Papers by Author: Boonchoat Paosawatyanyong

Abstract: An affordable 6-cm diameter magnetron sputtering source was designed and constructed using a neodymium cylindrical permanent magnet inner stud and an outer ring magnet. Both magnets were set in isolation from a water-cooled disk behind the target. In this work, our magnetron sputtering source was employed to deposit copper thin films by changing the outer magnet ring. The outer magnate ring diameter sizes were 29 mm (I.D.)/39 mm (O.D.) and 30 mm (I.D.)/50 mm (O.D.). At the same applied bias voltage, the discharge current of the magnetron with a big outer magnet was higher than that of one with a small outer magnet. According to XRD pattern and AFM image of copper films, the degree of (111) and (200) orientations and surface roughness were increased in the case of films grown by magnetron with bigger outer magnet. The cross-sectional and plane-view SEM images showed that the grain size and film thickness were increased in the case of films grown by magnetron with bigger outer magnet. These results should be because the radial motion of secondary electron emitted from sputtering in front of target surface was increased with a bigger magnet.

Abstract: An efficient Sonogashira-type coupling reaction of terminal alkynes and aryl bromides by microwave activation with short reaction time under mild conditions are presented. It is illustrated herein that the traditional Sonogashira coupling reaction can be achieved with a much more efficient yet environmentally friendly condition. In contrary to the usually required 10 mol% Pd loading and the use of conventional heating at 60 °C for 24 h in order for a reaction to proceed satisfactorily, with a 100 W microwave activation, the reaction of terminal alkynes with substituted aryl bromides can be achieved with only a 2.5 mol% Pd in 10 min. The yield was improved with microwave irradiation.

Abstract: Electrospun polyacrylonitrile (PAN) fabrics were prepared by electrospinning with 7%w/v concentration to dissolve in dimethylformamide (DMF) and spinning time 12 h. Radio frequency inductively couple plasma (RF-ICP) at 13.56 MHz were used to improve PAN fabrics surface by O2 gas in plasma treatment that became to hydrophilic properties of PAN fabrics surface. Physical properties were determined by scanning electron microscopy (SEM) and contact angle measurement which found that characterized on PAN fabrics surface after plasma treatment with increased treated time had been damaged on these fabrics surface which measured contact angle measurement with water were range 29.3 to 74.7. Chemical properties were analysed by fourier transform infrared spectroscopy (FTIR) that had been found peak intensities of aliphatic C-H band at 1450 and 2930 cm-1 and peak intensities of cyclic C=O bands at 1732 cm-1 and peak intensities of saturated nitriles at 2243 cm-1 and peak intensities of hydroxyl O-H band at 3600-3650 cm-1.

Abstract: In this work, an inductively-coupled rf plasma reactor was utilized in the nitriding process for surface hardness improvement of aluminium-copper alloy 2011. Substrate bias at 400V was used in the pre-sputtering step to eliminate the aluminium oxide on the samples. Plasma nitriding was carried out in a N2-H2 admixture at total pressure of 1 torr. The process length was varied from 9 to 36 hours while the input rf power and substrate temperature were varied from 100 to 300 W and kept at 400 oC, respectively. A negative bias voltage up to 400 V was used in the nitriding process. Glancing incident-angle x-ray diffraction (GIXRD) results showed the hexagonal crystal structure of AlN on samples. The roughness increased slightly when the voltage increase up to 400V and was investigated by Scanning Electron Micrograph (SEM). Electron Probe Microscopy Analysis (EPMA) and Energy Dispersive X-ray Analysis (EDX) were used to detect the N atoms in specimens. Significant increases of surface hardness are observed after plasma nitriding.

Abstract: This research is focused on improving electrical conductivity of conjugated polythiophene films fabricated by microwave plasma assisted polymerization process. Polythiophene thin films with 300 nm to 1.5 micron thickness were deposited on glass substrates in a highly uniform fashion as evident by Scanning Electron Microscopic analysis. An efficient incorporation of the iodine dopant into the films was also successfully performed to give thin films with 120-250 nm thickness. The films were characterized by various spectroscopic methods. Attenuated total reflectance-Fourier transform infrared spectroscopy showed absorption frequencies of important functional groups mostly characteristics of thiophene. The doped fabricated films exhibited UV-vis spectra indicative of increased -conjugation (439-535 nm). Results from energy-dispersive X-ray spectroscopy confirmed the presence of iodine in the films of upto 10%. Electrical conductive measurements revealed that the undoped films has the conductivity in the range of 1.4×10-5 to 1.0×10-4 S/cm.

Abstract: A Radio Frequency Inductively Couple Plasma Reactor (RFICP) was designed and set up for DLC deposition onto aluminum substrates using CH4-H2 admixture precursor gas. Plasma parameters of the discharge during the deposition process were measured using Langmuir probe technique. The structure and morphology of the DLC films were characterized by SEM and Raman spectroscopy. SEM images show granule morphology which yield smaller grain size with increasing of RF power. It was found that the structure and composition of DLC films are controlled by changes in the RF power. Raman spectrum of DLC films show two typpical modes of the graphite lattice labelled as ‘G’ and ‘D’ modes. The G peak position shift to higher wave number and the ratio of the peak intensity ID/IG increases with increasing RF power. DLC samples yield good ohmic characteristics with decreasing resistivity in films grown at higher RF power. Both electrical and structural characteristics indicated that the films contain more graphitic content of sp2 hybridization with increasing RF power in the plasma process.

Abstract: A compact dc magnetron sputtering system capable of silver thin films depositions was designed and constructed. The novel small footprint sputtering head with target diameter of 52 mm was constructed utilizing powerful neodymium alloy magnet. Silver metal was sputter-deposited under various powers. Plasma parameters were analyzed by using the sweeping-bias single langmuir probe. The electron temperatures of the plasma glow were constant at approximately 2 eV even with the increasing of input power whereas plasma density increases with the increasing of the input power. The X-ray diffraction analysis (XRD) and scanning electron microscope (SEM) were used to study the crystalline structure and the surface morphology of the obtained silver thin films. Crystalline orientations of (111) and (200) in the silver films deposited on slide glass substrates were revealed from XRD pattern. The highest degrees of (111) and (200) orientations was obtained at the sputtering power between 0.228 and 0.265 Wcm-2. Sub-micron crystalline silver grain structure were observed using SEM micrographs. Facetted grain size and deposition rate of silver thin films increases as the sputtering power increases.