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Synthesis of (BiSe) <sub/> 1+ <i>δ</i> </sub> (Bi <sub/>2</sub> Se <sub/>3</sub> ) <sub/> 1+ <i>γ</i> </sub> (BiSe) <sub/> 1+ <i>δ</i> </sub> TiSe <sub/>2</sub> by Directed Self-Assembly of a Designed Precursor
摘要： The synthesis, structure and properties of a new three constituent heterostructure containing BiSe, Bi2Se3, and TiSe2 layers, each with a different structural motif, is reported. (BiSe)1+δ(Bi2Se3)1+γ(BiSe)1+δTiSe2, where δ and γ are the misfit parameters representing the differences in the in-plane packing density of the constituents, forms via a self-assembly process during low-temperature annealing from precursors with a range of compositions and repeat period thicknesses. This indicates that the compound exists in a relatively broad and deep free-energy minima in the energy landscape. The formation was followed as a function of annealing temperature using X-ray diffraction to determine optimum annealing temperatures and stability range. High-resolution electron microscopy images revealed the layering sequence of the constituents and a supercell within the BiSe layers created by periodic anti-phase boundaries. Temperature dependent electrical transport measurements show unexpected changes in carrier mobility and concentration relative to (BiSe)1.15TiSe2. This study suggests that new ternary and multinary phases containing fragments of known binary phases can be synthesized via precursors that mimic the desired product and that the properties of these new phases with ultrathin constituent thicknesses will probably be different from that expected based on composite behavior.
关键词： X-ray diffraction,electron microscopy,heterostructure,BiSe,self-assembly,TiSe2,Bi2Se3,electrical transport
更新于2025-09-04 15:30:14
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Single-crystal investigation of the proposed type-II Weyl semimetal CeAlGe
摘要： We present details of materials synthesis, crystal structure, and anisotropic magnetic properties of single crystals of CeAlGe, a proposed type-II Weyl semimetal. Single-crystal x-ray diffraction con?rms that CeAlGe forms in a noncentrosymmetric I 41md space group, in line with predictions of nontrivial topology. Magnetization, speci?c heat, and electrical transport measurements were used to con?rm antiferromagnetic order below 5 K, with an estimated magnon excitation gap of (cid:2) = 9.11 K from heat capacity and hole-like carrier density of 1.4 × 1020 cm?3 from Hall effect measurements. The easy magnetic axis is along the [100] crystallographic direction, indicating that the moment lies in the tetragonal ab plane below 7 K. A spin-?op transition to less than 1 μB /Ce is observed to occur below 30 kOe at 1.8 K in the M (H ) (H(cid:2)a) data. Small magnetic ?elds of 3 and 30 kOe are suf?cient to suppress magnetic order when applied along the a and c axes, respectively, resulting in a complex T –H phase diagram for H(cid:2)a and a simpler one for H(cid:2)c.
关键词： Weyl semimetal,CeAlGe,electrical transport measurements,single-crystal x-ray diffraction,antiferromagnetic order,magnetization,specific heat
更新于2025-09-04 15:30:14