Hanna Ohlin, Bryan Benz, Lucia Romano, Ulrich Vogt
Metal-assisted chemical etching of silicon is a promising method for fabricating nanostructures with a high aspect ratio. To define a pattern for the catalyst, lift-off processes are commonly used. The lift-off step however is often a process bottle neck due to low yield, especially for smaller structures. To bypass the lift-off process, other methods such as electroplating can be utilized. In this paper, we suggest an electroplated bi-layer catalyst for vapour phase metal-assisted chemical etching as an alternative to the commonly utilised lift-off process. Samples were successfully etched in vapour, and resulting structures had feature sizes down to 10 nm.
{"title":"Lift-off free catalyst for metal assisted chemical etching of silicon in vapour phase","authors":"Hanna Ohlin, Bryan Benz, Lucia Romano, Ulrich Vogt","doi":"arxiv-2408.03702","DOIUrl":"https://doi.org/arxiv-2408.03702","url":null,"abstract":"Metal-assisted chemical etching of silicon is a promising method for\u0000fabricating nanostructures with a high aspect ratio. To define a pattern for\u0000the catalyst, lift-off processes are commonly used. The lift-off step however\u0000is often a process bottle neck due to low yield, especially for smaller\u0000structures. To bypass the lift-off process, other methods such as\u0000electroplating can be utilized. In this paper, we suggest an electroplated\u0000bi-layer catalyst for vapour phase metal-assisted chemical etching as an\u0000alternative to the commonly utilised lift-off process. Samples were\u0000successfully etched in vapour, and resulting structures had feature sizes down\u0000to 10 nm.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The development of fast and strong microactuators that can be integrated in microdevices is an essential challenge due to a lack of appropriate driving principles. In this paper, a membrane actuator powered by internal combustion of hydrogen and oxygen in a chamber with a volume of 3.1 nanoliters is demonstrated. The combustion in such a small volume is possible only for an extremely high surface-to-volume (S/V) ratio on the order of 10^7 1/m. The fuel with this S/V is prepared electrochemically in a special regime that produces only nanobubbles. A cloud of nanobubbles merges, forming a microbubble, which explodes, increasing the volume 500 times in 10us. The actuator generates an instantaneous force up to 0.5N and is able to move a body 11,000 times more massive than itself. The natural response time of about 10ms is defined by the incubation time needed to produce an exploding bubble. The device demonstrates reliable cyclic actuation at a frequency of 1Hz restricted by the effect of electrolyte aging. After 40,000 explosions, no significant wear in the chamber is observed. Due to record-breaking acceleration and standard microfabrication techniques, the actuator can be used as a universal engine for various microdevices including micro-electro-mechanical systems, microfluidics, microrobotics, wearable and implantable devices.
{"title":"A fast and strong microactuator powered by internal combustion of hydrogen and oxygen","authors":"Ilia Uvarov, Pavel Shlepakov, Vitaly Svetovoy","doi":"arxiv-2408.03103","DOIUrl":"https://doi.org/arxiv-2408.03103","url":null,"abstract":"The development of fast and strong microactuators that can be integrated in\u0000microdevices is an essential challenge due to a lack of appropriate driving\u0000principles. In this paper, a membrane actuator powered by internal combustion\u0000of hydrogen and oxygen in a chamber with a volume of 3.1 nanoliters is\u0000demonstrated. The combustion in such a small volume is possible only for an\u0000extremely high surface-to-volume (S/V) ratio on the order of 10^7 1/m. The fuel\u0000with this S/V is prepared electrochemically in a special regime that produces\u0000only nanobubbles. A cloud of nanobubbles merges, forming a microbubble, which\u0000explodes, increasing the volume 500 times in 10us. The actuator generates an\u0000instantaneous force up to 0.5N and is able to move a body 11,000 times more\u0000massive than itself. The natural response time of about 10ms is defined by the\u0000incubation time needed to produce an exploding bubble. The device demonstrates\u0000reliable cyclic actuation at a frequency of 1Hz restricted by the effect of\u0000electrolyte aging. After 40,000 explosions, no significant wear in the chamber\u0000is observed. Due to record-breaking acceleration and standard microfabrication\u0000techniques, the actuator can be used as a universal engine for various\u0000microdevices including micro-electro-mechanical systems, microfluidics,\u0000microrobotics, wearable and implantable devices.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The uncrewed aerial systems industry is rapidly expanding due to advancements in smaller electronics, smarter sensors, advanced flight controllers, and embedded perception modules leveraging artificial intelligence. These technological progress have opened new indoor applications for UAS, including warehouse inventory management, security inspections of public spaces and facilities, and underground exploration. Despite the innovative designs from UAS manufacturers, there are no existing standards to ensure UAS and human safety in these environments. This study explores developing and evaluating micro-lattice structures for impact resistance in lightweight UAS. We examine patch designs using Face-Centered Cubic (FCC), Diamond (D), Kelvin (K), and Gyroid (GY) patterns and detail the processes for creating samples for impact and compression tests, including manufacturing and testing protocols. Our evaluation includes compression and impact tests to assess structural behavior, revealing the influence of geometry, compactness, and material properties. Diamond and Kelvin patterns were particularly effective in load distribution and energy absorption over the compression tests. Impact tests demonstrated significant differences in response between flexible and rigid materials, with flexible patches exhibiting superior energy dissipation and structural integrity under dynamic loading. The study provides a detailed analysis of specific energy absorption (SEA) and efficiency, offering insights into optimal micro-lattice structure designs for impact resistance in lightweight UAS applications.
{"title":"Polymer Micro-Lattice buffer structure Free Impact absorption","authors":"Louis Catar, Ilyass Tabiai, David St-Onge","doi":"arxiv-2408.02909","DOIUrl":"https://doi.org/arxiv-2408.02909","url":null,"abstract":"The uncrewed aerial systems industry is rapidly expanding due to advancements\u0000in smaller electronics, smarter sensors, advanced flight controllers, and\u0000embedded perception modules leveraging artificial intelligence. These\u0000technological progress have opened new indoor applications for UAS, including\u0000warehouse inventory management, security inspections of public spaces and\u0000facilities, and underground exploration. Despite the innovative designs from\u0000UAS manufacturers, there are no existing standards to ensure UAS and human\u0000safety in these environments. This study explores developing and evaluating\u0000micro-lattice structures for impact resistance in lightweight UAS. We examine\u0000patch designs using Face-Centered Cubic (FCC), Diamond (D), Kelvin (K), and\u0000Gyroid (GY) patterns and detail the processes for creating samples for impact\u0000and compression tests, including manufacturing and testing protocols. Our evaluation includes compression and impact tests to assess structural\u0000behavior, revealing the influence of geometry, compactness, and material\u0000properties. Diamond and Kelvin patterns were particularly effective in load\u0000distribution and energy absorption over the compression tests. Impact tests\u0000demonstrated significant differences in response between flexible and rigid\u0000materials, with flexible patches exhibiting superior energy dissipation and\u0000structural integrity under dynamic loading. The study provides a detailed analysis of specific energy absorption (SEA)\u0000and efficiency, offering insights into optimal micro-lattice structure designs\u0000for impact resistance in lightweight UAS applications.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mathematically, topological invariants arise from the parallel transport of eigenstates on the energy bands, which, in physics, correspond to the adiabatic dynamical evolution of transient states. It determines the presence of boundary states, while lacking direct measurements. Here, we develop time-varying programmable coupling circuits between acoustic cavities to mimic the Hamiltonians in the Brillouin zone, with which excitation and adiabatic evolution of bulk states are realized in a unit cell. By extracting the Berry phases of the bulk band, topological invariants, including the Zak phase for the SSH model and the Chern number for the AAH model, are obtained convincingly. The bulk state evolution also provides insight into the topological charges of our newly developed non-Abelian models, which are also verified by observing the adiabatic eigenframe rotation. Our work not only provides a general recipe for telling various topological invariants but also sheds light on transient acoustic wave manipulations.
{"title":"Direct measurement of topological invariants through temporal adiabatic evolution of bulk states in the synthetic Brillouin zone","authors":"Zhao-Xian Chen, Yuan-hong Zhang, Xiao-Chen Sun, Ruo-Yang Zhang, Jiang-Shan Tang, Xin Yang, Xue-Feng Zhu, Yan-Qing Lu","doi":"arxiv-2408.02984","DOIUrl":"https://doi.org/arxiv-2408.02984","url":null,"abstract":"Mathematically, topological invariants arise from the parallel transport of\u0000eigenstates on the energy bands, which, in physics, correspond to the adiabatic\u0000dynamical evolution of transient states. It determines the presence of boundary\u0000states, while lacking direct measurements. Here, we develop time-varying\u0000programmable coupling circuits between acoustic cavities to mimic the\u0000Hamiltonians in the Brillouin zone, with which excitation and adiabatic\u0000evolution of bulk states are realized in a unit cell. By extracting the Berry\u0000phases of the bulk band, topological invariants, including the Zak phase for\u0000the SSH model and the Chern number for the AAH model, are obtained\u0000convincingly. The bulk state evolution also provides insight into the\u0000topological charges of our newly developed non-Abelian models, which are also\u0000verified by observing the adiabatic eigenframe rotation. Our work not only\u0000provides a general recipe for telling various topological invariants but also\u0000sheds light on transient acoustic wave manipulations.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Trevor R. Smith, Spencer McDermott, Vatsalkumar Patel, Ross Anthony, Manu Hedge, Andrew P. Knights, Ryan B. Lewis
The explosion of artificial intelligence, possible end of Moore's law, dawn of quantum computing and continued exponential growth of data communications traffic have brought new urgency to the need for laser integration on the diversified Si platform. While diode lasers on III-V platforms have long powered internet data communications and other optoelectronic technologies, direct integration with Si remains problematic. A paradigm-shifting solution requires exploring new and unconventional materials and integration approaches. In this work, we show that a sub-10-nm ultra-thin Si$_{1-x}$Ge$_x$ buffer layer fabricated by an oxidative solid-phase epitaxy process can facilitate extraordinarily efficient strain relaxation. The Si$_{1-x}$Ge$_x$ layer is formed by ion implanting Ge into Si(111) and selectively oxidizing Si atoms in the resulting ion-damaged layer, precipitating a fully strain-relaxed Ge-rich layer between the Si substrate and surface oxide. The efficient strain relaxation results from the high oxidation temperature, producing a periodic network of dislocations at the substrate interface, coinciding with modulations of the Ge content in the Si$_{1-x}$Ge$_x$ layer and indicating the presence of defect-mediated diffusion of Si through the layer. The epitaxial growth of high-quality GaAs is demonstrated on this ultra-thin Si$_{1-x}$Ge$_x$ layer, demonstrating a promising new pathway for integrating III-V lasers directly on the Si platform.
{"title":"Ultra-thin strain-relieving Si$_{1-x}$Ge$_x$ layers enabling III-V epitaxy on Si","authors":"Trevor R. Smith, Spencer McDermott, Vatsalkumar Patel, Ross Anthony, Manu Hedge, Andrew P. Knights, Ryan B. Lewis","doi":"arxiv-2408.03253","DOIUrl":"https://doi.org/arxiv-2408.03253","url":null,"abstract":"The explosion of artificial intelligence, possible end of Moore's law, dawn\u0000of quantum computing and continued exponential growth of data communications\u0000traffic have brought new urgency to the need for laser integration on the\u0000diversified Si platform. While diode lasers on III-V platforms have long\u0000powered internet data communications and other optoelectronic technologies,\u0000direct integration with Si remains problematic. A paradigm-shifting solution\u0000requires exploring new and unconventional materials and integration approaches.\u0000In this work, we show that a sub-10-nm ultra-thin Si$_{1-x}$Ge$_x$ buffer layer\u0000fabricated by an oxidative solid-phase epitaxy process can facilitate\u0000extraordinarily efficient strain relaxation. The Si$_{1-x}$Ge$_x$ layer is\u0000formed by ion implanting Ge into Si(111) and selectively oxidizing Si atoms in\u0000the resulting ion-damaged layer, precipitating a fully strain-relaxed Ge-rich\u0000layer between the Si substrate and surface oxide. The efficient strain\u0000relaxation results from the high oxidation temperature, producing a periodic\u0000network of dislocations at the substrate interface, coinciding with modulations\u0000of the Ge content in the Si$_{1-x}$Ge$_x$ layer and indicating the presence of\u0000defect-mediated diffusion of Si through the layer. The epitaxial growth of\u0000high-quality GaAs is demonstrated on this ultra-thin Si$_{1-x}$Ge$_x$ layer,\u0000demonstrating a promising new pathway for integrating III-V lasers directly on\u0000the Si platform.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We show theoretically that essentially perfect elastostatic mechanical cloaking of a circular inclusion in a homogeneous surrounding medium can be achieved by means of a simple cloak comprising three concentric annuli, each formed of a homogeneous isotropic linear elastic material of prescribed shear modulus. Importantly, we find that the same combination of annuli will cloak any possible mode of imposed deformation or loading, for any randomly chosen admixture of imposed compression, pure shear and simple shear, without the need to re-design the cloak for different deformation modes. A full range of circular inclusions can be cloaked in this way, from soft to stiff. In consequence, we suggest that an inclusion of any arbitrary shape can also be cloaked, by first enveloping it in a stiff circle, then cloaking the combined structure with three annuli as described. Given that a single inclusion can be fully cloaked in this way, even at near field close to the cloaking perimeter, it also follows that multiple such neutral inclusions arranged with arbitrarily high packing fraction in a surrounding medium can also be cloaked. We confirm this by direct simulation. This indicates a possible route to fabricating composite materials with the same global mechanical response as a counterpart homogeneous material, and with uniform strain and stress fields outwith the cloaked inclusions.
{"title":"Simple and effective mechanical cloaking","authors":"Suzanne M. Fielding","doi":"arxiv-2408.02323","DOIUrl":"https://doi.org/arxiv-2408.02323","url":null,"abstract":"We show theoretically that essentially perfect elastostatic mechanical\u0000cloaking of a circular inclusion in a homogeneous surrounding medium can be\u0000achieved by means of a simple cloak comprising three concentric annuli, each\u0000formed of a homogeneous isotropic linear elastic material of prescribed shear\u0000modulus. Importantly, we find that the same combination of annuli will cloak\u0000any possible mode of imposed deformation or loading, for any randomly chosen\u0000admixture of imposed compression, pure shear and simple shear, without the need\u0000to re-design the cloak for different deformation modes. A full range of\u0000circular inclusions can be cloaked in this way, from soft to stiff. In\u0000consequence, we suggest that an inclusion of any arbitrary shape can also be\u0000cloaked, by first enveloping it in a stiff circle, then cloaking the combined\u0000structure with three annuli as described. Given that a single inclusion can be\u0000fully cloaked in this way, even at near field close to the cloaking perimeter,\u0000it also follows that multiple such neutral inclusions arranged with arbitrarily\u0000high packing fraction in a surrounding medium can also be cloaked. We confirm\u0000this by direct simulation. This indicates a possible route to fabricating\u0000composite materials with the same global mechanical response as a counterpart\u0000homogeneous material, and with uniform strain and stress fields outwith the\u0000cloaked inclusions.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ding Wang, Ping Wang, Shubham Mondal, Mingtao Hu, Yuanpeng Wu, Danhao Wang, Kai Sun, Zetian Mi
The pursuit of extreme device miniaturization and the exploration of novel physical phenomena have spurred significant interest in crystallographic phase control and ferroelectric switching in reduced dimensions. Recently, wurtzite ferroelectrics have emerged as a new class of functional materials, offering intriguing piezoelectric and ferroelectric properties, CMOS compatibility, and seamless integration with mainstream semiconductor technology. However, the exploration of crystallographic phase and ferroelectric switching in reduced dimensions, especially in nanostructures, has remained a largely uncharted territory. In this study, we present the first comprehensive investigation into the crystallographic phase transition of ScAlN nanowires across the full Sc compositional range. While a gradual transition from wurtzite to cubic phase was observed with increasing Sc composition, we further demonstrated that a highly ordered wurtzite phase ScAlN could be confined at the ScAlN/GaN interface for Sc contents surpassing what is possible in conventional films, holding great potential to addressing the fundamental high coercive field of wurtzite ferroelectrics. In addition, we provide the first evidence of ferroelectric switching in ScAlN nanowires, a result that holds significant implications for future device miniaturization. Our demonstration of tunable ferroelectric ScAlN nanowires opens new possibilities for nanoscale, domain, alloy, strain, and quantum engineering of wurtzite ferroelectrics, representing a significant stride towards the development of next-generation, miniaturized devices based on wurtzite ferroelectrics.
{"title":"Nanoscale Engineering of Wurtzite Ferroelectrics: Unveiling Phase Transition and Ferroelectric Switching in ScAlN Nanowires","authors":"Ding Wang, Ping Wang, Shubham Mondal, Mingtao Hu, Yuanpeng Wu, Danhao Wang, Kai Sun, Zetian Mi","doi":"arxiv-2408.02576","DOIUrl":"https://doi.org/arxiv-2408.02576","url":null,"abstract":"The pursuit of extreme device miniaturization and the exploration of novel\u0000physical phenomena have spurred significant interest in crystallographic phase\u0000control and ferroelectric switching in reduced dimensions. Recently, wurtzite\u0000ferroelectrics have emerged as a new class of functional materials, offering\u0000intriguing piezoelectric and ferroelectric properties, CMOS compatibility, and\u0000seamless integration with mainstream semiconductor technology. However, the\u0000exploration of crystallographic phase and ferroelectric switching in reduced\u0000dimensions, especially in nanostructures, has remained a largely uncharted\u0000territory. In this study, we present the first comprehensive investigation into\u0000the crystallographic phase transition of ScAlN nanowires across the full Sc\u0000compositional range. While a gradual transition from wurtzite to cubic phase\u0000was observed with increasing Sc composition, we further demonstrated that a\u0000highly ordered wurtzite phase ScAlN could be confined at the ScAlN/GaN\u0000interface for Sc contents surpassing what is possible in conventional films,\u0000holding great potential to addressing the fundamental high coercive field of\u0000wurtzite ferroelectrics. In addition, we provide the first evidence of\u0000ferroelectric switching in ScAlN nanowires, a result that holds significant\u0000implications for future device miniaturization. Our demonstration of tunable\u0000ferroelectric ScAlN nanowires opens new possibilities for nanoscale, domain,\u0000alloy, strain, and quantum engineering of wurtzite ferroelectrics, representing\u0000a significant stride towards the development of next-generation, miniaturized\u0000devices based on wurtzite ferroelectrics.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yansong Hao, Annick De Backer, Scott David Findlay, Sandra Van Aert
Through a simulation-based study we develop a statistical model-based quantification method for atomic resolution first moment scanning transmission electron microscopy (STEM) images. This method uses the uniformly weighted least squares estimator to determine the unknown structure parameters of the images and to isolate contributions from individual atomic columns. In this way, a quantification of the projected potential per atomic column is achieved. Since the integrated projected potential of an atomic column scales linearly with the number of atoms it contains, it can serve as a basis for atom counting. The performance of atom counting from first moment STEM imaging is compared to that from traditional HAADF STEM in the presence of noise. Through this comparison, we demonstrate the advantage of first moment STEM images to attain more precise atom counts. Finally, we compare the integrated intensities extracted from first-moment images of a wedge-shaped sample to those values from the bulk crystal. The excellent agreement found between these values proves the robustness of using bulk crystal simulations as a reference library. This enables atom counting for samples with different shapes by comparison with these library values.
{"title":"Towards atom counting from first moment STEM images: methodology and possibilities","authors":"Yansong Hao, Annick De Backer, Scott David Findlay, Sandra Van Aert","doi":"arxiv-2408.02405","DOIUrl":"https://doi.org/arxiv-2408.02405","url":null,"abstract":"Through a simulation-based study we develop a statistical model-based\u0000quantification method for atomic resolution first moment scanning transmission\u0000electron microscopy (STEM) images. This method uses the uniformly weighted\u0000least squares estimator to determine the unknown structure parameters of the\u0000images and to isolate contributions from individual atomic columns. In this\u0000way, a quantification of the projected potential per atomic column is achieved.\u0000Since the integrated projected potential of an atomic column scales linearly\u0000with the number of atoms it contains, it can serve as a basis for atom\u0000counting. The performance of atom counting from first moment STEM imaging is\u0000compared to that from traditional HAADF STEM in the presence of noise. Through\u0000this comparison, we demonstrate the advantage of first moment STEM images to\u0000attain more precise atom counts. Finally, we compare the integrated intensities\u0000extracted from first-moment images of a wedge-shaped sample to those values\u0000from the bulk crystal. The excellent agreement found between these values\u0000proves the robustness of using bulk crystal simulations as a reference library.\u0000This enables atom counting for samples with different shapes by comparison with\u0000these library values.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gaojie Zhang, Jie Yu, Hao Wu, Li Yang, Wen Jin, Bichen Xiao, Wenfeng Zhang, Haixin Chang
Two-dimensional (2D) van der Waals (vdW) magnets are crucial for ultra-compact spintronics. However, so far, no vdW crystal has exhibited tunable above-room-temperature intrinsic ferromagnetism in the 2D ultrathin regime. Here, we report the tunable above-room-temperature intrinsic ferromagnetism in ultrathin vdW crystal Fe$_{3+x}$GaTe$_2$ ($x$ = 0 and 0.3). By increasing the Fe content, the Curie temperature (TC) and room-temperature saturation magnetization of bulk Fe$_{3+x}$GaTe$_2$ crystals are enhanced from 354 to 376 K and 43.9 to 50.4 emu/g, respectively. Remarkably, the robust anomalous Hall effect in 3-nm Fe$_{3.3}$GaTe$_2$ indicate a record-high TC of 340 K and a large room-temperature perpendicular magnetic anisotropy energy of 6.6 * 10^5 J/m$^3$, superior to other ultrathin vdW ferromagnets. First-principles calculations reveal the asymmetric density of states and an additional large spin exchange interaction in ultrathin Fe$_{3+x}$GaTe$_2$ responsible for robust intrinsic ferromagnetism and higher Tc. This work opens a window for above-room-temperature ultrathin 2D magnets in vdW-integrated spintronics.
{"title":"Above-room-temperature intrinsic ferromagnetism in ultrathin van der Waals crystal Fe$_{3+x}$GaTe$_2$","authors":"Gaojie Zhang, Jie Yu, Hao Wu, Li Yang, Wen Jin, Bichen Xiao, Wenfeng Zhang, Haixin Chang","doi":"arxiv-2408.02259","DOIUrl":"https://doi.org/arxiv-2408.02259","url":null,"abstract":"Two-dimensional (2D) van der Waals (vdW) magnets are crucial for\u0000ultra-compact spintronics. However, so far, no vdW crystal has exhibited\u0000tunable above-room-temperature intrinsic ferromagnetism in the 2D ultrathin\u0000regime. Here, we report the tunable above-room-temperature intrinsic\u0000ferromagnetism in ultrathin vdW crystal Fe$_{3+x}$GaTe$_2$ ($x$ = 0 and 0.3).\u0000By increasing the Fe content, the Curie temperature (TC) and room-temperature\u0000saturation magnetization of bulk Fe$_{3+x}$GaTe$_2$ crystals are enhanced from\u0000354 to 376 K and 43.9 to 50.4 emu/g, respectively. Remarkably, the robust\u0000anomalous Hall effect in 3-nm Fe$_{3.3}$GaTe$_2$ indicate a record-high TC of\u0000340 K and a large room-temperature perpendicular magnetic anisotropy energy of\u00006.6 * 10^5 J/m$^3$, superior to other ultrathin vdW ferromagnets.\u0000First-principles calculations reveal the asymmetric density of states and an\u0000additional large spin exchange interaction in ultrathin Fe$_{3+x}$GaTe$_2$\u0000responsible for robust intrinsic ferromagnetism and higher Tc. This work opens\u0000a window for above-room-temperature ultrathin 2D magnets in vdW-integrated\u0000spintronics.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141936881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Changhuang Huang, Kechun Bai, Yanyan Zhu, David Andelman, Xingkun Man
Functional nanoparticles (NPs) have gained significant attention as a promising application in various fields, including sensor, smart coating, drug delivery, and more. Here, we propose a novel mechanism assisted by machine-learning workflow to accurately predict phase diagram of NPs, which elegantly achieves tunability of shapes and internal structures of NPs using self-assembly of block-copolymers (BCP). Unlike most of previous studies, we obtain onion-like and mesoporous NPs in neutral environment and hamburger-like NPs in selective environment. Such novel phenomenon is obtained only by tailoring the topology of a miktoarm star BCP chain architecture without the need for any further treatment. Moreover, we demonstrate that the BCP chain architecture can be used as a new strategy for tuning the lamellar asymmetry of NPs. We show that the asymmetry between A and B lamellae in striped ellipsoidal and onion-like particles increases as the volume fraction of the A-block increases, beyond the level reached by linear BCPs. In addition, we find an extended region of onion-like structure in the phase diagram of A-selective environment, as well as the emergence of an inverse onion-like structure in the B-selective one. Our findings provide a valuable insight into the design and fabrication of nanoscale materials with customized properties, opening up new possibilities for advanced applications in sensing, materials science, and beyond.
功能性纳米粒子（NPs）在传感器、智能涂层、药物输送等多个领域的应用前景广阔，因而备受关注。在此，我们提出了一种由机器学习工作流程辅助的新机制，以准确预测纳米粒子的相图，从而利用嵌段聚合物（BCP）的自我组装实现了纳米粒子形状和内部结构的可调节性。与以往大多数研究不同的是，我们在中性环境中获得了洋葱状和介孔状 NPs，在选择性环境中获得了汉堡包状 NPs。这种新现象只需对米克托臂星型 BCP 链结构的拓扑结构进行裁剪即可获得，无需任何进一步处理。此外，我们还证明了 BCP 链结构可以作为一种新的策略来调整 NPs 的片层不对称性。我们发现，随着 A 嵌段体积分数的增加，条纹状椭圆形颗粒和洋葱状颗粒中 A 和 B 嵌段之间的不对称性也会增加，超过了线性 BCP 所达到的水平。此外，我们还发现在 A 选择性环境的相图中出现了洋葱状结构的延伸区域，以及在 B 选择性环境中出现了反洋葱状结构。我们的发现为设计和制造具有定制特性的纳米级材料提供了宝贵的见解，为传感、材料科学等领域的先进应用开辟了新的可能性。
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