Thermal Conductivity of Amorphous NbO_x Thin Films and Its Effect on Volatile Memristive Switching

Metal–oxide–metal (MOM) devices based on niobium oxide exhibit threshold switching (or current-controlled negative differential resistance) due to thermally induced conductivity changes produced by Joule heating. A detailed understanding of the device characteristics therefore relies on an understanding of the thermal properties of the niobium oxide film and the MOM device structure. In this study, we use time-domain thermoreflectance to determine the thermal conductivity of amorphous NbO_x films as a function of film composition and temperature. The thermal conductivity is shown to vary between 0.86 and 1.25 W·m^–1·K^–1 over the composition (x = 1.9 to 2.5) and temperature (293 to 453 K) ranges examined, and to increase with temperature for all compositions. The impact of these thermal conductivity variations on the quasistatic current–voltage (I–V) characteristics and oscillator dynamics of MOM devices is then investigated using a lumped-element circuit model. Understanding such effects is essential for engineering functional devices for nonvolatile memory and brain-inspired computing applications.