AlO x /LiF composite protection layer for Cr-doped (Bi,Sb) 2 Te 3 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.