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Kumaar D, Can M, Weigand H, Yarema O, Wintersteller S, Grange R, Wood V, Yarema M. Phase-Controlled Synthesis and Phase-Change Properties of Colloidal Cu-Ge-Te Nanoparticles. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2024; 36:6598-6607. [PMID: 39005536 PMCID: PMC11238340 DOI: 10.1021/acs.chemmater.4c01009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 06/07/2024] [Accepted: 06/10/2024] [Indexed: 07/16/2024]
Abstract
Phase-change memory (PCM) technology has recently attracted a vivid interest for neuromorphic applications, in-memory computing, and photonic integration due to the tunable refractive index and electrical conductivity between the amorphous and crystalline material states. Despite this, it is increasingly challenging to scale down the device dimensions of conventionally sputtered PCM memory arrays, restricting the implementation of PCM technology in mass applications such as consumer electronics. Here, we report the synthesis and structural study of sub-10 nm Cu-Ge-Te (CGT) nanoparticles as suitable candidates for low-cost and ultrasmall PCM devices. We show that our synthesis approach can accurately control the structure of the CGT colloids, such as composition-tuned CGT amorphous nanoparticles as well as crystalline CGT nanoparticles with trigonal α-GeTe and tetragonal Cu2GeTe3 phases. In situ characterization techniques such as high-temperature X-ray diffraction and X-ray absorption spectroscopy reveal that Cu doping in GeTe improves the thermal properties and amorphous phase stability of the nanoparticles, in addition to nanoscale effects, which enhance the nonvolatility characteristics of CGT nanoparticles even further. Moreover, we demonstrate the thin-film fabrication of CGT nanoparticles and characterize their optical properties with spectroscopic ellipsometry measurements. We reveal that CGT nanoparticle thin films exhibit a negative reflectivity change and have good reflectivity contrast in the near-IR spectrum. Our work promotes the possibility to use PCM in nanoparticle form for applications such as electro-optical switching devices, metalenses, reflectivity displays, and phase-change IR devices.
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Affiliation(s)
- Dhananjeya Kumaar
- Chemistry and Materials Design, Institute for Electronics, Department of Information Technology and Electrical Engineering, ETH Zürich, 8092 Zürich, Switzerland
| | - Matthias Can
- Chemistry and Materials Design, Institute for Electronics, Department of Information Technology and Electrical Engineering, ETH Zürich, 8092 Zürich, Switzerland
| | - Helena Weigand
- Optical Nanomaterial Group, Institute for Quantum Electronics, Department of Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Olesya Yarema
- Materials and Device Engineering, Institute for Electronics, Department of Information Technology and Electrical Engineering, ETH Zürich, 8092 Zürich, Switzerland
| | - Simon Wintersteller
- Chemistry and Materials Design, Institute for Electronics, Department of Information Technology and Electrical Engineering, ETH Zürich, 8092 Zürich, Switzerland
| | - Rachel Grange
- Optical Nanomaterial Group, Institute for Quantum Electronics, Department of Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Vanessa Wood
- Materials and Device Engineering, Institute for Electronics, Department of Information Technology and Electrical Engineering, ETH Zürich, 8092 Zürich, Switzerland
| | - Maksym Yarema
- Chemistry and Materials Design, Institute for Electronics, Department of Information Technology and Electrical Engineering, ETH Zürich, 8092 Zürich, Switzerland
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Qin F, Hu L, Zhu Y, Li Y, Wang H, Wu H, Peng J, Shi W, Aydemir U, Ding X. Enhanced Thermoelectric Performance and Low Thermal Conductivity in Cu 2GeTe 3 with Identified Localized Symmetry Breakdown. Inorg Chem 2023; 62:7273-7282. [PMID: 37116190 DOI: 10.1021/acs.inorgchem.3c00350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
Highly efficient and eco-friendly thermoelectric generators rely on low-cost and nontoxic semiconductors with high symmetry and ultralow lattice thermal conductivity κL. We report the rational synthesis of the novel cubic (Ag, Se)-doped Cu2GeTe3 semiconductors. A localized symmetry breakdown (LSB) was found in the composition of Cu1.9Ag0.1GeTe1.5Se1.5 (i.e., CAGTS15) with an ultralow κL of 0.37 W/mK at 723 K, the lowest value outperforming all Cu2GeCh3 (Ch = S, Se, and Te). A joint investigation of synchrotron X-ray techniques identifies the LSB embedded into the cubic CAGTS15 host matrix. This LSB is an Ångström-scale orthorhombic symmetry unit, characteristic of multiple bond lengths, large anisotropic atomic displacements, and distinct local chemical coordination of anions. Computational results highlight that such an unusual orthorhombic symmetry demonstrates low-frequency phonon modes, which become softer and more predominant with increasing temperatures. This unconventional LSB promotes bond complexity and phonon scattering, highly beneficial for extraordinarily low lattice thermal conductivity.
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Affiliation(s)
- Feiyu Qin
- State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China
| | - Lei Hu
- State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China
| | - Yingcai Zhu
- School of Materials Science and Engineering, Beihang University, Beijing 100191, China
| | - Yushan Li
- State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China
| | - Haitao Wang
- State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China
| | - Haijun Wu
- State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China
| | - Jun Peng
- School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Wen Shi
- School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
| | - Umut Aydemir
- Department of Chemistry, Koc University, Sariyer, Istanbul 34450, Turkey
- Koç University Boron and Advanced Materials Application and Research Center (KUBAM), Sariyer, Istanbul 34450, Turkey
| | - Xiangdong Ding
- State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China
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Zhao Y, Liu M, Zhang W, Sun X, Wang W, Zhang W, Tang M, Ren W, Sun M, Feng W, Wang W. Solution-phase controlled synthesis of Cu 3NbSe 4 nanocrystals for optoelectronic applications. Dalton Trans 2022; 51:16937-16944. [DOI: 10.1039/d2dt02438a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cu3NbSe4 nanocrystals with a cubic phase, monodisperse size and uniform shape synthesized by a facile colloidal method exhibit excellent optoelectronic properties.
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Affiliation(s)
- Yutong Zhao
- School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, Shandong, P. R. China
- The Key Laboratory of Life-Organic Analysis, Qufu Normal University, Qufu 273165, Shandong, P. R. China
| | - Mengxue Liu
- School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, Shandong, P. R. China
| | - Wenqian Zhang
- School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, Shandong, P. R. China
- The Key Laboratory of Life-Organic Analysis, Qufu Normal University, Qufu 273165, Shandong, P. R. China
| | - Xue Sun
- School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, Shandong, P. R. China
- The Key Laboratory of Life-Organic Analysis, Qufu Normal University, Qufu 273165, Shandong, P. R. China
| | - Wenliang Wang
- School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, Shandong, P. R. China
- The Key Laboratory of Life-Organic Analysis, Qufu Normal University, Qufu 273165, Shandong, P. R. China
| | - Wenxiu Zhang
- School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, Shandong, P. R. China
| | - Mengqi Tang
- School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, Shandong, P. R. China
| | - Wenqing Ren
- School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, Shandong, P. R. China
| | - Mingyu Sun
- School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, Shandong, P. R. China
| | - Wenling Feng
- School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, Shandong, P. R. China
- The Key Laboratory of Life-Organic Analysis, Qufu Normal University, Qufu 273165, Shandong, P. R. China
| | - Weihua Wang
- School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, Shandong, P. R. China
- The Key Laboratory of Life-Organic Analysis, Qufu Normal University, Qufu 273165, Shandong, P. R. China
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