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Impedance characteristics under different voltages of n-β-FeSi2/p-Si heterojunctions constructed via facing target sputtering
(2023-10-01)
Borwornpornmetee, Nattakorn
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Chaleawpong, Rawiwan
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Charoenyuenyao, Peerasil
;
Nopparuchikun, Adison
;
Paosawatyanyong, Boonchoat
Utilizing a substrate temperature of 600 °C, n-semiconducting iron disilicide (β-FeSi<inf>2</inf>)/p-silicon heterojunctions have been constructed with direct-current sputtering and a couple of facing FeSi<inf>2</inf> targets. The impedance examination was carried out under a voltage ranging from −1 V to 1 V. Each complex impedance arch unveiled only one arc with its center beneath the real axis. Elevated voltage facilitates a reduction in the semicircle size. Based on the simulated equivalent circuit model, the heterojunctions possessed high parallel resistance and a constant phase element (CPE) at the grain boundary, raising the V. The CPE for the grain, grain boundary, and junction implied behavior close to the ideal capacitor. The dielectric loss tangent results indicated that the heterojunctions exhibited leakage behavior. From the alternating-current conductivity plots, the plateau and dispersion areas were revealed at low and high frequencies, respectively. The direct-current conductivity was 9.49 × 10−3 S cm−1 at −1 V and elevated to 8.87 × 10−2 S cm−1 at 1 V, due to the augmented charge carriers. Jonscher's power law fitting exposed that the constructed heterojunction exhibited short-range hopping within the boundary of the neighborhood.
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Investigation of morphological surface features, wetting behavior and mechanical traits under various substrate temperatures for beta iron disilicide prepared via facing-targets sputtering
(2022-08-01)
Charoenyuenyao, Peerasil
;
Chaleawpong, Rawiwan
;
Borwornpornmetee, Nattakorn
;
Paosawatyanyong, Boonchoat
;
Sittimart, Phongsaphak
Using facing-targets sputtering, semiconducting iron disilicide (β-FeSi<inf>2</inf>) film layers were sputtered and coated on Si wafers owning (111) orientation. Under experimental conditions, the heating temperatures of the substrate (T<inf>substrate</inf>) were varied at 525 °C, 550 °C, 600 °C and 660 °C. The acquired XRD patterns indicated a strong β(202/220) peak of around 29.1° for the β-FeSi<inf>2</inf> films prepared at a T<inf>substrate</inf> of at least 600 °C. The β-FeSi<inf>2</inf> film surface prepared at a T<inf>substrate</inf> of 525 °C comprised several crystallites, which were arranged to form a grain format at a higher T<inf>substrate</inf>. The root mean square roughness for the film surface prepared at a T<inf>substrate</inf> of 525 °C was 0.49 nm, where it increased to 0.98 nm, 2.39 nm, and 4.23 nm at T<inf>substrate</inf> of 550 °C, 600 °C, and 660 °C, respectively. The films prepared at a T<inf>substrate</inf> of 525 °C exhibited an average contact angle (θ<inf>CA</inf>) of 91.15°, and improved to 103.80° after employing a T<inf>substrate</inf> of 660 °C. These results hinted at the possibility of employing the β-FeSi<inf>2</inf> films prepared at all T<inf>substrate</inf> in the hydrophobic surface application. The estimated hardness and elastic modulus of the β-FeSi<inf>2</inf> films prepared at T<inf>substrate</inf> of 525 °C were 12.78 GPa and 190.98 GPa, respectively, which increased to 21.27 GPa and 248.67 GPa, respectively, for the films prepared at 660 °C. According to mechanical results, the β-FeSi<inf>2</inf> films prepared at 660 °C exhibited the potential to be developed for use in hard coating application.
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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
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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 × 10−4 S m−1 at 0 V, which reduced to 2.67 × 10−5 S m−1 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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Physical properties of fe3si films coated through facing targets sputtering after microwave plasma treatment
(2021-08-01)
Borwornpornmetee, Nattakorn
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Charoenyuenyao, Peerasil
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Chaleawpong, Rawiwan
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Paosawatyanyong, Boonchoat
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Phatthanakun, Rungrueang
Fe<inf>3</inf>Si films are deposited onto the Si(111) wafer using sputtering with parallel facing targets. Surface modification of the deposited Fe<inf>3</inf>Si film is conducted by using a microwave plasma treatment under an Ar atmosphere at different powers of 50, 100 and, 150 W. After the Ar plasma treatment, the crystallinity of the coated Fe<inf>3</inf>Si films is enhanced, in which the orientation peaks, including (220), (222), (400), and (422) of the Fe<inf>3</inf>Si are sharpened. The extinction rule suggests that the B<inf>2</inf>–Fe<inf>3</inf>Si crystallites are the film’s dominant composition. The stoichiometry of the Fe<inf>3</inf>Si surfaces is marginally changed after the treatment. An increase in microwave power damages the surface of the Fe<inf>3</inf>Si films, resulting in the generation of small pinholes. The roughness of the Fe<inf>3</inf>Si films after being treated at 150 W is insignificantly increased compared to the untreated films. The untreated Fe<inf>3</inf>Si films have a hydrophobic surface with an average contact angle of 101.70◦ . After treatment at 150 W, it turns into a hydrophilic surface with an average contact angle of 67.05◦ because of the reduction in the hydrophobic carbon group and the increase in the hydrophilic oxide group. The hardness of the untreated Fe<inf>3</inf>Si is ~9.39 GPa, which is kept at a similar level throughout each treatment power.
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Photovoltaic, capacitance-voltage, conductance-voltage, and electrical impedance characteristics of p-type silicon/intrinsic-silicon/n-type semiconducting iron disilicide heterostructures built via facing target direct-current sputtering
(2020-09-01)
Chaleawpong, Rawiwan
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Promros, Nathaporn
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Charoenyuenyao, Peerasil
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Borwornpornmetee, Nattakorn
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Sittisart, Pattarapol
p-Type silicon (Si)/intrinsic Si/n-type semiconducting iron disilicide heterostructures were built via facing target direct-current sputtering. To assess the photovoltaic properties, the current density-voltage characteristic curves were recorded in conditions of dark and under irradiation via an Air Mass 1.5 solar simulator (100 mW/cm2). The built heterostructures demonstrated effective rectifying behavior along with a rather substantial leakage current. The open-circuit voltage and the short-circuit photocurrent density values were 178.00 mV and 10.08 mA/cm2, respectively. The assessed energy conversion efficiency was approximately 0.75%. The series resistance (R<inf>s</inf>) values at 0 V appraised by the Nicollian-Goetzberger technique were 60.28 Ω at 2 MHz, and 4.13 × 103 Ω at 10 kHz. Their interface state density values evaluated through the Hill-Coleman method were 1.38 × 1012 cm−2/eV at 10 kHz and 1.31 × 1011 cm−2/eV at 2 MHz. The R<inf>s</inf> and interface states occurring in the heterostructure interface zone should be the potential determinant of the degeneration of the photovoltaic properties. The characteristics of the real (Z’) and imaginary components of impedance under the changing voltages manifested a shape of one semicircle having a semicircular midpoint beneath the Z’ coordinate. An equivalent circuit model that was related with the heterostructure behavior should be assembled from the parallel association of resistance and constant phase element connected with R<inf>s</inf>.
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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
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Promros, Nathaporn
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Zkria, Abdelrahman
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Charoenyuenyao, Peerasil
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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−1 and 1585 cm−1 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 × 109 Hz1/2 cm/W and 1.34 × 1010 Hz1/2 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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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
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Promros, Nathaporn
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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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Production of p-Type Si/n-Type β-FeSi2 Heterojunctions Using Facing-Targets Direct-Current Sputtering and Evaluation of Their Resistance and Interface State Density
(2018-10-24)
Chaleawpong, Rawiwan
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Promros, Nathaporn
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Charoenyuenyao, Peerasil
;
Nopparuchikun, Adison
;
Sittimart, Phongsaphak
Without a post-annealing procedure, the β-FeSi<inf>2</inf> thin films are epitaxially grown on Si(111) wafer substrates via facing-targets direct-current sputtering. During epitaxial growth, the temperature for heating of substrates is maintained at 600 °C. The resultant p-type Si/n-type β-FeSi<inf>2</inf> heterojunctions are produced. At room temperature, a large leakage current under an applied reverse bias voltage together with a small photo-detective performance is observed from the measured dark and irradiated current density–voltage curves of the created heterojunctions. Both of the conductance–voltage (G/ω–V) and capacitance–voltage (C–V) measurements at different frequencies (f) in the range of 5 kHz–1 MHz are performed in the dark at room temperature. The interface state density (N<inf>ss</inf>) and series resistance (R<inf>s</inf>) in the created p-type Si/n-type β-FeSi<inf>2</inf> heterojunctions are computed and analyzed from the measured C–V–f and G/ω–V–f curves. N<inf>ss</inf> is found to be 3.48 × 1012 eV−1 cm−2 at 5 kHz and decreased to 4.68 × 1011 eV−1 cm−2 at 1 MHz. Moreover, the values of R<inf>s</inf> at zero bias are 2.21 kΩ at 5 kHz and 13.66 Ω at 1 MHz. These results review the presence of N<inf>ss</inf> and R<inf>s</inf> in the created heterojunctions, and they can be the cause to degrade the heterojunction performance.
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Surface morphology and wettability for thin films of beta-iron disilicide produced through direct-current sputtering utilizing a pair of facing targets
(2018-08-14)
Charoenyuenyao, Peerasil
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Promros, Nathaporn
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Chaleawpong, Rawiwan
;
Yoshitake, Tsuyoshi
In the current work, beta-FeSi2 films were epitaxially produced onto Si(111) wafer substrates via usage of facing-targets direct-current sputtering (FTDCS). The temperature for substrate heating was maintained at 600 °C and the sputtering pressure was set at 1.33 × 10-1 Pa. The surface morphology and contact angles of the beta-FeSi<inf>2</inf> films were explored consistently in this research. Images of three-dimensional AFM and FESEM for the beta-FeSi2 film surface revealed a smooth surface with a root mean square roughness of 1.31 nm and a porous area. The average contact angle between the dropped water and beta-FeSi<inf>2</inf> film surface was found to be 98.7°, establishing that the surface of the beta-FeSi<inf>2</inf> films was hydrophobic. The acquired experimental results revealed the commencement of the hydrophobic surface feature of the beta-FeSi<inf>2</inf> films produced via FTDCS approach.

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