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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
;
Chaleawpong, Rawiwan
;
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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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 × 10−4 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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