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    Observations of the initial stages on reactive gas-timing sputtered TaO thin films by dynamic in situ spectroscopic ellipsometery
    (2019-06-01)
    Chittinan, D.
    ;
    Buranasiri, P.
    ;
    Lertvanithphol, T.
    ;
    Eiamchai, P.
    ;
    Patthanasettakul, V.
    Dynamic in-situ spectroscopic ellipsometry (iSE) was employed to investigate the growth mechanism of the tantalum oxide (TaO) film on silicon wafer substrate deposited by reactive gas-timing RF magnetron sputtering compared with conventional reactive sputtering. The effect of reactive gas timing parameter on physical structure and optical property were analyzed by both the continuous and island film growth model with Tauc-Lorentz optical model. The variation of refractive index, film thickness and void volume fraction were obtained from dynamic fits of iSE data indicated that the growth process of the amorphous TaO thin films was divided into two regimes: the nucleation stage and continuous-layer stage. These stages were observed during deposition although the initial film growth stage corresponds to the island film growth model. The study demonstrates that sputtered TaO by the RGT technique at the O<inf>2</inf> on-off gas timing has played a crucial factor in improving the formation of nucleation stage and that the deposited TaO thin films were high deposition rate with high refractive index. The complementary field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) showed a good agreement with the film thickness and morphology obtained from dynamic iSE measurement. The real-time monitoring of iSE offers important evidences to understand the growth mechanism of reactive gas-timing technique.
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    Investigation of optical characteristics of the evaporated Ta2O5 thin films based on ellipsometry and spectroscopy
    (2017-01-01)
    Prachachet, R.
    ;
    Buranasiri, P.
    ;
    Horprathum, M.
    ;
    Eiamchai, P.
    ;
    Limwichean, S.
    The tantalum oxide (Ta<inf>2</inf>O<inf>5</inf>) thin films were prepared by the ion-assisted electron-beam evaporation system. With the fixed film thickness at 200 nm, the deposition conditions were performed based on oxygen flow rate the ion assistance during the film deposition. The prepared thin films were characterized by spectroscopic ellipsometry in order to determine their physical and optical properties. From the ellipsometric measurements, the physical structures of the thin films and the optical dispersions were constructed, and then analyzed for the results of film thickness and optical constants. The thin films were also measured by the UV-Vis-NIR spectrophotometry for the optical transmission. The measured transmission was analyzed with the Swanepoel method, whose results also yielded the thickness and the refractive index. Finally, the thin films were examined by the scanning electron microscopy (SEM) in order to observe physical microstructures. This study explored the physical and optical analyses based on the spectroscopic ellipsometry and the spectrophotometry, with the confirmations from the SEM micrographs. The results from the analyses would be compared and thoroughly discussed.
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    High performance metal surface coating using Ta2O5 thin film prepared by D. C. magnetron sputtering
    (2014-01-01)
    Khemasiri, Narathon
    ;
    Chananonnawathorn, Chanunthorn
    ;
    Horprathum, Mati
    ;
    Eiamchai, Pitak
    ;
    Chindaudom, Pongpan
    Tantalum oxide (Ta<inf>2</inf>O<inf>5</inf>) thin films were deposited as the protective layers for the metal surface finishing by the DC reactive magnetron sputtering system. The effect of the Ta<inf>2</inf>O<inf>5</inf> film thickness, ranging from 25 nm to 200 nm, on the physical properties and the anti-corrosive performance were investigated. The grazing-incidence X-ray diffraction (GIXRD) and the atomic force microscopy (AFM) were used to examine the crystal structures and the surface topologies of the prepared films, respectively. The XRD results showed that the Ta<inf>2</inf>O<inf>5</inf> thin films were all amorphous. The AFM micrographs demonstrated the film morphology with quite smooth surface features. The surface roughness tended to be rough when the film thickness was increased. To examine the protective performance of the films, the poteniostat and galvanometer was utilized to examine the electrochemical activities with the 1M NaCl as the corrosive electrolyte. The results from the I-V polarization curves (Tafel slope) indicated that, with the Ta<inf>2</inf>O<inf>5</inf> thin film, the current density was significantly reduced by 3 orders of magnitude when compared with the blank sample. Such results were observed because of fully encapsulated surface of the samples were covered with the sputtered Ta<inf>2</inf>O<inf>5</inf> thin films. The study also showed that the Ta<inf>2</inf>O<inf>5</inf> thin film deposited at 50 nm yielded the most extreme protective performance. The Ta<inf>2</inf>O<inf>5</inf> thin films therefore could be optimized for the smallest film thickness for highly potential role in the protective performance of the metal surface finishing products. © (2014) Trans Tech Publications, Switzerland.
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    Determination of thickness and optical properties of tantalum oxide thin films by spectroscopic ellipsometry
    (2014-01-01)
    Chananonnawathorn, Chanunthorn
    ;
    Khemasiri, Narathon
    ;
    Srichaiyaperk, Thanat
    ;
    Samransuksamer, Benjarong
    ;
    Horprathum, Mati
    Tantalum oxide (Ta<inf>2</inf>O<inf>5</inf>) thin films were prepared, at different deposition time, by a DC reactive magnetron sputtering. During the deposition, a high-quality tantalum target was sputtered under argon and oxygen ambience on to silicon (100) and glass substrates. The prepared thin films were systematically characterized for both physical and optical properties based on spectroscopic ellipsometry (SE), and consequently confirmed by several methods. With the SE physical models, we could determine the thin film thickness as well as their inhomogeneity. The films thickness results were directly confirmed by field-emission scanning electron microscopy (FE-SEM) used to observe cross-sections, and surface profiler used to measure the physical thickness of the films. With the SE optical models, we applied both the Cauchy and Tauc-Lorentz dispersions in order to obtain the optical constants, to be directly compared with those from the Swanepoel method (SM). Our result showed that from the SE analyses, the SE physical model was obtained as the multi-layer configurations. The obtained Ta<inf>2</inf>O<inf>5</inf> thin film thickness was closely related with the measured result from the FE-SEM cross-sectional micrographs and the surface profiler. For the optical characteristic, the double layer physical model was best optimized with the Tauc Lorentz dispersion model for the most accurate results. In comparison, the SM technique also demonstrated a capability to determine both the film thickness and its refractive index only from some samples. Therefore, this study proved that the SE technique successfully and accurately determine both the physical and optical properties of the Ta<inf>2</inf>O<inf>5</inf> thin films. © (2014) Trans Tech Publications, Switzerland.
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    Effect of operated pressure on anticorrosive behavior of Ta2O5 thin film grown by D.C. reactive magnetron sputtering system
    (2013-10-29)
    Khemasiri, Narathon
    ;
    Chananonnawathorn, Chanunthorn
    ;
    Horprathum, Mati
    ;
    Rayanasukha, Yossawat
    ;
    Phromyothin, Darinee
    Tantalum oxide (Ta<inf>2</inf>O<inf>5</inf>) thin films, 100 nm thick were deposited by D.C. reactive magnetron sputtering system at different operated pressure on unheated p-type silicon (100) wafer and 304 stainless substrates. Their crystalline structure, film surface morphology and optical properties, as well as anticorrosive behavior, were investigated. The structure and morphology of films were characterized by grazing-incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM). The optical properties were determined by spectroscopic ellipsometry (SE). The corrosion performances of the films were investigated through potentiostat and immersion tests in 1 M NaCl solutions. The results showed that as-deposited Ta<inf>2</inf>O<inf>5</inf> thin films were amorphous. The refractive index varied from 2.06 to 2.17 (at 550 nm) with increasing operated pressure. The corrosion rate of Ta<inf>2</inf>O<inf>5</inf> thin film improves as the operated pressure decreases. The Ta<inf>2</inf>O<inf>5</inf> thin films deposited at 3 mTorr operated pressure could be exhibited high performance anticorrosive behavior. © (2013) Trans Tech Publications, Switzerland.