2017, Paik, Hanjong, Chen, Zhen, Lochocki, Edward, Seidner H., Ariel, Verma, Amit, Tanen, Nicholas, Park, Jisung, Uchida, Masaki, Shang, ShunLi, Zhou, Bi-Cheng, Brützam, Mario, Uecker, Reinhard, Liu, Zi-Kui, Jena, Debdeep, Shen, Kyle M., Muller, David A., Schlom, Darrell G.

Epitaxial La-doped BaSnO3 films were grown in an adsorption-controlled regime by molecular-beam epitaxy, where the excess volatile SnOx desorbs from the film surface. A film grown on a (001) DyScO3 substrate exhibited a mobility of 183 cm2 V-1 s-1 at room temperature and 400 cm2 V-1 s-1 at 10 K despite the high concentration (1.2 × 1011 cm-2) of threading dislocations present. In comparison to other reports, we observe a much lower concentration of (BaO)2 Ruddlesden-Popper crystallographic shear faults. This suggests that in addition to threading dislocations, other defects - possibly (BaO)2 crystallographic shear defects or point defects - significantly reduce the electron mobility.

2017, Hilmi, Isom, Lotnyk, Andriy, Gerlach, Jürgen W., Schumacher, Philipp, Rauschenbach, Bernd

An attempt to deposit a high quality epitaxial thin film of a two-dimensionally bonded (layered) chalcogenide material with van-der-Waals (vdW) epitaxy is of strong interest for non-volatile memory application. In this paper, the epitaxial growth of an exemplary layered chalcogenide material, i.e., stoichiometric Sb2Te3 thin films, is reported. The films were produced on unreconstructed highly lattice-mismatched Si(111) substrates by pulsed laser deposition (PLD). The films were grown by vdW epitaxy in a two-dimensional mode. X-ray diffraction measurements and transmission electron microscopy revealed that the films possess a trigonal Sb2Te3 structure. The single atomic Sb/Te termination layer on the Si surface was formed initializing the thin film growth. This work demonstrates a straightforward method to deposit vdW-epitaxial layered chalcogenides and, at the same time, opens up the feasibility to fabricate chalcogenide vdW heterostructures by PLD.

2018, Zaumseil, P., Hou, Y., Schubert, M.A., von den Driesch, N., Stange, D., Rainko, D., Virgilio, M., Buca, D., Capellini, G.

We report on the direct observation of lattice relaxation and Sn segregation of GeSn/Ge/Si heterostructures under annealing. We investigated strained and partially relaxed epi-layers with Sn content in the 5 at. %-12 at. % range. In relaxed samples, we observe a further strain relaxation followed by a sudden Sn segregation, resulting in the separation of a β-Sn phase. In pseudomorphic samples, a slower segregation process progressively leads to the accumulation of Sn at the surface only. The different behaviors are explained by the role of dislocations in the Sn diffusion process. The positive impact of annealing on optical emission is also discussed.