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10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Thermally induced structural evolution and nanoscale interfacial dynamics in Bi-Sb-Te layered nanostructures

Layered chalcogenides, including Bi-Sb-Te ternary alloys and heterostructures, are renowned as thermoelectric and topological insulators and have recently been highlighted as plasmonic building blocks beyond noble metals. Here, we conduct joint in situ transmission electron microscopy and density functional theory calculations to investigate the temperature-dependent nanoscale dynamics and interfacial properties, identifying the role of native defects and edge configurations in the anisotropic sublimation of Bi 2 Te 3 -Sb 2 Te 3 heterostructures and Sb 2-x Bi x Te 3 alloys. We report structural dynamics, including edge evolution, layer-by-layer sublimation, and the formation and coalescence of thermally induced polygonal nanopores. These nanopores are initiated by preferential dissociation of tellurium, reducing thermal stability in heterostructures. Triangular and quasi-hexagonal configurations dominate nanopore structures in heterostructures. Our calculations reveal antisite defects (Te Sb and Te Bi ) as key players in defect-assisted sublimation. These findings enhance our understanding of nanoscale dynamics and assist in designing tunable low-dimensional chalcogenides.

Bi2Te3-Sb2Te3 heterostructure↗
NASA NTRS2000

Micromachined Thermoelectric Sensors and Arrays and Process for Producing

Linear arrays with up to 63 micromachined thermopile infrared detectors on silicon substrates have been constructed and tested. Each detector consists of a suspended silicon nitride membrane with 11 thermocouples of sputtered Bi-Te and Bi-Sb-Te thermoelectric elements films. At room temperature and under vacuum these detectors exhibit response times of 99 ms, zero frequency D* values of 1.4 x 10(exp 9) cmHz(exp 1/2)/W and responsivity values of 1100 V/W when viewing a 1000 K blackbody source. The only measured source of noise above 20 mHz is Johnson noise from the detector resistance. These results represent the best performance reported to date for an array of thermopile detectors. The arrays are well suited for uncooled dispersive point spectrometers. In another embodiment, also with Bi-Te and Bi-Sb-Te thermoelectric materials on micromachined silicon nitride membranes, detector arrays have been produced with D* values as high as 2.2 x 10(exp 9) cm Hz(exp 1/2)/W for 83 ms response times.

Foote, Marc C.↗
NASA NTRS2001

Progress towards high-performance thermopile imaging arrays

The purpose of this present work is to improve thermopile 2-D arrays substantially by combining Bi-Te and Bi-Sb-Te thermoelectric materials with a unique pixel structure and low-noise readout circuitry.

detector thermopile infrared uncooled array imagin↗
NASA NTRS2003

Surface-Micromachined Planar Arrays of Thermopiles

Planar two-dimensional arrays of thermopiles intended for use as thermal-imaging detectors are to be fabricated by a process that includes surface micromachining. These thermopile arrays are designed to perform better than do prior two-dimensional thermopile arrays. The lower performance of prior two-dimensional thermopile arrays is attributed to the following causes: The thermopiles are made from low-performance thermoelectric materials. The devices contain dielectric supporting structures, the thermal conductances of which give rise to parasitic losses of heat from detectors to substrates. The bulk-micromachining processes sometimes used to remove substrate material under the pixels, making it difficult to incorporate low-noise readout electronic circuitry. The thermoelectric lines are on the same level as the infrared absorbers, thereby reducing fill factor. The improved pixel design of a thermopile array of the type under development is expected to afford enhanced performance by virtue of the following combination of features: Surface-micromachined detectors are thermally isolated through suspension above readout circuitry. The thermopiles are made of such high-performance thermoelectric materials as Bi-Te and Bi-Sb-Te alloys. Pixel structures are supported only by the thermoelectric materials: there are no supporting dielectric structures that could leak heat by conduction to the substrate.

Foote, Marc C.↗
DOE OSTI2020

Materials Data on Bi(SbTe2)3 by Materials Project

Bi(SbTe2)3 is MAX Phase-like structured and crystallizes in the monoclinic Cm space group. The structure is two-dimensional and consists of two Bi(SbTe2)3 sheets oriented in the (1, 0, 0) direction. Bi3+ is bonded to six Te2- atoms to form BiTe6 octahedra that share corners with three equivalent SbTe6 octahedra, edges with two equivalent BiTe6 octahedra, and edges with seven SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. There are a spread of Bi–Te bond distances ranging from 3.11–3.26 Å. There are three inequivalent Sb3+ sites. In the first Sb3+ site, Sb3+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with three equivalent SbTe6 octahedra, edges with four equivalent BiTe6 octahedra, and edges with five SbTe6 octahedra. The corner-sharing octahedral tilt angles are 2°. There are a spread of Sb–Te bond distances ranging from 3.01–3.25 Å. In the second Sb3+ site, Sb3+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with three equivalent SbTe6 octahedra, edges with two equivalent BiTe6 octahedra, and edges with seven SbTe6 octahedra. The corner-sharing octahedral tilt angles are 2°. There are a spread of Sb–Te bond distances ranging from 3.04–3.22 Å. In the third Sb3+ site, Sb3+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with three equivalent BiTe6 octahedra, an edgeedge with one BiTe6 octahedra, and edges with eight SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. There are a spread of Sb–Te bond distances ranging from 3.03–3.21 Å. There are six inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to one Bi3+ and five Sb3+ atoms to form edge-sharing TeBiSb5 octahedra. In the second Te2- site, Te2- is bonded to two equivalent Bi3+ and four Sb3+ atoms to form edge-sharing TeBi2Sb4 octahedra. In the third Te2- site, Te2- is bonded in a 6-coordinate geometry to two equivalent Bi3+ and one Sb3+ atom. In the fourth Te2- site, Te2- is bonded in a 6-coordinate geometry to one Bi3+ and two equivalent Sb3+ atoms. In the fifth Te2- site, Te2- is bonded in a 6-coordinate geometry to three Sb3+ atoms. In the sixth Te2- site, Te2- is bonded in a 6-coordinate geometry to three Sb3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BiSbTe2 by Materials Project

SbBiSbTe3Bi2SbTe3 is MAX Phase-like structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of one antimony molecule; one Bi2SbTe3 sheet oriented in the (0, 0, 1) direction; and one BiSbTe3 sheet oriented in the (0, 0, 1) direction. In the Bi2SbTe3 sheet, there are two inequivalent Bi1+ sites. In the first Bi1+ site, Bi1+ is bonded to six Te2- atoms to form BiTe6 octahedra that share corners with six equivalent SbTe6 octahedra, edges with six equivalent BiTe6 octahedra, and a faceface with one SbTe6 octahedra. The corner-sharing octahedral tilt angles are 45°. There are three shorter (3.07 Å) and three longer (3.33 Å) Bi–Te bond lengths. In the second Bi1+ site, Bi1+ is bonded in a 3-coordinate geometry to three equivalent Te2- atoms. All Bi–Te bond lengths are 3.75 Å. Sb3+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with six equivalent BiTe6 octahedra, edges with six equivalent SbTe6 octahedra, and a faceface with one BiTe6 octahedra. The corner-sharing octahedral tilt angles are 45°. There are three shorter (3.04 Å) and three longer (3.22 Å) Sb–Te bond lengths. There are three inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to three equivalent Bi1+ and three equivalent Sb3+ atoms to form distorted edge-sharing TeBi3Sb3 pentagonal pyramids. In the second Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent Bi1+ atoms. In the third Te2- site, Te2- is bonded in a 6-coordinate geometry to three equivalent Bi1+ and three equivalent Sb3+ atoms. In the BiSbTe3 sheet, Bi1+ is bonded to six Te2- atoms to form BiTe6 octahedra that share corners with six equivalent SbTe6 octahedra, edges with six equivalent BiTe6 octahedra, and a faceface with one SbTe6 octahedra. The corner-sharing octahedral tilt angles are 45°. There are three shorter (3.08 Å) and three longer (3.30 Å) Bi–Te bond lengths. Sb3+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with six equivalent BiTe6 octahedra, edges with six equivalent SbTe6 octahedra, and a faceface with one BiTe6 octahedra. The corner-sharing octahedral tilt angles are 45°. There are three shorter (3.04 Å) and three longer (3.25 Å) Sb–Te bond lengths. There are three inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to three equivalent Bi1+ and three equivalent Sb3+ atoms to form distorted edge-sharing TeBi3Sb3 pentagonal pyramids. In the second Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent Bi1+ atoms. In the third Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent Sb3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BiSbTe3 by Materials Project

BiSbTe3 is MAX Phase-like structured and crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three BiSbTe3 sheets oriented in the (0, 0, 1) direction. Bi3+ is bonded to six Te2- atoms to form BiTe6 octahedra that share corners with three equivalent SbTe6 octahedra, edges with three equivalent SbTe6 octahedra, and edges with six equivalent BiTe6 octahedra. The corner-sharing octahedral tilt angles are 2°. There are three shorter (3.08 Å) and three longer (3.28 Å) Bi–Te bond lengths. Sb3+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with three equivalent BiTe6 octahedra, edges with three equivalent BiTe6 octahedra, and edges with six equivalent SbTe6 octahedra. The corner-sharing octahedral tilt angles are 2°. There are three shorter (3.03 Å) and three longer (3.21 Å) Sb–Te bond lengths. There are three inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to three equivalent Bi3+ and three equivalent Sb3+ atoms to form edge-sharing TeBi3Sb3 octahedra. In the second Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent Bi3+ atoms. In the third Te2- site, Te2- is bonded in a 6-coordinate geometry to three equivalent Sb3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Bi2Sb2Te3 by Materials Project

(BiSb)2Te3 is Caswellsilverite-like structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Bi3+ is bonded to three equivalent Bi3+ and three equivalent Te2- atoms to form distorted BiBi3Te3 octahedra that share corners with three equivalent SbTe6 octahedra, corners with three equivalent TeBi3Sb3 octahedra, edges with three equivalent SbTe6 octahedra, edges with three equivalent TeBi3Sb3 octahedra, and edges with six equivalent BiBi3Te3 octahedra. The corner-sharing octahedral tilt angles are 10°. All Bi–Bi bond lengths are 3.08 Å. All Bi–Te bond lengths are 3.52 Å. Sb is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with three equivalent BiBi3Te3 octahedra, corners with three equivalent SbTe6 octahedra, edges with three equivalent BiBi3Te3 octahedra, and edges with nine equivalent SbTe6 octahedra. The corner-sharing octahedra tilt angles range from 0–10°. There are three shorter (3.06 Å) and three longer (3.21 Å) Sb–Te bond lengths. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to three equivalent Bi3+ and three equivalent Sb atoms to form TeBi3Sb3 octahedra that share corners with three equivalent BiBi3Te3 octahedra, corners with three equivalent TeSb6 octahedra, edges with three equivalent BiBi3Te3 octahedra, and edges with nine TeBi3Sb3 octahedra. The corner-sharing octahedra tilt angles range from 4–10°. In the second Te2- site, Te2- is bonded to six equivalent Sb atoms to form a mixture of edge and corner-sharing TeSb6 octahedra. The corner-sharing octahedral tilt angles are 4°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Bi(SbTe2)3 by Materials Project

BiSbTe3Sb2Te3 is MAX Phase-like structured and crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three BiSbTe3 sheets oriented in the (0, 0, 1) direction and three Sb2Te3 sheets oriented in the (0, 0, 1) direction. In each BiSbTe3 sheet, Bi3+ is bonded to six Te2- atoms to form BiTe6 octahedra that share corners with three equivalent SbTe6 octahedra, edges with three equivalent SbTe6 octahedra, and edges with six equivalent BiTe6 octahedra. The corner-sharing octahedral tilt angles are 2°. There are three shorter (3.08 Å) and three longer (3.26 Å) Bi–Te bond lengths. Sb3+ is bonded to six Te2- atoms to form SbTe6 octahedra that share corners with three equivalent BiTe6 octahedra, edges with three equivalent BiTe6 octahedra, and edges with six equivalent SbTe6 octahedra. The corner-sharing octahedral tilt angles are 2°. There are three shorter (3.03 Å) and three longer (3.19 Å) Sb–Te bond lengths. There are three inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 6-coordinate geometry to three equivalent Sb3+ atoms. In the second Te2- site, Te2- is bonded in a 6-coordinate geometry to three equivalent Bi3+ atoms. In the third Te2- site, Te2- is bonded to three equivalent Bi3+ and three equivalent Sb3+ atoms to form edge-sharing TeBi3Sb3 octahedra. In each Sb2Te3 sheet, there are two inequivalent Sb3+ sites. In the first Sb3+ site, Sb3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing SbTe6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are three shorter (3.04 Å) and three longer (3.21 Å) Sb–Te bond lengths. In the second Sb3+ site, Sb3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing SbTe6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are three shorter (3.04 Å) and three longer (3.21 Å) Sb–Te bond lengths. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to six Sb3+ atoms to form edge-sharing TeSb6 octahedra. In the second Te2- site, Te2- is bonded in a 6-coordinate geometry to three equivalent Sb3+ atoms.

36 MATERIALS SCIENCE↗