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Bi2Se3topological insulators (TIs) are grown on AlN(0001)/Si(111) substrates by molecular beam epitaxy. In a one-step growth at optimum temperature of 300 °C, Bi2Se3bonds strongly with AlN without forming interfacial reaction layers. This produces high epitaxial quality Bi2Se3single crystals with a perfect registry with the substrate and abrupt interfaces, allowing thickness scaling down to three quintuple layers (QL) without jeopardizing film quality. It is found by angle-resolved photoelectron spectroscopy that, remarkably, Bi2Se3films maintain the 3D TI properties at very low thickness of 3QL (∼2.88 nm), exhibiting top surface gapless metallic states in the form of a Dirac cone.

We report on the electrochemical preparation of GaAs porous substrates, their heat treatment in As rich environment and their overgrowth by metalorganic vapor phase epitaxy (MOVPE). The goal is to demonstrate that porous substrates are capable of accommodating strain at the interface with lattice mismatched In(x)Ga(1-x)As layers.

We report on the electrochemical preparation of GaAs porous substrates, their heat treatment in As rich environment and their overgrowth by metalorganic vapor phase epitaxy (MOVPE). The goal is to demonstrate that porous substrates are capable of accommodating strain at the interface with lattice mismatched In(x)Ga(1-x)As layers.