We report temperature-dependent hot carrier dynamics in liquid-phase epitaxy-grown GaSb1−xBix epilayers with dilute amounts of Bi (x ≾ 0.4%). Degenerate pump–probe (λ = 800 nm) transient reflectivity (PPTR) was used to investigate the carrier dynamics in the epilayers. The PPTR signal consists of two transient processes (fast and slow) at all temperatures for all epilayers. The fast, hot carrier relaxation time, which is attributed to the combined effect of intervalley scattering and thermalization of carriers below cryogenic temperatures (<100 K), is observed to increase with an increase in temperature (≈0.8–2 ps at 6.6 K and ≈4–5 ps at 300 K). However, at higher temperatures (>100 K), the interband CHSH-Auger recombination process affects the band-to-band recombination, leading to an increase in the slower decay time. The findings offer crucial insights for optimizing GaSbBi for hot carrier solar cell applications.
{"title":"Temperature-dependent ultrafast hot carrier dynamics in the dilute bismide alloy GaSb1−xBix (x ≾ 0.4%)","authors":"Akant Sagar Sharma, S. J. Sreerag, R. N. Kini","doi":"10.1063/5.0179135","DOIUrl":"https://doi.org/10.1063/5.0179135","url":null,"abstract":"We report temperature-dependent hot carrier dynamics in liquid-phase epitaxy-grown GaSb1−xBix epilayers with dilute amounts of Bi (x ≾ 0.4%). Degenerate pump–probe (λ = 800 nm) transient reflectivity (PPTR) was used to investigate the carrier dynamics in the epilayers. The PPTR signal consists of two transient processes (fast and slow) at all temperatures for all epilayers. The fast, hot carrier relaxation time, which is attributed to the combined effect of intervalley scattering and thermalization of carriers below cryogenic temperatures (&lt;100 K), is observed to increase with an increase in temperature (≈0.8–2 ps at 6.6 K and ≈4–5 ps at 300 K). However, at higher temperatures (&gt;100 K), the interband CHSH-Auger recombination process affects the band-to-band recombination, leading to an increase in the slower decay time. The findings offer crucial insights for optimizing GaSbBi for hot carrier solar cell applications.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"11 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139481704","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}
Yilong Jiang, Junhui Sun, Yangyang Lu, Lei Chen, Liang Jiang, Shiyu Du, Linmao Qian
The activation volume, which quantifies the response of the chemical reactions to the applied stress, plays a central role in controlling the mechanochemical reactions for applications including lubricity, wear, and the topographic fabrication of the surfaces under stress. However, the physical interpretations of the activation volume remain scientifically intriguing and largely unexplored. Here, density functional theory calculations are used to investigate the general rules of charge transfer underlying activation volume in controlling the typically mechanochemical reaction process. It is found that the activation volume could be decoupled into the electronic contributions from interface chemistry and bulk physical deformation, which are commonly linear dependent on the contact pressure. Therefore, the activation volume may, indeed, be derived from the stress-driven charge transfer underlying cooperative competition between interfacial chemistry and the bulk region. This competition is related to the stiffness change from the bulk to slab. The magnitude of the stiffness change represents the degree to which the interface atoms modify the bulk properties, which is directly related to the contribution of different regions to the activation volume. This work may open up the understanding of the activation volume from dynamic electron transfer to engineer mechanochemical reactions, different from the existing insights into the geometric dimensionality of the contact configuration.
{"title":"Decoupling activation volume via dynamic electron transfer in stress-driven chemical reactions","authors":"Yilong Jiang, Junhui Sun, Yangyang Lu, Lei Chen, Liang Jiang, Shiyu Du, Linmao Qian","doi":"10.1063/5.0166063","DOIUrl":"https://doi.org/10.1063/5.0166063","url":null,"abstract":"The activation volume, which quantifies the response of the chemical reactions to the applied stress, plays a central role in controlling the mechanochemical reactions for applications including lubricity, wear, and the topographic fabrication of the surfaces under stress. However, the physical interpretations of the activation volume remain scientifically intriguing and largely unexplored. Here, density functional theory calculations are used to investigate the general rules of charge transfer underlying activation volume in controlling the typically mechanochemical reaction process. It is found that the activation volume could be decoupled into the electronic contributions from interface chemistry and bulk physical deformation, which are commonly linear dependent on the contact pressure. Therefore, the activation volume may, indeed, be derived from the stress-driven charge transfer underlying cooperative competition between interfacial chemistry and the bulk region. This competition is related to the stiffness change from the bulk to slab. The magnitude of the stiffness change represents the degree to which the interface atoms modify the bulk properties, which is directly related to the contribution of different regions to the activation volume. This work may open up the understanding of the activation volume from dynamic electron transfer to engineer mechanochemical reactions, different from the existing insights into the geometric dimensionality of the contact configuration.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"115 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139481980","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}
We study an air–crown glass planar interface that includes a thin layer of a cholesteric liquid crystal doped with silver spheres of nanometer size. We propose a new theoretical model for the propagation of electromagnetic waves through the liquid crystal part and use the Marcuvitz–Schwinger form of the Maxwell equations to compute guided surface wave profiles. The results suggest the presence of anisotropic surface modes with negligible attenuation. The dependence of the surface wave parameters on the liquid crystal layer parameters can be used in liquid crystal-based sensors.
{"title":"Electromagnetic guided waves in composite liquid crystal-based interfaces","authors":"G. Reyes, P. Panayotaros, J. A. Reyes","doi":"10.1063/5.0174413","DOIUrl":"https://doi.org/10.1063/5.0174413","url":null,"abstract":"We study an air–crown glass planar interface that includes a thin layer of a cholesteric liquid crystal doped with silver spheres of nanometer size. We propose a new theoretical model for the propagation of electromagnetic waves through the liquid crystal part and use the Marcuvitz–Schwinger form of the Maxwell equations to compute guided surface wave profiles. The results suggest the presence of anisotropic surface modes with negligible attenuation. The dependence of the surface wave parameters on the liquid crystal layer parameters can be used in liquid crystal-based sensors.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"41 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139461766","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}
VO2 polymorphs present a unique opportunity to unravel diverse electronic properties possessed by their metastable phases. A highly reproducible, single-phase, and inexpensive synthesis method is challenging for obtaining VO2 polymorphs. Recent years have witnessed some exciting success in the growth and application of a wide range of VO2 polymorphs. This comprehensive review article delves into different polymorphs, including VO2(x) (x = A, B, M, R, C, P, and D), and investigates their distinct physical attributes. The primary focus of this article centers on providing a thorough overview of the recent progress made in stabilizing VO2(A) and VO2(B) polymorphs, emphasizing the significance of the coexistence of nanodomains at the film–substrate interface in stabilizing specific metastable phases. Additionally, the review article delves into advancements in understanding the phase transition mechanism, adjusting the order parameter in resistivity, and modifying the metal–insulator transition (MIT) temperature through doping. It also summarizes the structural, optical, electronic, and interface properties of these polymorphs and highlights their potential applications in next-generation electronic devices, particularly in the fields of sensing and energy storage.
{"title":"Metastable marvels: Navigating VO2 polymorphs for next-gen electronics and energy solutions","authors":"Neetu Vishwakarma, Abhijith Ambadi Remadevi, Deepak Kumar, Ankur Solanki, Abhimanyu Singh Rana, Amar Srivastava","doi":"10.1063/5.0179343","DOIUrl":"https://doi.org/10.1063/5.0179343","url":null,"abstract":"VO2 polymorphs present a unique opportunity to unravel diverse electronic properties possessed by their metastable phases. A highly reproducible, single-phase, and inexpensive synthesis method is challenging for obtaining VO2 polymorphs. Recent years have witnessed some exciting success in the growth and application of a wide range of VO2 polymorphs. This comprehensive review article delves into different polymorphs, including VO2(x) (x = A, B, M, R, C, P, and D), and investigates their distinct physical attributes. The primary focus of this article centers on providing a thorough overview of the recent progress made in stabilizing VO2(A) and VO2(B) polymorphs, emphasizing the significance of the coexistence of nanodomains at the film–substrate interface in stabilizing specific metastable phases. Additionally, the review article delves into advancements in understanding the phase transition mechanism, adjusting the order parameter in resistivity, and modifying the metal–insulator transition (MIT) temperature through doping. It also summarizes the structural, optical, electronic, and interface properties of these polymorphs and highlights their potential applications in next-generation electronic devices, particularly in the fields of sensing and energy storage.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"11 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139461998","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}
P.-C. Wang, K. T. Cavanagh, J. S. Gordineer, N. M. Caprotti
Scanning x-ray microbeam topography and fluorescence experiments were conducted in situ to study the electromigration behavior of a 0.5 μm thick, 10 μm wide, and 200 μm long Al(0.25 at. % Cu) conductor line with 1.5 μm-thick SiO2 passivation on a single crystal Si substrate. The strain sensitivity of x-ray topography measurement allowed detailed examination of the electromigration-induced stress distribution and evolution in the conductor line in response to the depletion of Cu solute early in the electromigration process. Upon electromigration at 0.4 MA/cm2 and 303 °C, a short-range stress gradient was quickly induced by Al migration in the Cu-depleted cathode region to counteract further Al flow. The stress gradient was fully developed during the 5.3 h incubation time, extending over the critical Blech length of about 66 μm from the cathode end. Plastic deformation then occurred at the downstream end of the Cu-depleted region. The preferential electromigration of Cu did not cause detectable stress change outside the Cu-depleted region, except for the significant stress development from the Al2Cu precipitation at the anode end which appeared to initiate the fracture in the passivation. Preliminary finite difference modeling was undertaken to simulate the experimental observations, from which important parameters dictating electromigration in Al(Cu) line were extracted: an apparent effective valence of −5.6 and −1.9 for Cu and Al in Al(Cu), respectively, and a critical Cu concentration of 0.16 at. % above which Al grain boundary diffusion is effectively blocked.
{"title":"Characterization of electromigration-induced short-range stress development in Al(0.25 at. % Cu) conductor line","authors":"P.-C. Wang, K. T. Cavanagh, J. S. Gordineer, N. M. Caprotti","doi":"10.1063/5.0178543","DOIUrl":"https://doi.org/10.1063/5.0178543","url":null,"abstract":"Scanning x-ray microbeam topography and fluorescence experiments were conducted in situ to study the electromigration behavior of a 0.5 μm thick, 10 μm wide, and 200 μm long Al(0.25 at. % Cu) conductor line with 1.5 μm-thick SiO2 passivation on a single crystal Si substrate. The strain sensitivity of x-ray topography measurement allowed detailed examination of the electromigration-induced stress distribution and evolution in the conductor line in response to the depletion of Cu solute early in the electromigration process. Upon electromigration at 0.4 MA/cm2 and 303 °C, a short-range stress gradient was quickly induced by Al migration in the Cu-depleted cathode region to counteract further Al flow. The stress gradient was fully developed during the 5.3 h incubation time, extending over the critical Blech length of about 66 μm from the cathode end. Plastic deformation then occurred at the downstream end of the Cu-depleted region. The preferential electromigration of Cu did not cause detectable stress change outside the Cu-depleted region, except for the significant stress development from the Al2Cu precipitation at the anode end which appeared to initiate the fracture in the passivation. Preliminary finite difference modeling was undertaken to simulate the experimental observations, from which important parameters dictating electromigration in Al(Cu) line were extracted: an apparent effective valence of −5.6 and −1.9 for Cu and Al in Al(Cu), respectively, and a critical Cu concentration of 0.16 at. % above which Al grain boundary diffusion is effectively blocked.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"41 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139462107","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}
K. Huynh, Y. Wang, M. E. Liao, J. Tweedie, P. Reddy, M. H. Breckenridge, R. Collazo, Z. Sitar, K. Sierakowski, M. Bockowski, X. Huang, M. Wojcik, M. S. Goorsky
Annealing Mg-implanted homoepitaxial GaN at temperatures above 1400 °C eliminates the formation of inversion domains and leads to improved dopant activation efficiency. Extended defects, in the form of inversion domains, contain electrically inactive Mg after post-implantation annealing at temperatures as high as 1300 °C (one GPa N2 overpressure), which results in a low dopant activation efficiency. Triple-axis x-ray data reveal that implant-induced strain is fully relieved after annealing at 1300 °C for 10 min, indicating that strain-inducing point defects formed during implantation have reconfigured and inversion domains are formed. However, annealing at temperatures of 1400–1500 °C (one GPa N2 overpressure) eliminates the presence of the inversion domains. While residual defects, such as dislocation loops, still exist after annealing at and above 1400 °C, chemical analysis at multiple dislocation loops shows no sign of Mg segregation. Meanwhile, an overall decreasing trend in the dislocation loop density is observed after annealing at the higher temperatures and longer times. Additionally, once inversion domains are formed and the samples are cooled to room temperature, they are shown to dissolve with subsequent annealing above 1400 °C. While such defects have been observed before, the important finding that such defects can be dissolved with a short, higher temperature step is key. Earlier work [Breckenridge et al., J. Appl. Phys. Lett. 118, 022101 (2021)] addressing electrical measurements of these types of samples showed that annealing at 1400 °C leads to a dopant activation efficiency that is an order of magnitude higher than that observed at 1300 °C. This work complements earlier work by identifying the inversion domains, which incorporate Mg, and points to the benefits, in terms of defect density and p-type dopant activation, of using higher temperature (>1400 °C) annealing cycles to activate Mg in GaN, even if the Mg-containing inversion domains had been formed during lower temperature annealing.
在高于 1400 °C 的温度下退火镁植入同位层氮化镓可消除反转域的形成，从而提高掺杂活化效率。在高达 1300 ℃ 的温度（一 GPa N2 超压）下进行植入后退火后，反转畴形式的扩展缺陷含有电性不活泼的镁，导致掺杂活化效率较低。三轴 X 射线数据显示，在 1300 ℃ 退火 10 分钟后，植入诱导的应变完全释放，这表明植入过程中形成的应变诱导点缺陷已经重组并形成了反转畴。然而，在 1400-1500 °C 的温度下退火（1 GPa 的 N2 过压），反转畴就不复存在了。虽然在 1400 ℃ 及以上退火后仍存在残余缺陷（如位错环），但对多个位错环进行的化学分析显示没有镁偏析的迹象。同时，退火温度越高、时间越长，差排环密度总体上呈下降趋势。此外，一旦形成反转畴并将样品冷却至室温，它们就会在 1400 °C 以上的退火过程中溶解。虽然以前也观察到过这种缺陷，但重要的发现是，这种缺陷可以在短时间、较高温度下溶解。早先的工作[Breckenridge 等人，J. Appl. Phys. Lett. 118, 022101 (2021)]对这些类型的样品进行了电学测量，结果表明 1400 ℃ 退火导致的掺杂活化效率比 1300 ℃ 观察到的效率高一个数量级。这项工作通过确定含有镁的反转域对先前的工作进行了补充，并指出，即使含镁反转域是在较低温度退火过程中形成的，使用较高温度（>1400 °C）退火循环来激活氮化镓中的镁，在缺陷密度和 p 型掺杂剂活化方面也有好处。
{"title":"Dissolution of Mg-enriched defects in implanted GaN and increased p-type dopant activation","authors":"K. Huynh, Y. Wang, M. E. Liao, J. Tweedie, P. Reddy, M. H. Breckenridge, R. Collazo, Z. Sitar, K. Sierakowski, M. Bockowski, X. Huang, M. Wojcik, M. S. Goorsky","doi":"10.1063/5.0179623","DOIUrl":"https://doi.org/10.1063/5.0179623","url":null,"abstract":"Annealing Mg-implanted homoepitaxial GaN at temperatures above 1400 °C eliminates the formation of inversion domains and leads to improved dopant activation efficiency. Extended defects, in the form of inversion domains, contain electrically inactive Mg after post-implantation annealing at temperatures as high as 1300 °C (one GPa N2 overpressure), which results in a low dopant activation efficiency. Triple-axis x-ray data reveal that implant-induced strain is fully relieved after annealing at 1300 °C for 10 min, indicating that strain-inducing point defects formed during implantation have reconfigured and inversion domains are formed. However, annealing at temperatures of 1400–1500 °C (one GPa N2 overpressure) eliminates the presence of the inversion domains. While residual defects, such as dislocation loops, still exist after annealing at and above 1400 °C, chemical analysis at multiple dislocation loops shows no sign of Mg segregation. Meanwhile, an overall decreasing trend in the dislocation loop density is observed after annealing at the higher temperatures and longer times. Additionally, once inversion domains are formed and the samples are cooled to room temperature, they are shown to dissolve with subsequent annealing above 1400 °C. While such defects have been observed before, the important finding that such defects can be dissolved with a short, higher temperature step is key. Earlier work [Breckenridge et al., J. Appl. Phys. Lett. 118, 022101 (2021)] addressing electrical measurements of these types of samples showed that annealing at 1400 °C leads to a dopant activation efficiency that is an order of magnitude higher than that observed at 1300 °C. This work complements earlier work by identifying the inversion domains, which incorporate Mg, and points to the benefits, in terms of defect density and p-type dopant activation, of using higher temperature (&gt;1400 °C) annealing cycles to activate Mg in GaN, even if the Mg-containing inversion domains had been formed during lower temperature annealing.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"54 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139461707","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}
Min Zhu, Nan Zhang, Dandan Ma, Xiaobin Yan, Faqi Zhan, Yuehong Zheng, Xuefeng Lu, Peiqing La
A series of Sr0.7Ba0.3Nb2O6−δ/x wt. % Ti (x = 1, 3, 5, and 10) composite ceramic thermoelectric materials were prepared, and the mechanism for improving their thermoelectric properties was explored. The experimental results demonstrate that nano-additive titanium powder undergoes oxidation to form TiO2 during sintering. However, under annealing in a reducing atmosphere, oxidation reactions further deplete the lattice oxygen, leading to an increased generation of oxygen vacancies and enhanced carrier concentration, ultimately leading to successful resistivity reduction. The samples consistently exhibit low thermal conductivity values below 2.0 W m−1 K−1 due to crystal defects, complex structure, and phonon scattering at the grain boundaries. The sample doped with 5 wt. %. Ti exhibits the lowest resistivity and highest PF value (409.3 μW/m K2 at 1073 K). Consequently, the figure of merit of Sr0.7Ba0.3Nb2O6−δ with 5 wt. % Ti attains its maximum value of 0.30 at 1073 K, representing a 50% increase compared to that of the undoped sample Sr0.7Ba0.3Nb2O6−δ (0.20 at 1073 K).
制备了一系列 Sr0.7Ba0.3Nb2O6-δ/x wt. % Ti（x = 1、3、5 和 10）复合陶瓷热电材料，并探索了改善其热电特性的机理。实验结果表明，纳米添加剂钛粉在烧结过程中会氧化形成 TiO2。然而，在还原气氛中退火时，氧化反应会进一步耗尽晶格中的氧，导致氧空位生成增加，载流子浓度提高，最终成功降低电阻率。由于晶体缺陷、结构复杂以及晶界的声子散射，样品的热导率始终低于 2.0 W m-1 K-1。掺杂 5 wt.钛的样品电阻率最低，PF 值最高（1073 K 时为 409.3 μW/m K2）。因此，掺有 5 wt. % Ti 的 Sr0.7Ba0.3Nb2O6-δ 的优点值在 1073 K 时达到最大值 0.30，比未掺杂的样品 Sr0.7Ba0.3Nb2O6-δ 的优点值（1073 K 时为 0.20）增加了 50%。
{"title":"Enhancement of thermoelectric properties in Sr0.7Ba0.3Nb2O6−δ-based ceramics via nano-sized Ti as additive","authors":"Min Zhu, Nan Zhang, Dandan Ma, Xiaobin Yan, Faqi Zhan, Yuehong Zheng, Xuefeng Lu, Peiqing La","doi":"10.1063/5.0177326","DOIUrl":"https://doi.org/10.1063/5.0177326","url":null,"abstract":"A series of Sr0.7Ba0.3Nb2O6−δ/x wt. % Ti (x = 1, 3, 5, and 10) composite ceramic thermoelectric materials were prepared, and the mechanism for improving their thermoelectric properties was explored. The experimental results demonstrate that nano-additive titanium powder undergoes oxidation to form TiO2 during sintering. However, under annealing in a reducing atmosphere, oxidation reactions further deplete the lattice oxygen, leading to an increased generation of oxygen vacancies and enhanced carrier concentration, ultimately leading to successful resistivity reduction. The samples consistently exhibit low thermal conductivity values below 2.0 W m−1 K−1 due to crystal defects, complex structure, and phonon scattering at the grain boundaries. The sample doped with 5 wt. %. Ti exhibits the lowest resistivity and highest PF value (409.3 μW/m K2 at 1073 K). Consequently, the figure of merit of Sr0.7Ba0.3Nb2O6−δ with 5 wt. % Ti attains its maximum value of 0.30 at 1073 K, representing a 50% increase compared to that of the undoped sample Sr0.7Ba0.3Nb2O6−δ (0.20 at 1073 K).","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"8 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139461736","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}
Twisha Titirsha, Md. Maruf Hossain Shuvo, John M. Gahl, Syed Kamrul Islam
Gallium oxide (Ga2O3) is a promising ultra-wide bandgap material offering a large bandgap (>4.7 eV) and high critical electric fields. The increasing demand for electronic devices for high-power applications in electric automobiles, high-performance computing, green energy technologies, etc., requires higher voltages and currents with enhanced efficiency. Vertical transistors, such as fin-shaped field-effect transistors (FinFETs) have emerged to meet the growing need with improved current handling capabilities, reduced resistance, and enhanced thermal performance. However, to fully exploit the Ga2O3 power transistors, precise and reliable physics-driven models are crucial. Therefore, a comprehensive surface potential model has been developed in this work for a vertical Ga2O3 FinFET. The electric potential across the channel is explained by analyzing the two-dimensional (2D) Poisson equation employing parabolic approximation. Such a surface potential model is instrumental in determining the performance of the Ga2O3 FinFET as it affects the threshold voltage, the drain current, and fringing capacitance. Exploiting the surface potentials, a fringing capacitance model is derived which is crucial in analyzing the speed of the device in compact integrated circuits. In addition, statistical analysis of the Ga2O3 FinFET using the Monte Carlo simulation technique is performed to determine the leakage current fluctuation due to doping variations. The validation of the analytical model with experimental results confirms the effectiveness and prospects of the developed models in the rapid development and characterization of next-generation high-performance vertical Ga2O3 power transistors.
{"title":"Physics-based modeling of surface potential and leakage current for vertical Ga2O3 FinFET","authors":"Twisha Titirsha, Md. Maruf Hossain Shuvo, John M. Gahl, Syed Kamrul Islam","doi":"10.1063/5.0181720","DOIUrl":"https://doi.org/10.1063/5.0181720","url":null,"abstract":"Gallium oxide (Ga2O3) is a promising ultra-wide bandgap material offering a large bandgap (>4.7 eV) and high critical electric fields. The increasing demand for electronic devices for high-power applications in electric automobiles, high-performance computing, green energy technologies, etc., requires higher voltages and currents with enhanced efficiency. Vertical transistors, such as fin-shaped field-effect transistors (FinFETs) have emerged to meet the growing need with improved current handling capabilities, reduced resistance, and enhanced thermal performance. However, to fully exploit the Ga2O3 power transistors, precise and reliable physics-driven models are crucial. Therefore, a comprehensive surface potential model has been developed in this work for a vertical Ga2O3 FinFET. The electric potential across the channel is explained by analyzing the two-dimensional (2D) Poisson equation employing parabolic approximation. Such a surface potential model is instrumental in determining the performance of the Ga2O3 FinFET as it affects the threshold voltage, the drain current, and fringing capacitance. Exploiting the surface potentials, a fringing capacitance model is derived which is crucial in analyzing the speed of the device in compact integrated circuits. In addition, statistical analysis of the Ga2O3 FinFET using the Monte Carlo simulation technique is performed to determine the leakage current fluctuation due to doping variations. The validation of the analytical model with experimental results confirms the effectiveness and prospects of the developed models in the rapid development and characterization of next-generation high-performance vertical Ga2O3 power transistors.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"5 14","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139438473","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}
Murilo O. Silva, G. M. Moreira, M. Bettega, R. F. da Costa
We report on elastic and electronically inelastic integral and differential cross sections for electron collisions with the 2H-pyran and 4H-pyran molecules. The scattering calculations were performed with the Schwinger multichannel method and aimed to (i) investigate the formation of resonant states, (ii) assign and compare the resonance spectrum of these isomers, and (iii) evaluate the influence of multichannel coupling effects upon elastic and electronically inelastic scattering processes. In the elastic channel, calculations carried out at the static-exchange and static-exchange plus polarization levels of approximation revealed the presence of three shape resonances for each one of the pyran isomers. For the 2H-pyran molecule, we found two resonances related to the formation of long-lived π∗ anion states that are centered at 1.38 or 1.32 eV (π1∗) and 4.54 or 4.46 eV (π2∗), depending on the polarization model used in the calculations, and a broad resonance of σ∗ character located around 9.50–10.00 eV. The resonances observed in the case of the 4H-pyran molecule have the same character with centers located at 2.08 or 2.20 eV (π1∗), 3.92 or 3.94 eV (π2∗), and 9.24–10.00 or 9.50–10.00 eV (σ∗), depending on the polarization model used in the calculations. The difference in the position of the resonances when comparing the results for the 2HPY and 4HPY molecules is explained in terms of the inductive effect. The electronically inelastic calculations employed the minimal orbital basis for single configuration interactions strategy and considered up to 129 open channels for 2H-pyran and up to 249 open channels for 4H-pyran. According to these levels of channel coupling, we computed integral and differential cross sections for the excitation from the ground state to the 13A′, 23A′, 11A′′, and 21A′ electronic excited states of 2H-pyran and to the 13B2, 13A1, 11B1, and 11B2 electronic excited states of 4H-pyran. As a general trend, for both isomers, we observed that the magnitude of the cross sections is reduced as more channels are considered open in the scattering calculations. We also obtained the total ionization cross sections for 2H- and 4H-pyran using the binary-encounter-Bethe model, which next was summed to the elastic and electronically inelastic cross sections to estimate the total cross sections. As a whole, these results correspond to the first set of cross sections for these targets published to date. Such an effort is aimed at addressing the demand of different communities regarding the expansion of the cross section data set for electron collisions with molecules of technological, environmental, and biological relevance, a need that has been raised by several reviews on the subject.
{"title":"Elastic and electronically inelastic scattering of electrons by 2H-pyran and 4H-pyran molecules","authors":"Murilo O. Silva, G. M. Moreira, M. Bettega, R. F. da Costa","doi":"10.1063/5.0187724","DOIUrl":"https://doi.org/10.1063/5.0187724","url":null,"abstract":"We report on elastic and electronically inelastic integral and differential cross sections for electron collisions with the 2H-pyran and 4H-pyran molecules. The scattering calculations were performed with the Schwinger multichannel method and aimed to (i) investigate the formation of resonant states, (ii) assign and compare the resonance spectrum of these isomers, and (iii) evaluate the influence of multichannel coupling effects upon elastic and electronically inelastic scattering processes. In the elastic channel, calculations carried out at the static-exchange and static-exchange plus polarization levels of approximation revealed the presence of three shape resonances for each one of the pyran isomers. For the 2H-pyran molecule, we found two resonances related to the formation of long-lived π∗ anion states that are centered at 1.38 or 1.32 eV (π1∗) and 4.54 or 4.46 eV (π2∗), depending on the polarization model used in the calculations, and a broad resonance of σ∗ character located around 9.50–10.00 eV. The resonances observed in the case of the 4H-pyran molecule have the same character with centers located at 2.08 or 2.20 eV (π1∗), 3.92 or 3.94 eV (π2∗), and 9.24–10.00 or 9.50–10.00 eV (σ∗), depending on the polarization model used in the calculations. The difference in the position of the resonances when comparing the results for the 2HPY and 4HPY molecules is explained in terms of the inductive effect. The electronically inelastic calculations employed the minimal orbital basis for single configuration interactions strategy and considered up to 129 open channels for 2H-pyran and up to 249 open channels for 4H-pyran. According to these levels of channel coupling, we computed integral and differential cross sections for the excitation from the ground state to the 13A′, 23A′, 11A′′, and 21A′ electronic excited states of 2H-pyran and to the 13B2, 13A1, 11B1, and 11B2 electronic excited states of 4H-pyran. As a general trend, for both isomers, we observed that the magnitude of the cross sections is reduced as more channels are considered open in the scattering calculations. We also obtained the total ionization cross sections for 2H- and 4H-pyran using the binary-encounter-Bethe model, which next was summed to the elastic and electronically inelastic cross sections to estimate the total cross sections. As a whole, these results correspond to the first set of cross sections for these targets published to date. Such an effort is aimed at addressing the demand of different communities regarding the expansion of the cross section data set for electron collisions with molecules of technological, environmental, and biological relevance, a need that has been raised by several reviews on the subject.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"10 18","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139437996","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}
We present an atomistic simulation of thermoelectric properties in cove-edged graphene nanoribbons (CGNRs) via the nonequilibrium Green's function. Different from gapless zigzag graphene nanoribbons (ZGNRs), CGNRs exhibit a noticeable bandgap. Such a bandgap can be modulated by varying three structural parameters (namely, the width N, the distance between adjacent coves m, as well as the shortest offset n) of CGNRs, which can give rise to the transition from semiconducting to semi-metallic. Due to the less dispersive phonon bands and the decrease in the number of phonon channels of CGNRs, they are found to have the lower phonon thermal conductance than ZGNRs. Modulation of CGNRs can produce over tenfold improvement of the maximum of ZT compared to ZGNRs. This improvement is due to the promotion of the Seebeck coefficient together with the degradation of the phonon thermal conductance of CGNRs compared to ZGNRs.
{"title":"Atomistic simulation of thermoelectric properties in cove-edged graphene nanoribbons","authors":"Zhong-Xiang Xie, Xue-Kun Chen, Xia Yu, Yuan-Xiang Deng, Yong Zhang, Wu-Xing Zhou, Pin-Zhen Jia","doi":"10.1063/5.0184595","DOIUrl":"https://doi.org/10.1063/5.0184595","url":null,"abstract":"We present an atomistic simulation of thermoelectric properties in cove-edged graphene nanoribbons (CGNRs) via the nonequilibrium Green's function. Different from gapless zigzag graphene nanoribbons (ZGNRs), CGNRs exhibit a noticeable bandgap. Such a bandgap can be modulated by varying three structural parameters (namely, the width N, the distance between adjacent coves m, as well as the shortest offset n) of CGNRs, which can give rise to the transition from semiconducting to semi-metallic. Due to the less dispersive phonon bands and the decrease in the number of phonon channels of CGNRs, they are found to have the lower phonon thermal conductance than ZGNRs. Modulation of CGNRs can produce over tenfold improvement of the maximum of ZT compared to ZGNRs. This improvement is due to the promotion of the Seebeck coefficient together with the degradation of the phonon thermal conductance of CGNRs compared to ZGNRs.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"110 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139461898","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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