  A detailed understanding of quantization conductance (QC), their correlation
with resistive switching phenomena and controlled manipulation of quantized
states is crucial for realizing atomic-scale multilevel memory elements. Here,
we demonstrate highly stable and reproducible quantized conductance states
(QC-states) in Al/Niobium oxide/Pt resistive switching devices. Three levels of
control over the QC-states, required for multilevel quantized state memories,
like, switching ON to different quantized states, switching OFF from quantized
states, and controlled inter-state switching among one QC states to another has
been demonstrated by imposing limiting conditions of stop-voltage and current
compliance. The well defined multiple QC-states along with a working principle
for switching among various states show promise for implementation of
multilevel memory devices.
