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@article{1475038, author = {Springholz, Günter and Wimmer, S. and Groiss, H. and Albu, M. and Hofer, F. and Caha, Ondřej and Kriegner, D. and Stangl, J. and Bauer, Günther and Holý, Václav}, article_location = {COLLEGE PK}, article_number = {5}, doi = {http://dx.doi.org/10.1103/PhysRevMaterials.2.054202}, keywords = {SINGLE DIRAC CONE; TOPOLOGICAL-INSULATOR; BI-SE; THERMOELECTRIC-MATERIALS; CRYSTAL-STRUCTURE; THIN-FILMS; BI2SE3; SURFACE; PHASES; DIFFRACTION}, language = {eng}, issn = {2475-9953}, journal = {PHYSICAL REVIEW MATERIALS}, title = {Structural disorder of natural BimSen superlattices grown by molecular beam epitaxy}, url = {https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.2.054202}, volume = {2}, year = {2018} }
TY - JOUR ID - 1475038 AU - Springholz, Günter - Wimmer, S. - Groiss, H. - Albu, M. - Hofer, F. - Caha, Ondřej - Kriegner, D. - Stangl, J. - Bauer, Günther - Holý, Václav PY - 2018 TI - Structural disorder of natural BimSen superlattices grown by molecular beam epitaxy JF - PHYSICAL REVIEW MATERIALS VL - 2 IS - 5 SP - "054202-1" - "054202-14" EP - "054202-1" - "054202-14" PB - AMER PHYSICAL SOC SN - 24759953 KW - SINGLE DIRAC CONE KW - TOPOLOGICAL-INSULATOR KW - BI-SE KW - THERMOELECTRIC-MATERIALS KW - CRYSTAL-STRUCTURE KW - THIN-FILMS KW - BI2SE3 KW - SURFACE KW - PHASES KW - DIFFRACTION UR - https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.2.054202 N2 - The structure and morphology of BimSen epitaxial layers with compositions ranging from Bi2Se3 to the Bi1Se1 grown by molecular beam epitaxy with different flux compositions are investigated by transmission electron microscopy, high-resolution x-ray diffraction, and atomic force microscopy. It is shown that the lattice structure changes significantly as a function of the beam flux composition, i.e., Se/BiSe flux ratio that determines the stoichiometry of the layers. A perfect Bi2Se3 phase is formed only with a sufficiently high additional Se flux, whereas Bi1Se1 is obtained when only a BiSe compound source without additional Se is used. For intermediate values of the excess Se flux during growth, Bi2Se3-delta layers are obtained with the Se deficit delta varying between 0 and 1. This Se deficit is accommodated by incorporation of additional Bi-Bi double layers into the Bi2Se3 structure that otherwise exclusively consists of Se-Bi-Se-Bi-Se quintuple layers. While a periodic insertion of such Bi double layers would result in the formation of natural BimSen superlattices, we find that this Bi double-layer insertion is rather stochastic with a high degree of disorder depending on the film composition. Therefore, the structure of such epilayers is better described by a one-dimensional paracrystal model, consisting of disordered sequences of quintuple and double layers rather than by strictly periodic natural superlattices. From detailed analysis of the x-ray diffraction data, we determine the dependence of the lattice parameters a and c and distances of the individual (0001) planes d(j) as a function of composition, evidencing that only the in-plane lattice parameter a shows a linear dependence on composition. The simulation of the diffraction curves with the random stacking paracrystal model yields an excellent agreement with the experimental data and it brings quantitative information on the randomness of the stacking sequence, which is compared to growth modeling using Monte Carlo simulations. The analysis of transmission electron microscopy data furthermore confirms that the Bi-Bi bilayers contain a large amount of vacancies of up to 25%. Conductivity and Hall data confirm that BimSen phases containing Bi-Bi double layers exhibit a rather semimetallic behavior. ER -
SPRINGHOLZ, Günter, S. WIMMER, H. GROISS, M. ALBU, F. HOFER, Ondřej CAHA, D. KRIEGNER, J. STANGL, Günther BAUER a Václav HOLÝ. Structural disorder of natural BimSen superlattices grown by molecular beam epitaxy. \textit{PHYSICAL REVIEW MATERIALS}. COLLEGE PK: AMER PHYSICAL SOC, 2018, roč.~2, č.~5, s.~''054202-1'' - ''054202-14'', 14 s. ISSN~2475-9953. Dostupné z: https://dx.doi.org/10.1103/PhysRevMaterials.2.054202.
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