Thutiyaporn Thiwawong

A Humidity Sensor Based on Silver Nanoparticles Thin Film Prepared by Electrostatic Spray Deposition Process

In this work, thin film of silver nanoparticles for humidity sensor application was deposited by electrostatic spray deposition technique. The influence of the deposition times on properties of films was studied. The crystal structures of sample films, their surface morphology, and optical properties have been investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and UV-VIS spectrophotometer, respectively. The crystalline structure of silver nanoparticles thin film was found in the orientation of (100) and (200) planes of cubic structure at diffraction angles 2θ  =  38.2° and 44.3°, respectively. Moreover, the silver nanoparticles thin films humidity sensor was fabricated onto the interdigitated electrodes. The sensor exhibited the humidity adsorption and desorption properties. The sensing mechanisms of the device were also elucidated by complex impedance analysis.

Electrical bistable properties of ZnO nanoparticles thin film prepared by electrostatic spray deposition technique

Thin films of zinc oxide nanoparticles (ZnO NPs) for bistable device was prepared by electrostatic spray deposition technique based on an indium-tin oxide/ZnO NPs/aluminum (ITO/ZnO NPs /Al) structure. The characterizations of ZnO NPs films were performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM). The influence of the deposition time on properties of films was also investigated. Moreover, the effect of deposition time on the bistable properties can be performed by current-voltage (I-V) measurements. The conduction mechanism of the bistable device was analyzed by theoretical model.

CoPc/CdS Hybrid Photovoltaic Device

The organic-inorganic hybrid photovoltaic (PV) cells based on cadmium sulphide (CdS) and cobalt phthalocyanine (CoPc) films have been fabricated and characterized their PV performance. This investigated the effects of the organic and inorganic layer thickness on the photovoltaic properties, these thickness was controlled at various values such as 10, 30 and 50 nm. However, the performance of the hybrid photovoltaic cells was depending on the organic layer thickness. The optimize results of PV cell with CoPc 10 nm and CdS 30 nm showed an open-circuit voltage (Voc) = 0.536 V, a short-circuit current density (Jsc) = 0.1020 mA/cm2, a fill factor FF = 0.281 and a power conversion efficiency (η) = 0.01536 % under the AM1.5 conditions. Efficiency is enhanced by 22 times with the addition of a buffer layer, bathocuproine (BCP) 5 nm, the power conversion efficiency (η) value from 0.01536 to 0.34571%.

Charge Transfer Mechanism in Organic Memory Device

In this paper, the conduction mechanism in organic bistable memory device was investigated by both experimental and theoretical method. The current voltage (J-V) characteristics showed the electrical bistable properties between an initial low-conductivity state and a high-conductivity state upon application of an external electric field at room temperature. The current transition exhibited a very narrow voltage range that causes an abrupt increase of current. The on-state and the off-state were proposed by space-charge-limited current and thermionic emission model, respectively. That supported by the experimental data to explained the charge transfer mechanism in organic memory device.

Preparation of copper doped zinc oxide nanoparticles by precipitation process for humidity sensing device

In this work, nanoparticles of copper-doped zinc oxide were synthesized using the precipitation process at different copper doping molars. The structure of the synthesized nanoparticles was examined by X-ray diffraction and X-ray photoelectron spectroscopy. From the results, it was indicated that the nanoparticles were composed of mixed copper oxide-zinc oxide. To fabricate the humidity sensor, the nanoparticles were dispersed in ethanol and deposited on an electrode using the electrostatic spray deposition technique. The humidity sensing behavior was assessed at various humidity levels in a closed vessel of saturated salt solution. Moreover, the response times for the device were recorded. The Cole-Cole plot of the real and imaginary parts of impedance could be useful for description of the equivalent circuit that indicates the mechanism for humidity sensing behavior.In this work, nanoparticles of copper-doped zinc oxide were synthesized using the precipitation process at different copper doping molars. The structure of the synthesized nanoparticles was examined by X-ray diffraction and X-ray photoelectron spectroscopy. From the results, it was indicated that the nanoparticles were composed of mixed copper oxide-zinc oxide. To fabricate the humidity sensor, the nanoparticles were dispersed in ethanol and deposited on an electrode using the electrostatic spray deposition technique. The humidity sensing behavior was assessed at various humidity levels in a closed vessel of saturated salt solution. Moreover, the response times for the device were recorded. The Cole-Cole plot of the real and imaginary parts of impedance could be useful for description of the equivalent circuit that indicates the mechanism for humidity sensing behavior.

Modification of Structural and Vibrational Properties of ZnO Nanoparticles Prepared by Simple Chemical Precipitation Method

In this work, zinc oxide (ZnO) nanoparticles were synthesized by simple chemical precipitation method in the present of zinc nitrate as zinc precursor and sodium hydroxide as hydroxide precursor. The vitamin C was used as modifier media to modify the structural properties of ZnO nanoparticles. The microstructures of ZnO nanoparticles were characterized by field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). Selected area electron diffraction (SAED) patterns showed that polycrystalline hexagonal phase of ZnO. The defects and impurity contents in nanoparticles were investigated by Fourier transform infrared (FT-IR) spectroscopy. The results show few carboxylate and hydroxyl impurities for larger particles when addition modifier increases. Surface areas of nanoparticles were measured by Brunauer Emmett Teller (BET) method. In addition, the results exhibited the dramatically change in structural properties of ZnO nanoparticles due to the effect of vitamin C.

Supercapacitive Properties of Cobalt Oxide Thin Films Prepared by Electrostatic Spray Deposition Technique at Different Substrate Temperature

In this work, cobalt oxide thin films were prepared by electrostatic spray deposition (ESD) technique. The influence of the substrate temperatures on properties of film was investigated. Phase transformation of cobalt oxide thin films due to the effect of different substrate temperature was also observed. Cyclic voltammetry was used to measure the performance of cobalt oxide supercapacitor. At higher substrate temperature, the cobalt oxide thin films exhibit the high specific capacitance due to the effect of phase transformation in cobalt oxide films.

Effect of Annealing Temperature on Structural and Optical Properties of Cobalt Oxide Thin Films Prepared by Electrostatic Spray Deposition Technique

In this work, cobalt oxide thin films were prepared by electrostatic spray deposition (ESD) technique on glass substrate. The influence of the annealing temperature on properties of cobalt oxide film was investigated. The structural, optical and morphology of cobalt oxide thin films were characterized by X-ray diffraction (XRD), Raman spectroscopy, UV-Visible spectrophotometer, scanning electron microscope, respectively. The crystalline parameters such as crystalline size of films can be obtained from XRD spectra. Phase transformation due to the different annealing temperature in cobalt oxide film has been observed. Moreover, at the higher annealing temperature, the optical band gap in cobalt oxide films were shifted to lower value due to the change in crystalline size and the defect sites in films.

Effect of Substrate Temperature of on Properties of Cobalt Oxide Thin Films Prepared by Electrostatic Spray Deposition Technique

In this work, the influence of the substrate temperature on properties of cobalt oxide thin films has been reported. Cobalt oxide thin films were prepared by electrostatic spray deposition technique on glass substrate at different temperature of the substrate. The properties of cobalt oxide films were characterized by X-Ray diffraction (XRD), scanning electron microscope, Raman spectroscopy, UV-visible spectrophotometer, respectively. In additional, the crystalline structural parameters can be performed from XRD data. Phase transformation of cobalt oxide films due to different substrate temperature was observed. Moreover, the optical properties of films were depended on the quantity of phase transition in cobalt oxide film.

Effect of Hydroxide Concentration and Adding Ascorbic Acid on Morphology Shape of Zinc Oxide Nanostructure Prepared by Simple Chemical Precipitation Method

A chemical precipitation method was used to prepare zinc oxide (ZnO) nanostructure in the present of zinc nitrate and ammonium hydroxide as zinc precursor and hydroxide precursor respectively. The effect of the hydroxide concentration and the effect of adding ascorbic acid as modifier into the mixture solution on the morphology property of zinc oxide was studied. The morphology and the structural of ZnO nanostructures were investigated by field-emission scanning electron microscope (FE-SEM) and X-ray diffractometer (XRD) techniques, respectively. The results showed that the basicity solution and adding stabilizer are important parameters on the morphology and structural properties of ZnO nanostructure. At a low hydroxide concentration, ZnO exhibited flower-like structure with short petal. With a further increase to higher concentration, ZnO crystal have more crystal directional growth. When the ascorbic acid was added, the morphology changed to particle-like structure. ZnO nanostructure with different shape might be used for specific applications such as gas sensor etc.