AlO_x/LiF composite protection layer for Cr-doped (Bi, Sb)₂Te₃ quantum anomalous Hall films

We have realized robust quantum anomalous Hall samples by protecting Cr-doped (Bi, Sb)₂Te₃ topological insulator films with a combination of LiF and AlO_x capping layers. The AlO_x/LiF composite capping layer well keeps the quantum anomalous Hall states of Cr-doped (Bi, Sb)₂Te₃ films and effectively prevent them from degradation induced by ambient conditions. The progress is a key step towards the realization of the quantum phenomena in heterostructures and devices based on quantum anomalous Hall system.