• Korean Journal of Materials Research
• /
• v.24 no.10
• /
• pp.543-549
• /
• 2014

A zinc oxide (ZnO) hybrid structure was successfully fabricated on a glass substrate by metal organic chemical vapor deposition (MOCVD). In-situ growth of a multi-dimensional ZnO hybrid structure was achieved by adjusting the growth temperature to determine the morphologies of either film or nanorods without any catalysts such as Au, Cu, Co, or Sn. The ZnO hybrid structure was composed of one-dimensional (1D) nanorods grown continuously on the two-dimensional (2D) ZnO film. The ZnO film of 2D mode was grown at a relatively low temperature, whereas the ZnO nanorods of 1D mode were grown at a higher temperature. The change of the morphologies of these materials led to improvements of the electrical and optical properties. The ZnO hybrid structure was characterized using various analytical tools. Scanning electron microscopy (SEM) was used to determine the surface morphology of the nanorods, which had grown well on the thin film. The structural characteristics of the polycrystalline ZnO hybrid grown on amorphous glass substrate were investigated by X-ray diffraction (XRD). Hall-effect measurement and a four-point probe were used to characterize the electrical properties. The hybrid structure was shown to be very effective at improving the electrical and the optical properties, decreasing the sheet resistance and the reflectance, and increasing the transmittance via refractive index (RI) engineering. The ZnO hybrid structure grown by MOCVD is very promising for opto-electronic devices as Photoconductive UV Detectors, anti-reflection coatings (ARC), and transparent conductive oxides (TCO).

• Asian-Australasian Journal of Animal Sciences
• /
• v.23 no.11
• /
• pp.1527-1534
• /
• 2010

Trace minerals such as zinc, copper, and manganese are essential cofactors for hundreds of cellular enzymes and transcription factors in all animal species, and thus participate in a wide variety of biochemical processes. Immune development and response, tissue and bone development and integrity, protection against oxidative stress, and cellular growth and division are just a few examples. Deficiencies in trace minerals can lead to deficits in any of these processes, as well as reductions in growth performance. As such, most animal diets are supplemented with inorganic and/or organic forms of trace minerals. Inorganic trace minerals (ITM) such as sulfates and oxides form the bulk of trace mineral supplementation, but these forms of minerals are well known to be prone to dietary antagonisms. Feeding high-quality chelated trace minerals or other classes of organic trace minerals (OTM) can provide the animal with more bioavailable forms of the minerals. Interestingly, many, if not most, published experiments show little or no difference in the bioavailability of OTMs versus ITMs. In some cases, it appears that there truly is no difference. However, real differences in bioavailability can be masked if source comparisons are not made on the linear portion of the dose-response curve. When highly bioavailable chelated minerals are fed, they will better supply the biochemical systems of the cells of the animal, leading to a wide variety of benefits in both poultry and swine. Indeed, the use of certain chelated trace minerals has been shown to enhance mineral uptake, and improve the immune response, oxidative stress management, and tissue and bone development and strength. Furthermore, the higher bioavailability of these trace minerals allows the producer to achieve similar or improved performance, at reduced levels of trace mineral inclusion.

• Korean Journal of Materials Research
• /
• v.21 no.1
• /
• pp.67-71
• /
• 2011

La doped CuO-ZnO-$Al_2O_3$ powders are prepared by sol-gel method with aluminum isopropoxide and primary distilled water as precursor and solvent. In this synthesized process, the obtained metal oxides caused the precursor such as copper (II) nitrate hydrate and zinc (II) nitrate hexahydrate were added. To improve the surface areas of La doped CuO-ZnO-$Al_2O_3$ powder, sorbitan (z)-mono-9-octadecenoate (Span 80) was added. The synthesized powder was calcined at various temperatures. The dopant was found to affect the surface area and particle size of the mixed oxide, in conjunction with the calcined temperature. The structural analysis and textual properties of the synthesized powder were measured with an X-ray Diffractometer (XRD), a Field-Emission Scanning Electron Microscope (FE-SEM), Bruner-Emmett-Teller surface analysis (BET), Thermogravimetry-Differential Thermal analysis (TG/DTA), $^{27}Al$ solid state Nuclear Magnetic Resonance (NMR) and transform infrared microspectroscopy (FT-IR). An increase of surface area with Span 80 was observed on La doped CuO-ZnO-$Al_2O_3$ powders from $25m^2$/g to $41m^2$/g.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.5
• /
• pp.539-543
• /
• 2012

Cellulose Electro-Active Paper (EAPap) is attractive as a biomimetic actuator because of its merits: it is lightweight, operates in dry conditions, has a large displacement output, has a low actuation voltage, and has low power consumption. Cellulose is regenerated so as to align its microfibrils, which results in a piezoelectric paper. When chemically bonded and mixed with carbon nanotubes, titanium oxide, zinc oxide, tin oxides, the cellulose EAPap can be used as a hybrid nanocomposite that has versatile properties and that can meet the requirements of many application devices. This paper presents trends in recent research on the cellulose EAPap, mainly on material preparation and its use in devices, including biosensors, chemical sensors, flexible transistors, and actuators. This paper also explains wirelessly driving technology for the cellulose EAPap, which is attractive for use in biomimetic robotics and micro-aerial vehicles.

• Journal of Sensor Science and Technology
• /
• v.24 no.1
• /
• pp.15-21
• /
• 2015

Transparent and conductive multilayer thin films consisting of three alternating layers FZTO/Ag/$WO_3$ have been fabricated by radio-frequency (RF) sputtering for the applications as transparent conducting oxides and the structural and optical properties of the resulting films were carefully studied. The single layer fluorine doped zinc tin oxide (FZTO) and tungsten oxide ($WO_3$) films grown at room temperature are found to have an amorphous structure. Multilayer structured electrode with a few nm Ag layer embedded in FZTO/Ag/$WO_3$ (FAW) was fabricated and showed the optical transmittance of 87.60 % in the visible range (${\lambda}=380{\sim}770nm$), quite low electrical resistivity of ${\sim}10^{-5}{\Omega}cm$ and the corresponding figure of merit ($T^{10}/R_s$) is equivalent to $3.0{\times}10^{-2}{\Omega}^{-1}$. The resultant power conversion efficiency of 2.50% of the multilayer based OPV is lower than that of the reference commercial ITO. Asymmetric D/M/D multilayer is a promising transparent conducting electrode material due to its low resistivity, high transmittance, low temperature deposition and low cost components.

• Journal of the Semiconductor & Display Technology
• /
• v.16 no.2
• /
• pp.94-97
• /
• 2017

Amorphous Si has been used for data processing circuits in flat panel displays. However, low mobility of the amorphous Si is a limiting factor for the data transmission speed. Metal oxides such as ZnO have been studied to replace the amorphous Si. ZnO is a wide bandgap (3.3 eV) semiconductor with high mobility and good optical transparency. When ZnO is grown by sputtering with $O_2$ as an oxidizer, there can be many ion species arising from $O_2$ decomposition. $O^+$, $O_2{^+}$, and $O^-$ ions are expected to be the most abundant species, and it is not clear which one contributes to the ZnO growth. We applied alternating substrate voltage (0 V and -70 V) during sputtering growth. We studied changes in transistor characteristics induced by the voltage switching. We also compared ZnO grown by dc and rf sputtering. ZnO film was grown at $450^{\circ}C$ substrate temperature. ZnO thin-film transistor grown with these methods showed $7.5cm^2/Vsec$ mobility, $10^6$ on-off ratio, and -2 V threshold voltage.

• Korean Journal of Materials Research
• /
• v.31 no.3
• /
• pp.150-155
• /
• 2021

Zinc oxide (ZnO) based transparent conducting oxides (TCO) thin films, are used in many applications such as solar cells, flat panel displays, and LEDs due to their wide bandgap nature and excellent electrical properties. In the present work, fluorine and aluminium-doped ZnO targets are prepared and thin films are deposited on soda-lime glass substrate using a RF magnetron sputtering unit. The aluminium concentration is fixed at 2 wt%, and the fluorine concentration is adjusted between 0 to 2.0 wt% with five different concentrations, namely, Al2ZnO98(AZO), F0.5AZO97.5(FAZO1), F1AZO97(FAZO2), F1.5AZO96.5(FAZO3), and F2AZO96(FAZO4). Thin films are deposited with an RF power of 40 W and working pressure of 5 m Torr at 270 ℃. The morphological analysis performed for the thin film reveals that surface roughness decreases in FAZO1 and FAZO2 samples when doped with a small amount of fluorine. Further, optical and electrical properties measured for FAZO1 sample show average optical transmissions of over 89 % in the visible region and 82.5 % in the infrared region, followed by low resistivity and sheet resistance of 3.59 × 10-4 Ωcm and 5.52 Ω/sq, respectively. In future, these thin films with excellent optoelectronic properties can be used for thin-film solar cell and other optoelectronics applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.151-151
• /
• 2009

Recently, there has been increasing interest in amorphous oxide semiconductors to find alternative materials for an amorphous silicon or organic semiconductor layer as a channel in thin film transistors(TFTs) for transparent electronic devices owing to their high mobility and low photo-sensitivity. The fabriction of amorphous oxide-based TFTs at room temperature on plastic substrates is a key technology to realize transparent flexible electronics. Amorphous oxides allows for controllable conductivity, which permits it to be used both as a transparent semiconductor or conductor, and so to be used both as active and source/drain layers in TFTs. One of the materials that is being responsible for this revolution in the electronics is indium-zinc-tin oxide(IZTO). Since this is relatively new material, it is important to study the properties of room-temperature deposited IZTO thin films and exploration in a possible integration of the material in flexible TFT devices. In this research, we deposited IZTO thin films on polyethylene naphthalate substrate at room temperature by using magnetron sputtering system and investigated their properties. Furthermore, we revealed the fabrication and characteristics of top-gate-type transparent TFTs with IZTO layers, seen in Fig. 1. The experimental results show that by varying the oxygen flow rate during deposition, it can be prepared the IZTO thin films of two-types; One a conductive film that exhibits a resistivity of $2\times10^{-4}$ ohm${\cdot}$cm; the other, semiconductor film with a resistivity of 9 ohm${\cdot}$cm. The TFT devices with IZTO layers are optically transparent in visible region and operate in enhancement mode. The threshold voltage, field effect mobility, on-off current ratio, and sub-threshold slope of the TFT are -0.5 V, $7.2\;cm^2/Vs$, $\sim10^7$ and 0.2 V/decade, respectively. These results will contribute to applications of select TFT to transparent flexible electronics.

• Journal of the Korean Vacuum Society
• /
• v.6 no.1
• /
• pp.9-19
• /
• 1997

The reaction mechanisms of dry cleaning with UV-excited chlorine radical for Zn, Fe and Ti trace contaminants on the Si wafer have been studied by SEM, AFM and XPS analyses in this work. The patterned Zn, Fe and Ti films were deposited on the Si wafer surface by thermal evaporation and changes in the surface morphology after dry cleaning with $Cl_2$and UV/$Cl_2$at $200^{\circ}C$ were studied by optical microscopy and SEM. In addition, changes in the surface roughness of Si wafer with the cleaning was observed by AFM. The chemical bonding states of the Zn, Fe and Ti deposited silicon surface were observed with in-line XPS analysis. Zn and Fe were easily cleaned in the form of volatile zinc-chloride and iron-chloride as verified by the surface morphology changes. Ti which forms involatile oxides was not easily removed at room temperature but was slightly removed by UV/$Cl_2$at elevated temperature of $200^{\circ}C$. It was also found that the surface roughness of the Si wafer increased after $Cl_2$and UV/$Cl_2$cleaning. Therefore, the metallic contaminants on the Si wafer can be easily removed at lower temperature without surface damage by a continuous process using wet cleaning followed by UV/$Cl_2$dry cleaning.

• Membrane Journal
• /
• v.30 no.3
• /
• pp.158-172
• /
• 2020

In the aspect of saving energy and water, facilitating the separation membrane for the water treatment has been rising recently as one of the possible solutions. However, microbial biofouling effect is the biggest obstacle that hinders reaching higher permeability over a prolonged period of nanofiltration operation. To solve this problem and fully utilize the filtration membranes with enhanced performance, largely two kinds of solutions are studied and the first and the most commonly mentioned type is the one using the silver nanoparticles. Since silver nanoparticles are important to be well tailored on membrane surface, various methods have been applied and suggested. Using silver nanoparticles however also has the drawbacks or possible toxicity risks, raising the need for other types of utilizing non silver particles to functionalize the membrane, such as copper, graphene or zinc oxides, and amine moieties. Each attempt included in either kind has produced some notable results in killing, preventing, or repelling the bacteria while at the same time, left some unsolved points to be evaluated. In this review, the effects of metal nanoparticles and other materials on the antifouling properties of water treatment membranes are summarized.