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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Silicon Quantum Dots with Counted Antimony Donor Implants

Deterministic control over the location and number of donors is crucial to donor spin quantum bits (qubits) in semiconductor based quantum computing. A focused ion beam is used to implant close to quantum dots. Ion detectors are integrated next to the quantum dots to sense the implants. The numbers of ions implanted can be counted to a precision of a single ion. Regular coulomb blockade is observed from the quantum dots. Charge offsets indicative of donor ionization, are observed in devices with counted implants.

Singh, Meenakshi↗
DOE OSTI2023

Pyrolyzer Assisted Vapor Transport Deposition of Antimony-doped Cadmium Telluride

A new method for in-situ Sb doping of CdTe that uses a modified vapor transport deposition system is described. This modification enables control of the Sb concentration with a pyrolysis stage to enhance the doping efficiency. CdTe:Sb films under different deposition conditions are characterized by SEM, XRD, and CV measurements for determining morphology, crystal structure, and hole concentration. Variations of the Sb dopant heater and pyrolyzer temperatures do not affect the CdTe morphology and crystal structure. However, CV measurements show that a higher dopant heater or pyrolyzer temperature leads to higher hole concentration. In this study, CdTe: Sb films achieve a hole concentration of 1016 cm-3 and 10% doping efficiency when the dopant heater is 600C and the pyrolyzer temperature is 1100C. This demonstrates a path to produce high hole concentration polycrystalline CdTe film with a low concentration of dopant-induced defect.

14 SOLAR ENERGY↗
DOE OSTI2019

Mechanism and Kinetics of Stibnite Chloridizing with Calcium Chloride-Oxygen at 500 °C to 650 °C

Copper concentrates with high levels of toxic impurity elements such as As, Sb Bi, must be pretreated before processing in the current smelting/converting refineries. The classical method for the pretreatment of dirty copper concentrates is partial oxidizing roasting, where the impurities are eliminated through the gas phase. However, volatilization of antimony and bismuth in conventional roasting processes using air or oxygen-deficient air is hardly achieved since antimony and bismuth remain in the calcine as non-volatile oxides. The chloridizing of stibnite with calcium chloride was studied as an alternative to volatilize antimony from impure copper concentrates because the vapor pressure of antimony chloride is higher than the vapor pressures of antimony oxide or sulfide at low temperatures. Thus, in the present work, the kinetic study of chloridizing of antimony from stibnite using calcium chloride as the chloridizing agent was studied at roasting temperatures 500 °C to 650 °C. The salient aspects determined in this study are that the chloridizing of stibnite starts with the formation of Sb{sub 2}O{sub 3} followed by the chloridizing of this oxide by chlorine gas. The formation of antimony oxide Sb{sub 6}O{sub 13} deters the complete elimination of antimony from stibnite. By using the unreacted shrinking core model 1 − (1 − α){sup 1/3} = k{sub r}t, the chloridizing rate of stibnite with CaCl{sub 2} and oxygen was found to be of 0.6 order with respect to the oxygen partial pressure, and the calculated energy of activation is 62 kJ mol{sup −1} in the range from 500 °C to 650 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Atomic Structure, Dynamics, Changes in Chemical Bonding and Semiconductor-Metal Transition in Sb 2 Se 3 : A Remarkable Material for Quantum Networks and Energy Applications

Antimony sesquiselenide has become an outstanding functional material for photovoltaics, energy storage and transformation, memory and photonic applications. Sb 2 Se 3 is one of the most successful emerging solar light absorbers and has also been identified as a highly promising ultralow-loss phase-change material (PCM) for next-generation coherent nanophotonic processors, photonic tensor cores, quantum and neuromorphic networks. Unlike benchmark telluride PCMs, Sb 2 Se 3 features a quasi-one-dimensional (1D) crystalline structure consisting of (Sb 4 Se 6 ) ∞ ribbons, lacks the typical PCM chemical bonding, and undergoes an extended semiconductor-metal transition above the melting point. Consequently, the origin of high optical contrast between crystalline (SET) and amorphous (RESET) logic states remains elusive and presents a significant challenge. Using high-energy X-ray diffraction and Raman spectroscopy over a wide temperature range, supported by first-principles simulations and complemented by thermal, optical and electrical measurements, as well as by 121 Sb-Mossbauer spectroscopy, the quasi-1D network of orthorhombic antimony sesquiselenide was found to undergo significant evolution in amorphous and supercooled Sb 2 Se 3 , leading to lower coordination, shorter interatomic distances and a higher p-electron density on antimony, indicating changes in chemical bonding. The observed novel Sb 2 Se 3 nanocrystalline polymorph, characterized by trigonal antimony coordination and more isolated Sb-Se ribbons, could help reduce multiple trapping defect states in the bandgap, which are typical of orthorhombic Sb 2 Se 3 , thereby enhancing the power-conversion efficiency of photovoltaic devices. Semimetallic and metallic liquid Sb 2 Se 3 exhibit a gradual transformation into a denser 2D and/or 3D network with higher antimony coordination. Localized electron states in the pseudogap are becoming extended, leading to an increase in electronic conductivity σ following the relationship σ ∝ N(E F ) 2 . Liquid Sb 2 Se 3 also appears to be strongly fragile, with a nonmonotonic change in viscosity and higher atomic mobility in the metallic liquid. Furthermore, these results explain extraordinary functionalities of Sb 2 Se 3 for photonic and energy applications.

antimony↗
DOE OSTI2013

Surface and interfacial reaction study of half cycle atomic layer deposited HfO{sub 2} on chemically treated GaSb surfaces

An in situ half-cycle atomic layer deposition/X-ray photoelectron spectroscopy (XPS) study was conducted in order to investigate the evolution of the HfO{sub 2} dielectric interface with GaSb(100) surfaces after sulfur passivation and HCl etching, designed to remove the native oxides. With the first pulses of tetrakis(dimethylamido)hafnium(IV) and water, a decrease in the concentration of antimony oxide states present on the HCl-etched surface is observed, while antimony sulfur states diminished below the XPS detection limit on sulfur passivated surface. An increase in the amount of gallium oxide/sulfide is seen, suggesting oxygen or sulfur transfers from antimony to gallium during antimony oxides/sulfides decomposition.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗