Nathan D. Rock, Haobo Yang, Brian Eisner, Aviva Levin, Arkka Bhattacharyya, Sriram Krishnamoorthy, Praneeth Ranga, Michael A. Walker, Larry Wang, Ming Kit Cheng, Wei Zhao, Michael A. Scarpulla
Diffusion of native defects such as vacancies and their interactions with impurities are fundamental to semiconductor crystal growth, device processing, and design. However, the transient equilibration of native defects is difficult to directly measure. We used (AlxGa1−x)2O3/Ga2O3 superlattices (SLs) to detect and analyze transient diffusion of cation vacancies during annealing in O2 at 1000–1100 °C. Using a novel finite difference scheme for diffusion with time- and space-varying diffusion constants, we determined diffusion constants for Al, Fe, and cation vacancies, including the vacancy concentration dependence for Al. In the case of SLs grown on Sn-doped β-Ga2O3 (010) substrates, gradients observed in the extent of Al diffusion indicate a supersaturation of vacancies in the substrates that transiently diffuse through the SLs coupled strongly to Sn and thus slowed compared to undoped cases. In the case of SLs grown on (010) Fe-doped substrates, the Al diffusion is uniform through the SLs, indicating a depth-uniform concentration of vacancies. We find no evidence for the introduction of VGa from the free surface at rates sufficient to affect Al diffusion at at. % concentrations, establishing an upper bound on surface injection. In addition, we show that unintentional impurities in Sn-doped Ga2O3 such as Fe, Ni, Mn, Cu, and Li also diffuse toward the surface and accumulate. Many of these likely have fast interstitial diffusion modes capable of destabilizing devices, thus suggesting that impurities may require further reduction. This work provides a method to measure transients in diffusion-mediating native defects otherwise hidden in common processes such as ion implantation, etching, and film growth.
{"title":"Utilizing (Al, Ga)2O3/Ga2O3 superlattices to measure cation vacancy diffusion and vacancy-concentration-dependent diffusion of Al, Sn, and Fe in β-Ga2O3","authors":"Nathan D. Rock, Haobo Yang, Brian Eisner, Aviva Levin, Arkka Bhattacharyya, Sriram Krishnamoorthy, Praneeth Ranga, Michael A. Walker, Larry Wang, Ming Kit Cheng, Wei Zhao, Michael A. Scarpulla","doi":"10.1063/5.0206398","DOIUrl":"https://doi.org/10.1063/5.0206398","url":null,"abstract":"Diffusion of native defects such as vacancies and their interactions with impurities are fundamental to semiconductor crystal growth, device processing, and design. However, the transient equilibration of native defects is difficult to directly measure. We used (AlxGa1−x)2O3/Ga2O3 superlattices (SLs) to detect and analyze transient diffusion of cation vacancies during annealing in O2 at 1000–1100 °C. Using a novel finite difference scheme for diffusion with time- and space-varying diffusion constants, we determined diffusion constants for Al, Fe, and cation vacancies, including the vacancy concentration dependence for Al. In the case of SLs grown on Sn-doped β-Ga2O3 (010) substrates, gradients observed in the extent of Al diffusion indicate a supersaturation of vacancies in the substrates that transiently diffuse through the SLs coupled strongly to Sn and thus slowed compared to undoped cases. In the case of SLs grown on (010) Fe-doped substrates, the Al diffusion is uniform through the SLs, indicating a depth-uniform concentration of vacancies. We find no evidence for the introduction of VGa from the free surface at rates sufficient to affect Al diffusion at at. % concentrations, establishing an upper bound on surface injection. In addition, we show that unintentional impurities in Sn-doped Ga2O3 such as Fe, Ni, Mn, Cu, and Li also diffuse toward the surface and accumulate. Many of these likely have fast interstitial diffusion modes capable of destabilizing devices, thus suggesting that impurities may require further reduction. This work provides a method to measure transients in diffusion-mediating native defects otherwise hidden in common processes such as ion implantation, etching, and film growth.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"171 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197807","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}
N. Kase, Y. Kawamura, Y. Kobayashi, T. Inoue, K. Tanaka, N. Miyakawa
Large bulk single crystals of InGaZn3O6 (InGaO3(ZnO)3 or IGZO-13) have been successfully grown using an optical floating zone method under a flow of dry-air at high pressure. These crystals exhibit a distinct blue hue in their as-grown state, with notable enhancement in transparency attainable through O2 annealing. Comparative analysis with IGZO-11 reveals a substantial reduction in conductivity following O2 annealing. Moreover, a pronounced in-plane/out-of-plane conductive anisotropy ranging from 100 to 450 is observed, surpassing that of IGZO-11 under similar in-plane conductivity conditions. This increase in electrical conducting anisotropy is ascribed to the incorporation of ZnO blocks amid the two InO layers, aligned along the c axis. Based on these findings, it is concluded that the contribution of In-5s orbitals likely assumes a predominant role, surpassing that of other cations from an experimental standpoint.
{"title":"Electrical conductivity anisotropy of InGaZn3O6 single crystals by pressurized optical floating zone growth and its oxygen annealing effect","authors":"N. Kase, Y. Kawamura, Y. Kobayashi, T. Inoue, K. Tanaka, N. Miyakawa","doi":"10.1063/5.0218948","DOIUrl":"https://doi.org/10.1063/5.0218948","url":null,"abstract":"Large bulk single crystals of InGaZn3O6 (InGaO3(ZnO)3 or IGZO-13) have been successfully grown using an optical floating zone method under a flow of dry-air at high pressure. These crystals exhibit a distinct blue hue in their as-grown state, with notable enhancement in transparency attainable through O2 annealing. Comparative analysis with IGZO-11 reveals a substantial reduction in conductivity following O2 annealing. Moreover, a pronounced in-plane/out-of-plane conductive anisotropy ranging from 100 to 450 is observed, surpassing that of IGZO-11 under similar in-plane conductivity conditions. This increase in electrical conducting anisotropy is ascribed to the incorporation of ZnO blocks amid the two InO layers, aligned along the c axis. Based on these findings, it is concluded that the contribution of In-5s orbitals likely assumes a predominant role, surpassing that of other cations from an experimental standpoint.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"48 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197808","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}
Jing Zhou, Lisen Huang, Sherry Lee Koon Yap, Dennis Jing Xiong Lin, Bingjin Chen, Shaohai Chen, Seng Kai Wong, Jinjun Qiu, James Lourembam, Anjan Soumyanarayanan, Sze Ter Lim
Current-induced spin–orbit torque (SOT) facilitates the ultrafast electrical manipulation of magnetic tunnel junction (MTJ), which is a leading non-volatile technology for the microelectronic industry. The key bottleneck to the commercial application of SOT-MTJ is the absence of a practicable symmetry-breaking scheme to switch perpendicular magnetization without an external magnetic field. Here, we demonstrate the wafer-scale realization of internalized field-free switching in perpendicular SOT-MTJ using conventional materials and device structure. We utilize a dual-function tungsten (W) spacer, which generates sizable SOT while concomitantly breaking symmetry via interlayer exchange coupling (IEC). Tuning the W thickness enables field-free switching with two types of IEC. An optimized combination of SOT and IEC ensures competitive switching performance, with our device exhibiting excellent thermal stability, low switching current density, and fast operating speed. This work builds the long-sought bridge between SOT manipulation of magnetization and wafer-scale field-free perpendicular MTJ. It underscores the urgent need to incorporate perpendicular SOT-MTJ in integrated circuits for applications in logic, memory, and unconventional computing.
电流诱导的自旋轨道力矩（SOT）促进了磁性隧道结（MTJ）的超快电气操控，而磁性隧道结是微电子行业的一项领先非易失性技术。SOT-MTJ 商业化应用的关键瓶颈在于缺乏一种可行的对称性破坏方案，无法在没有外部磁场的情况下切换垂直磁化。在这里，我们展示了利用传统材料和器件结构在晶圆级实现垂直 SOT-MTJ 内化无磁场开关的方法。我们利用双重功能的钨（W）间隔物，在产生可观的 SOT 的同时，通过层间交换耦合（IEC）打破对称性。调整钨的厚度可以实现两种 IEC 的无场切换。SOT 和 IEC 的优化组合确保了具有竞争力的开关性能，我们的器件具有出色的热稳定性、较低的开关电流密度和较快的工作速度。这项工作在 SOT 磁化操纵和晶圆级无磁场垂直 MTJ 之间架起了一座长期寻求的桥梁。它强调了将垂直 SOT-MTJ 集成到逻辑、存储器和非传统计算应用的集成电路中的迫切需要。
{"title":"Synergizing intrinsic symmetry breaking with spin–orbit torques for field-free perpendicular magnetic tunnel junction","authors":"Jing Zhou, Lisen Huang, Sherry Lee Koon Yap, Dennis Jing Xiong Lin, Bingjin Chen, Shaohai Chen, Seng Kai Wong, Jinjun Qiu, James Lourembam, Anjan Soumyanarayanan, Sze Ter Lim","doi":"10.1063/5.0221776","DOIUrl":"https://doi.org/10.1063/5.0221776","url":null,"abstract":"Current-induced spin–orbit torque (SOT) facilitates the ultrafast electrical manipulation of magnetic tunnel junction (MTJ), which is a leading non-volatile technology for the microelectronic industry. The key bottleneck to the commercial application of SOT-MTJ is the absence of a practicable symmetry-breaking scheme to switch perpendicular magnetization without an external magnetic field. Here, we demonstrate the wafer-scale realization of internalized field-free switching in perpendicular SOT-MTJ using conventional materials and device structure. We utilize a dual-function tungsten (W) spacer, which generates sizable SOT while concomitantly breaking symmetry via interlayer exchange coupling (IEC). Tuning the W thickness enables field-free switching with two types of IEC. An optimized combination of SOT and IEC ensures competitive switching performance, with our device exhibiting excellent thermal stability, low switching current density, and fast operating speed. This work builds the long-sought bridge between SOT manipulation of magnetization and wafer-scale field-free perpendicular MTJ. It underscores the urgent need to incorporate perpendicular SOT-MTJ in integrated circuits for applications in logic, memory, and unconventional computing.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"27 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197804","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}
Monolayer and few-layer CoPS3 have been successfully synthesized via an Au-assisted exfoliation technique, with their transport properties subsequently investigated by conductive atomic force microscopy. Rectification effects can be observed in CoPS3 nanosheets due to the Schottky junction formation at the Au/CoPS3 interface, especially in configurations comprising two or more layer flakes. The distinct transport properties between monolayer and few-layer samples demonstrate that the charge transport behavior in the vertical direction is associated with the van der Waals gap. The calculated electron affinity for CoPS3 is about 4.84 eV, as revealed by the thermionic emission model. The results obtained contribute to the knowledge base concerning the transport characteristics of ultrathin MPX3, facilitating further exploration of the transport behavior of these materials and their potential applications in novel electronic devices.
{"title":"Unveiling charge transport in monolayer and few-layer CoPS3/metal contact: Insight from C-AFM","authors":"Mouhui Yan, Haotian Wang, Wenqi Wei, Tianxiang Zhu, Guanghui Cao, Jianxin Zhong, Wei Ren","doi":"10.1063/5.0222472","DOIUrl":"https://doi.org/10.1063/5.0222472","url":null,"abstract":"Monolayer and few-layer CoPS3 have been successfully synthesized via an Au-assisted exfoliation technique, with their transport properties subsequently investigated by conductive atomic force microscopy. Rectification effects can be observed in CoPS3 nanosheets due to the Schottky junction formation at the Au/CoPS3 interface, especially in configurations comprising two or more layer flakes. The distinct transport properties between monolayer and few-layer samples demonstrate that the charge transport behavior in the vertical direction is associated with the van der Waals gap. The calculated electron affinity for CoPS3 is about 4.84 eV, as revealed by the thermionic emission model. The results obtained contribute to the knowledge base concerning the transport characteristics of ultrathin MPX3, facilitating further exploration of the transport behavior of these materials and their potential applications in novel electronic devices.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"97 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197809","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}
Xiangjun Liu, Yue Hu, Yikun Ju, Pu Yang, Naisi Shen, Anqi Yang, Rui Wu, Bairong Fang, Liangle Liu
Tissue repair and regeneration have long been a focus of research, with growing evidence highlighting the role played by immunomodulation. The repair of tissue cells can be significantly promoted through the localized immunomodulation of tissues. Hydrogels are increasingly used in this field due to their biocompatibility, versatility, and relative ease of fabrication. This Review highlights the critical role of inflammation and immune development in the complex process of tissue repair after injury, highlighting the dynamic interactions between immune cells that ultimately influence the outcome of tissue healing. We also summarize the precise functions of immune cells and their responses in various tissue injury scenarios, which are critical for harnessing the full potential of immunomodulatory strategies to promote tissue repair. We discuss recent advances in drug-carrying hydrogels, which offer promising avenues for tissue regeneration with precise control of the immune environment for constructive tissue repair. Further advances in our understanding of the mechanisms driving inflammation and immune cell behavior during tissue injury are expected to foster the development of increasingly effective hydrogel-based immunomodulatory strategies to promote tissue repair and regeneration.
{"title":"Immunomodulatory hydrogels for tissue repair and regeneration","authors":"Xiangjun Liu, Yue Hu, Yikun Ju, Pu Yang, Naisi Shen, Anqi Yang, Rui Wu, Bairong Fang, Liangle Liu","doi":"10.1063/5.0228692","DOIUrl":"https://doi.org/10.1063/5.0228692","url":null,"abstract":"Tissue repair and regeneration have long been a focus of research, with growing evidence highlighting the role played by immunomodulation. The repair of tissue cells can be significantly promoted through the localized immunomodulation of tissues. Hydrogels are increasingly used in this field due to their biocompatibility, versatility, and relative ease of fabrication. This Review highlights the critical role of inflammation and immune development in the complex process of tissue repair after injury, highlighting the dynamic interactions between immune cells that ultimately influence the outcome of tissue healing. We also summarize the precise functions of immune cells and their responses in various tissue injury scenarios, which are critical for harnessing the full potential of immunomodulatory strategies to promote tissue repair. We discuss recent advances in drug-carrying hydrogels, which offer promising avenues for tissue regeneration with precise control of the immune environment for constructive tissue repair. Further advances in our understanding of the mechanisms driving inflammation and immune cell behavior during tissue injury are expected to foster the development of increasingly effective hydrogel-based immunomodulatory strategies to promote tissue repair and regeneration.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"3 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197831","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}
Wafer-scale rare-earth iron garnet (RIG) single crystal thick films were fabricated on 3-in. gadolinium gallium garnet (GGG) substrates using liquid phase epitaxy. The terahertz transmittance of the RIG crystals improved after removing the GGG substrate by polishing. The time-domain spectra at Terahertz (THz) frequencies indicate the existence of a magneto-optical effect in RIG samples. The results indicate that the RIG samples exhibit a high refractive index of ∼4.50 within the 0.1–1.0 THz frequency range, a transmittance of around 40%, and an absorption rate of only 10–50 cm−1. The Faraday rotation angles of the thick single-crystal films of the RIG samples were measured using a THz-TDS system. The RIG has a thickness of ∼330 μm. The Faraday rotation angles of RIG crystals at THz frequencies can reach up to 16° when an external magnetic field of 0.18 T is applied. The Verdet constants of the RIG sample were calculated to be ∼120°/mm/T. To improve the transmittance of the RIG sample, epoxy resin and polymethylpentene (TPX) were used as anti-reflective films. The transmittance of the RIG sample increased by ∼5% for the 80 μm thick epoxy and about 10% for the 320 μm thick TPX. Therefore, this RIG single crystal thick film can achieve a low loss, a high transmittance, and a strong magneto-optical effect in the terahertz region with the cooperation of a reflection-reducing film. It is expected to have wide applications in terahertz magnetic polarization conversion, non-reciprocal phase shifters, and isolators.
{"title":"Enhancing terahertz magneto-optical effects in wafer-scale RIG single crystal thick films with anti-reflective coatings for improved transmittance","authors":"Qiang Xue, Yuan-Jing Zhang, Qing-Hui Yang, Huai-Wu Zhang, Qi-Ye Wen","doi":"10.1063/5.0219811","DOIUrl":"https://doi.org/10.1063/5.0219811","url":null,"abstract":"Wafer-scale rare-earth iron garnet (RIG) single crystal thick films were fabricated on 3-in. gadolinium gallium garnet (GGG) substrates using liquid phase epitaxy. The terahertz transmittance of the RIG crystals improved after removing the GGG substrate by polishing. The time-domain spectra at Terahertz (THz) frequencies indicate the existence of a magneto-optical effect in RIG samples. The results indicate that the RIG samples exhibit a high refractive index of ∼4.50 within the 0.1–1.0 THz frequency range, a transmittance of around 40%, and an absorption rate of only 10–50 cm−1. The Faraday rotation angles of the thick single-crystal films of the RIG samples were measured using a THz-TDS system. The RIG has a thickness of ∼330 μm. The Faraday rotation angles of RIG crystals at THz frequencies can reach up to 16° when an external magnetic field of 0.18 T is applied. The Verdet constants of the RIG sample were calculated to be ∼120°/mm/T. To improve the transmittance of the RIG sample, epoxy resin and polymethylpentene (TPX) were used as anti-reflective films. The transmittance of the RIG sample increased by ∼5% for the 80 μm thick epoxy and about 10% for the 320 μm thick TPX. Therefore, this RIG single crystal thick film can achieve a low loss, a high transmittance, and a strong magneto-optical effect in the terahertz region with the cooperation of a reflection-reducing film. It is expected to have wide applications in terahertz magnetic polarization conversion, non-reciprocal phase shifters, and isolators.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"71 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197823","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}
Lucia Varbaro, Lukas Korosec, Chih-Ying Hsu, Duncan T. L. Alexander, Nicolas Jaouen, Jean-Marc Triscone
Rare-earth nickelates (chemical formula RNiO3, R being a rare-earth cation) display a temperature-dependent metal-to-insulator transition (MIT) together with a breathing distortion of the NiO6 octahedra units at a temperature ranging from 0 to 600 K depending on the size of the R cation. Their rich phase diagram is also characterized by a paramagnetic to antiferromagnetic transition that occurs at the same temperature as the MIT for R = Pr, Nd, while it arises at lower temperatures for all the other members of the series. In this work, we have investigated the order of the MIT in a portion of the phase diagram spanning from SmNiO3 to NdNiO3 by means of temperature dependent transport measurements and resonant elastic x-ray scattering performed on high quality epitaxial SmxNd1−xNiO3 solid solution thin films. Our results show that the order of the metal-to-insulator transition does not depend on whether or not the MIT is coupled with the magnetic transition.
稀土镍酸盐（化学式 RNiO3，R 为稀土阳离子）显示出一种随温度变化的金属-绝缘体转变（MIT），同时根据 R 阳离子的大小，NiO6 八面体单元在 0 至 600 K 的温度范围内发生呼吸变形。它们丰富的相图还具有顺磁性向反铁磁性转变的特征，对于 R = Pr、Nd，顺磁性向反铁磁性转变发生的温度与 MIT 相同，而对于该系列的所有其他成员，顺磁性向反铁磁性转变发生的温度较低。在这项工作中，我们通过在高质量的 SmxNd1-xNiO3 外延固溶体薄膜上进行温度相关传输测量和共振弹性 X 射线散射，研究了从 SmNiO3 到 NdNiO3 相图中的部分 MIT 的阶次。我们的研究结果表明，金属到绝缘体转变的顺序并不取决于 MIT 是否与磁转变耦合。
{"title":"Role of the coupling of the electronic transitions on the order of the metal-to-insulator phase transition in nickelates","authors":"Lucia Varbaro, Lukas Korosec, Chih-Ying Hsu, Duncan T. L. Alexander, Nicolas Jaouen, Jean-Marc Triscone","doi":"10.1063/5.0221334","DOIUrl":"https://doi.org/10.1063/5.0221334","url":null,"abstract":"Rare-earth nickelates (chemical formula RNiO3, R being a rare-earth cation) display a temperature-dependent metal-to-insulator transition (MIT) together with a breathing distortion of the NiO6 octahedra units at a temperature ranging from 0 to 600 K depending on the size of the R cation. Their rich phase diagram is also characterized by a paramagnetic to antiferromagnetic transition that occurs at the same temperature as the MIT for R = Pr, Nd, while it arises at lower temperatures for all the other members of the series. In this work, we have investigated the order of the MIT in a portion of the phase diagram spanning from SmNiO3 to NdNiO3 by means of temperature dependent transport measurements and resonant elastic x-ray scattering performed on high quality epitaxial SmxNd1−xNiO3 solid solution thin films. Our results show that the order of the metal-to-insulator transition does not depend on whether or not the MIT is coupled with the magnetic transition.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"137 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197810","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}
Qi Song, Zhiren He, Brendan D. Faeth, Christopher T. Parzyck, Anna Scheid, Chad J. Mowers, Yufan Feng, Qing Xu, Sonia Hasko, Jisung Park, Matthew R. Barone, Y. Eren Suyolcu, Peter A. van Aken, Betül Pamuk, Craig J. Fennie, Phil D. C. King, Kyle M. Shen, Darrell G. Schlom
The growing interest in the growth and study of thin films of low-dimensional metallic delafossites, with the general formula ABO2, is driven by their potential to exhibit electronic and magnetic characteristics that are not accessible in bulk systems. The layered structure of these compounds introduces unique surface states as well as electronic and structural reconstructions, making the investigation of their surface behavior pivotal to understanding their intrinsic electronic structure. In this work, we study the surface phenomena of epitaxially grown PtCoO2, PdCoO2, and PdCrO2 films, utilizing a combination of molecular-beam epitaxy and angle-resolved photoemission spectroscopy. Through precise control of surface termination and treatment, we discover a pronounced 3×3 surface reconstruction in PtCoO2 films and PdCoO2 films, alongside a 2 × 2 surface reconstruction observed in PdCrO2 films. These reconstructions have not been reported in prior studies of delafossites. Furthermore, our computational investigations demonstrate the BO2 surface’s relative stability compared to the A-terminated surface and the significant reduction in surface energy facilitated by the reconstruction of the A-terminated surface. These experimental and theoretical insights illuminate the complex surface dynamics in metallic delafossites, paving the way for future explorations of their distinctive properties in low-dimensional studies.
对通式为 ABO2 的低维金属 delafossites 薄膜的生长和研究兴趣与日俱增，这是因为它们有可能表现出块状系统无法获得的电子和磁性特征。这些化合物的层状结构引入了独特的表面态以及电子和结构重构，因此研究它们的表面行为对了解其内在电子结构至关重要。在这项工作中，我们结合分子束外延和角度分辨光发射光谱，研究了外延生长的 PtCoO2、PdCoO2 和 PdCrO2 薄膜的表面现象。通过精确控制表面终止和处理，我们在铂钴氧化物薄膜和钯钴氧化物薄膜中发现了明显的 3×3 表面重构，同时在钯铬氧化物薄膜中观察到了 2×2 表面重构。这些重构现象在之前的三角晶研究中从未报道过。此外，我们的计算研究表明，与 A 端表面相比，BO2 表面相对稳定，而且 A 端表面的重构可显著降低表面能量。这些实验和理论见解阐明了金属三角晶复杂的表面动力学，为今后在低维研究中探索其独特性质铺平了道路。
{"title":"Surface reconstructions and electronic structure of metallic delafossite thin films","authors":"Qi Song, Zhiren He, Brendan D. Faeth, Christopher T. Parzyck, Anna Scheid, Chad J. Mowers, Yufan Feng, Qing Xu, Sonia Hasko, Jisung Park, Matthew R. Barone, Y. Eren Suyolcu, Peter A. van Aken, Betül Pamuk, Craig J. Fennie, Phil D. C. King, Kyle M. Shen, Darrell G. Schlom","doi":"10.1063/5.0217540","DOIUrl":"https://doi.org/10.1063/5.0217540","url":null,"abstract":"The growing interest in the growth and study of thin films of low-dimensional metallic delafossites, with the general formula ABO2, is driven by their potential to exhibit electronic and magnetic characteristics that are not accessible in bulk systems. The layered structure of these compounds introduces unique surface states as well as electronic and structural reconstructions, making the investigation of their surface behavior pivotal to understanding their intrinsic electronic structure. In this work, we study the surface phenomena of epitaxially grown PtCoO2, PdCoO2, and PdCrO2 films, utilizing a combination of molecular-beam epitaxy and angle-resolved photoemission spectroscopy. Through precise control of surface termination and treatment, we discover a pronounced 3×3 surface reconstruction in PtCoO2 films and PdCoO2 films, alongside a 2 × 2 surface reconstruction observed in PdCrO2 films. These reconstructions have not been reported in prior studies of delafossites. Furthermore, our computational investigations demonstrate the BO2 surface’s relative stability compared to the A-terminated surface and the significant reduction in surface energy facilitated by the reconstruction of the A-terminated surface. These experimental and theoretical insights illuminate the complex surface dynamics in metallic delafossites, paving the way for future explorations of their distinctive properties in low-dimensional studies.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"45 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197825","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}
Metal–organic frameworks (MOFs), as novel porous crystalline materials with high porosity and a large specific surface area, have been increasingly utilized for CO2 adsorption. Machine learning (ML) combined with molecular simulations is used to identify MOFs with high CO2 adsorption capacity from millions of MOF structures. In this study, 23 structural and molecular features and 765 calculated features were proposed for the ML model and trained on a hypothetical MOF dataset for CO2 adsorption at different pressures. The calculated features improved the prediction accuracy of the ML model by 15%–20% and revealed its interpretability, consistent with the analysis of the interaction potential. Subsequently, the importance of the relevant features was ranked at different pressures. Regardless of the pressure, the molecular structure and pore size were the most critical factors. van der Waals force-related descriptors gained more competitive advantages at low pressures, whereas electrical-field-related descriptors gradually dominated at high pressures. Overall, this study provides a novel perspective to guide the initial high-throughput screening of MOFs as high-performance CO2 adsorption materials.
金属有机框架（MOFs）作为具有高孔隙率和大比表面积的新型多孔结晶材料，越来越多地被用于二氧化碳吸附。机器学习（ML）与分子模拟相结合，可从数百万个 MOF 结构中识别出具有高二氧化碳吸附能力的 MOF。本研究为 ML 模型提出了 23 个结构和分子特征以及 765 个计算特征，并在不同压力下吸附 CO2 的假定 MOF 数据集上进行了训练。计算出的特征将 ML 模型的预测准确率提高了 15%-20%，并揭示了其可解释性，这与相互作用位势分析是一致的。随后，对不同压力下相关特征的重要性进行了排序。与范德华力相关的描述因子在低压下更具竞争优势，而与电场相关的描述因子则在高压下逐渐占据主导地位。总之，本研究提供了一个新的视角，可指导对作为高性能二氧化碳吸附材料的 MOFs 进行初步的高通量筛选。
{"title":"Interpretable machine learning for materials discovery: Predicting CO2 adsorption properties of metal–organic frameworks","authors":"Yukun Teng, Guangcun Shan","doi":"10.1063/5.0222154","DOIUrl":"https://doi.org/10.1063/5.0222154","url":null,"abstract":"Metal–organic frameworks (MOFs), as novel porous crystalline materials with high porosity and a large specific surface area, have been increasingly utilized for CO2 adsorption. Machine learning (ML) combined with molecular simulations is used to identify MOFs with high CO2 adsorption capacity from millions of MOF structures. In this study, 23 structural and molecular features and 765 calculated features were proposed for the ML model and trained on a hypothetical MOF dataset for CO2 adsorption at different pressures. The calculated features improved the prediction accuracy of the ML model by 15%–20% and revealed its interpretability, consistent with the analysis of the interaction potential. Subsequently, the importance of the relevant features was ranked at different pressures. Regardless of the pressure, the molecular structure and pore size were the most critical factors. van der Waals force-related descriptors gained more competitive advantages at low pressures, whereas electrical-field-related descriptors gradually dominated at high pressures. Overall, this study provides a novel perspective to guide the initial high-throughput screening of MOFs as high-performance CO2 adsorption materials.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"30 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197826","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}
Chirality-induced spin selectivity (CISS) allows for the generation of spin currents without the need for ferromagnets or external magnetic fields, enabling innovative spintronic device designs. One example is a chiral spin valve composed of ferromagnetic and chiral materials, in which the resistance depends on both the magnetization direction of the ferromagnet and the chirality of the chiral material. So far, chiral spin valves have predominately employed chiral organic molecules, which have limited device applications. Chiral perovskites, which combine the properties of inorganic perovskites with chiral organic molecules, provide an excellent platform for exploring CISS-based devices. However, previous chiral perovskite-based spin valves exhibited magnetoresistance (MR) only at low temperatures. Here, we report room temperature MR in a chiral spin valve consisting of chiral perovskites/AlOx/perpendicular ferromagnet structures. It is observed that the chiral MR increases with rising temperature, suggesting the crucial role of phonon-induced enhancement of spin–orbit coupling in CISS in our device. Furthermore, we enhanced the chiral MR by introducing chiral molecules with amplified chirality. This highlights the potential of chirality engineering to improve CISS and the associated chiral MR, thereby opening possibilities for chiral spin valves tailored for cutting-edge spintronic applications.
{"title":"Room temperature chiral magnetoresistance in a chiral-perovskite-based perpendicular spin valve","authors":"Min-Gu Kang, In-Kook Hwang, Hee-Chang Kyung, Jaimin Kang, Donghyeon Han, Soogil Lee, Junyoung Kwon, Kyung-Jin Lee, Jihyeon Yeom, Byong-Guk Park","doi":"10.1063/5.0221834","DOIUrl":"https://doi.org/10.1063/5.0221834","url":null,"abstract":"Chirality-induced spin selectivity (CISS) allows for the generation of spin currents without the need for ferromagnets or external magnetic fields, enabling innovative spintronic device designs. One example is a chiral spin valve composed of ferromagnetic and chiral materials, in which the resistance depends on both the magnetization direction of the ferromagnet and the chirality of the chiral material. So far, chiral spin valves have predominately employed chiral organic molecules, which have limited device applications. Chiral perovskites, which combine the properties of inorganic perovskites with chiral organic molecules, provide an excellent platform for exploring CISS-based devices. However, previous chiral perovskite-based spin valves exhibited magnetoresistance (MR) only at low temperatures. Here, we report room temperature MR in a chiral spin valve consisting of chiral perovskites/AlOx/perpendicular ferromagnet structures. It is observed that the chiral MR increases with rising temperature, suggesting the crucial role of phonon-induced enhancement of spin–orbit coupling in CISS in our device. Furthermore, we enhanced the chiral MR by introducing chiral molecules with amplified chirality. This highlights the potential of chirality engineering to improve CISS and the associated chiral MR, thereby opening possibilities for chiral spin valves tailored for cutting-edge spintronic applications.","PeriodicalId":7985,"journal":{"name":"APL Materials","volume":"62 1","pages":""},"PeriodicalIF":6.1,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225268","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：