Epitaxial growth and structural characteristics of metastable β-In2Se3 thin films on H-terminated Si(111) substrates are studied. The In2Se3 thin films grown below the β-to-α phase transition temperature (453 K) are characterized to be strained β-In2Se3 mixed with significant γ-In2Se3 phases. The pure-phased single-crystalline β-In2Se3 can be reproducibly achieved by in situ annealing the as-deposited poly-crystalline In2Se3 within the phase equilibrium temperature window of β-In2Se3. It is suggeted that the observed γ-to-β phase transition triggered by quite a low annealing temperature should be a rather lowered phase transition barrier of the epitaxy-stabilized In2Se3 thin-film system at a state far from thermodynamic equilibrium.
The growth of In2Se3/Bi2Se3 superlattices (SLs) by molecular beam epitaxy at an elevated temperature is explored. The crystalline phase structure of In2Se3 layers in the as-grown SLs is determined to be α-In2Se3. The diffusion of In from In2Se3 to Bi2Se3 is significantly promoted, while Bi diffusion into In2Se3 layers is insignificant as manifested by the in situ lattice evolution analysis, so that the achieved SL structure is of graded (Bi1−xInx)2Se3 solid-solution layers periodically separated by α-In2Se3 layers. The lattice vibration characteristics due to phonon confinement in the achieved SLs are also exhibited.
The growth of γ-In2Se3 thin films on mica by molecular beam epitaxy is studied. Single-crystalline γ-In2Se3 is achieved at a relatively low growth temperature. An ultrathin β-In2Se3 buffer layer is observed to nucleate and grow through a process of self-organization at initial deposition, which facilitates subsequent monolithic epitaxy of single-crystalline γ-In2Se3 at low temperature. Strong room-temperature photoluminescence and moderate optoelectronic response are observed in the achieved γ-In2Se3 thin films.
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