  Memristors have been at the forefront of nanoelectronics research for the
last decade, offering a valuable component to reconfigurable computing. Their
attributes have been studied extensively along with applications that leverage
their state-dependent programmability in a static fashion. However, practical
applications of memristor-based AC circuits have been rather sparse, with only
a few examples found in the literature where their use is emulated at higher
frequencies. In this work, we study the behavior of metal-oxide memristors
under an AC perturbation in a range of frequencies, from 10^3 to 10^7 Hz.
Metal-oxide memristors are found to behave as RC low-pass filters and they
present a variable cut-off frequency when their state is switched, thus
providing a window of reconfigurability when used as filters. We further study
this behaviour across distinct material systems and we show that the usable
reconfigurability window of the devices can be tailored to encompass specific
frequency ranges by amending the devices' capacitance. This study extends
current knowledge on metal-oxide memristors by characterising their frequency
dependent characteristics, providing useful insights for their use in
reconfigurable AC circuits.
