6.4  Sensitivity

The sensitivity of the memristive charge (flux)-based sensing scheme is determined by the value of the memristance (memductance) modulation with respect to the charge (flux) applied to the memristor. The amount of charge needed to pass through the memristor to change the memristance from its minimum to its maximum value for the TiO2   memristor is relatively high and is in the range of tens to hundreds of microcoulombs for a nanometer-scale motion of the doping front as the mobility of dopants (oxygen vacancies) in the TiO2   thin film is quite low (      - 10   2 - 1  - 1
~  10    cm   s   V    [69]). However, it turns out that it is in the range of nanocoulombs to picocoulombs in the spintronic memristors for a micrometer-scale motion of the magnetic domain wall (extracted from data presented in [171, 172, 94]) Therefore, the memristive sensor based on the TiO2   memristors can measure capacitances in the range of to microfarad to nanofarad. Because spin-based memristors can be more finely tuned compared to the TiO2   memristor [167, 64], they are promising for measuring capacitances of 3-6 orders of magnitude smaller than that measured by using the TiO 2   memristor. Nano-scale feature size, low cost and the integration capabilities are other advantages of spintronic memristors [96].