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6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Synthesis and Electrical Properties of a New Compound (BiSe) 0.97 (Bi 2 Se 3 ) 1.26 (BiSe) 0.97 (MoSe 2 ) Containing Metallic 1T-MoSe 2

The synthesis and electrical properties of a new misfit compound containing BiSe, Bi 2 Se 3 , and MoSe 2 constituent layers are reported. The reaction pathway involves competition between the formation of (BiSe) 1+x (Bi 2 Se 3 ) 1+y (BiSe) 1+x (MoSe 2 ) and [(Bi 2 Se 3 ) 1+y ] 2 (MoSe 2 ). Excess Bi and Se are required in the precursor to synthesize (BiSe) 1+x (Bi 2 Se 3 ) 1+y (BiSe) 1+x (MoSe 2 ). High-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) confirm the stacking sequence of the heterostructure. Small grains of both 2H- and 1T-MoSe 2 are observed in the MoSe 2 layers. X-ray photoelectron spectroscopy (XPS) indicates that there is a significantly higher percentage of 1T-MoSe 2 in (BiSe) 1+x (Bi 2 Se 3 ) 1+y (BiSe) 1+x (MoSe 2 ) than in (BiSe) 0.97 (MoSe 2 ), suggesting that more charge transfer to MoSe 2 occurs due to the additional BiSe layer. The additional charge transfer results in (BiSe) 1+x (Bi 2 Se 3 ) 1+y (BiSe) 1+x (MoSe 2 ) having a low resistivity (14–19 μΩ m) with metallic temperature dependence. Furthermore, the heterogeneous mix of MoSe 2 polytypes observed in the XPS complicates the interpretation of the Hall data as two bands contribute to the electrical continuity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on BiSe by Materials Project

BiSe crystallizes in the orthorhombic Fmm2 space group. The structure is two-dimensional and consists of two BiSe sheets oriented in the (0, 0, 1) direction. Bi2+ is bonded to five equivalent Se2- atoms to form a mixture of edge and corner-sharing BiSe5 square pyramids. There are a spread of Bi–Se bond distances ranging from 2.95–3.02 Å. Se2- is bonded to five equivalent Bi2+ atoms to form a mixture of distorted edge and corner-sharing SeBi5 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Manipulating topological properties in Bi 2 Se 3 / BiSe /transition metal dichalcogenide heterostructures with interface charge transfer

Heterostructures of topological insulator Bi 2 Se 3 on transition metal dichalcogenides (TMDCs) offer a new materials platform for studying novel quantum states by exploiting the interplay among topological orders, charge orders and magnetic orders. Here, the diverse interface attributes, such as material combination, charge re-arrangement, defect and strain, can be utilized to manipulate the quantum properties of this class of materials. Recent experiments of Bi 2 Se 3 /NbSe 2 heterostructures show signatures of strong Rashba band splitting due to the presence of a BiSe buffer layer, but the atomic level mechanism is not fully understood. We conduct first-principles studies of the Bi 2 Se3/BiSe/TMDC heterostructures with five different TMDC substrates (1T phase VSe 2 , MoSe 2 , TiSe 2 , and 2H phase NbSe 2 , MoSe 2 ). We find significant charge transfer at both BiSe/TMDC and Bi 2 Se 3 /BiSe interfaces driven by the work function difference, which stabilizes the BiSe layer as an electron donor and creates interface dipole. The electric field of the interface dipole breaks the inversion symmetry in the Bi 2 Se 3 layer, leading to the giant Rashba band splitting in two quintuple layers and the recovery of the Dirac point in three quintuple layers, with the latter otherwise only occurring in thicker samples with at least six Bi 2 Se 3 quintuple layers. Besides, we find that strain can significantly affect the charge transfer at the interfaces. Our study presents a promising avenue for tuning topological properties in heterostructures of two-dimensional materials, with potential applications in quantum devices.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BiSe by Materials Project

BiSe is Calaverite-like structured and crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of two bismuth molecules and two Bi2Se3 sheets oriented in the (0, 0, 1) direction. In each Bi2Se3 sheet, there are two inequivalent Bi2+ sites. In the first Bi2+ site, Bi2+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. There are three shorter (2.91 Å) and three longer (3.09 Å) Bi–Se bond lengths. In the second Bi2+ site, Bi2+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. There are three shorter (2.89 Å) and three longer (3.12 Å) Bi–Se bond lengths. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Bi2+ atoms. In the second Se2- site, Se2- is bonded to six Bi2+ atoms to form edge-sharing SeBi6 octahedra. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Bi2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BiSe by Materials Project

BiSe is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Bi2+ is bonded to six equivalent Se2- atoms to form a mixture of edge and corner-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Bi–Se bond lengths are 3.08 Å. Se2- is bonded to six equivalent Bi2+ atoms to form a mixture of edge and corner-sharing SeBi6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni3(BiSe)2 by Materials Project

Ni3Bi2Se2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Ni sites. In the first Ni site, Ni is bonded in a distorted linear geometry to four Bi and two equivalent Se atoms. There are two shorter (2.77 Å) and two longer (2.86 Å) Ni–Bi bond lengths. Both Ni–Se bond lengths are 2.31 Å. In the second Ni site, Ni is bonded in a distorted linear geometry to four Bi and two equivalent Se atoms. There are a spread of Ni–Bi bond distances ranging from 2.77–2.90 Å. Both Ni–Se bond lengths are 2.31 Å. In the third Ni site, Ni is bonded in a distorted linear geometry to four Bi and two equivalent Se atoms. There are two shorter (2.80 Å) and two longer (2.85 Å) Ni–Bi bond lengths. Both Ni–Se bond lengths are 2.31 Å. There are two inequivalent Bi sites. In the first Bi site, Bi is bonded in a 6-coordinate geometry to six Ni atoms. In the second Bi site, Bi is bonded in a 6-coordinate geometry to six Ni atoms. Se is bonded in a 3-coordinate geometry to three Ni atoms.

36 MATERIALS SCIENCE↗