Iron Selenide Nanowire Bundles for Microwave Communication Technology

Abstract

Herein, stacked layers of FeSe2 deposited onto ytterbium substrates using the thermal evaporation technique under a vacuum pressure of 10−5 mbar are observed to form nanowire bundles (NBs). Structural investigations on these NBs have shown the preferred growth of orthorhombic FeSe2 in addition to hexagonal ytterbium selenide as a minor phase in the structure of FeSe2. Impedance spectroscopy analyses conducted in the frequency domain of 0.01–1.80 GHz show that FeSe2 stacks can exhibit a negative capacitance effect and bandstop filter characteristics. For these bandstop filters, the refection coefficient (), the voltage standing wave ratios (), and the return loss () spectra display optimum values at a notch frequency of 0.87 GHz. In addition, computational analysis using Lorentz oscillator model has shown that the negativity of the capacitance is dominated by two oscillators centered at 0.08 and 1.25 GHz. On the other hand, the insertion of aluminum nanosheets between the stacked layers of FeSe2 has been observed to decrease the negativity of the capacitance, increase the values of and , and bring the closer to ideality. FeSe2 nanowire bundles resulting from FeSe2 stacks comprising Al nanosheets are considered suitable for microwave communication technology.