Promros, Nathaporn

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Promros, Nathaporn
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Promros, N.
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nathaporn.pr@kmitl.ac.th

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    Impact of annealing temperature and carbon doping on the wetting and surface morphology of semiconducting iron disilicide formed via radio frequency magnetron sputtering
    (2020-09-01)
    Charoenyuenyao, Peerasil
    ;
    Promros, Nathaporn
    ;
    Chaleawpong, Rawiwan
    ;
    Borwornpornmetee, Nattakorn
    ;
    Sittisart, Pattarapol
    Iron disilicide (FeSi<inf>2</inf>) films were formed onto Si(111) substrates via radio-frequency magnetron sputtering at room temperature (RT) and 560 °C. The effects of annealing temperature and carbon (C) doping concentration on the physical properties of FeSi<inf>2</inf> films were investigated. For annealing conditions, the crystallinity of the unannealed FeSi<inf>2</inf> films was enhanced after annealing. The surface of unannealed FeSi<inf>2</inf> films consisted of many small crystallites, which were clustered after annealing at 500 °C. The root mean square roughness (R<inf>rms</inf>) of the unannealed FeSi<inf>2</inf> films increased from 0.94 nm to 5.32 nm after air-annealing at 500 °C. The surface of the unannealed FeSi<inf>2</inf> films exhibited an average contact angle (θ<inf>CA</inf>) of 102.35°, which decreased to 41.70° after annealing at 500 °C. For C-doping conditions, the X-ray diffraction patterns for the undoped and C-doped FeSi<inf>2</inf> revealed β(202/220) and β(404/440) peaks. The undoped FeSi<inf>2</inf> film surfaces presented many small grains with grain boundaries, where the C-doped FeSi<inf>2</inf> films displayed a finer surface. R<inf>rms</inf> of the undoped FeSi<inf>2</inf> film surface was 15.71 nm, which decreased to 10.59 nm for 3.0 at.% C-doped FeSi<inf>2</inf> films. The average θ<inf>CA</inf> of the undoped FeSi<inf>2</inf> films was 108.35°, and this reduced slightly to 103.65° for 3.0 at.% C-doped films. Based on the obtained results, it was shown that the as-formed FeSi<inf>2</inf> and FeSi<inf>2</inf> films after annealing at 100 and 300 °C formed at T<inf>sub</inf> of RT, together with the undoped and C-doped FeSi<inf>2</inf> films formed at T<inf>sub</inf> of 560 °C, could potentially be employed for hydrophobic coating applications.
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    Diode parameters and ultraviolet light detection characteristics of n-type silicon/p-type nanocrystalline diamond heterojunctions at different temperatures
    (2020-09-01)
    Chaleawpong, Rawiwan
    ;
    Promros, Nathaporn
    ;
    Zkria, Abdelrahman
    ;
    Charoenyuenyao, Peerasil
    ;
    Abubakr, Eslam
    n-Type silicon (Si)/p-type boron (B)-doped ultrananocrystalline diamond (UNCD) heterojunctions were manufactured through coaxial arc plasma deposition, and were examined in terms of the diode parameters and ultraviolet (UV) photodetection at different temperatures. The structure of the deposited films was examined by Raman spectroscopy and a field emission scanning electron microscope. The Raman spectra revealed two wide peaks centered at the positions of 1345 cm<sup>−1</sup> and 1585 cm<sup>−1</sup> that represented the D and G peaks, respectively. At 300 K, the current density-voltage characteristics showed a considerable high leakage current, which was reduced over two orders of magnitude at 150 K. The ideality factor (n) increased from 2.82 at 300 K to 6.37 at 150 K. In parallel, the barrier height was reduced from 0.75 eV at 300 K to 0.43 eV at 150 K. Through Norde's approach, the series resistance values were found to be 4.33 kΩ at 300 K and 277.52 kΩ at 150 K, which increased by decreasing the temperature because of the increased n and the lack of carrier mobility in the B-doped UNCD/a-C:H films. Although a small UV response was observed at 300 K, the photocurrent at 150 K was over two orders of magnitude above the dark current at zero voltage. The detectivity values at 0 V were 2.37 × 10<sup>9</sup> Hz<sup>1/2</sup> cm/W and 1.34 × 10<sup>10</sup> Hz<sup>1/2</sup> cm/W at 300 K and 150 K, respectively. This research proposed a comprehensive study on the n-type Si/p-type UNCD heterojunctions as candidate photodiodes for UV photodetection applications.
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    Epitaxial growth of β-FeSi2 thin films on Si(111) substrates by radio frequency magnetron sputtering and their application to near-infrared photodetection
    (2016-01-01)
    Promros, Nathaporn
    ;
    Baba, Ryuji
    ;
    Takahara, Motoki
    ;
    Mostafa, Tarek M.
    ;
    Sittimart, Phongsaphak
    β-FeSi2 thin films were epitaxially grown on p-type Si(111) substrates at a substrate temperature of 560 C and Ar pressure of 2.66 10<sup>-1</sup> Pa by radio-frequency magnetron sputtering (RFMS) using a sintered FeSi2 target, without postannealing. The resultant n-type β-FeSi2/p-type Si heterojunctions were evaluated as near-infrared photodiodes. Three epitaxial variants of β-FeSi2 were confirmed by X-ray diffraction analysis. The heterojunctions exhibited typical rectifying action at room temperature. At 300 K, the heterojunctions showed a substantial leakage current and minimal response for irradiation of near-infrared light. At 50 K, the leakage current was markedly reduced and the ratio of the photocurrent to dark current was considerably enhanced. The detectivity at 50 K was estimated to be 3.0 10<sup>11</sup> cm Hz<sup>1/2</sup>/W at a zero bias voltage. Their photodetection was inferior to those of similar heterojunctions prepared using facing-target direct-current sputtering (FTDCS) in our previous study. This inferiority is likely because β-FeSi2 films prepared using RFMS are located in plasma and are damaged by it.
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    Fabrication of mesa structural n-type nanocrystalline-FeSi2/p-type Si heterojunction photodiodes by liftoff technique combined with photolithography
    (2013-12-01)
    Funasaki, Suguru
    ;
    Promros, Nathaporn
    ;
    Iwasaki, Ryuhei
    ;
    Takahara, Motoki
    ;
    Shaban, Mahmoud
    Mesa structural n-type nanocrystalline (NC) FeSi<inf>2</inf>/p-type Si heterojunctions were fabricated by a liftoff technique combined with photolithography in order to improve the diode performance, particularly to reduce the parasitic capacitance. Their current-voltage characteristics were experimentally studied in the dark and under illumination using a 1.31 μm laser at room temperature. Their junction capacitance density and leakage current density were evidently reduced as compared with those of the normal structural diodes. The mesa diode exhibits a good rectifying action with a rectification ratio of approximately three orders of magnitude at bias voltages of ±1 V. The photodetection was clearly observed owing to the suppression in the dark current. The estimated detectivity is 2.0 × 10<sup>9</sup> cm√Hz/W at zero bias, which is an order of magnitude larger than that of the normal structural diodes. This should be because the formation of interface states is reduced accompanied by the interface area reduction. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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    Electrical characteristics of n-type nanocrystalline FeSi2/intrinsic Si/ p-type Si heterojunctions prepared by facing-targets direct-current sputtering
    (2014-01-01)
    Promros, Nathaporn
    ;
    Funasaki, Suguru
    ;
    Iwasaki, Ryuhei
    ;
    Yoshitake, Tsuyoshi
    n-Type nanocrystalline FeSi<inf>2</inf>/intrinsic Si/p-type Si heterojunctions were prepared by FTDCS. In order to estimate their diode parameters such as ideality factor, barrier height and series resistance, their current-voltage characteristics were measured in the temperature range from 300 to 77 K and analyzed on the basis of thermionic emission theory and Cheung's method. Based on thermionic emission theory, the ideality factor was calculated from the slope of the linear part from the forward lnJ-V characteristics. The barrier height was calculated once the saturation current density was derived from the straight line intercept of lnJ-V plot at a zero voltage. The obtained results exhibit an increase of ideality factor and a decrease of barrier height at low temperatures, which might be owing to inhomogeneity of material and non-uniformity of charge at the interface. Based on Cheung's method, the ideality factor and barrier height were estimated from y-axis intercept of dV/d(lnJ)-J plot and y-axis intercept of H(J)-J plot, respectively. The series resistance was analyzed from the slopes of dV/d(lnJ)-J and H(J)-J plots. The values of ideality factor and barrier height obtained from this method are in agreement with those obtained from the thermionic emission theory. The obtained series resistances from dV/d(lnJ)-J and H(J)-J plots, which were approximately equal to each others, were increased as the temperature decreased. This result should be owing to the increased ideality factor and remarkably reduced carrier concentrations at low temperatures. © (2014) Trans Tech Publications, Switzerland.
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    Near-infrared photodetection of β-FeSi2/Si heterojunction photodiodes at low temperatures
    (2013-01-21)
    Izumi, Shota
    ;
    Shaban, Mahmoud
    ;
    Promros, Nathaporn
    ;
    Nomoto, Keita
    ;
    Yoshitake, Tsuyoshi
    n-type β-FeSi<inf>2</inf>/p-type Si heterojunction photodiodes were fabricated by facing-targets direct-current sputtering, and their near-infrared photodetection properties were studied in the temperature range of 50-300 K. At 300 K, devices biased at -5 V exhibited a current responsivity of 16.6 mA/W. The measured specific detectivity was remarkably improved from 3.5 × 10 <sup>9</sup> to 1.4 × 10<sup>11</sup> cmHz<sup>1/2</sup>/W as the devices were cooled from 300 K down to 50 K. This improvement is mainly attributable to distinguished suppression in heterojunction leakage current at low temperatures. The obtained results indicate that β-FeSi<inf>2</inf>/Si heterojunctions offer high potential to be employed as near-infrared photodetectors that are compatible with the current Si technology. © 2013 American Institute of Physics.
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    Determining the Annealing Temperature Dependency of Wetting and Mechanical Features on Fe3Si Films
    (2023-08-01)
    Borwornpornmetee, Nattakorn
    ;
    Achirawongwat, Chawapon
    ;
    Traiprom, Thawichai
    ;
    Saekow, Bunpot
    ;
    Porntheeraphat, Supanit
    The impact of thermal annealing under temperature alteration on the wetting and mechanical attributes of Fe<inf>3</inf>Si films built through facing target sputtering (FTS) is an essential topic for study in order to identify their characteristics under varying temperatures. Consequently, we introduced a thermal annealing process in a vacuum for two hours under varying temperatures of 300, 600, and 900 °C to our Fe<inf>3</inf>Si films created via FTS. The primary purpose of this current research is to examine the effect of the thermal annealing technique under temperature alteration on the wetting and mechanical traits of Fe<inf>3</inf>Si films. In this research, Fe<inf>3</inf>Si films were built onto the Si wafer by FTS and divided for use in thermal annealing under temperature alteration. The structural, morphological, wetting, and mechanical traits of the Fe<inf>3</inf>Si films under thermal annealing are provided in the present work. Based on our information, this work represents an original study on the change in wetting and mechanical traits of Fe<inf>3</inf>Si films through thermal annealing under temperature alteration.
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    Investigation into the impedance, dielectric behavior, and conductivity within p-silicon/n-nanocrystalline iron disilicide heterojunctions and equivalent circuit model in relation to temperature
    (2025-03-15)
    Borwornpornmetee, Nattakorn
    ;
    Sittimart, Phongsaphak
    ;
    Traiprom, Thawichai
    ;
    Paosawatyanyong, Boonchoat
    ;
    Yoshitake, Tsuyoshi
    The p-Si/n-nanocrystalline FeSi<inf>2</inf> heterojunctions constructed through facing-targets sputtering were characterized for impedance under various frequencies and temperatures of between 160−400 K. Imaginary and real impedance plots for all temperatures demonstrated single semicircular arc with negative temperature dependency. From the arc, a circuit model equivalent to electrode resistance serially connected to several loops, each consisting of a parallel circuit comprising a resistance//constant phase element (Q), corresponding to the crystallite, crystallite boundary, and interface. All resistances increased with decreasing temperatures, while the Q values decreased but behaved as ideal capacitors for all temperatures. The dielectric constants versus increasing temperature demonstrated a linear increase. At 300 K and 1 MHz, the dielectric constant was 24.5 with 0.1 loss tangent, denoting its possible usage for filtration and storage. The alternating-current conductivities disclosed that direct-current conductivities increased as the temperature increased. The exponents from Jonscher's fit were 1 or less around 180 K and the values beyond 1 at higher temperatures, indicating the shift from long transitional transport to localized hopping transport. The activation energy based on conductivities was higher than the one based on relaxation times, implying that excess charge led to more energy requirements for transportation.
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    Photodetection characteristics of heterojunctions comprising p-type ultrananocrystalline diamond films and n-type Si substrates at low temperatures
    (2017-01-01)
    Hanada, Takanori
    ;
    Ohmagari, Shinya
    ;
    Zkria, Abdelrahman
    ;
    Promros, Nathaporn
    ;
    Yoshitake, Tsuyoshi
    0.06 at.% boron-doped p-type ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films were deposited on n-type Si substrates by pulsed laser deposition, and the resultant heterojunctions were evaluated as photodiodes in the deep-ultraviolet range. The rectifying action of the heterojunctions were improved accompanied by a reduction in the leakage current with decreasing temperature. The leakage current was decreased by more than three orders of magnitude at 60 K as compared with that at 300 K. Although the detectivity for 254 nm monochromatic light was gradually enhanced with decreasing temperature, the illumination current at reverse voltages was decreased along with the decrease in the leakage current. This might be because a spike due to a heterojunction band offset gets higher in the conduction band at low temperatures and it act as a barrier for photogenerated electrons flowing from the UNCD/a-C:H film to the Si substrate.
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    Physical feature exploration of nanocrystalline FeSi2 surface with argon plasma etching under varying power
    (2023-12-01)
    Borwornpornmetee, Nattakorn
    ;
    Sittimart, Phongsaphak
    ;
    Phatthanakun, Rungrueang
    ;
    Nakajima, Hideki
    ;
    Paosawatyanyong, Boonchoat
    Nanocrystalline (NC) FeSi<inf>2</inf> films were created on Si(111) wafers via direct-current sputtering with facing targets at an ambient temperature, then the films were etched by Ar plasma generated through microwave source at different powers of 50, 100, and 150 W. The surface morphology of the as-coated NC FeSi<inf>2</inf> films showed numerous small uniform crystallites and root-mean-square roughness of 4.65 Å. The surface for each etched NC FeSi<inf>2</inf> film showed appearance of holes and slight increase in the roughness as the power increased. X-ray photoelectron spectra showed that the etching decreased the content of hydrophobic carbon and increased the presence of polar oxide group on the NC FeSi<inf>2</inf> films as the power increased. These changes should be the factor behind the shift from hydrophobic state to hydrophilic state. The contact angle of the unetched NC FeSi<inf>2</inf> film surface was 100.55°, which is hydrophobic. The NC FeSi<inf>2</inf> film's surface reached a minimum contact angle of 35.65°, which belong to hydrophilic state, when the etching power was increased to 150 W. The mechanical properties of NC FeSi<inf>2</inf> films rarely affect by Ar plasma. The change in surface state to nearly superhydrophilic after plasma etching indicate possibility to develop NC FeSi<inf>2</inf> into a self-cleaning surface coating material.