arXiv: Materials Science最新文献

英文中文

A pathway towards high throughput Quantum Monte Carlo simulations for alloys: A case study of two-dimensional (2D) GaSₓSe₁₋ₓ 通往合金高通量量子蒙特卡罗模拟的途径:二维(2D) GaS的案例研究ₓSe₁ₓ

arXiv: Materials Science

Pub Date : 2021-07-13 DOI: 10.13016/M2UVJO-QHHM

D. Wines, Kayahan Saritas, C. Ataca

This work was supported by the National Science Foundation through the Division of Materials Research under NSF DMR-1726213.

这项工作得到了美国国家科学基金会材料研究部在NSF DMR-1726213的支持。

引用次数: 0

Data analytics accelerates the experimental discovery of new thermoelectric materials with extremely high figure of merit 数据分析加速了具有极高价值的新型热电材料的实验发现

arXiv: Materials Science

Pub Date : 2021-04-16 DOI: 10.21203/rs.3.rs-926972/v1

S. Levchenko, Yaqiong Zhong, Xiaojuan Hu, Debalaya Sarker, Qingrui Xia, Liangliang Xu, Chao Yang, Zhongkang Han, J. Cui

Thermoelectric (TE) materials are among very few sustainable yet feasible energy solutions of present time. This huge promise of energy harvesting is contingent on identifying/designing materials having higher efficiency than presently available ones. However, due to the vastness of the chemical space of materials, only its small fraction was scanned experimentally and/or computationally so far. Employing a compressed-sensing based symbolic regression in an active-learning framework, we have not only identified a trend in materials’ compositions for superior TE performance, but have also predicted and experimentally synthesized several extremely high performing novel TE materials. Among these, we found polycrystalline p-type Cu0.45Ag0.55GaTe2 to possess an experimental figure of merit as high as ~2.8 at 827 K. This is a breakthrough in the field, because all previously known thermoelectric materials with a comparable figure of merit are either unstable or much more difficult to synthesize, rendering them unusable in large-scale applications. The presented methodology demonstrates the importance and tremendous potential of physically informed descriptors in material science, in particular for relatively small data sets typically available from experiments at well-controlled conditions.

热电材料是目前为数不多的可持续但可行的能源解决方案之一。这种能量收集的巨大前景取决于识别/设计比现有材料效率更高的材料。然而，由于材料的化学空间很大，迄今为止，只有很小一部分被实验和/或计算扫描。在主动学习框架中采用基于压缩感知的符号回归，我们不仅确定了材料成分具有优越TE性能的趋势，而且还预测并实验合成了几种高性能的新型TE材料。其中，我们发现多晶p型Cu0.45Ag0.55GaTe2在827 K时具有高达~2.8的实验优值。这是该领域的一个突破，因为所有已知的具有类似性能的热电材料要么不稳定，要么难以合成，这使得它们无法在大规模应用中使用。所提出的方法证明了物理信息描述符在材料科学中的重要性和巨大潜力，特别是对于通常在良好控制条件下从实验中获得的相对较小的数据集。

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引用次数: 1

Thermal laser evaporation of elements from across the periodic table 热激光蒸发元素周期表中的元素

arXiv: Materials Science

Pub Date : 2021-03-23 DOI: 10.2351/7.0000348

Thomas J. Smart, J. Mannhart, W. Braun

We propose and demonstrate that thermal laser evaporation can be applied to all solid, non-radioactive elements in the periodic table. By depositing thin films, we achieve growth rates exceeding 1 angstrom/s with output laser powers less than 500 W, using identical beam parameters for many different elements. The source temperature is found to vary linearly with laser power within the examined power range. High growth rates are possible using free-standing sources for most of the elements tested, eliminating the need for crucibles.

我们提出并证明热激光蒸发可以应用于元素周期表中所有固体，非放射性元素。通过沉积薄膜，我们实现了超过1埃/秒的生长速度，输出激光功率小于500瓦，使用相同的光束参数对许多不同的元素。在检测的功率范围内，光源温度随激光功率呈线性变化。对于大多数测试元素，使用独立的来源可以实现高增长率，从而消除了对坩埚的需要。

引用次数: 6

Perpendicular magnetic anisotropy in ultra-thin Cu2Sb-type (Mn–Cr)AlGe films fabricated onto thermally oxidized silicon substrates 热氧化硅衬底上制备的超薄cu2sb型(Mn-Cr)AlGe薄膜的垂直磁各向异性

arXiv: Materials Science

Pub Date : 2021-03-14 DOI: 10.1063/5.0049899

T. Kubota, K. Ito, R. Umetsu, K. Takanashi

Perpendicularly magnetized films showing small saturation magnetization, $M_mathrm{s}$, are essential for spin-transfer-torque writing type magnetoresistive random access memories, STT-MRAMs. An intermetallic compound, {(Mn-Cr)AlGe} of the Cu$_2$Sb-type crystal structure was investigated, in this study, as a material showing the low $M_mathrm{s}$ ($sim 300$ kA/m) and high-perpendicular magnetic anisotropy, $K_mathrm{u}$. The layer thickness dependence of $K_mathrm{u}$ and effects of Mg-insertion layers at top and bottom (Mn-Cr)AlGe$|$MgO interfaces were studied in film samples fabricated onto thermally oxidized silicon substrates to realize high-$K_mathrm{u}$ in the thickness range of a few nanometer. Optimum Mg-insertion thicknesses were 1.4 and 3.0 nm for the bottom and the top interfaces, respectively, which were relatively thick compared to results in similar insertion effect investigations on magnetic tunnel junctions reported in previous studies. The cross-sectional transmission electron microscope images revealed that the Mg-insertion layers acted as barriers to interdiffusion of Al-atoms as well as oxidization from the MgO layers. The values of $K_mathrm{u}$ were about $7 times 10^5$ and $2 times 10^5$ J/m$^3$ at room temperature for 5 and 3 nm-thick (Mn-Cr)AlGe films, respectively, with the optimum Mg-insertion thicknesses. The $K_mathrm{u}$ at a few nanometer thicknesses is comparable or higher than those reported in perpendicularly magnetized CoFeB films which are conventionally used in MRAMs, while the $M_mathrm{s}$ value is one third or less smaller than those of the CoFeB films. The developed (Mn-Cr)AlGe films are promising from the viewpoint of not only the magnetic properties, but also the compatibility to the silicon process in the film fabrication.

垂直磁化薄膜具有小的饱和磁化强度$M_ mathm {s}$，是自旋转移转矩写入型磁阻随机存取存储器(stt - mrm)的必要材料。本文研究了Cu$_2$ sb型晶体结构的金属间化合物{(Mn-Cr)AlGe}，作为具有低$M_mathrm{s}$ ($sim 300$ kA/m)和高垂直磁各向异性$K_mathrm{u}$的材料。在热氧化硅衬底上制备薄膜样品，研究了$K_ mathm {u}$的层厚依赖关系和(Mn-Cr)AlGe$|$MgO界面顶部和底部的mg插入层的影响，以实现在几纳米厚度范围内的高$K_ mathm {u}$。底部和顶部界面的最佳mg插入厚度分别为1.4 nm和3.0 nm，与以往类似的磁性隧道结插入效果研究结果相比，该厚度相对较厚。横截面透射电镜图像显示，镁插入层对al原子的相互扩散和MgO层的氧化起着屏障作用。在室温下，5 nm和3 nm厚度的(Mn-Cr)AlGe薄膜的$K_ maththrm {u}$分别约为$7 × 10^5$和$2 × 10^5$ J/m$^3$，此时插入mg的厚度最佳。在几个纳米厚度上的$K_ mathm {u}$与常规用于mram的垂直磁化CoFeB薄膜的值相当或更高，而$M_ mathm {s}$值比CoFeB薄膜的值小三分之一或更小。所制备的(Mn-Cr)AlGe薄膜不仅具有磁性，而且在薄膜制备过程中与硅工艺的相容性也很好。

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引用次数: 4

The Mesoscale Crystallinity of Nacreous Pearls 珍珠的中尺度结晶度

arXiv: Materials Science

Pub Date : 2021-03-11 DOI: 10.21203/RS.3.RS-278534/V1

J. Gim, Alden Koch, L. Otter, B. Savitzky, S. Erland, L. Estroff, Dorrit Jacob, R. Hovden

A pearl’s distinguished beauty and toughness is attributable to the periodic stacking of aragonite tablets known as nacre. Nacre is a naturally occurring mesocrystal that remarkably arises in the absence of translational symmetry. Gleaning the inspiring biomineral design of a pearl requires quantifying its structural coherence and understanding the stochastic processes that govern formation. By characterizing the entire structure of pearls (~3 mm) in cross-section at high resolution, we show nacre is a medium-range mesocrystal formed through nanoparticle assembly processes. Self-correcting growth mechanisms actively remedy disorder and topological defects of the tablets and act as a countervailing force to paracrystallinity (i.e. long-range disorder). Nacre has a correlation length of roughly 16 tablets (~5.5 µm) despite persistent fluctuations and topological defects. For longer distances (> 25 tablets, ~8.5 µm), the frequency spectrum of nacre tablets follows f-1.5 behavior suggesting growth is coupled to external stochastic processes—a universality found across disparate natural phenomena which now includes pearls.

珍珠独特的美丽和韧性归功于文石片的周期性堆积，即珠层。珍珠质是一种自然产生的中晶，在没有平移对称的情况下显著地出现。收集珍珠的鼓舞人心的生物矿物设计需要量化其结构一致性和理解控制形成的随机过程。通过高分辨率表征珍珠的整个结构(~ 3mm)，我们发现珍珠是一种通过纳米颗粒组装过程形成的中等范围的介晶。自我纠正生长机制积极地弥补片剂的无序和拓扑缺陷，并对准结晶性(即远程无序)起抵消作用。尽管存在持续的波动和拓扑缺陷，珍珠层的相关长度约为16片(~5.5µm)。对于较长距离(bbb25片，~8.5 μ m)，珠光片的频谱遵循f-1.5行为，表明生长与外部随机过程相耦合-这是在不同的自然现象中发现的普遍性，现在包括珍珠。

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引用次数: 0

Polycrystal plasticity and grain boundary evolution: A unified dislocation-based diffuse-interface approach 多晶塑性和晶界演化:基于位错的扩散界面方法

arXiv: Materials Science

Pub Date : 2021-02-01 DOI: 10.13140/RG.2.2.28625.45923

Junyang He, N. Admal

Grain structure plays a key role in the mechanical properties of alloy materials. Engineering the grain structure requires a comprehensive understanding of the evolution of grain boundaries (GBs) when a material is subjected to various manufacturing processes. To this end, we present a computationally efficient framework to describe the co-evolution of bulk plasticity and GBs. We represent GBs as diffused geometrically necessary dislocations, whose evolution describes GB plasticity. Under this representation, the evolution of GBs and bulk plasticity can be described in unison using the evolution equation for the plastic deformation gradient, an equation central to classical crystal plasticity theories. In addition, we outline a method to introduce a synthetic potential to drive migration of a flat GB within our diffuse-interface framework. We validate the framework by simulating the evolution of a triple junction, and demonstrate its computational efficiency. We further leverage this framework to study the migration of a flat GB driven by a potential difference, subject to different sets of available slip systems and mechanical boundary conditions.

晶粒组织对合金材料的力学性能起着关键作用。工程晶粒结构需要对晶界(GBs)的演变有全面的了解，当材料受到各种制造工艺。为此，我们提出了一个计算效率高的框架来描述体塑性和gb的共同演化。我们将GB表示为扩散的几何必要位错，其演化描述了GB塑性。在这种表示下，可以用塑性变形梯度演化方程(经典晶体塑性理论的核心方程)来统一描述GBs和体塑性的演化。此外，我们还概述了一种方法，该方法引入了一种综合潜力，以在我们的扩散接口框架内驱动平面GB的迁移。我们通过模拟三结点的演化来验证该框架，并证明了其计算效率。我们进一步利用这一框架来研究由电位差驱动的平面GB的迁移，受不同可用滑移系统和机械边界条件的影响。

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引用次数: 0

A crystal symmetry-invariant Kobayashi--Warren--Carter grain boundary model and its implementation using a thresholding algorithm 晶体对称不变的Kobayashi- Warren- Carter晶界模型及其阈值算法实现

arXiv: Materials Science

Pub Date : 2021-02-01 DOI: 10.13140/RG.2.2.27993.54881

Jaekwang Kim, M. Jacobs, S. Osher, N. Admal

One of the most important aims of grain boundary modeling is to predict the evolution of a large collection of grains in phenomena such as abnormal grain growth, coupled grain boundary motion, and recrystallization that occur under extreme thermomechanical loads. A unified framework to study the coevolution of grain boundaries with bulk plasticity has recently been developed by Admal et al. (2018), which is based on modeling grain boundaries as continuum dislocations governed by an energy based on the Kobayashi--Warren--Carter (KWC) model (Kobayashi et al., 1998, 2000). While the resulting unified model demonstrates coupled grain boundary motion and polygonization (seen in recrystallization), it is restricted to grain boundary energies of the Read--Shockley type, which applies only to small misorientation angles. In addition, the implementation of the unified model using finite elements inherits the computational challenges of the KWC model that originate from the singular diffusive nature of its governing equations. The main goal of this study is to generalize the KWC functional to grain boundary energies beyond the Read--Shockley-type that respect the bicrystallography of grain boundaries. The computational challenges of the KWC model are addressed by developing a thresholding method that relies on a primal dual algorithm and the fast marching method, resulting in an O(NlogN) algorithm, where N is the number of grid points. We validate the model by demonstrating the Herring angle relation, followed by a study of the grain microstructure evolution in a two-dimensional face-centered cubic copper polycrystal with crystal symmetry-invariant grain boundary energy data obtained from the lattice matching method of Runnels et al. (2016a,b).

晶界建模最重要的目的之一是预测在极端热机械载荷下发生的异常晶粒生长、耦合晶界运动和再结晶等现象中大量晶粒的演化。Admal等人(2018)最近开发了一个统一的框架来研究晶界与体塑性的共同演化，该框架基于将晶界建模为由基于Kobayashi- Warren- Carter (KWC)模型的能量控制的连续位错(Kobayashi et al.， 1998,2000)。虽然所得的统一模型显示了耦合的晶界运动和多边形化(见于再结晶)，但它仅限于Read- Shockley类型的晶界能量，这仅适用于小的取向偏差角。此外，使用有限元的统一模型的实现继承了KWC模型的计算挑战，这些挑战源于其控制方程的奇异扩散性质。本研究的主要目的是将KWC泛函推广到考虑晶界双晶学的Read—shockley型之外的晶界能。KWC模型的计算挑战通过开发一种阈值方法来解决，该方法依赖于原始对偶算法和快速前进方法，从而产生O(NlogN)算法，其中N是网格点的数量。我们通过展示Herring角关系验证了该模型，然后利用Runnels等人(2016a,b)的晶格匹配方法获得的晶体对称性不变晶界能量数据，研究了二维面心立方铜多晶的晶粒微观结构演变。

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引用次数: 2

Sintering BFO targets for sputtering 烧结BFO溅射靶材

arXiv: Materials Science

Pub Date : 2021-02-01 DOI: 10.34049/bcc.52.C.0047

G. Orr, A. Goryachev, G. Golan

Ceramic $BiFeO_{3}$ samples were prepared by rapid sintering at $880^OC$. Two compositions were examined. A $56/44 Bi_{2}O_{3}/Fe_{2}O_{3} mole%$ composition and a $56Bi_{2}O_{3}cdot44Fe_{2}O_{3}+6.5wt%,NaCl$ composition. The samples were heat treated at different times up to $8$ minutes and the phase content was examined as a function of the time using XRD measurements and analysis. It was demonstrated that using both compositions, maximum $BiFeO_{3}$ phase content is obtained after $3.5$ minutes. In the former approximately $50%$ of the material transformed to $BiFeO_{3}$ while in the latter $98.5%$.

采用$880^OC$快速烧结法制备了$BiFeO_{3}$陶瓷样品。检查了两种成分。56/44美元 Bi_ {2} O_ {3} / Fe_ {2} O_{3} 摩尔 %组成和56美元Bi_ {2} O_ {3} cdot44Fe_ {2} O_ {3} + 6.5 wt % ,氯化钠组成。样品经过不同时间的热处理，最长可达8分钟，并使用XRD测量和分析来检测相含量作为时间的函数。结果表明，两种组合物均在3.5 min后得到最大的$BiFeO_{3}$相含量。在前者中，大约$ 50% $的材料转化为$BiFeO_{3}$，而在后者中$ 98.5% $。

引用次数: 1

Comparison of measured and simulated spin-wave mode spectra of magnetic nanostructures. 磁性纳米结构自旋波模式光谱的测量与模拟比较

arXiv: Materials Science

Pub Date : 2021-01-01 DOI: 10.1063/5.0039188

H T Nembach, R D McMichael, M L Schneider, J M Shaw, T J Silva

Motivated by the importance of magnetization dynamics in nanomagnets for the development and optimization of magnetic devices and sensors, we measured and modeled spin wave spectra in patterned elliptical nanomagnets. Ferromagnetic resonance spectra for multiple nanomagnets of Ni₈₀Fe₂₀, fabricated by electron-beam lithography to have nominal short-axes of 200 nm or 100 nm, were measured by use of heterodyne magneto-optical microwave microscopy. Scanning electron microscope images taken of the same nanomagnets were used to define element shapes for micromagnetic simulations. The measured spectra show significant differences between nominally identical nanomagnets, which could be only partially attributed to uncontrolled shape variations in the patterning process, as evidenced by the limited agreement between the measured and simulated spectra. Agreement between measurements and simulations was improved by including a zone of reduced magnetization and exchange at the edges of the nanomagnets in the simulations. Our results show that the reduction of shape variations between individual magnetic random-access memory elements can potentially improve their performance. However, unambiguous determination of materials parameters in nanomagnets based on analysis and modeling of spin wave spectra remains problematic.

考虑到纳米磁体的磁化动力学对磁性器件和传感器的开发和优化的重要性，我们测量了椭圆纳米磁体的自旋波谱并建立了模型。利用外差磁光微波显微镜测量了电子束光刻制备的短轴标称为200 nm和100 nm的Ni80Fe20纳米磁体的铁磁共振谱。同样的纳米磁铁的扫描电子显微镜图像被用来定义微磁模拟的元素形状。实测光谱显示名义上相同的纳米磁体之间存在显著差异，这只能部分归因于图像化过程中不受控制的形状变化，正如测量光谱和模拟光谱之间有限的一致性所证明的那样。在模拟中，在纳米磁铁的边缘加入一个磁化和交换降低的区域，提高了测量和模拟之间的一致性。我们的研究结果表明，减少单个磁性随机存取存储器元件之间的形状变化可以潜在地提高它们的性能。然而，基于自旋波谱分析和建模的纳米磁体材料参数的明确确定仍然存在问题。

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引用次数: 0

Effect of different device parameters on tin-based perovskite solar cell coupled with In2S3 electron transport layer and CuSCN and Spiro-OMeTAD alternative hole transport layers for high-efficiency performance 不同器件参数对锡基钙钛矿太阳能电池耦合In2S3电子传输层和CuSCN和Spiro-OMeTAD替代空穴传输层的高效性能的影响

arXiv: Materials Science

Pub Date : 2020-12-16 DOI: 10.1080/15567036.2020.1820628

Intekhab Alam, Md Ali Ashraf

SCAPS 1-D was used for the simulation of lead-free environmentally benign methylammonium tin-iodide (CH3NH3SnI3) based solar cell. Indium sulphide (In2S3) was utilized as the electron transport layer (ETL) for its high carrier mobility and optimized band structure, unlike traditional titanium oxide (TiO2) ETL. Traditional expensive spiro-OMeTAD (C81H68N4O8) and cheaper cuprous thiocyanate (CuSCN) were utilized alternatively as hole transport layer (HTL) to observe the effect of different HTL on cell performance. We investigated the trend in electrical measurements by altering parameters such as thickness, defect density, valence band (VB) effective density of state and bandgap of the absorber layer, interfacial trap densities and defect density of ETL. At optimum condition, the device revealed the highest efficiency of 18.45% for CuSCN (HTL) and 19.32% for spiro-OMeTAD (HTL) configuration. The effect of working temperature, the wavelength of light and band-to-band radiative recombination rate was also observed for both configurations. All these simulation results will help to fabricate eco-friendly high-efficiency perovskite solar cell by replacing the commonly used toxic lead-based perovskite.

利用SCAPS 1-D对无铅环境友好型碘化锡甲基铵(CH3NH3SnI3)基太阳能电池进行了模拟。与传统的氧化钛(TiO2) ETL不同，利用硫化铟(In2S3)作为电子传输层(ETL)具有较高的载流子迁移率和优化的能带结构。采用传统昂贵的螺旋- ometad (C81H68N4O8)和廉价的硫氰酸亚铜(CuSCN)交替作为空穴传输层(HTL)，观察不同HTL对电池性能的影响。我们通过改变ETL的厚度、缺陷密度、吸收层的价带(VB)有效态密度和带隙、界面阱密度和缺陷密度等参数来研究电测量的趋势。在最佳条件下，CuSCN (HTL)和spiro-OMeTAD (HTL)的效率最高，分别为18.45%和19.32%。研究了工作温度、光波长和波段间辐射复合率对两种构型的影响。这些模拟结果将有助于替代常用的有毒铅基钙钛矿，制造环保高效的钙钛矿太阳能电池。

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引用次数: 40

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