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Zhang H, Ahmadi M, Ginanjar WW, Blake GR, Kooi BJ. Effects of Intermixing in Sb 2Te 3/Ge 1+xTe Multilayers on the Thermoelectric Power Factor. ACS APPLIED MATERIALS & INTERFACES 2023; 15:22672-22683. [PMID: 37122126 PMCID: PMC10176324 DOI: 10.1021/acsami.3c00869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Over the past few decades, telluride-based chalcogenide multilayers, such as PbSeTe/PbTe, Bi2Te3/Sb2Te3, and Bi2Te3/Bi2Se3, were shown to be promising high-performance thermoelectric films. However, the stability of performance in operating environments, in particular, influenced by intermixing of the sublayers, has been studied rarely. In the present work, the nanostructure, thermal stability, and thermoelectric power factor of Sb2Te3/Ge1+xTe multilayers prepared by pulsed laser deposition are investigated by transmission electron microscopy and Seebeck coefficient/electrical conductivity measurements performed during thermal cycling. Highly textured Sb2Te3 films show p-type semiconducting behavior with superior power factor, while Ge1+xTe films exhibit n-type semiconducting behavior. The elemental mappings indicate that the as-deposited multilayers have well-defined layered structures. Upon heating to 210 °C, these layer structures are unstable against intermixing of sublayers; nanostructural changes occur on initial heating, even though the highest temperature is close to the deposition temperature. Furthermore, the diffusion is more extensive at domain boundaries leading to locally inclined structures there. The Sb2Te3 sublayers gradually dissolve into Ge1+xTe. This dissolution depends markedly on the relative Ge1+xTe film thickness. Rather, full dissolution occurs rapidly at 210 °C when the Ge1+xTe sublayer is substantially thicker than that of Sb2Te3, whereas the dissolution is very limited when the Ge1+xTe sublayer is substantially thinner. The resulting variations of the nanostructure influence the Seebeck coefficient and electrical conductivity and thus the power factor in a systematic manner. Our results shed light on a previously unreported correlation of the power factor with the nanostructural evolution of unstable telluride multilayers.
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Affiliation(s)
- Heng Zhang
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Majid Ahmadi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Wastu Wisesa Ginanjar
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Graeme R Blake
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Bart J Kooi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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Yimam DT, Van Der Ree AJT, Abou El Kheir O, Momand J, Ahmadi M, Palasantzas G, Bernasconi M, Kooi BJ. Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films. NANOMATERIALS 2022; 12:nano12101717. [PMID: 35630939 PMCID: PMC9143932 DOI: 10.3390/nano12101717] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 05/04/2022] [Accepted: 05/16/2022] [Indexed: 11/16/2022]
Abstract
Integration of the prototypical GeSbTe (GST) ternary alloys, especially on the GeTe-Sb2Te3 tie-line, into non-volatile memory and nanophotonic devices is a relatively mature field of study. Nevertheless, the search for the next best active material with outstanding properties is still ongoing. This search is relatively crucial for embedded memory applications where the crystallization temperature of the active material has to be higher to surpass the soldering threshold. Increasing the Ge content in the GST alloys seems promising due to the associated higher crystallization temperatures. However, homogeneous Ge-rich GST in the as-deposited condition is thermodynamically unstable, and phase separation upon annealing is unavoidable. This phase separation reduces endurance and is detrimental in fully integrating the alloys into active memory devices. This work investigated the phase separation of Ge-rich GST alloys, specifically Ge5Sb2Te3 or GST523, into multiple (meta)stable phases at different length scales in melt-quenched bulk and annealed thin film. Electron microscopy-based techniques were used in our work for chemical mapping and elemental composition analysis to show the formation of multiple phases. Our results show the formation of alloys such as GST213 and GST324 in all length scales. Furthermore, the alloy compositions and the observed phase separation pathways agree to a large extent with theoretical results from density functional theory calculations.
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Affiliation(s)
- Daniel Tadesse Yimam
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands; (D.T.Y.); (A.J.T.V.D.R.); (J.M.); (M.A.); (G.P.)
| | - A. J. T. Van Der Ree
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands; (D.T.Y.); (A.J.T.V.D.R.); (J.M.); (M.A.); (G.P.)
| | - Omar Abou El Kheir
- Department of Materials Science, University of Milano-Bicocca, Via R. Cozzi 55, I-20125 Milano, Italy; (O.A.E.K.); (M.B.)
| | - Jamo Momand
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands; (D.T.Y.); (A.J.T.V.D.R.); (J.M.); (M.A.); (G.P.)
| | - Majid Ahmadi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands; (D.T.Y.); (A.J.T.V.D.R.); (J.M.); (M.A.); (G.P.)
| | - George Palasantzas
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands; (D.T.Y.); (A.J.T.V.D.R.); (J.M.); (M.A.); (G.P.)
| | - Marco Bernasconi
- Department of Materials Science, University of Milano-Bicocca, Via R. Cozzi 55, I-20125 Milano, Italy; (O.A.E.K.); (M.B.)
| | - Bart J. Kooi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands; (D.T.Y.); (A.J.T.V.D.R.); (J.M.); (M.A.); (G.P.)
- Correspondence:
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Ten Brink GH, Zhu X, Guo W, Blauw K, Assink L, Svetovoy VB, Kooi BJ, Palasantzas G. Wetting of surfaces decorated by gas-phase synthesized silver nanoparticles: Effects of Ag adatoms, nanoparticle aging, and surface mobility. J Chem Phys 2021; 155:214701. [PMID: 34879663 DOI: 10.1063/5.0070497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The wetting state of surfaces can be rendered to a highly hydrophobic state by the deposition of hydrophilic gas phase synthesized Ag nanoparticles (NPs). The aging of Ag NPs leads to an increase in their size, which is also associated with the presence of Ag adatoms on the surface between the NPs that have a strong effect on the wetting processes. Furthermore, surface airborne hydrocarbons were removed by UV-ozone treatment, providing deeper insight into the apparent mobility of the NPs on different surfaces and their subsequent ripening and aging. In addition, the UV-ozone treatment revealed the presence of adatoms during the magnetron sputtering process. This surface treatment lowers the initial contact angle of the substrates and facilitates the mobility of Ag NPs and adatoms on the surface of substrates. Adatoms co-deposited on clean high surface energy substrates will nucleate on Ag NPs that will remain closely spherical and preserve the pinning effect due to the water nanomeniscus. If the adatoms are co-deposited on a UV-ozone cleaned low surface energy substrate, their mobility is restricted, and they will nucleate in two-dimensional islands and/or nanoclusters on the surface instead of connecting to existing Ag NPs. This growth results in a rough surface without overhangs, where the wetting state is reversed from hydrophobic to hydrophilic. Finally, different material surfaces of transmission electron microscopy grids revealed strong differences in the sticking coefficient for the Ag NPs, suggesting another factor that can strongly affect their wetting properties.
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Affiliation(s)
- Gert H Ten Brink
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Xiaotian Zhu
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Weiteng Guo
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - K Blauw
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - L Assink
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - V B Svetovoy
- A. N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky Prospect 31 Bld. 4, 119071 Moscow, Russia
| | - Bart J Kooi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - George Palasantzas
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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de Graaf S, Momand J, Mitterbauer C, Lazar S, Kooi BJ. Resolving hydrogen atoms at metal-metal hydride interfaces. SCIENCE ADVANCES 2020; 6:eaay4312. [PMID: 32064349 PMCID: PMC6994207 DOI: 10.1126/sciadv.aay4312] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Accepted: 11/22/2019] [Indexed: 05/21/2023]
Abstract
Hydrogen as a fuel can be stored safely with high volumetric density in metals. It can, however, also be detrimental to metals, causing embrittlement. Understanding fundamental behavior of hydrogen at the atomic scale is key to improve the properties of metal-metal hydride systems. However, currently, there is no robust technique capable of visualizing hydrogen atoms. Here, we demonstrate that hydrogen atoms can be imaged unprecedentedly with integrated differential phase contrast, a recently developed technique performed in a scanning transmission electron microscope. Images of the titanium-titanium monohydride interface reveal stability of the hydride phase, originating from the interplay between compressive stress and interfacial coherence. We also uncovered, 30 years after three models were proposed, which one describes the position of hydrogen atoms with respect to the interface. Our work enables previously unidentified research on hydrides and is extendable to all materials containing light and heavy elements, including oxides, nitrides, carbides, and borides.
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Affiliation(s)
- Sytze de Graaf
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, Netherlands
- Corresponding author. (S.d.G.); (B.J.K.)
| | - Jamo Momand
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, Netherlands
| | | | - Sorin Lazar
- Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, Netherlands
| | - Bart J. Kooi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, Netherlands
- Corresponding author. (S.d.G.); (B.J.K.)
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Guo W, Chen B, Do VL, ten Brink GH, Kooi BJ, Svetovoy VB, Palasantzas G. Effect of Airborne Hydrocarbons on the Wettability of Phase Change Nanoparticle Decorated Surfaces. ACS NANO 2019; 13:13430-13438. [PMID: 31625718 PMCID: PMC6887839 DOI: 10.1021/acsnano.9b06909] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 10/18/2019] [Indexed: 06/01/2023]
Abstract
We present here a detailed study of the wettability of surfaces nanostructured with amorphous and crystalline nanoparticles (NPs) derived from the phase-change material Ge2Sb2Te5 (GST). Particular attention was devoted to the effect of airborne surface hydrocarbons on surface wetting. Our analysis illustrates that a reversible hydrophilic-hydrophobic wettability switch is revealed by combined ultraviolet-ozone (UV-O3) treatments and exposure to hydrocarbon atmospheres. Indeed, the as-prepared surfaces exhibited a hydrophilic state after thermal annealing or UV-O3 treatment which can partially remove hydrocarbon contaminants, while a hydrophobic state was realized after exposure to hydrocarbon atmosphere. Using high-angle annular dark-field scanning transmission electron microscopy for the specially designed GST NP decorated graphene substrates, a network of hydrocarbon connecting GST NPs was observed. Our findings indicate that airborne hydrocarbons can significantly enhance the hydrophobicity of nanostructured surfaces. Finally, the experiments reveal that previously defined hydrophilic materials can be used for the design of hydrophobic surfaces even if the meniscus is highly adhered to a solid surface, which is in agreement with our qualitative model involving the contribution of the nanomeniscus formed between the substrate and a decorating NP.
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Affiliation(s)
- Weiteng Guo
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Bin Chen
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Van Lam Do
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Gert H. ten Brink
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Bart J. Kooi
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Vitaly B. Svetovoy
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
- A.
N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciencies, Leninsky prospect 31 bld. 4, 119071 Moscow, Russia
| | - George Palasantzas
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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