, and 400 °C presented sensitivities of 2.7×10^-4 V/ppm, 1.0×10^-4 V/ppm, 2.3×10^-4 V/ppm, and 1.5×10^-4 V/ppm with R² values of 0.997, 0.994, 0.904, 0.999 and resolutions of 3.7 ppm/mV, 9.9 ppm/mV, 4.4 ppm/mV, and 6.6 ppm/mV, respectively. Furthermore, this research study had proven that high quality gas sensors may be fabricated at a lower cost.

Abstract: In this study, conducting polyaniline (PANI) Emeraldine salt molecules were coated on polyethylene (PE) board using successive ionic layer adsorption and reaction (SILAR) technique. The number of dipping cycles were varied and the surface conductivity of the samples were measured using four-point probe technique. Fourier Transform Infrared (FTIR) spectroscopy was also done to verify the identities of the coated samples. Results show that PANI Emeraldine salt was successfully coated on PE board as indicated by the peaks of FTIR spectra. Surface conductivity of the PANI Emeraldine salt coated PE board increases with increased number of dipping cycles due to increases interconnectivity of PANI molecules. The conductivity decreases after reaching an optimum point at 80 dipping cycles due to either hindrance of movement of charges or the breaking away of chunks of PANI molecules. These results opens up several applications such as memory devices and erasable circuit boards.

Abstract: Polyaniline emeraldine salt (PAni-ES) was successfully deposited on paper through layer-by-layer technique. In this method, a paper was alternately dipped in aniline monomer and an oxidizing agent for different dipping cycles. This process produced green PAni-ES on paper. The morphology of the samples showed polymeric networks with pores, fiber-like structures and aggregates. There is a transition from frequency-independent to frequency-dependent conductivities of the samples. The conductivity increased with increasing number of dipping cycles. The frequency-dependent conductivities follow the power-law behavior reflecting conducting network and hopping mechanisms. Lastly, the conductivities with frequency followed a scaling behavior reflecting a common physical mechanism in PAni-ES on paper.

Abstract: Pb_xCd_1-xS quantum dots (QDs) was successfully deposited on TiO₂ mesoporous film as TiO₂ mesoporous photoanode using successive ionic layer adsorption and reaction (SILAR) method for quantum dot sensitized solar cells (QDSSCs). Quantum dot sensitized solar cells (QDSSCs) were prepared by sandwiching the TiO₂ mesoporous photoanode with Cu₂S counter electrode. Single layer of Pb_xCd_1-xS, PbS and CdS and multilayer of PbS/CdS/ZnS as well as multilayer PbS/Pb_xCd_1-xS/CdS/ZnS were prepared for characterizations. The characterizations including X-ray Diffraction Spectroscopy (XRD), Field Emission Scanning Electron Microscopy (FESEM), UV-visible spectrophotometer and Current-density voltage (J-V) measurement were carried out to study the effects of number of SILAR cycles of Pb_xCd_1-xS interlayer for molar fraction, x of 0.2 in QDSSCs. Pb_xCd_1-xS interlayer with four SILAR cycles is incorporated between PbS and CdS layer will increase the efficiency in QDSSCS.

Abstract: SILAR method is adopted for the deposition of titanium dioxide (TiO₂) thin films. Titanium trichloride and ammonium hydroxide are used as the cationic and anionic precursors respectively. Deposition parameters such as growth rate, individual dipping and rinsing times and precursor concentration are optimized to obtain uniform, adherent films. As-deposited TiO₂ films are annealed at 300°C and 400° C. The crystallization behaviour of TiO₂ thin films is analysed by X-ray diffraction. Optical constants of the films are evaluated using UV-Vis spectrophotometry. Effect of deposition parameters on the optical properties of the films is analysed.The direct and indirect band gap values of the TiO₂ thin films is in the range of 3.4-3.8 eV and 2.1-3.8 eV respectively.