Enhancement of the electrical properties of Au/MgSe/Au microwave resonators via pulsed laser welding of MgSe and Au nanosheets

Abstract

Herein, stacked nanosheets of Au (50 nm) and MgSe (100 nm) are fabricated by the thermal evaporation technique and welded by pulsed lasers of wavelengths of 1064 nm within few seconds. Au/MgSe (AMA) and welded Au/MgSe (PLW) interfaces are coated with another Au point contact and employed as microwave resonators. It is observed that both AMA and PLW devices are of amorphous structure. The laser welding technique resulted in formation clusters composed of very dense grains of Mg1.37AuSe1.18 and other clusters composed of Mg1.16Se. In addition, the impedance spectroscopy measurements on these nano-thick devices have shown their novel ability to perform as negative capacitance sources and as band-stop filters. The pulsed laser welding of these microwave resonators increased their ac conductivities by increasing the hopping sites in the devices. The density of localized states near the Fermi level is increased by ~ 21% and the scattering time constant between hopping sites is shortened via laser welding. As microwave resonators, the pulsed laser welding process shifted the notch frequency from 1.0 to 2.16 GHz, improved the negativity of the capacitance, increased the return loss values and lowered the voltage standing wave ratios to 1.0. The features of the AMA microwave resonators before and after the pulsed laser welding nominate them for use as band-stop filters and as negative capacitance sources