An accurate and efficient heat bath method plays a key role in atomic simulations of the thermal and mechanical properties of single-crystal silicon. Here, focusing on the single-crystal silicon (111) layer, which is a crucial lattice structure commonly employed as a substrate for chips, we propose a heat jet approach for finite temperature atomic simulations of silicon layers. First, we formulate the linearized dynamic equations for the silicon atoms and calculate the dispersion relation and lattice wave solutions. Then, an appropriate matching boundary condition is chosen for designing the two-way boundary condition, which allows incoming waves to inject into the lattice system while eliminating boundary reflections. Combining the two-way boundary condition and phonon heat source, the heat jet approach for the silicon (111) layer is proposed. Numerical tests illustrate the accuracy and effectiveness of the heat jet approach in simultaneously resolving thermal fluctuations and controlling temperature. Furthermore, we simulate the propagation of a Gaussian hump at a given temperature with the heat jet approach compared to the Nosé–Hoover heat bath. Numerical results demonstrate that the heat jet approach can well describe the movement of large structural deformations among thermal fluctuations without boundary reflections.
{"title":"Heat jet approach for finite temperature atomic simulations of single-crystal silicon layers","authors":"Xuewei Xia, Lei Zhang, Baiyili Liu","doi":"10.1063/5.0214505","DOIUrl":"https://doi.org/10.1063/5.0214505","url":null,"abstract":"An accurate and efficient heat bath method plays a key role in atomic simulations of the thermal and mechanical properties of single-crystal silicon. Here, focusing on the single-crystal silicon (111) layer, which is a crucial lattice structure commonly employed as a substrate for chips, we propose a heat jet approach for finite temperature atomic simulations of silicon layers. First, we formulate the linearized dynamic equations for the silicon atoms and calculate the dispersion relation and lattice wave solutions. Then, an appropriate matching boundary condition is chosen for designing the two-way boundary condition, which allows incoming waves to inject into the lattice system while eliminating boundary reflections. Combining the two-way boundary condition and phonon heat source, the heat jet approach for the silicon (111) layer is proposed. Numerical tests illustrate the accuracy and effectiveness of the heat jet approach in simultaneously resolving thermal fluctuations and controlling temperature. Furthermore, we simulate the propagation of a Gaussian hump at a given temperature with the heat jet approach compared to the Nosé–Hoover heat bath. Numerical results demonstrate that the heat jet approach can well describe the movement of large structural deformations among thermal fluctuations without boundary reflections.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141880583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Benjamin A. Jorns, Matthew Byrne, Parker Roberts, Leanne Su, Ethan Dale, Richard R. Hofer
A stability criterion is derived for mode transitions in the discharge current oscillations of a magnetically shielded Hall thruster. The two-equation model evaluated in Paper I for these large-amplitude (>100% background), low-frequency (<25 kHz) current oscillations is generalized and then validated with measurements from a 9 kW class test article. It is shown that the model can re-create quantitatively trends in both oscillation amplitude and frequency with discharge voltage and current. The validated model is non-dimensionalized and applied to derive an analytical stability criterion for the onset of large-amplitude oscillations. The resulting expression depends on several properties, including discharge current, discharge voltage, neutral transit time in the channel, length of the acceleration zone, magnetic field strength, and channel area. The criterion is leveraged to inform two mitigation strategies—changing magnetic field strength and controlling anode temperature— for adjusting the stability margin of the thruster. The criterion is also employed to motivate a physical explanation for why mode transitions occur and, in turn, why the stability margin differs between shielded and unshielded thrusters.
针对磁屏蔽霍尔推进器放电电流振荡中的模式转换，推导出了一种稳定性准则。论文 I 评估了这些大振幅（>100% 背景）、低频率（<25 kHz）电流振荡的双方程模型，并对其进行了归纳，然后用 9 kW 级试验品的测量结果进行了验证。结果表明，该模型可以定量地再现振荡幅度和频率随放电电压和电流变化的趋势。经过验证的模型被非尺寸化，并应用于推导大振幅振荡开始时的分析稳定性准则。由此得出的表达式取决于多个属性，包括放电电流、放电电压、中性点在通道中的传输时间、加速区长度、磁场强度和通道面积。利用该准则可为两种缓解策略提供信息--改变磁场强度和控制阳极温度--以调整推进器的稳定裕度。该标准还用于解释为何会发生模式转换，以及为何屏蔽和非屏蔽推进器的稳定裕度不同。
{"title":"Mode transitions in a magnetically shielded Hall thruster. II. Stability criterion","authors":"Benjamin A. Jorns, Matthew Byrne, Parker Roberts, Leanne Su, Ethan Dale, Richard R. Hofer","doi":"10.1063/5.0205985","DOIUrl":"https://doi.org/10.1063/5.0205985","url":null,"abstract":"A stability criterion is derived for mode transitions in the discharge current oscillations of a magnetically shielded Hall thruster. The two-equation model evaluated in Paper I for these large-amplitude (&gt;100% background), low-frequency (&lt;25 kHz) current oscillations is generalized and then validated with measurements from a 9 kW class test article. It is shown that the model can re-create quantitatively trends in both oscillation amplitude and frequency with discharge voltage and current. The validated model is non-dimensionalized and applied to derive an analytical stability criterion for the onset of large-amplitude oscillations. The resulting expression depends on several properties, including discharge current, discharge voltage, neutral transit time in the channel, length of the acceleration zone, magnetic field strength, and channel area. The criterion is leveraged to inform two mitigation strategies—changing magnetic field strength and controlling anode temperature— for adjusting the stability margin of the thruster. The criterion is also employed to motivate a physical explanation for why mode transitions occur and, in turn, why the stability margin differs between shielded and unshielded thrusters.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141880589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Low-temperature, low-pressure Cu-to-Cu direct bonding technology is a promising solution for next-generation high-density interconnects. Previous studies have shown that many properties of nanomaterials are determined by their structural characteristics. Therefore, the effect of the nanostructure (i.e., twin crystal and twin boundary, TB, sizes) on the bonding mechanism and mechanical response of the direct bonding of (111)-oriented nanotwinned Cu (NT-Cu) is studied using molecular dynamics simulations, where TB size means the TB layer thickness in terms of the number of atoms. The simulation results show that NT-Cu with extremely small twin crystals (e.g., 0.625 nm) have poor diffusivity. The number of dislocations induced by plastic deformation increases with increasing twin crystal size during stretching processes, degrading mechanical strength. The strain hardening of bonded NT-Cu with extremely small twin crystals (e.g., 0.625 nm) is dominated by the strong barrier created by a high density of TBs, whereas that with twin crystal sizes of 2.5–10 nm is dominated by dislocation–TB and dislocation–grain boundary interactions. Bonded NT-Cu with 2–6 atoms per TB layer exhibits softening at initial plastic deformation due to the onset of partial collapse of TBs; however, the strength then significantly increases with a further increase in strain due to strain hardening.
{"title":"Atomistic simulations of effects of nanostructure on bonding mechanism and mechanical response of direct bonding of (111)-oriented nanotwinned Cu","authors":"Cheng-Da Wu, Chien-Fu Liao","doi":"10.1063/5.0217053","DOIUrl":"https://doi.org/10.1063/5.0217053","url":null,"abstract":"Low-temperature, low-pressure Cu-to-Cu direct bonding technology is a promising solution for next-generation high-density interconnects. Previous studies have shown that many properties of nanomaterials are determined by their structural characteristics. Therefore, the effect of the nanostructure (i.e., twin crystal and twin boundary, TB, sizes) on the bonding mechanism and mechanical response of the direct bonding of (111)-oriented nanotwinned Cu (NT-Cu) is studied using molecular dynamics simulations, where TB size means the TB layer thickness in terms of the number of atoms. The simulation results show that NT-Cu with extremely small twin crystals (e.g., 0.625 nm) have poor diffusivity. The number of dislocations induced by plastic deformation increases with increasing twin crystal size during stretching processes, degrading mechanical strength. The strain hardening of bonded NT-Cu with extremely small twin crystals (e.g., 0.625 nm) is dominated by the strong barrier created by a high density of TBs, whereas that with twin crystal sizes of 2.5–10 nm is dominated by dislocation–TB and dislocation–grain boundary interactions. Bonded NT-Cu with 2–6 atoms per TB layer exhibits softening at initial plastic deformation due to the onset of partial collapse of TBs; however, the strength then significantly increases with a further increase in strain due to strain hardening.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141880588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lavina Backman, Brett M. Hunter, Mark L. Weaver, Elizabeth J. Opila
Ultra-high temperature ceramics (UHTCs), most notably transition metal carbides and borides, exhibit melting temperatures exceeding 3000 °C, making them appropriate candidates to withstand the extreme temperatures (∼2000 °C) expected to occur at the leading edges of hypersonic vehicles. However, their propensity to react rapidly with oxygen limits their sustained application. The high entropy paradigm enables the exploration of novel UHTC compositions that may improve on the oxidation resistance of conventional refractory mono-carbides and -diborides. The oxidation kinetics of candidate high entropy group IV + V (HfZrTiTaNb)C and (HfZrTiTaNb)B2 materials were evaluated at 1500–1800 °C using Joule heating in one atmosphere 0.1%–1% oxygen/argon gas mixtures for times up to 15 min. Possible mechanisms based on the resulting complex time, temperature, and oxygen partial pressure dependencies are discussed. The carbides formed porous and intergranular oxides. Oxidation resistance was improved upon a continuous external scale formation. The diborides formed dense external scales and exhibited better oxidation resistance compared to the carbides. This improvement was attributed to the formation of liquid boria. Both compositions showed an unexpected reduction in material consumption at 1800 °C for all times tested, compared to results at lower temperatures. An in-depth analysis of the composition and morphology of the oxide scale and sub-surface regions for specimens tested at 1800 °C revealed that the formation of denser group IV-rich (Hf, Zr, Ti) oxides mitigated the formation of the otherwise detrimental liquid-forming group V (Ta, Nb) oxides, leading to the improved oxidation resistance.
超高温陶瓷（UHTC），主要是过渡金属碳化物和硼化物，熔化温度超过 3000 ℃，因此适合承受高超音速飞行器前缘的极端温度（2000 ℃）。然而，它们与氧气发生快速反应的倾向限制了它们的持续应用。高熵范例使人们能够探索新型超高真空技术成分，从而提高传统难熔单碳化物和二硼化物的抗氧化性。在 1500-1800 °C的温度下，在 0.1%-1% 氧气/氩气混合物中使用焦耳加热法评估了候选高熵 IV + V 组 (HfZrTiTaNb)C 和 (HfZrTiTaNb)B2 材料的氧化动力学，时间最长达 15 分钟。根据由此产生的复杂的时间、温度和氧分压依赖关系，讨论了可能的机制。碳化物形成了多孔和晶间氧化物。持续的外部鳞片形成提高了抗氧化性。与碳化物相比，二硼化物形成了致密的外部鳞片，表现出更好的抗氧化性。这种改善归因于液态硼化物的形成。与较低温度下的结果相比，这两种成分在 1800 °C 的所有测试时间内都意外地减少了材料消耗。对在 1800 °C下测试的试样的氧化鳞片和次表面区域的成分和形态进行深入分析后发现，富含IV族（Hf、Zr、Ti）的高密度氧化物的形成减轻了原本不利于形成液态的V族（Ta、Nb）氧化物的形成，从而提高了抗氧化性。
{"title":"Invited Article: The oxidation kinetics and mechanisms observed during ultra-high temperature oxidation of (HfZrTiTaNb)C and (HfZrTiTaNb)B2","authors":"Lavina Backman, Brett M. Hunter, Mark L. Weaver, Elizabeth J. Opila","doi":"10.1063/5.0206227","DOIUrl":"https://doi.org/10.1063/5.0206227","url":null,"abstract":"Ultra-high temperature ceramics (UHTCs), most notably transition metal carbides and borides, exhibit melting temperatures exceeding 3000 °C, making them appropriate candidates to withstand the extreme temperatures (∼2000 °C) expected to occur at the leading edges of hypersonic vehicles. However, their propensity to react rapidly with oxygen limits their sustained application. The high entropy paradigm enables the exploration of novel UHTC compositions that may improve on the oxidation resistance of conventional refractory mono-carbides and -diborides. The oxidation kinetics of candidate high entropy group IV + V (HfZrTiTaNb)C and (HfZrTiTaNb)B2 materials were evaluated at 1500–1800 °C using Joule heating in one atmosphere 0.1%–1% oxygen/argon gas mixtures for times up to 15 min. Possible mechanisms based on the resulting complex time, temperature, and oxygen partial pressure dependencies are discussed. The carbides formed porous and intergranular oxides. Oxidation resistance was improved upon a continuous external scale formation. The diborides formed dense external scales and exhibited better oxidation resistance compared to the carbides. This improvement was attributed to the formation of liquid boria. Both compositions showed an unexpected reduction in material consumption at 1800 °C for all times tested, compared to results at lower temperatures. An in-depth analysis of the composition and morphology of the oxide scale and sub-surface regions for specimens tested at 1800 °C revealed that the formation of denser group IV-rich (Hf, Zr, Ti) oxides mitigated the formation of the otherwise detrimental liquid-forming group V (Ta, Nb) oxides, leading to the improved oxidation resistance.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141880584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An experimental evaluation is presented of a two-equation model for the low frequency (<25 kHz), large amplitude (>100% of mean) discharge oscillations exhibited by a 9-kW class magnetically shielded Hall thruster. The model is based on a theoretical treatment of the “breathing mode” oscillations in Hall thrusters (Barral and Peradzyński, “A new breath for the breathing mode,” IEPC-2009-070) and includes governing equations for fluctuations in the discharge current and the spatially averaged neutral density in the thruster channel. The derivation of the governing equations is reviewed, and the key simplifying assumptions are formulated in terms of comparisons between the magnitudes of relative fluctuations in spatially averaged plasma properties. Experimental measurements are performed of these plasma properties at an operating condition of 300 V discharge voltage and 10 A discharge current. It is found that all quantities of interest such as drift speed, electric field, and temperature fluctuate on the timescale of the low frequency oscillations. However, the relative phasing of these properties combine in such that the key assumptions of the model are satisfied—all but the neutral density and discharge fluctuations can be neglected in the equations for neutral density and current oscillations. A physical interpretation of the validity of the assumptions is presented, and the model is discussed in the context of its extensibility to other operating conditions. The validated model forms the basis for a parametric study presented in Part II of mode transitions and the criterion for these transitions in a magnetically shielded Hall thruster.
对9千瓦级磁屏蔽霍尔推进器表现出的低频（<25千赫）、大振幅（>平均值的100%）放电振荡的双方程模型进行了实验评估。该模型基于对霍尔推进器中 "呼吸模式 "振荡的理论处理（Barral 和 Peradzyński，"呼吸模式的新呼吸"，IEPC-2009-070），包括推进器通道中放电电流波动和空间平均中性密度的控制方程。我们回顾了指导方程的推导过程，并根据空间平均等离子体特性相对波动幅度之间的比较，提出了关键的简化假设。在放电电压为 300 V、放电电流为 10 A 的工作条件下，对这些等离子体特性进行了实验测量。结果发现，漂移速度、电场和温度等所有相关量都在低频振荡的时间尺度上波动。然而，这些属性的相对相位结合使得模型的关键假设得以满足--在中性密度和电流振荡方程中，除了中性密度和放电波动之外，其他所有波动都可以忽略。本文对假设的有效性进行了物理解释，并结合模型对其他运行条件的可扩展性进行了讨论。经过验证的模型构成了第二部分中关于磁屏蔽霍尔推进器中模式转换和这些转换标准的参数研究的基础。
{"title":"Mode transitions in a magnetically shielded Hall thruster. I. Experimentally informed model","authors":"Benjamin A. Jorns, Ethan Dale, Richard R. Hofer","doi":"10.1063/5.0205983","DOIUrl":"https://doi.org/10.1063/5.0205983","url":null,"abstract":"An experimental evaluation is presented of a two-equation model for the low frequency (&lt;25 kHz), large amplitude (&gt;100% of mean) discharge oscillations exhibited by a 9-kW class magnetically shielded Hall thruster. The model is based on a theoretical treatment of the “breathing mode” oscillations in Hall thrusters (Barral and Peradzyński, “A new breath for the breathing mode,” IEPC-2009-070) and includes governing equations for fluctuations in the discharge current and the spatially averaged neutral density in the thruster channel. The derivation of the governing equations is reviewed, and the key simplifying assumptions are formulated in terms of comparisons between the magnitudes of relative fluctuations in spatially averaged plasma properties. Experimental measurements are performed of these plasma properties at an operating condition of 300 V discharge voltage and 10 A discharge current. It is found that all quantities of interest such as drift speed, electric field, and temperature fluctuate on the timescale of the low frequency oscillations. However, the relative phasing of these properties combine in such that the key assumptions of the model are satisfied—all but the neutral density and discharge fluctuations can be neglected in the equations for neutral density and current oscillations. A physical interpretation of the validity of the assumptions is presented, and the model is discussed in the context of its extensibility to other operating conditions. The validated model forms the basis for a parametric study presented in Part II of mode transitions and the criterion for these transitions in a magnetically shielded Hall thruster.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141880587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhen Guo Ban, Yan Shi, Ning Qian Huang, Zan Kui Meng, Shi Chen Zhu
Photoexcitation is a powerful way to induce phase transition of strongly correlated materials and dynamically control terahertz (THz) devices integrated with photoinduced phase transition (PIPT) materials. To clarify controversies over the physical mechanism between electronic insulator-metal transition (IMT) and structural phase transition (SPT) of photoexcited vanadium dioxide (VO2), the underlying atomic and electronic state changes during photoinduced monoclinic-to-rutile phase transition are illustrated, and the separation with different thresholds between the quasi-instantaneous IMT and the ultrafast SPT is discovered. Below the SPT threshold, there exist metastable states exhibiting the metal-like monoclinic phases, i.e., the strongest metallicity and weak monoclinic phases, when the bond lengths of the V–V pairs are closest. By analyzing the electronic transport properties of these metal-like monoclinic phases, the THz response of the whole phase transition process can be characterized for first time through the quantum-electromagnetic dispersion modeling method. The THz properties of the practical VO2 film are simulated and the great alignments between the measurements and the simulations verify the proposed analysis method, which provides a powerful exploration path and insights for the theoretical analysis and design verification of PIPT materials and their optoelectronic THz devices.
{"title":"Metal-like monoclinic phase and terahertz characteristics in ultrafast phase transition of photoexcited VO2","authors":"Zhen Guo Ban, Yan Shi, Ning Qian Huang, Zan Kui Meng, Shi Chen Zhu","doi":"10.1063/5.0215012","DOIUrl":"https://doi.org/10.1063/5.0215012","url":null,"abstract":"Photoexcitation is a powerful way to induce phase transition of strongly correlated materials and dynamically control terahertz (THz) devices integrated with photoinduced phase transition (PIPT) materials. To clarify controversies over the physical mechanism between electronic insulator-metal transition (IMT) and structural phase transition (SPT) of photoexcited vanadium dioxide (VO2), the underlying atomic and electronic state changes during photoinduced monoclinic-to-rutile phase transition are illustrated, and the separation with different thresholds between the quasi-instantaneous IMT and the ultrafast SPT is discovered. Below the SPT threshold, there exist metastable states exhibiting the metal-like monoclinic phases, i.e., the strongest metallicity and weak monoclinic phases, when the bond lengths of the V–V pairs are closest. By analyzing the electronic transport properties of these metal-like monoclinic phases, the THz response of the whole phase transition process can be characterized for first time through the quantum-electromagnetic dispersion modeling method. The THz properties of the practical VO2 film are simulated and the great alignments between the measurements and the simulations verify the proposed analysis method, which provides a powerful exploration path and insights for the theoretical analysis and design verification of PIPT materials and their optoelectronic THz devices.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141880585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Phase field modeling and computer simulations were conducted to uncover the fundamental mechanism behind the peak in damping capacity observed in BaTiO3-reinforced composites, considering both insulating and conductive cases. The damping capacity curve obtained from these simulations, which varies with temperature, reveals dual peaks near Tc for both cases. The first peak, labeled Peak I, occurs below Tc and is attributed to temperature-induced domain reorientation. The second peak, labeled Peak II, occurs above Tc and arises from stress-induced phase transitions between paraelastic and ferroelastic states. This transition results in a double-loop strain–stress hysteresis, akin to the polarization-field hysteresis observed in ferroelectric systems at and above Tc. Between Peak I and Peak II, there is a dip in damping capacity just below Tc, caused by the diminished ferroelasticity of BaTiO3 particles near this critical temperature. In composite materials, the dual peaks merge into a single peak due to the heterogeneous nature of Tc, influenced by various factors that either raise or lower Tc. This convergence aligns with experimental observations.
{"title":"Temperature-dependent damping mechanism in ferroelastic-reinforced composites","authors":"Wenting Xiang, Min Tang, Wenhui Zhu, Jingheng Chai, Qi Wu, Zihan Zhang, Xiaoxu Guo, Zheng Yang, Yongke Yan, Liwei D. Geng","doi":"10.1063/5.0218133","DOIUrl":"https://doi.org/10.1063/5.0218133","url":null,"abstract":"Phase field modeling and computer simulations were conducted to uncover the fundamental mechanism behind the peak in damping capacity observed in BaTiO3-reinforced composites, considering both insulating and conductive cases. The damping capacity curve obtained from these simulations, which varies with temperature, reveals dual peaks near Tc for both cases. The first peak, labeled Peak I, occurs below Tc and is attributed to temperature-induced domain reorientation. The second peak, labeled Peak II, occurs above Tc and arises from stress-induced phase transitions between paraelastic and ferroelastic states. This transition results in a double-loop strain–stress hysteresis, akin to the polarization-field hysteresis observed in ferroelectric systems at and above Tc. Between Peak I and Peak II, there is a dip in damping capacity just below Tc, caused by the diminished ferroelasticity of BaTiO3 particles near this critical temperature. In composite materials, the dual peaks merge into a single peak due to the heterogeneous nature of Tc, influenced by various factors that either raise or lower Tc. This convergence aligns with experimental observations.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141880586","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Michael P. McGarry, Simeon J. Gilbert, Luke Yates, Melissa L. Meyerson, Paul G. Kotula, William B. Bachman, Peter A. Sharma, Jack D. Flicker, Michael P. Siegal, Laura B. Biedermann
Granular metals (GMs), consisting of metal nanoparticles separated by an insulating matrix, frequently serve as a platform for fundamental electron transport studies. However, few technologically mature devices incorporating GMs have been realized, in large part because intrinsic defects (e.g., electron trapping sites and metal/insulator interfacial defects) frequently impede electron transport, particularly in GMs that do not contain noble metals. Here, we demonstrate that such defects can be minimized in molybdenum–silicon nitride (Mo–SiNx) GMs via optimization of the sputter deposition atmosphere. For Mo–SiNx GMs deposited in a mixed Ar/N2 environment, x-ray photoemission spectroscopy shows a 40%–60% reduction of interfacial Mo-silicide defects compared to Mo–SiNx GMs sputtered in a pure Ar environment. Electron transport measurements confirm the reduced defect density; the dc conductivity improved (decreased) by 104–105 and the activation energy for variable-range hopping increased 10×. Since GMs are disordered materials, the GM nanostructure should, theoretically, support a universal power law (UPL) response; in practice, that response is generally overwhelmed by resistive (defective) transport. Here, the defect-minimized Mo–SiNx GMs display a superlinear UPL response, which we quantify as the ratio of the conductivity at 1 MHz to that at dc, Δσω. Remarkably, these GMs display a Δσω up to 107, a three-orders-of-magnitude improved response than previously reported for GMs. By enabling high-performance electric transport with a non-noble metal GM, this work represents an important step toward both new fundamental UPL research and scalable, mature GM device applications.
{"title":"Interfacial defect reduction enhances universal power law response in Mo–SiNx granular metals","authors":"Michael P. McGarry, Simeon J. Gilbert, Luke Yates, Melissa L. Meyerson, Paul G. Kotula, William B. Bachman, Peter A. Sharma, Jack D. Flicker, Michael P. Siegal, Laura B. Biedermann","doi":"10.1063/5.0211080","DOIUrl":"https://doi.org/10.1063/5.0211080","url":null,"abstract":"Granular metals (GMs), consisting of metal nanoparticles separated by an insulating matrix, frequently serve as a platform for fundamental electron transport studies. However, few technologically mature devices incorporating GMs have been realized, in large part because intrinsic defects (e.g., electron trapping sites and metal/insulator interfacial defects) frequently impede electron transport, particularly in GMs that do not contain noble metals. Here, we demonstrate that such defects can be minimized in molybdenum–silicon nitride (Mo–SiNx) GMs via optimization of the sputter deposition atmosphere. For Mo–SiNx GMs deposited in a mixed Ar/N2 environment, x-ray photoemission spectroscopy shows a 40%–60% reduction of interfacial Mo-silicide defects compared to Mo–SiNx GMs sputtered in a pure Ar environment. Electron transport measurements confirm the reduced defect density; the dc conductivity improved (decreased) by 104–105 and the activation energy for variable-range hopping increased 10×. Since GMs are disordered materials, the GM nanostructure should, theoretically, support a universal power law (UPL) response; in practice, that response is generally overwhelmed by resistive (defective) transport. Here, the defect-minimized Mo–SiNx GMs display a superlinear UPL response, which we quantify as the ratio of the conductivity at 1 MHz to that at dc, Δσω. Remarkably, these GMs display a Δσω up to 107, a three-orders-of-magnitude improved response than previously reported for GMs. By enabling high-performance electric transport with a non-noble metal GM, this work represents an important step toward both new fundamental UPL research and scalable, mature GM device applications.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141880515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This report (I) aims to investigate defect behavior during the growth of heavily phosphorus (P)-doped Czochralski silicon (HP-Cz-Si) crystals. The defects and P chemical states in as-grown crystals with a resistivity of 0.6 mΩ cm and the wafers annealed at around 600 °C were evaluated by transmission electron microscopy and hard x-ray electron spectroscopy (HAXPES). Micro-dislocation loops (MDLs) were observed in the bottom portion of the crystal, and larger stacking faults (SFs), including complex dislocation clusters, were observed in the middle portion. HAXPES revealed two different P states, P1 and P2. P1 was attributed to a substitutional P (Ps). The P2 present in as-grown crystals was found to be electrically active, while the newly formed P2 after annealing was electrically inactive, indicating that they are in different states. HAXPES evaluation of HP-Cz-Si after electron irradiation showed similar behavior to P2 after annealing, suggesting that P-vacancy (V) clusters are formed when the crystals are held at temperatures below 600 °C during crystal growth. Combining the experimental results with our theoretical analysis in the report (II) based on density functional theory calculations, we identified the following defect formation mechanisms. Interstitial P (Pi) atoms introduced at the melting point become supersaturated during cooling to 600 °C, and MDLs are generated by the aggregation of Si self-interstitials (Is) released through a position exchange from Pi to Ps. In crystal portions with a long residence time below 600 °C, supersaturated Ps transforms into P–V clusters, and Is generated simultaneously are absorbed by the MDLs, which grow into SFs containing dislocation clusters.
本报告（I）旨在研究重磷（P）掺杂的佐赫拉尔斯基硅（HP-Cz-Si）晶体生长过程中的缺陷行为。通过透射电子显微镜和硬 X 射线电子显微镜（HAXPES）评估了电阻率为 0.6 mΩ cm 的未生长晶体和在 600 °C 左右退火的晶片中的缺陷和 P 化学态。在晶体底部观察到微位错环（MDL），在中间部分观察到较大的堆叠断层（SF），包括复杂的位错簇。HAXPES 揭示了两种不同的 P 态，即 P1 和 P2。P1 属于置换 P (Ps)。生长晶体中的 P2 具有电活性，而退火后新形成的 P2 则不具有电活性，这表明它们处于不同的状态。对电子辐照后的 HP-Cz-Si 进行的 HAXPES 评估显示了与退火后 P2 相似的行为，这表明晶体生长过程中晶体温度低于 600 ℃ 时会形成 P 空穴 (V) 簇。结合实验结果和报告（II）中基于密度泛函理论计算的理论分析，我们确定了以下缺陷形成机制。在熔点处引入的间隙 P（Pi）原子在冷却到 600 °C时会变得过饱和，通过从 Pi 到 Ps 的位置交换释放出的硅自间隙（Is）聚集产生 MDL。
{"title":"Defect behavior during growth of heavily phosphorus-doped Czochralski silicon crystals. I. Experimental study","authors":"Masataka Hourai, Yasuhito Narushima, Kazuhisa Torigoe, Naoya Nonaka, Koutaro Koga, Toshiaki Ono, Hiroshi Horie, Koji Sueoka","doi":"10.1063/5.0216898","DOIUrl":"https://doi.org/10.1063/5.0216898","url":null,"abstract":"This report (I) aims to investigate defect behavior during the growth of heavily phosphorus (P)-doped Czochralski silicon (HP-Cz-Si) crystals. The defects and P chemical states in as-grown crystals with a resistivity of 0.6 mΩ cm and the wafers annealed at around 600 °C were evaluated by transmission electron microscopy and hard x-ray electron spectroscopy (HAXPES). Micro-dislocation loops (MDLs) were observed in the bottom portion of the crystal, and larger stacking faults (SFs), including complex dislocation clusters, were observed in the middle portion. HAXPES revealed two different P states, P1 and P2. P1 was attributed to a substitutional P (Ps). The P2 present in as-grown crystals was found to be electrically active, while the newly formed P2 after annealing was electrically inactive, indicating that they are in different states. HAXPES evaluation of HP-Cz-Si after electron irradiation showed similar behavior to P2 after annealing, suggesting that P-vacancy (V) clusters are formed when the crystals are held at temperatures below 600 °C during crystal growth. Combining the experimental results with our theoretical analysis in the report (II) based on density functional theory calculations, we identified the following defect formation mechanisms. Interstitial P (Pi) atoms introduced at the melting point become supersaturated during cooling to 600 °C, and MDLs are generated by the aggregation of Si self-interstitials (Is) released through a position exchange from Pi to Ps. In crystal portions with a long residence time below 600 °C, supersaturated Ps transforms into P–V clusters, and Is generated simultaneously are absorbed by the MDLs, which grow into SFs containing dislocation clusters.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141880517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shaokang Liu, Bin Chao, Wenxin Fu, Kaixin Deng, Yan Li, Fangxin Zhang, Haihua Wu
The increasing electromagnetic pollution due to the widespread use of electronic devices has drawn attention to the development of high-efficiency electromagnetic wave absorption materials. In this study, polypropylene (PP)/Ni composite materials were prepared using the fused deposition modeling method, with PP as the matrix. The mechanical and absorption properties were investigated, showing that the PP-based materials exhibited good mechanical performance with a tensile strength of 25.3 MPa and an elongation at break of 32.1%. At a Ni content of 50% and a thickness of 1.9 mm, the composite material showed absorption properties of −24.31 dB and 5.6 GHz. The absorption bandwidth covered the entire X and Ku bands (6.4–18 GHz) with adjustable thickness ranging from 1.5 to 4 mm. The combination of excellent absorption and mechanical properties makes these materials promising for the fabrication of complex absorber devices.
由于电子设备的广泛使用，电磁污染日益严重，因此开发高效电磁波吸收材料备受关注。本研究以聚丙烯（PP）为基体，采用熔融沉积模型法制备了聚丙烯（PP）/镍复合材料。研究表明，聚丙烯基材料具有良好的机械性能和吸收性能，拉伸强度为 25.3 兆帕，断裂伸长率为 32.1%。镍含量为 50%、厚度为 1.9 毫米时，复合材料的吸收特性为 -24.31 dB，频率为 5.6 GHz。吸收带宽覆盖整个 X 和 Ku 波段（6.4-18 GHz），厚度可调范围为 1.5 至 4 毫米。出色的吸收性能和机械性能使这些材料有望用于制造复杂的吸收器设备。
{"title":"PP/Ni—3D printed composite materials for microwave absorption","authors":"Shaokang Liu, Bin Chao, Wenxin Fu, Kaixin Deng, Yan Li, Fangxin Zhang, Haihua Wu","doi":"10.1063/5.0208729","DOIUrl":"https://doi.org/10.1063/5.0208729","url":null,"abstract":"The increasing electromagnetic pollution due to the widespread use of electronic devices has drawn attention to the development of high-efficiency electromagnetic wave absorption materials. In this study, polypropylene (PP)/Ni composite materials were prepared using the fused deposition modeling method, with PP as the matrix. The mechanical and absorption properties were investigated, showing that the PP-based materials exhibited good mechanical performance with a tensile strength of 25.3 MPa and an elongation at break of 32.1%. At a Ni content of 50% and a thickness of 1.9 mm, the composite material showed absorption properties of −24.31 dB and 5.6 GHz. The absorption bandwidth covered the entire X and Ku bands (6.4–18 GHz) with adjustable thickness ranging from 1.5 to 4 mm. The combination of excellent absorption and mechanical properties makes these materials promising for the fabrication of complex absorber devices.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141880660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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