David Yang, Sung Soo Ha, Sungwook Choi, Jialun Liu, Daniel Treuherz, Nan Zhang, Zheyi An, Hieu Minh Ngo, Muhammad Mahmood Nawaz, Ana F. Suzana, Longlong Wu, Gareth Nisbet, Daniel G. Porter, Hyunjung Kim, Ian K. Robinson
Strontium titanate is a classic quantum paraelectric oxide material that has been widely studied in bulk and thin films. It exhibits a well-known cubic-to-tetragonal antiferrodistortive phase transition at 105 K, characterized by the rotation of oxygen octahedra. A possible second phase transition at lower temperature is suppressed by quantum fluctuations, preventing the onset of ferroelectric order. However, recent studies have shown that ferroelectric order can be established at low temperatures by inducing strain and other means. Here, we used in situ multi-reflection Bragg coherent X-ray diffraction imaging to measure the strain and rotation tensors for two strontium titanate microcrystals at low temperature. We observe strains induced by dislocations and inclusion-like impurities in the microcrystals. Based on radial magnitude plots, these strains increase in magnitude and spread as the temperature decreases. Pearson's correlation heatmaps show a structural transition at 50 K, which we associate with the formation of a low-temperature ferroelectric phase in the presence of strain. We do not observe any change in local strains associated with the tetragonal phase transition at 105 K.
钛酸锶是一种典型的量子顺电氧化物材料，已被广泛用于块体和薄膜研究。它在 105 K 时表现出众所周知的立方到四方的反铁电体相变，其特征是氧八面体的旋转。在较低温度下可能发生的第二次相变受到量子波动的抑制，从而阻碍了铁电秩序的形成。然而，最近的研究表明，通过诱导应变等手段，铁电有序可以在低温下建立。在这里，我们利用原位多反射布拉格相干 X 射线衍射成像技术测量了钛酸锶微晶在低温下的应变和旋转张量。我们观察到微晶中的位错和包涵状杂质引起的应变。根据径向幅值图，这些应变的幅值随着温度的降低而增大和扩散。皮尔逊相关热图显示了 50 K 时的结构转变，我们将其与在应变存在的情况下形成的低温铁电相联系起来。我们没有观察到与 105 K 时四方相变相关的局部应变的任何变化。
{"title":"Low temperature ferroelectric state in strontium titanate microcrystals using in situ multi-reflection Bragg coherent X-ray diffraction imaging","authors":"David Yang, Sung Soo Ha, Sungwook Choi, Jialun Liu, Daniel Treuherz, Nan Zhang, Zheyi An, Hieu Minh Ngo, Muhammad Mahmood Nawaz, Ana F. Suzana, Longlong Wu, Gareth Nisbet, Daniel G. Porter, Hyunjung Kim, Ian K. Robinson","doi":"arxiv-2409.07595","DOIUrl":"https://doi.org/arxiv-2409.07595","url":null,"abstract":"Strontium titanate is a classic quantum paraelectric oxide material that has\u0000been widely studied in bulk and thin films. It exhibits a well-known\u0000cubic-to-tetragonal antiferrodistortive phase transition at 105 K,\u0000characterized by the rotation of oxygen octahedra. A possible second phase\u0000transition at lower temperature is suppressed by quantum fluctuations,\u0000preventing the onset of ferroelectric order. However, recent studies have shown\u0000that ferroelectric order can be established at low temperatures by inducing\u0000strain and other means. Here, we used in situ multi-reflection Bragg coherent\u0000X-ray diffraction imaging to measure the strain and rotation tensors for two\u0000strontium titanate microcrystals at low temperature. We observe strains induced\u0000by dislocations and inclusion-like impurities in the microcrystals. Based on\u0000radial magnitude plots, these strains increase in magnitude and spread as the\u0000temperature decreases. Pearson's correlation heatmaps show a structural\u0000transition at 50 K, which we associate with the formation of a low-temperature\u0000ferroelectric phase in the presence of strain. We do not observe any change in\u0000local strains associated with the tetragonal phase transition at 105 K.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142188165","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}
Haifang Cai, Zhiwen Duan, Douglas S. Galvao, Kun Cai
We proposed a new two-dimensional carbon material named 2-(111) planar T-carbon, which is obtained by slicing bulk T-carbon along its (111) crystallographic direction. 2-(111) planar T-carbon's optical and electrical properties can be engineered via surface decoration. Comparing the DFT phonon spectra of pristine and five decorated 2-(111) planar T-carbon obtained by first-principles calculations, we conclude that surface decoration presents a promising, effective, and feasible strategy to improve the structural stability of 2-(111) planar T-carbon. The calculated band structures and electronic properties show direct electronic band gap values between 0.17 eV (-O= decorated) and 2.21 eV (Hydrogenated). Chemical decoration also promises blue or red energy shifts in its optical properties.
{"title":"A 2D T-carbon 2-(111) structure with tunable electric and optical properties via chemical decorations: a first-principles investigation","authors":"Haifang Cai, Zhiwen Duan, Douglas S. Galvao, Kun Cai","doi":"arxiv-2409.07329","DOIUrl":"https://doi.org/arxiv-2409.07329","url":null,"abstract":"We proposed a new two-dimensional carbon material named 2-(111) planar\u0000T-carbon, which is obtained by slicing bulk T-carbon along its (111)\u0000crystallographic direction. 2-(111) planar T-carbon's optical and electrical\u0000properties can be engineered via surface decoration. Comparing the DFT phonon\u0000spectra of pristine and five decorated 2-(111) planar T-carbon obtained by\u0000first-principles calculations, we conclude that surface decoration presents a\u0000promising, effective, and feasible strategy to improve the structural stability\u0000of 2-(111) planar T-carbon. The calculated band structures and electronic\u0000properties show direct electronic band gap values between 0.17 eV (-O=\u0000decorated) and 2.21 eV (Hydrogenated). Chemical decoration also promises blue\u0000or red energy shifts in its optical properties.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142188169","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}
Aaditya Bhat, Colin Gilgenbach, Junghwa Kim, James LeBeau
Robust atomic resolution structural characterization of point defects in 3D is a longstanding challenge for electron microscopy. Here, we evaluate multislice electron ptychography as a tool to carry out 3D atomic resolution characterization of point defects in silicon carbide as a model. Through multislice electron scattering simulations, subsequent ptychographic reconstructions, and data analysis, we show that intrinsic defects such as vacancies and substitutions beyond transition metals can be detected with a depth precision of approximately 0.1 nm with realistic sample and microscope conditions. Furthermore, the dependence of contrast at defect sites on electron energy and dose, as well as optimal acquisition parameters, are described. Overall, these results serve as a guidepost to experiments aiming to analyze point defects beyond extremely thin specimens or only heavy elements.
{"title":"Sensitivity of Multislice Electron Ptychography to Point Defects: A Case Study in SiC","authors":"Aaditya Bhat, Colin Gilgenbach, Junghwa Kim, James LeBeau","doi":"arxiv-2409.07663","DOIUrl":"https://doi.org/arxiv-2409.07663","url":null,"abstract":"Robust atomic resolution structural characterization of point defects in 3D\u0000is a longstanding challenge for electron microscopy. Here, we evaluate\u0000multislice electron ptychography as a tool to carry out 3D atomic resolution\u0000characterization of point defects in silicon carbide as a model. Through\u0000multislice electron scattering simulations, subsequent ptychographic\u0000reconstructions, and data analysis, we show that intrinsic defects such as\u0000vacancies and substitutions beyond transition metals can be detected with a\u0000depth precision of approximately 0.1 nm with realistic sample and microscope\u0000conditions. Furthermore, the dependence of contrast at defect sites on electron\u0000energy and dose, as well as optimal acquisition parameters, are described.\u0000Overall, these results serve as a guidepost to experiments aiming to analyze\u0000point defects beyond extremely thin specimens or only heavy elements.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142188164","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 short and intermediate-range order in GeO$_2$ glass are investigated by molecular dynamics using machine-learning interatomic potential trained on ab initio calculation data and compared with reverse Monte Carlo fitting of neutron diffraction data. To characterize the structural differences in each model, the total/partial structure factors, coordination number, ring size and shape distributions, and persistent homology analysis were performed. These results show that although the two approaches yield similar two-body correlations, they can lead to three-dimensional models with very different short and intermediate-range ordering. A clear difference was observed especially in the ring distributions; RMC models exhibit a broad distribution in the ring size distribution, while neural network potential molecular dynamics yield much narrower ring distributions. This confirms that the density functional approximation in the ab initio calculations determines the preferred network assembly more strictly than RMC with simple coordination constraints and neutron diffraction data with isotope substitution.
研究人员利用基于 abinitio 计算数据训练的机器学习原子间势，通过分子动力学研究了 GeO$_2$ 玻璃中的短程和中程阶次，并与中子衍射数据的反向蒙特卡罗拟合进行了比较。为了描述每个模型的结构差异，研究人员进行了总/部分结构因子、配位数、环尺寸和形状分布以及持久同源性分析。结果表明，尽管这两种方法产生了相似的二体相关性，但它们可以导致具有非常不同的短程和中程排序的三维模型。特别是在环的分布上观察到了明显的差异；RMC 模型在环的大小分布上表现出了宽广的分布，而神经网络势能分子动力学则产生了窄得多的环分布。这证实了 ab initio 计算中的密度函数近似比使用简单配位约束的 RMC 和同位素置换的中子衍射数据更严格地确定了首选的网络组装。
{"title":"Comparison of intermediate-range order in GeO$_2$ glass: molecular dynamics using machine-learning interatomic potential vs. reverse Monte Carlo fitting to experimental data","authors":"Kenta Matsutani, Shusuke Kasamatsu, Takeshi Usuki","doi":"arxiv-2409.06982","DOIUrl":"https://doi.org/arxiv-2409.06982","url":null,"abstract":"The short and intermediate-range order in GeO$_2$ glass are investigated by\u0000molecular dynamics using machine-learning interatomic potential trained on ab\u0000initio calculation data and compared with reverse Monte Carlo fitting of\u0000neutron diffraction data. To characterize the structural differences in each\u0000model, the total/partial structure factors, coordination number, ring size and\u0000shape distributions, and persistent homology analysis were performed. These\u0000results show that although the two approaches yield similar two-body\u0000correlations, they can lead to three-dimensional models with very different\u0000short and intermediate-range ordering. A clear difference was observed\u0000especially in the ring distributions; RMC models exhibit a broad distribution\u0000in the ring size distribution, while neural network potential molecular\u0000dynamics yield much narrower ring distributions. This confirms that the density\u0000functional approximation in the ab initio calculations determines the preferred\u0000network assembly more strictly than RMC with simple coordination constraints\u0000and neutron diffraction data with isotope substitution.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224523","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}
Rafael Marti VallsSwansea University, Rebecca GriffinSwansea UniversityThe University of Bath, Anne SawhneySwansea University, Celina Domingos-DlofoSwansea University, Tom DunlopSwansea University, Sam ReisSwansea University, Peter J. HollimanSwansea University, Jenny BakerSwansea UniversityThe University of Bath
In this work we demonstrate a NASICON film sintered in situ onto a fused silica substrate. This production method drastically reduces the manufacturing time by combining the use of a spray-coated sol-gel solution and near-infrared (NIR) ultrafast sintering technology. The first demonstration of NIR sintered ceramics at high temperatures (~1000$^circ$C).
{"title":"New approach for obtaining ceramic NASICON (Na$_3$Zr$_2$ (SiO$_4$)$_2$PO$_4$) films sintered in situ by a sol-gel method, using spray deposition and Near-Infra Red Sintering","authors":"Rafael Marti VallsSwansea University, Rebecca GriffinSwansea UniversityThe University of Bath, Anne SawhneySwansea University, Celina Domingos-DlofoSwansea University, Tom DunlopSwansea University, Sam ReisSwansea University, Peter J. HollimanSwansea University, Jenny BakerSwansea UniversityThe University of Bath","doi":"arxiv-2409.07436","DOIUrl":"https://doi.org/arxiv-2409.07436","url":null,"abstract":"In this work we demonstrate a NASICON film sintered in situ onto a fused\u0000silica substrate. This production method drastically reduces the manufacturing\u0000time by combining the use of a spray-coated sol-gel solution and near-infrared\u0000(NIR) ultrafast sintering technology. The first demonstration of NIR sintered\u0000ceramics at high temperatures (~1000$^circ$C).","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224521","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}
Haoming Howard Li, Qian Chen, Gerbrand Ceder, Kristin A. Persson
Advances in lithium-metal anodes have inspired interest in discovery of Li-free cathodes, most of which are natively found in their charged state. This is in contrast to today's commercial lithium-ion battery cathodes, which are more stable in their discharged state. In this study, we combine calculated cathode voltage information from both categories of cathode materials, covering 5577 and 2423 total unique structure pairs, respectively. The resulting voltage distributions with respect to the redox pairs and anion types for both classes of compounds emphasize design principles for high-voltage cathodes, which favor later Period 4 transition metals in their higher oxidation states and more electronegative anions like fluorine or polyaion groups. Generally, cathodes that are found in their charged, delithiated state are shown to exhibit voltages lower than those that are most stable in their lithiated state, in agreement with thermodynamic expectations. Deviations from this trend are found to originate from different anion distributions between redox pairs. In addition, a machine learning model for voltage prediction based on chemical formulae is constructed, and shows state-of-the-art performance when compared to two established composition-based ML models for materials properties predictions, Roost and CrabNet.
{"title":"Voltage Mining for (De)lithiation-stabilized Cathodes and a Machine Learning Model for Li-ion Cathode Voltage","authors":"Haoming Howard Li, Qian Chen, Gerbrand Ceder, Kristin A. Persson","doi":"arxiv-2409.06921","DOIUrl":"https://doi.org/arxiv-2409.06921","url":null,"abstract":"Advances in lithium-metal anodes have inspired interest in discovery of\u0000Li-free cathodes, most of which are natively found in their charged state. This\u0000is in contrast to today's commercial lithium-ion battery cathodes, which are\u0000more stable in their discharged state. In this study, we combine calculated\u0000cathode voltage information from both categories of cathode materials, covering\u00005577 and 2423 total unique structure pairs, respectively. The resulting voltage\u0000distributions with respect to the redox pairs and anion types for both classes\u0000of compounds emphasize design principles for high-voltage cathodes, which favor\u0000later Period 4 transition metals in their higher oxidation states and more\u0000electronegative anions like fluorine or polyaion groups. Generally, cathodes\u0000that are found in their charged, delithiated state are shown to exhibit\u0000voltages lower than those that are most stable in their lithiated state, in\u0000agreement with thermodynamic expectations. Deviations from this trend are found\u0000to originate from different anion distributions between redox pairs. In\u0000addition, a machine learning model for voltage prediction based on chemical\u0000formulae is constructed, and shows state-of-the-art performance when compared\u0000to two established composition-based ML models for materials properties\u0000predictions, Roost and CrabNet.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224524","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}
Acoustic phonons in piezoelectric materials strongly couple to electrons through a macroscopic electric field. We show that this coupling leads to a momentum-dependent divergence of the Fan-Migdal electron linewidth. We then develop a self-consistent theory for calculating electron linewidths, which not only removes this piezoelectric divergence but also considerably modifies the linewidth in nonpiezoelectric, polar materials. Our predictions await immediate experimental confirmation, and this self-consistent method should be broadly used in interpreting various experiments on the electronic properties of real materials.
{"title":"Self-consistent electron lifetimes for electron-phonon scattering","authors":"Jae-Mo Lihm, Samuel Poncé, Cheol-Hwan Park","doi":"arxiv-2409.07404","DOIUrl":"https://doi.org/arxiv-2409.07404","url":null,"abstract":"Acoustic phonons in piezoelectric materials strongly couple to electrons\u0000through a macroscopic electric field. We show that this coupling leads to a\u0000momentum-dependent divergence of the Fan-Migdal electron linewidth. We then\u0000develop a self-consistent theory for calculating electron linewidths, which not\u0000only removes this piezoelectric divergence but also considerably modifies the\u0000linewidth in nonpiezoelectric, polar materials. Our predictions await immediate\u0000experimental confirmation, and this self-consistent method should be broadly\u0000used in interpreting various experiments on the electronic properties of real\u0000materials.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224522","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 develop a 1D continuum model of twin branching in shape memory alloys. The free energy of the branched microstructure comprises the interfacial and elastic strain energy contributions, both expressed in terms of the average twin spacing treated as a continuous function of the position. The total free energy is then minimized, and the corresponding Euler-Lagrange equation is solved numerically using the finite element method. The model can be considered as a continuum counterpart of the recent discrete model of Seiner et al. (2020), and our results show a very good agreement with that model in the entire range of physically relevant parameters. Furthermore, our continuum setting facilitates incorporation of energy dissipation into the model. The effect of rate-independent dissipation on the evolution of the branched microstructure is thus studied. The results show that significant effects on the microstructure and energy of the system are expected only for relatively small domain sizes.
我们建立了形状记忆合金孪晶分支的一维连续模型。支化微结构的自由能包括界面能和弹性应变能，二者均以作为位置连续函数的平均孪晶间距表示。然后将总自由能最小化，并使用有限元法对相应的欧拉-拉格朗日方程进行数值求解。该模型可视为 Seiner 等人（2020 年）最新离散模型的连续对应模型，我们的结果表明，在整个物理相关参数范围内，该模型与该模型非常吻合。此外，我们的连续介质设置有助于将能量耗散纳入模型。因此，我们研究了与速率无关的耗散对支链微结构演化的影响。结果表明，只有相对较小的畴尺寸才会对系统的微观结构和能量产生重大影响。
{"title":"Twin branching in shape memory alloys: a 1D continuum model with energy dissipation effects","authors":"Stanislaw Stupkiewicz, Seyedshoja Amini, Mohsen Rezaee-Hajidehi","doi":"arxiv-2409.07382","DOIUrl":"https://doi.org/arxiv-2409.07382","url":null,"abstract":"We develop a 1D continuum model of twin branching in shape memory alloys. The\u0000free energy of the branched microstructure comprises the interfacial and\u0000elastic strain energy contributions, both expressed in terms of the average\u0000twin spacing treated as a continuous function of the position. The total free\u0000energy is then minimized, and the corresponding Euler-Lagrange equation is\u0000solved numerically using the finite element method. The model can be considered\u0000as a continuum counterpart of the recent discrete model of Seiner et al.\u0000(2020), and our results show a very good agreement with that model in the\u0000entire range of physically relevant parameters. Furthermore, our continuum\u0000setting facilitates incorporation of energy dissipation into the model. The\u0000effect of rate-independent dissipation on the evolution of the branched\u0000microstructure is thus studied. The results show that significant effects on\u0000the microstructure and energy of the system are expected only for relatively\u0000small domain sizes.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142188168","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}
Ricardo Vidrio, Cesar Saucedo, Vincenzo Lordi, Shimon Kolkowitz, Keith G. Ray, Robert J. Hamers, Jennifer T. Choy
Oxygen-terminated diamond has a wide breadth of applications, which include stabilizing near-surface color centers, semiconductor devices, and biological sensors. Despite the vast literature on characterizing functionalization groups on diamond, the chemical composition on the shallowest portion of the surface (< 1 nm) is challenging to probe with conventional techniques like XPS and FTIR. In this work, we demonstrate the use of angle-resolved XPS to probe the first ten nanometers of (100) single-crystalline diamond, showing the changes of the oxygen functional groups and the allotropes of carbon with respect to depth. With the use of consistent peak-fitting methods, the peak identities and relative peak binding energies were identified for sp2 carbon, ether, hydroxyl, carbonyl, and C-H groups. For the oxygen-terminated sample, we also quantified the thickness of the sp2 carbon layer situated on top of the bulk sp3 diamond bonded carbon to be 0.4 $pm$ 0.1 nm, based on the analysis of the Auger electron spectra and D-parameter calculations. These results indicate that the majority of the oxygen is bonded to the sp2 carbon layer on the diamond, and not directly on the sp3 diamond bonded carbon.
{"title":"Sub-nanometer-thick native sp2 carbon on oxidized diamond surfaces","authors":"Ricardo Vidrio, Cesar Saucedo, Vincenzo Lordi, Shimon Kolkowitz, Keith G. Ray, Robert J. Hamers, Jennifer T. Choy","doi":"arxiv-2409.06934","DOIUrl":"https://doi.org/arxiv-2409.06934","url":null,"abstract":"Oxygen-terminated diamond has a wide breadth of applications, which include\u0000stabilizing near-surface color centers, semiconductor devices, and biological\u0000sensors. Despite the vast literature on characterizing functionalization groups\u0000on diamond, the chemical composition on the shallowest portion of the surface\u0000(< 1 nm) is challenging to probe with conventional techniques like XPS and\u0000FTIR. In this work, we demonstrate the use of angle-resolved XPS to probe the\u0000first ten nanometers of (100) single-crystalline diamond, showing the changes\u0000of the oxygen functional groups and the allotropes of carbon with respect to\u0000depth. With the use of consistent peak-fitting methods, the peak identities and\u0000relative peak binding energies were identified for sp2 carbon, ether, hydroxyl,\u0000carbonyl, and C-H groups. For the oxygen-terminated sample, we also quantified\u0000the thickness of the sp2 carbon layer situated on top of the bulk sp3 diamond\u0000bonded carbon to be 0.4 $pm$ 0.1 nm, based on the analysis of the Auger\u0000electron spectra and D-parameter calculations. These results indicate that the\u0000majority of the oxygen is bonded to the sp2 carbon layer on the diamond, and\u0000not directly on the sp3 diamond bonded carbon.","PeriodicalId":501234,"journal":{"name":"arXiv - PHYS - Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142187919","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}
Arkajit Ghosh, Wenqian Wu, Tao Ma, Ashwin J. Shahani, Jian Wang, Amit Misra
Laser surface remelting of as-cast Al-Ge eutectic alloy is shown to produce ultrafine lamellar eutectic morphology with interlamellar spacing refined up to ~60 nm and composed of FCC Al solid solution and unusual AlxGey intermetallic phases that do not form during near-equilibrium solidification. The microstructures are characterized and analyzed using a combination of selected area electron diffraction, high-resolution scanning transmission electron microscopy, energy dispersive X-ray spectroscopy to obtain high-resolution elemental maps, and atomistic modeling using density functional theory followed by atomic-scale image simulation. Depending on the local solidification conditions, the crystallography of the AlxGey intermetallic phases in the eutectic microstructure is either monoclinic (C 2/c) or monoclinic (P 21), with high densities of defects in both cases. This is in sharp contrast to the as-cast alloys that showed nominally pure Al and Ge phases with significant solute partitioning and equilibrium FCC and diamond cubic crystal structures, respectively. Corresponding kinetic phase diagrams are proposed to interpret the evolution of nano-lamellar eutectic morphologies with equilibrium Al and metastable AlxGey phases, and to explain increased solid solubility in the Al phases manifested by precipitation of ultrafine clusters of Ge. The reasons for the formation of these metastable eutectics under laser rapid solidification are discussed from the perspective of the competitive growth criterion.
研究表明，激光表面重熔铸造的铝-锗共晶合金可产生超细层状共晶形态，层间间距细化至~60 nm，由 FCC Al 固溶体和不常见的 AlxGey 金属间相组成，这些金属间相在近平衡凝固过程中不会形成。对这些微观结构的表征和分析结合使用了选区电子衍射、高分辨率扫描透射电子显微镜、能量色散 X 射线光谱以获得高分辨率元素图谱，以及使用密度泛函理论建立原子模型，然后进行原子尺度图像模拟。根据局部凝固条件的不同，共晶微观结构中的 AlxGey 金属间相的晶体结构要么是单斜（C 2/c），要么是单斜（P 21），两种情况下的缺陷密度都很高。这种情况与铸造合金形成鲜明对比，铸造合金显示出名义上纯净的 Al 相和 Ge 相，它们分别具有显著的绝对分区和平衡 FCC 晶体结构以及金刚石立方晶体结构。我们提出了相应的动力学相图来解释纳米胶束共晶形态与平衡铝相和可蜕变的 AlxGey 相的演变，并解释了 Alphases 中固体溶解度的增加（表现为超细 Ge 簇的沉淀）。从竞争生长准则的角度讨论了在激光快速凝固条件下形成这些可蜕变共晶的原因。
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