【公開日：2025.06.10】【最終更新日：2025.05.19】
課題データ / Project Data
課題番号 / Project Issue Number
24JI0025
利用課題名 / Title
Atomic scale observation of semiconductor materials
利用した実施機関 / Support Institute
北陸先端科学技術大学院大学 / JAIST
機関外・機関内の利用 / External or Internal Use
外部利用/External Use
技術領域 / Technology Area
【横断技術領域 / Cross-Technology Area】（主 / Main）計測・分析/Advanced Characterization（副 / Sub）物質・材料合成プロセス/Molecule & Material Synthesis
【重要技術領域 / Important Technology Area】（主 / Main）高度なデバイス機能の発現を可能とするマテリアル/Materials allowing high-level device functions to be performed（副 / Sub）次世代ナノスケールマテリアル/Next-generation nanoscale materials
キーワード / Keywords
ナノカーボン/ Nano carbon,電子顕微鏡/ Electronic microscope,エレクトロデバイス/ Electronic device,原子層薄膜/ Atomic layer thin film
利用者と利用形態 / User and Support Type
利用者名（課題申請者）/ User Name (Project Applicant)
Zhang Jiaqi
所属名 / Affiliation
Zhengzhou University,College of Physics
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
利用形態 / Support Type
（主 / Main）機器利用/Equipment Utilization（副 / Sub）-
利用した主な設備 / Equipment Used in This Project
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
Abstract: This study aims to leverage the advanced imaging capabilities of Cs-corrected transmission electron microscopy (TEM) to investigate the structural and morphological properties of 5 nm diamond nanoparticles and PrMgSbBi thermoelectric materials at the atomic scale. The primary objective is to elucidate the crystallographic features, defect structures, and interfacial characteristics of these nanomaterials to enhance their performance in thermal management and energy conversion applications. Diamond nanoparticles, known for their exceptional thermal conductivity and chemical stability, are explored for use in high-performance thermal interface materials (TIMs) for electronics and as quantum sensors due to their nitrogen-vacancy (NV) centers. PrMgSbBi, a novel thermoelectric material, is examined for its potential in efficient energy harvesting and cooling systems, capitalizing on its tunable electrical and thermal properties. The Cs-corrected TEM enables sub-nanometer resolution, facilitating precise observation of lattice parameters, phase distributions, and nanostructural defects. Applications include optimizing diamond nanoparticle coatings for heat dissipation in GaN-based electronics and improving the thermoelectric figure of merit (zT) of PrMgSbBi for sustainable energy solutions. The contents of this study encompass sample preparation, high-resolution TEM imaging, electron diffraction analysis, and correlative spectroscopy to provide comprehensive insights into the materials’ nanoscale behavior and their suitability for next-generation technological advancements.
実験 / Experimental
Experimental SectionSample Preparation:
5 nm diamond nanoparticles (DNPs) were synthesized via a detonation process and purified through acid washing to remove amorphous carbon and impurities. The DNPs were dispersed in ethanol via ultrasonication for 30 minutes to achieve a homogeneous suspension. A 5 µL droplet of the suspension was deposited onto a lacey carbon-coated copper TEM grid and air-dried. PrMgSbBi thermoelectric materials were prepared via a solid-state reaction, where high-purity Pr, Mg, Sb, and Bi powders were mixed in stoichiometric ratios, sealed in a quartz ampoule under argon, and sintered at 900°C for 24 hours. The resulting ingot was pulverized into a fine powder, pressed into pellets, and annealed at 600°C for 12 hours. Thin TEM lamellae (~50 nm thick) of PrMgSbBi were prepared using a focused ion beam (FIB) lift-out technique with a Ga-ion source, followed by low-energy Ar-ion milling to minimize surface amorphization.Cs-Corrected TEM Imaging:
High-resolution imaging was performed using a Cs-corrected transmission electron microscope (JEOL JEM-ARM200F) operated at 200 kV, equipped with a spherical aberration corrector to achieve a point resolution of ~0.08 nm. The DNP samples were imaged in bright-field (BF) and high-angle annular dark-field (HAADF) modes to characterize particle size, morphology, and lattice structure. Selected area electron diffraction (SAED) patterns were acquired to confirm the diamond cubic phase. For PrMgSbBi, scanning transmission electron microscopy (STEM) with HAADF and energy-dispersive X-ray spectroscopy (EDS) was employed to map elemental distributions and phase segregation. Convergence angles were set to 20 mrad for imaging and 30 mrad for spectroscopy to optimize contrast and signal-to-noise ratio.Electron Diffraction and Spectroscopy:
SAED patterns of DNPs were analyzed to determine lattice parameters and detect defects such as stacking faults or twinning. For PrMgSbBi, convergent beam electron diffraction (CBED) was used to assess local crystal symmetry and strain. EDS and electron energy loss spectroscopy (EELS) were conducted to quantify elemental compositions and investigate electronic structures, particularly the plasmon and core-loss edges of Pr, Mg, Sb, and Bi. Spectra were collected with an energy resolution of 0.5 eV using a Gatan Quantum ER spectrometer.Data Analysis:
TEM images were processed using DigitalMicrograph software for fast Fourier transform (FFT) analysis to identify reciprocal lattice spacings. Particle size distributions of DNPs were measured from >200 particles using ImageJ. PrMgSbBi lattice parameters and defect densities were quantified using Gatan Microscopy Suite. EDS and EELS data were deconvoluted to extract quantitative compositional profiles and bonding information. All experiments were conducted at room temperature, with vacuum levels maintained at ~10-7 Torr to minimize contamination.
結果と考察 / Results and Discussion
Atomic-Resolution STEM Imaging of 5 nm Diamond Nanoparticles:
High-resolution scanning transmission electron microscopy (STEM) was conducted using a Cs-corrected JEOL JEM-ARM200F microscope operated at 200 kV to characterize 5 nm diamond nanoparticles (DNPs). Atomic-resolution images, obtained in high-angle annular dark-field (HAADF) mode, revealed exceptional crystallinity with clearly resolved lattice planes corresponding to the diamond cubic structure (space group Fd3m). Fast Fourier transform (FFT) analysis of the images yielded a lattice spacing of approximately 0.206 nm, consistent with the (111) planes of diamond. The DNPs exhibited a uniform size distribution (4.8 ± 0.5 nm) based on measurements of over 200 particles, displaying faceted morphologies primarily bounded by {111} and {100} surfaces. No amorphous carbon or graphitic (sp²) phases were observed, indicating high phase purity.Electron energy loss spectroscopy (EELS) was employed to examine the bonding characteristics of the DNPs. The carbon K-edge spectra showed a dominant peak at ~289 eV, indicative of σ* transitions associated with sp³-hybridized carbon, with no π* peak at ~285 eV, confirming the exclusive presence of sp³ bonding. This high crystallinity and pure sp³ bonding make the DNPs highly suitable for applications such as thermal interface materials in high-power GaN-based electronics and quantum sensing platforms utilizing nitrogen-vacancy (NV) centers. The absence of defects, such as stacking faults or twinning, in the STEM images further supports their potential for these advanced applications.Atomic-Resolution STEM Imaging and EDS Analysis of PrMgSbBi Thermoelectric Materials:
The PrMgSbBi thermoelectric material was investigated using STEM-HAADF imaging to elucidate its nanoscale structure and composition. Atomic-resolution images revealed a polycrystalline microstructure with an average grain size of approximately 10 nm, determined through statistical analysis across multiple regions of FIB-prepared lamellae. This nanoscale grain size is advantageous for thermoelectric applications, as it promotes phonon scattering, reducing thermal conductivity while preserving electrical conductivity. The high-resolution STEM images displayed distinct lattice fringes with a d-spacing of ~0.32 nm, corresponding to the primary crystallographic planes of the PrMgSbBi phase, which adopts a complex cubic structure.Energy-dispersive X-ray spectroscopy (EDS) was utilized to probe the elemental composition and distribution within the PrMgSbBi samples. EDS mapping and quantitative point analyses revealed a non-uniform distribution of Mg, with localized enrichment at grain boundaries and within certain grains. This suggests the presence of excess Mg, potentially incorporated as interstitial defects or forming Mg-rich secondary phases. Line scans across grain boundaries indicated Mg concentrations up to 10% higher than the nominal stoichiometry in these regions. Convergent beam electron diffraction (CBED) patterns further supported these findings, showing slight lattice distortions in Mg-rich areas, indicative of local strain. The incorporation of additional Mg may enhance the thermoelectric figure of merit (zT) by tuning the carrier concentration and electrical conductivity, but excessive Mg could introduce scattering centers that reduce carrier mobility. These observations highlight the need for precise control of Mg stoichiometry during synthesis to optimize thermoelectric performance.Complementary Analysis and Implications:
Selected area electron diffraction (SAED) patterns were acquired for both materials to confirm phase identity and crystallinity. The DNPs exhibited sharp diffraction spots consistent with the diamond cubic lattice, while PrMgSbBi showed a complex pattern reflective of its polycrystalline nature and potential secondary phases. For PrMgSbBi, EDS data confirmed the presence of Pr, Mg, Sb, and Bi in expected ratios within the bulk, with deviations primarily attributed to Mg enrichment. No significant impurities were detected, indicating high material purity.The atomic-resolution STEM imaging and EDS analysis provide critical insights into the nanoscale properties of these materials. The high crystallinity and exclusive sp³ bonding of the DNPs underscore their potential for robust thermal management and quantum technology applications. For PrMgSbBi, the 10 nm grain size and Mg incorporation offer opportunities to enhance thermoelectric efficiency through nanostructuring and compositional optimization. These findings guide future material design strategies, such as tailored doping to balance electrical and thermal transport in PrMgSbBi and surface modification of DNPs to improve their integration into composite systems for advanced technological applications.
図・表・数式 / Figures, Tables and Equations
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
we acknowledge the help of Prof. Oshima and doctor Aso.
成果発表・成果利用 / Publication and Patents
論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)
口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.
特許 / Patents
特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件