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8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Sb2S3 by Materials Project

Sb2S3 is Stibnite structured and crystallizes in the orthorhombic Pnma space group. The structure is two-dimensional and consists of two Sb2S3 sheets oriented in the (0, 0, 1) direction. there are two inequivalent Sb3+ sites. In the first Sb3+ site, Sb3+ is bonded to five S2- atoms to form SbS5 square pyramids that share corners with two equivalent SbS6 octahedra, edges with three equivalent SbS6 octahedra, and edges with four equivalent SbS5 square pyramids. The corner-sharing octahedral tilt angles are 9°. There are a spread of Sb–S bond distances ranging from 2.48–2.87 Å. In the second Sb3+ site, Sb3+ is bonded to six S2- atoms to form distorted SbS6 octahedra that share corners with two equivalent SbS5 square pyramids, edges with four equivalent SbS6 octahedra, and edges with three equivalent SbS5 square pyramids. There are a spread of Sb–S bond distances ranging from 2.55–3.21 Å. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a 2-coordinate geometry to three equivalent Sb3+ atoms. In the second S2- site, S2- is bonded to five Sb3+ atoms to form distorted edge-sharing SSb5 square pyramids. In the third S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to three Sb3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sb2S3 by Materials Project

Sb2S3 is Stibnite structured and crystallizes in the orthorhombic Pmn2_1 space group. The structure is two-dimensional and consists of two Sb2S3 sheets oriented in the (0, 0, 1) direction. there are four inequivalent Sb3+ sites. In the first Sb3+ site, Sb3+ is bonded in a 6-coordinate geometry to six S2- atoms. There are a spread of Sb–S bond distances ranging from 2.55–3.26 Å. In the second Sb3+ site, Sb3+ is bonded to five S2- atoms to form SbS5 square pyramids that share corners with two equivalent SbS6 octahedra, an edgeedge with one SbS6 octahedra, and edges with four SbS5 square pyramids. The corner-sharing octahedral tilt angles are 9°. There are a spread of Sb–S bond distances ranging from 2.49–2.86 Å. In the third Sb3+ site, Sb3+ is bonded to six S2- atoms to form distorted SbS6 octahedra that share corners with two equivalent SbS5 square pyramids, edges with two equivalent SbS6 octahedra, and edges with three SbS5 square pyramids. There are a spread of Sb–S bond distances ranging from 2.57–3.19 Å. In the fourth Sb3+ site, Sb3+ is bonded to five S2- atoms to form SbS5 square pyramids that share edges with two equivalent SbS6 octahedra and edges with four SbS5 square pyramids. There are a spread of Sb–S bond distances ranging from 2.48–2.88 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded in a 3-coordinate geometry to three Sb3+ atoms. In the second S2- site, S2- is bonded in a 3-coordinate geometry to three Sb3+ atoms. In the third S2- site, S2- is bonded to five Sb3+ atoms to form distorted edge-sharing SSb5 square pyramids. In the fourth S2- site, S2- is bonded in a distorted water-like geometry to three Sb3+ atoms. In the fifth S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to three Sb3+ atoms. In the sixth S2- site, S2- is bonded to five Sb3+ atoms to form distorted edge-sharing SSb5 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Effect of Laser Beam Profile on Rotating Lattice Single Crystal Growth in Sb2S3 Model Glass

Laser heating of chalcogenide glasses has successfully produced rotating lattice single crystals through a solid-solid transformation. To better understand the nature of complex, orientation-dependent lattice rotation, we designed heat profiles of the continuous wave laser by beam shaping, fabricated larger Sb2S3 crystal dots in Sb2S3 glass, and investigated the lattice rotation where the crystal could grow in all radial directions under a circular thermal gradient. The results show that the rate of lattice rotation is highly anisotropic and depends on crystallographic direction. The nature of this rotation is the same in crystals of different orientation relative to the surface. The growth directions that align with the slip planes show the highest rate of rotation and the rotation rate gradually decreases away from this direction. Additionally, the presence of multiple growth directions results in a complicated rotation system. We suggest that the growth front influences the density of dislocations introduced during growth under confinement and thus affects the lattice rotation rate in these crystals.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Phase transition mechanism and bandgap engineering of Sb2S3 at gigapascal pressures

Abstract Earth-abundant antimony trisulfide (Sb 2 S 3 ), or simply antimonite, is a promising material for capturing natural energies like solar power and heat flux. The layered structure, held up by weak van-der Waals forces, induces anisotropic behaviors in carrier transportation and thermal expansion. Here, we used stress as mechanical stimuli to destabilize the layered structure and observed the structural phase transition to a three-dimensional (3D) structure. We combined in situ x-ray diffraction (XRD), Raman spectroscopy, ultraviolet-visible spectroscopy, and first-principles calculations to study the evolution of structure and bandgap width up to 20.1 GPa. The optical band gap energy of Sb 2 S 3 followed a two-step hierarchical sequence at approximately 4 and 11 GPa. We also revealed that the first step of change is mainly caused by the redistribution of band states near the conduction band maximum. The second transition is controlled by an isostructural phase transition, with collapsed layers and the formation of a higher coordinated bulky structure. The band gap reduced from 1.73 eV at ambient to 0.68 eV at 15 GPa, making it a promising thermoelectric material under high pressure.

Cui, Zhongxun (ORCID:0000000275044177)↗
DOE OSTI2020

Materials Data on SnSb4S7 by Materials Project

SnSb4S7 is Stibnite-derived structured and crystallizes in the monoclinic P2_1/m space group. The structure is two-dimensional and consists of one SnSb2S4 ribbon oriented in the (0, 1, 0) direction and one Sb2S3 sheet oriented in the (0, 0, 1) direction. In the SnSb2S4 ribbon, Sn2+ is bonded to five S2- atoms to form distorted SnS5 square pyramids that share corners with two equivalent SbS5 square pyramids, edges with two equivalent SnS5 square pyramids, and edges with three equivalent SbS5 square pyramids. There are a spread of Sn–S bond distances ranging from 2.70–3.14 Å. There are two inequivalent Sb3+ sites. In the first Sb3+ site, Sb3+ is bonded in a 5-coordinate geometry to three S2- atoms. There are one shorter (2.46 Å) and two longer (2.56 Å) Sb–S bond lengths. In the second Sb3+ site, Sb3+ is bonded to five S2- atoms to form SbS5 square pyramids that share corners with two equivalent SnS5 square pyramids, edges with three equivalent SnS5 square pyramids, and edges with four equivalent SbS5 square pyramids. There are a spread of Sb–S bond distances ranging from 2.48–2.86 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a water-like geometry to two equivalent Sb3+ atoms. In the second S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to two equivalent Sn2+ and one Sb3+ atom. In the third S2- site, S2- is bonded to two equivalent Sn2+ and three equivalent Sb3+ atoms to form distorted edge-sharing SSn2Sb3 square pyramids. In the fourth S2- site, S2- is bonded in a 5-coordinate geometry to one Sn2+ and two equivalent Sb3+ atoms. In the Sb2S3 sheet, there are two inequivalent Sb3+ sites. In the first Sb3+ site, Sb3+ is bonded in a 6-coordinate geometry to six S2- atoms. There are a spread of Sb–S bond distances ranging from 2.54–3.29 Å. In the second Sb3+ site, Sb3+ is bonded to five S2- atoms to form edge-sharing SbS5 square pyramids. There are a spread of Sb–S bond distances ranging from 2.48–2.87 Å. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted trigonal non-coplanar geometry to three Sb3+ atoms. In the second S2- site, S2- is bonded to five Sb3+ atoms to form distorted edge-sharing SSb5 square pyramids. In the third S2- site, S2- is bonded in a distorted water-like geometry to three equivalent Sb3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Local Thermal Conductivity Patterning in Rotating Lattice Crystals of Anisotropic Sb 2 S 3

The ability to control material heat transport properties over space and time can drive advanced functionalities in thermal management for electronics and system-on-chip, and enable thermal circuits. Despite the technological relevance, there are limited demonstrations of local thermal property control. Rotating lattice single (RLS) crystals—formed via laser-induced crystallization of an amorphous substrate—offer a novel avenue for local crystal engineering, unlocking opportunities for microscale property patterning. Here, thermal conductivity (𝜅) imaging is applied to RLS crystals of Sb2S3 to resolve microscale 𝜅 variations across patterned regions. Amorphous areas exhibit 𝜅 as low as 0.6 Wm −1 K −1 , while crystalline regions display periodic 𝜅 variations from 0.7 to over 2.5 Wm −1 K −1 . These variations correspond to changes in crystal orientation, revealing marked 𝜅 anisotropy. The crystal out-of-plane direction (c axis)—featuring van der Waals bonds—shows amorphous-like transport, whereas in-plane directions (a, b axes) exhibit 3.5x and 1.7x larger 𝜅, respectively. First-principles calculations, in excellent agreement with experiments, suggest that the in-plane anisotropy originates from expressed Sb lone pairs, which impart a corrugation along the b axis affecting bond stiffness and 𝜅. These findings demonstrate microscale control of thermal properties via laser-processed metastructures, with significant implications for next-generation thermal management.

14 SOLAR ENERGY↗
NASA NTRS1972

Solid state image sensing arrays

The fabrication of a photodiode transistor image sensor array in silicon, and tests on individual elements of the array are described along with design for a scanning system for an image sensor array. The spectral response of p-n junctions was used as a technique for studying the optical-absorption edge in silicon. Heterojunction structures of Sb2S3- Si were fabricated and a system for measuring C-V curves on MOS structures was built.

Sadasiv, G.↗
NASA NTRSDate not supplied

The PCM is Dead! Long Live O-PCM!

The ability to reconfigure the optical behavior of a device enables free-space applications ranging from imaging to sensing and signal control. Such optical devices can be compacted via meta-surfaces, patterned structures with feature sizes below the incident wavelength. Leveraging geometry in addition to material properties and CMOS fabrication techniques has allowed meta-surfaces for lenses, holograms, beam steerers and more. To incorporate multiple optical functions into one device, various methods of device control have been implemented, such as stretching of flexible substrates, tuning the refractive index of the comprising meta-atoms via the electro-optic or the thermo-optic effects, phase transition materials such as VO2 and more. Chalcogenide glasses used as optical phase change materials, such as Ge¬2Sb2Te5 (GST), have gained increased traction in the optics community for potential use in the near infrared (NIR) and mid infrared (MIR) bands, including the telecom bands. Various chalcogenides such as Sb2Se3, Sb2S3, Ge2Sb¬2Se5 and Ge2Sb2Se4Te (GSST) have been investigated due to their broad NIR or MIR transparency window and large changes in refractive index. In their amorphous phase, these materials usually display a lower refractive index and low absorption when compared to their crystalline state which display a higher refractive index and typically larger extinction coefficients. The amorphous-crystalline reversible switching can be done via fast melt-quenching thermal processes triggered by laser or electrical impulses, relying on a substrate as a heat sink. The potential of PCMs in photonic devices can be limited by intrinsic material limitations as well as by device fabrication issues. To explore the cyclability of GSST, a PCM with large refractive index contrast and on-chip electrothermal switching on a silicon-on-insulator platform has been done to analyze potential failure mechanisms from both a material and device perspective. A brief outline of the instrumentation and phase change contrast analysis is provided. Dewetting of the PCM, delamination of and damage in the PECVD SiNx protective layer, elemental migration in the PCM and optical contrast decay have been observed in cycled GSST devices. Guidelines for device performance improvement are proposed, and an improved design with larger endurance is shown in progress.

reconfigurable photonics↗