  Material defects remain as the main bottleneck to the progress of topological
insulators (TIs). In particular, efforts to achieve thin TI samples with
dominant surface transport have always led to increased defects and degraded
mobilities, thus making it difficult to probe the quantum regime of the
topological surface states. Here, by utilizing a novel buffer layer scheme
composed of an In2Se3/(Bi0.5In0.5)2Se3 heterostructure, we introduce a quantum
generation of Bi2Se3 films with an order of magnitude enhanced mobilities than
before. This scheme has led to the first observation of the quantum Hall effect
in Bi2Se3.
