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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    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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    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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    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.
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    Reverse bias dependent impedance and dielectric properties of Al/n-NC FeSi2/p-Si/Pd heterostructures formed by facing-targets sputtering
    (2022-08-01)
    Borwornpornmetee, Nattakorn
    ;
    Chaleawpong, Rawiwan
    ;
    Charoenyuenyao, Peerasil
    ;
    Nopparuchikun, Adison
    ;
    Paosawatyanyong, Boonchoat
    Al/n-NC FeSi<inf>2</inf>/p-Si/Pd heterostructures were formed by facing-targets sputtering. From the dark J-V results, the device showed rectifying action with leakage current. In this work, impedance spectroscopy was employed to study the electrochemical characteristics of the heterostructures, which were inspected within a frequency (f) range from 20 Hz to 2 MHz. The range of the biased voltage (V) was −1 V to 0 V. All plots of real and imaginary impedances possessed single semi-circular arcs for all bias V values. The relaxation time was 2.00 μs at −1 V, and it became faster at 0 V with 0.42 μs. The equivalent circuit for the heterostructures consisted of series resistance (R<inf>s</inf>) combined with three sets of shunt circuits of resistance (R<inf>p</inf>) and a constant phase element (CPE), representing grain, grain boundary, and junction, respectively. The simulated R<inf>s</inf> and R<inf>p</inf> values decreased, while all CPE values increased as the biased V increased. For the dielectric properties, the real permittivity (ε′) values of 86.70 at 0 V and 20.22 at −1 V were disclosed at 100 Hz; all ε′ values decreased as the f value was increased. The loss tangent revealed to be very high due to dielectric loss being much higher than ε′ values, indicating the device to be leaky. The alternating conductivities plotted against f started at a low level in low f zones and grew exponentially when f reached higher values for all V values. Direct current conductivity was observed at 1.66 × 10<sup>−4</sup> S m<sup>−1</sup> at 0 V, which reduced to 2.67 × 10<sup>−5</sup> S m<sup>−1</sup> at −1 V. The dimensionless exponent of the conductivity results was higher than 1, indicating the hopping movement within the local site.
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    Investigation of electrical transport properties in heterojunctions comprised of silicon substrate and nanocrystalline iron disilicide films
    (2016-01-01)
    Promros, Nathaporn
    ;
    Sittimart, Phongsaphak
    ;
    Kaenrai, Weerasaruth
    In this study, n-type nanocrystalline FeSi<inf>2</inf>/p-type Si heterojunctions were fabricated using facing-target direct-current sputtering (FTDCS). The possible transportation mechanisms of carriers were investigated by analysing the dark J-V characteristics at temperatures ranging between 60 and 300 K. The ideality factor (n) was estimated from the slope of the linear region for the forward lnJ-V characteristics. The value of n was 1.87 at 300 K and nearly constant at temperatures ranging from 140 to 300 K, suggesting that a recombination process at the junction interface was dominant in the transportation mechanism of carriers. At temperatures below 140 K, the value of n increased by more than two and the value of A was virtually constant. Owing to the consistency of A, combined with the temperature dependent value of n, the implication is that a trap-assisted multi-step tunnelling mechanism governed the carrier transport. From the analysis of J-V characteristics, the value of barrier height was 0.58 eV at 300 K and decreased to 0.19 eV at 60 K.
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    Computation of Heterojunction Parameters at Low Temperatures in Heterojunctions Comprised of n-Type β -FeSi2 Thin Films and p-Type Si(111) Substrates Grown by Radio Frequency Magnetron Sputtering
    (2017-01-01)
    Sittimart, Phongsaphak
    ;
    Nopparuchikun, Adison
    ;
    Promros, Nathaporn
    In this study, n-type β-FeSi<inf>2</inf>/p-type Si heterojunctions, inside which n-type β-FeSi<inf>2</inf> films were epitaxially grown on p-type Si(111) substrates, were created using radio frequency magnetron sputtering at a substrate temperature of 560°C and Ar pressure of 2.66×10-1 Pa. The heterojunctions were measured for forward and reverse dark current density-voltage curves as a function of temperature ranging from 300 down to 20 K for computation of heterojunction parameters using the thermionic emission (TE) theory and Cheung's and Norde's methods. Computation using the TE theory showed that the values of ideality factor (n) were 1.71 at 300 K and 16.83 at 20 K, while the barrier height (φb) values were 0.59 eV at 300 K and 0.06 eV at 20 K. Both of the n and φb values computed using the TE theory were in agreement with those computed using Cheung's and Norde's methods. The values of series resistance (Rs) computed at 300 K and 20 K by Norde's method were 10.93 Ω and 0.15 MΩ, respectively, which agreed with the Rs values found through computation by Cheung's method. The dramatic increment of Rs value at low temperatures was likely attributable to the increment of n value at low temperatures.
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    Wetting state and mechanical property alteration for the Fe3Si films using rapid thermal annealing under various temperatures
    (2023-12-01)
    Borwornpornmetee, Nattakorn
    ;
    Traiprom, Thawichai
    ;
    Kusaba, Takafumi
    ;
    Sittimart, Phongsaphak
    ;
    Naragino, Hiroshi
    The current research demonstrates the modification of the wetting behavior and mechanical features as well as structure and morphology of Fe<inf>3</inf>Si films created via facing target sputtering by the rapid thermal annealing (RTA) with the set RTA temperatures (T<inf>RTA</inf>) of 200, 400, 600, and 800 °C. Following the RTA process, the crystallinity of Fe<inf>3</inf>Si developed under 400 °C or below. At the 600 °C and 800 °C T<inf>RTA</inf>, new crystal orientations emerged for FeSi and then β-FeSi<inf>2</inf>, respectively. Together with composition results, the Fe<inf>3</inf>Si films were proven to change into FeSi and then FeSi<inf>2</inf> under a high T<inf>RTA</inf> regime. At temperatures of 600 °C and 800 °C, large crystallites, including the scraggly interface, were observed. The root-mean-square roughness roughened slightly according to the RTA process at T<inf>RTA</inf> of 600 °C or above. The hydrophobic properties of the Fe<inf>3</inf>Si film surfaces became hydrophilic after the RTA procedure at a T<inf>RTA</inf> value above 400 °C. The hardness value of the Fe<inf>3</inf>Si films evidently increased through RTA at 600 °C and 800 °C. Thus, above 400 °C, the RTA process significantly alters the physical features of as-created Fe<inf>3</inf>Si films.
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    Corrigendum to “Wetting state and mechanical property alteration for the Fe3Si films using rapid thermal annealing under various temperatures” [Heliyon Volume 9, Issue 12, December 2023, Article e22511](S2405844023097190)(10.1016/j.heliyon.2023.e22511)
    (2025-05-01)
    Borwornpornmetee, Nattakorn
    ;
    Traiprom, Thawichai
    ;
    Kusaba, Takafumi
    ;
    Sittimart, Phongsaphak
    ;
    Naragino, Hiroshi
    In the original published version of this article, reference [22] was added in error: P. Du et al. tuned the mechanical properties of SiOC films with RTA under nitrogen ambient at different temperatures of 400, 600, and 800 °C for 10 min [21]. The treated SiOC films showed a change in residual stress, turning from compressive to tensile after RTA, and an improvement in hardness and Young's modulus as the temperatures were raised [22]. [22] Z. Bazhan, F.E. Ghodsi, J. Mazloom, Effect of phase transition induced by annealing temperature on wettability, optical and photocatalytic properties of nanostructured iron oxide thin film, J. Mater. Sci. Mater. Electron. 29 (2018) 11489–11497, https://doi.org/10.1007/s10854-018-9244-4. The reference and citation have been removed and the references have been renumbered accordingly. The intext citations have been updated to reflect this change. The correct version can be found below: P. Du et al. tuned the mechanical properties of SiOC films with RTA under nitrogen ambient at different temperatures of 400, 600, and 800 °C for 10 min [21]. The treated SiOC films showed a change in residual stress, turning from compressive to tensile after RTA, and an improvement in hardness and Young's modulus as the temperatures were raised. The authors apologize for the errors. Both the HTML and PDF versions of the article have been updated to correct the errors.
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    Modification of wetting and mechanical traits via rapid annealing under varying temperatures for β-FeSi2
    (2025-02-01)
    Borwornpornmetee, Nattakorn
    ;
    Traiprom, Thawichai
    ;
    Kusaba, Takafumi
    ;
    Sittimart, Phongsaphak
    ;
    Naragino, Hiroshi
    The examination on β-FeSi<inf>2</inf> thin films prepared via facing-target sputtering onto Si(111), subjected to rapid thermal annealing under varying temperatures of 200–800 °C, revealed numerous changes in the film’s physical traits. The energy-dispersive X-ray spectroscope findings corroborate the anticipated atomic composition, displaying strong Si and small Fe peaks, including C and Al impurities. The Fe/Si proportions barely changed after rapid annealing. Under 200 °C and 400 °C, the X-ray diffractometer spectra indicated that orientation (202/220) and (404/440) of β-FeSi<inf>2</inf> were improved by rapid annealing, while surface morphology also revealed gradual enhancement in grain structure and roughness. Temperatures of over 600 °C induced recrystallization of the films, resulting in the reduced orientation peak’s intensities, grain compression, and coarsening. These changes caused the air gap to collapse, turning the film’s surface hydrophilic with contact angles of 86.15° at 600 °C and 63.00° at 800 °C. In contrast, the films retained hydrophobicity with contact angles of 93.40° at 200 °C and 91.20° at 400 °C compared to the as-prepared films of 96.75°. The hardness and Young’s modulus improved with rising temperature to 15.2 GPa and 225.8 GPa at maximum. This has ramifications for their prospective use in self-cleaning and hard-coating applications.
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    Interface-state density estimation of n-type nanocrystalline FeSi2/p-type Si heterojunctions fabricated by pulsed laser deposition
    (2017-09-01)
    Nopparuchikun, Adison
    ;
    Promros, Nathaporn
    ;
    Sittimart, Phongsaphak
    ;
    Onsee, Peeradon
    ;
    Duangrawa, Asanlaya
    By utilizing pulsed laser deposition (PLD), heterojunctions comprised of n-type nanocrystalline (NC) FeSi<inf>2</inf>/ thin films and p-type Si substrates were fabricated at room temperature in this study. Both dark and illuminated current density-voltage (J-V ) curves for the heterojunctions were measured and analyzed at room temperature. The heterojunctions demonstrated a large reverse leakage current as well as a weak near-infrared light response. Based on the analysis of the dark forward J-V curves, at the V value ≤ 0.2 V, we show that a carrier recombination process was governed at the heterojunction interface. When the V value was > 0.2 V, the probable mechanism of carrier transportation was a space-charge limitedcurrent process. Both the measurement and analysis for capacitance-voltage-frequency (C-V-f ) and conductance-voltage-frequency (G-V-f ) curves were performed in the applied frequency ( f ) range of 50 kHz-2 MHz at room temperature. From the C-V-f and G-V-f curves, the density of interface states (Nss) for the heterojunctions was computed by using the Hill-Coleman method. The Nss values were 9.19 × 10<sup>12</sup> eV<sup>-1</sup> cm<sup>-2</sup> at 2 MHz and 3.15 × 10<sup>14</sup> eV<sup>-1</sup> cm<sup>-2</sup> at 50 kHz, which proved the existence of interface states at the heterojunction interface. These interface states are the probable cause of the degraded electrical performance in the heterojunctions.