Pub Date : 2026-01-06DOI: 10.1016/j.vacuum.2026.115074
Ziwen Zhu , Zhikang Wang , Xiaolong Luo , Qifei Zhang , Xiaogang You , Zhongwei Zhao
This study investigates electron beam refining (EBR) of the FGH4097 Ni-Co-based superalloy powders, with a focus on the element volatilization behavior and accurate control of alloy composition. A three-dimensional transient thermal model, coupled with element vaporization kinetics, is employed to predict the evolution of temperature field and associated compositional changes during EBR. The model incorporates the rotating Gaussian heat source, dynamic beam power control, multiphysics coupling, along with vaporization kinetics dependent on elemental interactions. Validation against experimental data confirms the model's accuracy and demonstrates its effectiveness in guiding EBR parameter optimization for precise control of elemental losses while maintaining alloy specifications.
{"title":"Numerical simulation on element volatilization behavior during electron beam refining of FGH4097 superalloy","authors":"Ziwen Zhu , Zhikang Wang , Xiaolong Luo , Qifei Zhang , Xiaogang You , Zhongwei Zhao","doi":"10.1016/j.vacuum.2026.115074","DOIUrl":"10.1016/j.vacuum.2026.115074","url":null,"abstract":"<div><div>This study investigates electron beam refining (EBR) of the FGH4097 Ni-Co-based superalloy powders, with a focus on the element volatilization behavior and accurate control of alloy composition. A three-dimensional transient thermal model, coupled with element vaporization kinetics, is employed to predict the evolution of temperature field and associated compositional changes during EBR. The model incorporates the rotating Gaussian heat source, dynamic beam power control, multiphysics coupling, along with vaporization kinetics dependent on elemental interactions. Validation against experimental data confirms the model's accuracy and demonstrates its effectiveness in guiding EBR parameter optimization for precise control of elemental losses while maintaining alloy specifications.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115074"},"PeriodicalIF":3.9,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1016/j.vacuum.2026.115069
Junchen Huang , Fenfang Lu , Zijian Zhang , Qian Liu , xinbo He , Xuanhui Qu
Graphite film/Cu composites were prepared by first applying a functional group layer to the graphite film surface, followed by Cu deposition. By converting mechanical bonding into chemical bonding, functional groups greatly strengthened the interfacial bonding. The interfacial shear strength force of the functionalized composites increased from 69 ± 3 kPa to 94 ± 4 kPa compared with the non-functionalized composites. Moreover, the functionalized composites exhibited remarkable flexibility as a result of the enhanced interfacial bonding. Reinforced interfacial bonding reduced phonon scattering, thereby increasing the thermal conductivity of the functionalized composites from 1023 ± 25 W m−1 K−1 to 1093 ± 34 W m−1 K−1. High thermal conductivity, superior mechanical properties, and inherent flexibility make the interface-engineered graphite film/Cu composites highly promising for use in flexible thermal management systems.
首先在石墨膜表面镀上官能团层，然后沉积Cu，制备了石墨膜/Cu复合材料。官能团通过将机械键转化为化学键，大大加强了界面键合。与未功能化复合材料相比，功能化复合材料的界面剪切强度从69±3 kPa增加到94±4 kPa。此外，由于界面结合增强，功能化复合材料表现出显著的柔韧性。增强的界面结合减少了声子散射，从而使功能化复合材料的导热系数从1023±25 W m−1 K−1提高到1093±34 W m−1 K−1。高导热性、优异的机械性能和固有的灵活性使得界面工程石墨膜/Cu复合材料在柔性热管理系统中具有很高的应用前景。
{"title":"Enhancing interfacial bonding of graphite film/Cu composites via functional group modification","authors":"Junchen Huang , Fenfang Lu , Zijian Zhang , Qian Liu , xinbo He , Xuanhui Qu","doi":"10.1016/j.vacuum.2026.115069","DOIUrl":"10.1016/j.vacuum.2026.115069","url":null,"abstract":"<div><div>Graphite film/Cu composites were prepared by first applying a functional group layer to the graphite film surface, followed by Cu deposition. By converting mechanical bonding into chemical bonding, functional groups greatly strengthened the interfacial bonding. The interfacial shear strength force of the functionalized composites increased from 69 ± 3 kPa to 94 ± 4 kPa compared with the non-functionalized composites. Moreover, the functionalized composites exhibited remarkable flexibility as a result of the enhanced interfacial bonding. Reinforced interfacial bonding reduced phonon scattering, thereby increasing the thermal conductivity of the functionalized composites from 1023 ± 25 W m<sup>−1</sup> K<sup>−1</sup> to 1093 ± 34 W m<sup>−1</sup> K<sup>−1</sup>. High thermal conductivity, superior mechanical properties, and inherent flexibility make the interface-engineered graphite film/Cu composites highly promising for use in flexible thermal management systems.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115069"},"PeriodicalIF":3.9,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1016/j.vacuum.2026.115070
Song Hu , Tingting Yao , Xinwei Wang , Yidan Fan , Xianfeng Wu , Beibei Qiao , Xuexi Yan , Yixiao Jiang , Kepeng Song , Chunlin Chen
YBa2Cu3O7-δ (YBCO) thin films have attracted considerable attention due to their remarkable superconducting properties, which include a high superconducting critical temperature (Tc) and elevated critical current density. The introduction of defects in YBCO has been shown to effectively pin flux vortices, thereby enhancing the critical current density under magnetic field conditions. In this study, the microstructure of YBCO thin films was examined through transmission electron microscopy (TEM). Atomic-resolution TEM imaging and energy-dispersive spectroscopy (EDS) elemental mapping were employed to elucidate the atomic structure, elemental distribution, and strain fields associated with defects in YBCO, including dislocations, stacking faults, and anti-phase boundaries. These defects may disrupt the formation of Cooper pairs and lead to a reduction in local Tc by altering the local coordination environment of the CuO2 planes. This research provides new insights into defect engineering within YBCO thin films and establishes a foundation for enhancing the performance of superconducting materials.
{"title":"Atomic-scale characterization of flux pinning defects in YBCO films","authors":"Song Hu , Tingting Yao , Xinwei Wang , Yidan Fan , Xianfeng Wu , Beibei Qiao , Xuexi Yan , Yixiao Jiang , Kepeng Song , Chunlin Chen","doi":"10.1016/j.vacuum.2026.115070","DOIUrl":"10.1016/j.vacuum.2026.115070","url":null,"abstract":"<div><div>YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> (YBCO) thin films have attracted considerable attention due to their remarkable superconducting properties, which include a high superconducting critical temperature (Tc) and elevated critical current density. The introduction of defects in YBCO has been shown to effectively pin flux vortices, thereby enhancing the critical current density under magnetic field conditions. In this study, the microstructure of YBCO thin films was examined through transmission electron microscopy (TEM). Atomic-resolution TEM imaging and energy-dispersive spectroscopy (EDS) elemental mapping were employed to elucidate the atomic structure, elemental distribution, and strain fields associated with defects in YBCO, including dislocations, stacking faults, and anti-phase boundaries. These defects may disrupt the formation of Cooper pairs and lead to a reduction in local T<sub>c</sub> by altering the local coordination environment of the CuO<sub>2</sub> planes. This research provides new insights into defect engineering within YBCO thin films and establishes a foundation for enhancing the performance of superconducting materials.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115070"},"PeriodicalIF":3.9,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1016/j.vacuum.2026.115065
Dun-Bao Ruan , Kuei-Shu Chang-Liao , Guan-Ting Liu , Yi-Hsuan Cheng , Chih-Cheng Chin , Jia-Cheng Liu , Ze-Fu Zhao , Kai-Jhih Gan
In order to balance the trade-off between oxygen passivation effect and side effects caused by excessive oxidation during Ge device fabrication, an appropriate rapid oxidation process is directly applied on the alloy-like hafnium nitride interfacial layer (IL). After detailed material analysis and comparison of electrical performance, the IL with 13.6 % Ge4+ content exhibits an ultralow equivalent oxide thickness value and relatively low gate leakage current, the lowest interface trap density, the least frequency dispersion, the highest drive current, the lowest subthreshold swing value, and the highest on/off current ratio among all samples. The improvement can be attributed to the removal of most border traps and oxygen vacancies without introducing possible side effects. The results are promising for improving the electrical performance of Ge MOS device.
{"title":"Improved electrical characteristics of p-substrate Ge MOS and Ge nMOSFET with appropriate rapid oxidation on hafnium nitride interfacial layer","authors":"Dun-Bao Ruan , Kuei-Shu Chang-Liao , Guan-Ting Liu , Yi-Hsuan Cheng , Chih-Cheng Chin , Jia-Cheng Liu , Ze-Fu Zhao , Kai-Jhih Gan","doi":"10.1016/j.vacuum.2026.115065","DOIUrl":"10.1016/j.vacuum.2026.115065","url":null,"abstract":"<div><div>In order to balance the trade-off between oxygen passivation effect and side effects caused by excessive oxidation during Ge device fabrication, an appropriate rapid oxidation process is directly applied on the alloy-like hafnium nitride interfacial layer (IL). After detailed material analysis and comparison of electrical performance, the IL with 13.6 % Ge<sup>4+</sup> content exhibits an ultralow equivalent oxide thickness value and relatively low gate leakage current, the lowest interface trap density, the least frequency dispersion, the highest drive current, the lowest subthreshold swing value, and the highest on/off current ratio among all samples. The improvement can be attributed to the removal of most border traps and oxygen vacancies without introducing possible side effects. The results are promising for improving the electrical performance of Ge MOS device.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115065"},"PeriodicalIF":3.9,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1016/j.vacuum.2026.115072
Wuxin Fan , Guoqiang Zhu , Botao Jiang , Baoxian Su , Xiaodong Liu , Chen Liu , Xu Liu , Hao Guo , Liang Wang , Eshov Bakhtiyor , Liangshun Luo , Yanqing Su , Jingjie Guo
Refractory high-entropy alloys struggle to balance strength and density at ultra-high temperatures. This work presents a novel dual-phase WNbMoTaVSi0.3 refractory high-entropy alloy, fabricated via arc melting, composed of BCC and M5Si3 phases. The BCC phase has three different compositions. The phase formation sequence was elucidated by CALPHAD-based thermodynamic simulation. The refractory high-entropy alloy achieves unprecedented properties: yield strengths of 1810.7 ± 57.4 MPa at 1473 K, 1413.4 ± 62.4 MPa at 1573 K, and 1291.1 ± 72.4 MPa at 1673 K, with peak strengths reaching 1932.3 ± 65.8 MPa, 1479.2 ± 68.6 MPa, and 1323.3 ± 79.6 MPa, respectively. Remarkably, the yield strength at 1473 K surpasses that of the matrix WNbMoTaV alloy (735 MPa) by 146.3 %, while the specific strength reaches 156.4 ± 5.1 MPa cm3/g. The outstanding strength is mainly due to the strengthening effect of solid solution and the strengthening effect provided by M5Si3 phase.
{"title":"A dual-phase refractory high-entropy alloy with extremely high specific strength and excellent ultra-high temperature strength","authors":"Wuxin Fan , Guoqiang Zhu , Botao Jiang , Baoxian Su , Xiaodong Liu , Chen Liu , Xu Liu , Hao Guo , Liang Wang , Eshov Bakhtiyor , Liangshun Luo , Yanqing Su , Jingjie Guo","doi":"10.1016/j.vacuum.2026.115072","DOIUrl":"10.1016/j.vacuum.2026.115072","url":null,"abstract":"<div><div>Refractory high-entropy alloys struggle to balance strength and density at ultra-high temperatures. This work presents a novel dual-phase WNbMoTaVSi<sub>0.3</sub> refractory high-entropy alloy, fabricated via arc melting, composed of BCC and M<sub>5</sub>Si<sub>3</sub> phases. The BCC phase has three different compositions. The phase formation sequence was elucidated by CALPHAD-based thermodynamic simulation. The refractory high-entropy alloy achieves unprecedented properties: yield strengths of 1810.7 ± 57.4 MPa at 1473 K, 1413.4 ± 62.4 MPa at 1573 K, and 1291.1 ± 72.4 MPa at 1673 K, with peak strengths reaching 1932.3 ± 65.8 MPa, 1479.2 ± 68.6 MPa, and 1323.3 ± 79.6 MPa, respectively. Remarkably, the yield strength at 1473 K surpasses that of the matrix WNbMoTaV alloy (735 MPa) by 146.3 %, while the specific strength reaches 156.4 ± 5.1 MPa cm<sup>3</sup>/g. The outstanding strength is mainly due to the strengthening effect of solid solution and the strengthening effect provided by M<sub>5</sub>Si<sub>3</sub> phase.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115072"},"PeriodicalIF":3.9,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-03DOI: 10.1016/j.vacuum.2026.115067
Qiaoru An, Feng Shi, Haisheng Fang
Radio frequency (RF) magnetron sputtering applies a high-frequency alternating voltage to the target, making it suitable for sputtering dielectric materials. In this study, a comprehensive numerical model combining the finite element method for electromagnetic fields, a fluid model for plasma discharge, and the Monte Carlo method for particle transport was developed. Periodic averages were used to represent long-term and continuous deposition for TiOx targets. Key outputs included electron density, sputtering flux, and deposition flux, enabling predictions of deposition rate, particle utilization, and the compositional ratio of the film. The parametric analyses show that a higher central electromagnetic coil current in the magnetron assembly, increased input power, and a lower O/Ti atomic ratio of target contribute to an increased deposition rate. Specifically, the deposition rate peaks at 1.5 Pa due to enhanced discharge, while higher pressures reduce it through increased collision frequency during particle transport. Furthermore, elevated gas pressure and a higher target O/Ti ratio reduce particle utilization and influence the O/Ti ratio in the deposited film. These findings contribute to improved control of deposition processes, enabling enhanced efficiency in RF magnetron sputtering applications.
{"title":"Particle deposition driven by plasma discharge in magnetron sputtering of TiOx compound targets","authors":"Qiaoru An, Feng Shi, Haisheng Fang","doi":"10.1016/j.vacuum.2026.115067","DOIUrl":"10.1016/j.vacuum.2026.115067","url":null,"abstract":"<div><div>Radio frequency (RF) magnetron sputtering applies a high-frequency alternating voltage to the target, making it suitable for sputtering dielectric materials. In this study, a comprehensive numerical model combining the finite element method for electromagnetic fields, a fluid model for plasma discharge, and the Monte Carlo method for particle transport was developed. Periodic averages were used to represent long-term and continuous deposition for TiO<sub>x</sub> targets. Key outputs included electron density, sputtering flux, and deposition flux, enabling predictions of deposition rate, particle utilization, and the compositional ratio of the film. The parametric analyses show that a higher central electromagnetic coil current in the magnetron assembly, increased input power, and a lower O/Ti atomic ratio of target contribute to an increased deposition rate. Specifically, the deposition rate peaks at 1.5 Pa due to enhanced discharge, while higher pressures reduce it through increased collision frequency during particle transport. Furthermore, elevated gas pressure and a higher target O/Ti ratio reduce particle utilization and influence the O/Ti ratio in the deposited film. These findings contribute to improved control of deposition processes, enabling enhanced efficiency in RF magnetron sputtering applications.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115067"},"PeriodicalIF":3.9,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-03DOI: 10.1016/j.vacuum.2025.115063
Yue Su, Jie Li, Shengli Wu, Wenbo Hu
The modification of MgO thin films through surface engineering has been widely investigated to enhance secondary electron emission (SEE) and air stability. Here, we propose two progressive hierarchical strategies based on Al and Au co-doped MgO thin film, designed as bilayer and trilayer sandwich structures with MgO-based functional layers. The optimized surface bilayer structure achieves a SEE coefficient (SEY) at Ep = 200 eV (δ200) above 4.5 with a low decay rate of ∼5 %. Integrating both strategies, the final surface sandwich structure shows excellent air stability, maintaining δ200 = 4.5 and a decay rate of only 4.25 % after 72 h air exposure. Compared with the previously reported co-doped film with a 2 nm Al2O3 passivation layer (CP2nm), our surface sandwich structure exhibits clear advantages in terms of SEE performance and stability. Specifically, the inital δ200 increases by 12 % at a comparable decay rate, wheras after 72 h of exposure to air, These results demonstrate that the hierarchical sandwich design effectively enhances both SEE performance and air stability, offering a superior strategy for MgO-based electron emission films.
{"title":"Function-layer-driven surface engineering for high-efficiency and stable secondary electron emission films","authors":"Yue Su, Jie Li, Shengli Wu, Wenbo Hu","doi":"10.1016/j.vacuum.2025.115063","DOIUrl":"10.1016/j.vacuum.2025.115063","url":null,"abstract":"<div><div>The modification of MgO thin films through surface engineering has been widely investigated to enhance secondary electron emission (SEE) and air stability. Here, we propose two progressive hierarchical strategies based on Al and Au co-doped MgO thin film, designed as bilayer and trilayer sandwich structures with MgO-based functional layers. The optimized surface bilayer structure achieves a SEE coefficient (SEY) at Ep = 200 eV (<em>δ</em><sub>200</sub>) above 4.5 with a low decay rate of ∼5 %. Integrating both strategies, the final surface sandwich structure shows excellent air stability, maintaining <em>δ</em><sub>200</sub> = 4.5 and a decay rate of only 4.25 % after 72 h air exposure. Compared with the previously reported co-doped film with a 2 nm Al<sub>2</sub>O<sub>3</sub> passivation layer (C<sub>P2nm</sub>), our surface sandwich structure exhibits clear advantages in terms of SEE performance and stability. Specifically, the inital <em>δ</em><sub>200</sub> increases by 12 % at a comparable decay rate, wheras after 72 h of exposure to air, These results demonstrate that the hierarchical sandwich design effectively enhances both SEE performance and air stability, offering a superior strategy for MgO-based electron emission films.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115063"},"PeriodicalIF":3.9,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-02DOI: 10.1016/j.vacuum.2026.115066
Zhixuan Liao , Nuoya Li , Zhicheng Zhang , Lilin Wang , Chenlong Chen
Well-aligned single-crystalline ZnGa2O4 nanowire arrays with high crystallinity and pronounced bottom interconnections were successfully epitaxially grown on c-plane GaN/LiGaO2 substrates by chemical vapor deposition (CVD). The nanowires, with diameters in the range of 40–120 nm, developed along seven equivalent crystallographic directions of [111], [ 11], [1 1], [11], [ 1], [1] and [ 1] via a Au-catalyzed vapor-liquid-solid (VLS) growth mechanism. The in-situ formation of a thin porous GaN interlayer on LiGaO2 effectively mitigated thermal decomposition of the substrate during high-temperature growth. Additionally, the inherent properties of GaN, such as high thermal conductivity, high breakdown field, and excellent electrical conductivity, offer significant potential for enhancing the performance and expanding the functional applications of ZnGa2O4-based devices. The morphology, microstructure, growth mechanism, and optical properties of the as-synthesized ZnGa2O4 nanowire arrays were systematically analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL). The approach presented here enables the epitaxial integration of well-interconnected ZnGa2O4 nanowire arrays, with the GaN buffer layer facilitating continuous conductive pathways between individual nanowires. The photoelectronic properties of the ZnGa2O4 photodetector were also evaluated, and the device fabricated using this nanowire array architecture exhibited a rapid transient response and high photocurrent density. These results suggest that the unique structural configuration of the ZnGa2O4 nanowire arrays holds promising potential for ultraviolet photodetection and other optoelectronic applications.
{"title":"Epitaxial growth and properties of ZnGa2O4 nanowire arrays on c-plane GaN/LiGaO2 substrate","authors":"Zhixuan Liao , Nuoya Li , Zhicheng Zhang , Lilin Wang , Chenlong Chen","doi":"10.1016/j.vacuum.2026.115066","DOIUrl":"10.1016/j.vacuum.2026.115066","url":null,"abstract":"<div><div>Well-aligned single-crystalline ZnGa<sub>2</sub>O<sub>4</sub> nanowire arrays with high crystallinity and pronounced bottom interconnections were successfully epitaxially grown on c-plane GaN/LiGaO<sub>2</sub> substrates by chemical vapor deposition (CVD). The nanowires, with diameters in the range of 40–120 nm, developed along seven equivalent crystallographic directions of [111], [<span><math><mrow><mover><mn>1</mn><mo>‾</mo></mover></mrow></math></span> 11], [1<span><math><mrow><mover><mn>1</mn><mo>‾</mo></mover></mrow></math></span> 1], [11<span><math><mrow><mover><mn>1</mn><mo>‾</mo></mover></mrow></math></span>], [<span><math><mrow><mover><mn>1</mn><mo>‾</mo></mover><mover><mn>1</mn><mo>‾</mo></mover></mrow></math></span> 1], [1<span><math><mrow><mover><mn>1</mn><mo>‾</mo></mover><mover><mn>1</mn><mo>‾</mo></mover></mrow></math></span>] and [<span><math><mrow><mover><mn>1</mn><mo>‾</mo></mover></mrow></math></span> 1<span><math><mrow><mover><mn>1</mn><mo>‾</mo></mover></mrow></math></span>] via a Au-catalyzed vapor-liquid-solid (VLS) growth mechanism. The in-situ formation of a thin porous GaN interlayer on LiGaO<sub>2</sub> effectively mitigated thermal decomposition of the substrate during high-temperature growth. Additionally, the inherent properties of GaN, such as high thermal conductivity, high breakdown field, and excellent electrical conductivity, offer significant potential for enhancing the performance and expanding the functional applications of ZnGa<sub>2</sub>O<sub>4</sub>-based devices. The morphology, microstructure, growth mechanism, and optical properties of the as-synthesized ZnGa<sub>2</sub>O<sub>4</sub> nanowire arrays were systematically analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL). The approach presented here enables the epitaxial integration of well-interconnected ZnGa<sub>2</sub>O<sub>4</sub> nanowire arrays, with the GaN buffer layer facilitating continuous conductive pathways between individual nanowires. The photoelectronic properties of the ZnGa<sub>2</sub>O<sub>4</sub> photodetector were also evaluated, and the device fabricated using this nanowire array architecture exhibited a rapid transient response and high photocurrent density. These results suggest that the unique structural configuration of the ZnGa<sub>2</sub>O<sub>4</sub> nanowire arrays holds promising potential for ultraviolet photodetection and other optoelectronic applications.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115066"},"PeriodicalIF":3.9,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145927247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-02DOI: 10.1016/j.vacuum.2026.115064
Tianyi Zhang , Weilun Deng , Guanghui Cao , Changsheng Zhai , Hongxing Zheng
Multiphase high-entropy alloys (HEAs) offer promising oxidation resistance for high-temperature applications, yet the influence of minor alloying elements on thermally grown oxide (TGO) evolution remains poorly understood. An equiatomic CoCrFeNiMo HEA with minor B and Si additions was fabricated through centrifugal rapid solidification. The as-cast microstructure consisted of a dendritic FCC matrix, blocky μ phase, and trace CrSi2 and Mo2B precipitates. Oxidation at 900 °C for 200 h exhibited two-stage kinetics: an early rapid stage (0–40 h, n = 2.14, k = 1.64 × 10−3 mgn·cm−2n·h−1) until Mo depletion, followed by a slow-growth stage (40–200 h, n = 14.95, k = 2.47 × 10−10 mgn·cm−2n·h−1) governed by Cr3+ diffusion through the Cr2O3 barrier. CrSi2 decomposition induces interfacial micropores that moderately compromise oxidation resistance, while B additions benefit performance through stable Mo2B formation. First-principles calculations indicate the μ phase exhibits higher thermal stability and lower oxidation reactivity than the FCC matrix. These findings support rational design of multiphase HEAs for high-temperature applications.
多相高熵合金（HEAs）在高温应用中具有良好的抗氧化性能，但少量合金元素对热生长氧化物（TGO）演化的影响尚不清楚。采用离心快速凝固法制备了加入少量B和Si的等原子CoCrFeNiMo HEA。铸态组织由枝晶FCC基体、块状μ相和微量CrSi2和Mo2B相组成。900℃下200 h的氧化动力学表现为两阶段：早期快速阶段（0-40 h, n = 2.14, k = 1.64 × 10−3 mgn·cm−2n·h−1）直到Mo耗尽，随后是Cr3+通过Cr2O3势垒扩散的缓慢生长阶段（40-200 h, n = 14.95, k = 2.47 × 10−10 mgn·cm−2n·h−1）。CrSi2分解导致界面微孔适度降低抗氧化性，而B的加入通过稳定的Mo2B形成有利于性能。第一性原理计算表明，与FCC基体相比，μ相具有较高的热稳定性和较低的氧化反应性。这些发现为高温应用多相HEAs的合理设计提供了依据。
{"title":"Two-stage oxidation mechanism and thermally grown oxide evolution in a CoCrFeNiMo high-entropy alloy with boron and silicon additions","authors":"Tianyi Zhang , Weilun Deng , Guanghui Cao , Changsheng Zhai , Hongxing Zheng","doi":"10.1016/j.vacuum.2026.115064","DOIUrl":"10.1016/j.vacuum.2026.115064","url":null,"abstract":"<div><div>Multiphase high-entropy alloys (HEAs) offer promising oxidation resistance for high-temperature applications, yet the influence of minor alloying elements on thermally grown oxide (TGO) evolution remains poorly understood. An equiatomic CoCrFeNiMo HEA with minor B and Si additions was fabricated through centrifugal rapid solidification. The as-cast microstructure consisted of a dendritic FCC matrix, blocky μ phase, and trace CrSi<sub>2</sub> and Mo<sub>2</sub>B precipitates. Oxidation at 900 °C for 200 h exhibited two-stage kinetics: an early rapid stage (0–40 h, <em>n</em> = 2.14, <em>k</em> = 1.64 × 10<sup>−3</sup> mg<sup><em>n</em></sup>·cm<sup>−2<em>n</em></sup>·h<sup>−1</sup>) until Mo depletion, followed by a slow-growth stage (40–200 h, <em>n</em> = 14.95, <em>k</em> = 2.47 × 10<sup>−10</sup> mg<sup><em>n</em></sup>·cm<sup>−2<em>n</em></sup>·h<sup>−1</sup>) governed by Cr<sup>3+</sup> diffusion through the Cr<sub>2</sub>O<sub>3</sub> barrier. CrSi<sub>2</sub> decomposition induces interfacial micropores that moderately compromise oxidation resistance, while B additions benefit performance through stable Mo<sub>2</sub>B formation. First-principles calculations indicate the μ phase exhibits higher thermal stability and lower oxidation reactivity than the FCC matrix. These findings support rational design of multiphase HEAs for high-temperature applications.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115064"},"PeriodicalIF":3.9,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145885214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, composite coatings reinforced with boride particles were synthesized on titanium substrates. In this way, both LaB6 and Ti thin films were deposited alternatively with subsequent low-energy high-current electron beam (LEHCEB) processing in a single vacuum cycle. The film thicknesses were selected so that the boron and titanium contents were close to the composition of the TiB2 compound. Upon LEHCEB processing, the effect of energy densities on the microstructures, both chemical and phase compositions, as well as wear resistance of the coatings was considered. It was found that they could comprise mixtures of predominantly TiB2 nanoparticles distributed in the submicrocrystalline titanium matrix at an energy density of 3.5 J/cm2. In this case, wear resistance of the coating significantly exceeded those of the titanium substrate. Increasing the energy density up to 4.5 and 5.5 J/cm2 promoted additional melting of the substrates and dilution of the molten films with titanium from them, reducing the proportions of boron in the coatings. These changes in their chemical compositions led to variations in the observed phases. In addition, the excessive heat input caused the formation of surface discontinuities, deteriorating wear resistance.
{"title":"Possibilities of controlling the formation of borides in the titanium surface layers by pulsed electron beam processing","authors":"Evgeniy Yakovlev, Mikhail Slobodyan, Andrey Solovyev, Evgeniy Pesterev, Vsevolod Petrov, Alexey Markov","doi":"10.1016/j.vacuum.2025.115061","DOIUrl":"10.1016/j.vacuum.2025.115061","url":null,"abstract":"<div><div>In this study, composite coatings reinforced with boride particles were synthesized on titanium substrates. In this way, both LaB<sub>6</sub> and Ti thin films were deposited alternatively with subsequent low-energy high-current electron beam (LEHCEB) processing in a single vacuum cycle. The film thicknesses were selected so that the boron and titanium contents were close to the composition of the TiB<sub>2</sub> compound. Upon LEHCEB processing, the effect of energy densities on the microstructures, both chemical and phase compositions, as well as wear resistance of the coatings was considered. It was found that they could comprise mixtures of predominantly TiB<sub>2</sub> nanoparticles distributed in the submicrocrystalline titanium matrix at an energy density of 3.5 J/cm<sup>2</sup>. In this case, wear resistance of the coating significantly exceeded those of the titanium substrate. Increasing the energy density up to 4.5 and 5.5 J/cm<sup>2</sup> promoted additional melting of the substrates and dilution of the molten films with titanium from them, reducing the proportions of boron in the coatings. These changes in their chemical compositions led to variations in the observed phases. In addition, the excessive heat input caused the formation of surface discontinuities, deteriorating wear resistance.</div></div>","PeriodicalId":23559,"journal":{"name":"Vacuum","volume":"246 ","pages":"Article 115061"},"PeriodicalIF":3.9,"publicationDate":"2025-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145885213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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