The experimental observation of intrinsic ferromagnetism in single layered chromium trihalides CrX3 (X = Cl, Br, I) has gained outstanding attention recently due to their possible implementation in spintronic devices. However, the reproducible preparation of highly crystalline chromium(III) halide nanolayers without stacking faults is still an experimental challenge. As chromium trihalides consist of adjacent layers with weak interlayer coupling, the preparation of ultrathin CrX3 nanosheets directly on substrates via vapor transport proves as an advantageous synthesis technique. It is demonstrated that vapor growth of ultrathin highly crystalline CrX3 micro‐ and nanosheets succeeds directly on yttrium stabilized zirconia substrates in a one‐step process via chemical vapor transport (CVT) in temperature gradients of 100 K (600 °C → 500 °C for CrCl3 and 650 °C → 550 °C for CrBr3 or CrI3) without a need for subsequent delamination. Due to simulation results, optimization of synthesis conditions is realized and phase pure CrX3 nanosheets with thicknesses ≤25 nm are obtained via short term CVT. The nanosheets morphology, crystallinity, and phase purity are analyzed by several techniques, including microscopy, diffraction, and spectroscopy. Furthermore, a potential subsequent delamination technique is demonstrated to give fast access to CrX3 monolayers using the example of CrCl3.

Im System Cu3Mo2O9/Zn3Mo2O9 existieren zwei Mischkristallreihen: Cu3(1‐x)Zn3xMo2O9 mit x = 0 bis x = 0.8 und x = 0.88 bis x = 1. Einkristalle von Cu3(1‐x)Zn3xMo2O9 (x = 0 bis x = 0.8) mit definierter Zusammensetzung wurden mittels Chemischen Transports mit dem Transportmittel Cl2 im Temperaturgefälle 973K→873K dargestellt. Die Mischkristalle wurden mittels Röntgenbeugung an polykristallinem Pulver und an Einkristallen sowie HRTEM charakterisiert.

In this work we report on the growth of single crystalline Bi 2 Se 3 nanostructures (nanoribbons, nanoflakes, and nanowires) by catalyst-free decomposition sublimation in sealed silica ampules. The nanostructures directly grow on Si/ SiO 2 substrates by a vapor−solid growth mechanism and show high degree of crystallinity with dimensions of >10 μm in length and simultaneously <10 nm in height (nanoribbons). In order to optimize the growth process in a reproducible way, thermodynamic calculations were realized. The high quality of as-grown nanostructures was confirmed by transmission electron microscopy including selected area electron diffraction as well as electrical transport measurements. Our electrical transport data are evidence, on the one hand, of the high crystal quality and efficiency of the synthesis by decomposition sublimation. On the other hand, the catalyst-free approach offers the chance to investigate crystals with high purity and to measure surface state properties. ■ INTRODUCTIONRecently, topological insulators (TI) have attracted great interest in the physics community, due to their unique surface states. Topological insulators exhibit a band gap in the bulk but have gapless edge states or metallic states on their surface. The surface states are stable against nonmagnetic disorder and protected by time-reversal symmetry (TRS). Moreover surface states exhibit fascinating electronic properties since they host Dirac Fermions with a locked spin-momentum behavior. These characteristics allow investigation of new physical phenomena which are specific to three-dimensional (3D) TI's surface states. 1−3 TI were theoretically predicted 4−6 and experimentally confirmed for the 3D-TI Bi 2 Se 3 and Bi 2 Te 3 by angle-resolved photoemission spectroscopy (ARPES) 7,8 and electrical transport measurements. 9,10The observation of quantum oscillations known as Shubnikov−de Haas (SdH) 11,12 oscillations allows a quantitative and systematic investigation of the two-dimensional (2D) surface states and bulk states by the precise determination of the Fermi wave vector k F of a given charge carrier population. Nevertheless, crystals with a very high quality are required in order to study quantum oscillations by electrical transport. Nanostructures are preferred for the specific study of the surface states, because they have many advantages compared to their bulk counterpart. Nanostructures of TI materials show a wide variety of morphologies, for instance, nanowires, nanotriangles, and nanoribbons. The large surface-to-volume ratio of nanostructures in comparison to the bulk material allow studies of surface effects 13 as well. The natural doping in Bi 2 Se 3 due to the presence of Se-vacancies leads to a contribution of the bulk carrier density to the conductivity. Therefore, for investigations of the surface states, ultrathin layers of Bi 2 Se 3 must be prepared. 14 Several methods for the fabrication of TI nanostructures are reported, for instance, mechanical exfoliation, 15,16 molecular beam epitaxy (MBE), 17−19 and ...

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Chemical Vapor Transport of Ternary Indium MolybdatesAn isothermal section of the phase diagram of the system In/Mo/O at 1273 K was established by isothermal equilibration and XRD analyses of quenched samples. The chemical vapor transport of In2Mo3O12 was investigated in dependence on mean transport temperature (823 K to 1123 K) and amount of transport agent (Cl2 or Br2). The observed transport behaviour is compared with results of thermodynamical calculations and the influence of mean temperature, transport agent and moisture contents is described in detail. Single crystals of the metal rich compound InMo4O6 were grown by chemical vapor transport in a temperature gradient 1273 K to 1173 K using H2O as transport agent. The gaseous compound In2MoO4(g) accounts for the chemical vapor transport of molybdenium compounds in the metal rich part of the ternary phase diagram In/Mo/O.