Chandrashekhar Savant, Thai-Son Nguyen, Kazuki Nomoto, Saurabh Vishwakarma, Siyuan Ma, Akshey Dhar, Yu-Hsin Chen, Joseph Casamento, David J. Smith, Huili Grace Xing, Debdeep Jena
We report a polarization-induced 2D electron gas (2DEG) at an epitaxial AlBN/GaN heterojunction grown on a SiC substrate. Using this 2DEG in a long conducting channel, we realize ultra-thin barrier AlBN/GaN high electron mobility transistors that exhibit current densities > 0.25 A/mm, clean current saturation, a low pinch-off voltage of −0.43 V, and a peak transconductance of ∼0.14 S/mm. Transistor performance in this preliminary realization is limited by the contact resistance. Capacitance–voltage measurements reveal that introducing ∼7% B in the epitaxial AlBN barrier on GaN boosts the relative dielectric constant of AlBN to ɛrAlBN∼16, higher than the AlN dielectric constant of ɛrAlN∼9. Epitaxial high-K barrier AlBN/GaN HEMTs can thus extend performance beyond the capabilities of current GaN transistors.
{"title":"Epitaxial high-K barrier AlBN/GaN HEMTs","authors":"Chandrashekhar Savant, Thai-Son Nguyen, Kazuki Nomoto, Saurabh Vishwakarma, Siyuan Ma, Akshey Dhar, Yu-Hsin Chen, Joseph Casamento, David J. Smith, Huili Grace Xing, Debdeep Jena","doi":"10.1063/5.0235294","DOIUrl":"https://doi.org/10.1063/5.0235294","url":null,"abstract":"We report a polarization-induced 2D electron gas (2DEG) at an epitaxial AlBN/GaN heterojunction grown on a SiC substrate. Using this 2DEG in a long conducting channel, we realize ultra-thin barrier AlBN/GaN high electron mobility transistors that exhibit current densities > 0.25 A/mm, clean current saturation, a low pinch-off voltage of −0.43 V, and a peak transconductance of ∼0.14 S/mm. Transistor performance in this preliminary realization is limited by the contact resistance. Capacitance–voltage measurements reveal that introducing ∼7% B in the epitaxial AlBN barrier on GaN boosts the relative dielectric constant of AlBN to ɛrAlBN∼16, higher than the AlN dielectric constant of ɛrAlN∼9. Epitaxial high-K barrier AlBN/GaN HEMTs can thus extend performance beyond the capabilities of current GaN transistors.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"26 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660577","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Joshua Olson, Robert Rockmore, Nathan D. Lemke, Sean Krzyzewski, Brian Kasch
Optical two-way time and frequency transfer (O-TWTFT) is an enabling technology that has applications ranging from fundamental investigations of relativity to the operation of global navigation satellite systems. Linear-optical-sampling (LOS) between optical frequency combs has been used to create very stable optical two-way time and frequency transfer links over free-space. Here, we demonstrate two-way time and frequency transfer using LOS between electro-optic frequency combs. This two-way electro-optic time and frequency transfer system demonstrated instabilities as low as 15 fs at 1 s of averaging time. These results show a pathway to highly stable, frequency agile, and low SWaP-C time transfer networks.
{"title":"Electro-optic time transfer with femtosecond stability","authors":"Joshua Olson, Robert Rockmore, Nathan D. Lemke, Sean Krzyzewski, Brian Kasch","doi":"10.1063/5.0240786","DOIUrl":"https://doi.org/10.1063/5.0240786","url":null,"abstract":"Optical two-way time and frequency transfer (O-TWTFT) is an enabling technology that has applications ranging from fundamental investigations of relativity to the operation of global navigation satellite systems. Linear-optical-sampling (LOS) between optical frequency combs has been used to create very stable optical two-way time and frequency transfer links over free-space. Here, we demonstrate two-way time and frequency transfer using LOS between electro-optic frequency combs. This two-way electro-optic time and frequency transfer system demonstrated instabilities as low as 15 fs at 1 s of averaging time. These results show a pathway to highly stable, frequency agile, and low SWaP-C time transfer networks.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"22 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
In this Letter, high-voltage enhancement-mode (E-mode) GaN-based power devices were demonstrated by employing an ultrathin barrier epitaxial structure. We investigated the effects of interface states introduced by the barrier etching process on the devices' reliability by fabricating and comparing metal–insulator–semiconductor (MIS)-field effect transistors (FETs) without an AlGaN barrier layer and MIS-high electron mobility transistors (MIS-HEMTs) with a barrier layer. The threshold voltages (Vth) of the fabricated MIS-HEMT and MIS-FET reach 0.14 and 2.5 V, respectively. Meanwhile, the fabricated devices exhibited a high off-state breakdown voltage over 1500 V. Compared to high interface trap density (Dit) at the SiN/GaN interface of MIS-FET, a much lower Dit was found at the SiN/AlGaN interface of MIS-HEMT owing to the barrier recess-free process. Thus, the MIS-HEMT exhibits a negligible Vth shift tested via positive bias temperature instability, which is crucial in the practical application for the E-mode operation. Furthermore, a scheme of extracting the Dit of the devices from the flatband voltages (VFB) shift of C–V curves was developed, and the accuracy of the scheme was verified by multi-frequency C–V tests.
{"title":"6-in. high-voltage GaN-based E-mode HEMTs with ultrathin barrier structures: Interface quality and its reliability","authors":"Nan Sun, Ronghua Wang, Huolin Huang, Jianxun Dai, Yun Lei, Qingyuan Zuo, Rong Han, Pengcheng Tao, Yanhong Liu, Yongshuo Ren, Wanxi Cheng, Huinan Liang","doi":"10.1063/5.0260365","DOIUrl":"https://doi.org/10.1063/5.0260365","url":null,"abstract":"In this Letter, high-voltage enhancement-mode (E-mode) GaN-based power devices were demonstrated by employing an ultrathin barrier epitaxial structure. We investigated the effects of interface states introduced by the barrier etching process on the devices' reliability by fabricating and comparing metal–insulator–semiconductor (MIS)-field effect transistors (FETs) without an AlGaN barrier layer and MIS-high electron mobility transistors (MIS-HEMTs) with a barrier layer. The threshold voltages (Vth) of the fabricated MIS-HEMT and MIS-FET reach 0.14 and 2.5 V, respectively. Meanwhile, the fabricated devices exhibited a high off-state breakdown voltage over 1500 V. Compared to high interface trap density (Dit) at the SiN/GaN interface of MIS-FET, a much lower Dit was found at the SiN/AlGaN interface of MIS-HEMT owing to the barrier recess-free process. Thus, the MIS-HEMT exhibits a negligible Vth shift tested via positive bias temperature instability, which is crucial in the practical application for the E-mode operation. Furthermore, a scheme of extracting the Dit of the devices from the flatband voltages (VFB) shift of C–V curves was developed, and the accuracy of the scheme was verified by multi-frequency C–V tests.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"61 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
E. Saavedra, V. L. Carvalho-Santos, S. Castillo-Sepúlveda, R. M. Corona, D. Altbir
Magnetic nanorings have potential applications in devices based on spintronics concepts. In this work, through micromagnetic simulations, we analyze the impact of changes in the size and position of the ring's hole on magnetization resonant modes in Permalloy eccentric nanorings. Our results show that the magnetization ground state forms a vortex centered either on the hole or on the geometric center of the nanoring, depending on the hole's position. The observed magnetic patterns yield spin wave modes that split when increasing the ring eccentricity. The new resonant frequencies are associated with hybridized radial and azimuthal modes, which form butterfly-like patterns, which are also observed in magnetic field-driven deviations of vortices from the center of nanodots. These findings offer a deeper understanding of the interplay between geometry and magnetization dynamics, which is crucial for designing magnetic nanostructures with specific functional properties.
{"title":"Dynamic susceptibility of eccentric nanorings","authors":"E. Saavedra, V. L. Carvalho-Santos, S. Castillo-Sepúlveda, R. M. Corona, D. Altbir","doi":"10.1063/5.0248970","DOIUrl":"https://doi.org/10.1063/5.0248970","url":null,"abstract":"Magnetic nanorings have potential applications in devices based on spintronics concepts. In this work, through micromagnetic simulations, we analyze the impact of changes in the size and position of the ring's hole on magnetization resonant modes in Permalloy eccentric nanorings. Our results show that the magnetization ground state forms a vortex centered either on the hole or on the geometric center of the nanoring, depending on the hole's position. The observed magnetic patterns yield spin wave modes that split when increasing the ring eccentricity. The new resonant frequencies are associated with hybridized radial and azimuthal modes, which form butterfly-like patterns, which are also observed in magnetic field-driven deviations of vortices from the center of nanodots. These findings offer a deeper understanding of the interplay between geometry and magnetization dynamics, which is crucial for designing magnetic nanostructures with specific functional properties.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"33 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pradip Dalapati, Subramaniam Arulkumaran, Hanlin Xie, Geok Ing Ng
In the present work, the role of ex situ Al2O3 passivation in in situ SiNx/AlN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) to boost device performance and thermal stability during the high-temperature operations has been thoroughly investigated. At room temperature (RT), the MIS-HEMT fabricated with an atomic layer deposited (ALD)-Al2O3 (MIS-HEMT B) exhibits higher maximum drain current (Id,max), peak transconductance (gm,max), and lower subthreshold slope (SS) and gate leakage current compared to MIS-HEMT A fabricated without ex situ Al2O3, signifying the effectiveness of the ALD-Al2O3 layer to passivate severe surface states. Of note, when the temperature rises from 298 to 423 K, the values of Id,max and gm,max decrease noticeably, while SS and gate leakage current increase considerably in both MIS-HEMTs A and B. However, MIS-HEMT B demonstrates a lower degradation rate in various device properties at 423 K compared to MIS-HEMT A, implying that ALD-Al2O3 passivation improves thermal stability. Additionally, ALD-Al2O3 passivation reduces the interface state density from 7.48 × 1012 to 5.3 × 1012 cm−2 eV−1, highlighting its critical role in improving overall device performance.
{"title":"Improved device performance in in situ SiNx/AlN/GaN MIS-HEMTs with ex situ Al2O3 passivation at elevated temperatures","authors":"Pradip Dalapati, Subramaniam Arulkumaran, Hanlin Xie, Geok Ing Ng","doi":"10.1063/5.0252966","DOIUrl":"https://doi.org/10.1063/5.0252966","url":null,"abstract":"In the present work, the role of ex situ Al2O3 passivation in in situ SiNx/AlN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) to boost device performance and thermal stability during the high-temperature operations has been thoroughly investigated. At room temperature (RT), the MIS-HEMT fabricated with an atomic layer deposited (ALD)-Al2O3 (MIS-HEMT B) exhibits higher maximum drain current (Id,max), peak transconductance (gm,max), and lower subthreshold slope (SS) and gate leakage current compared to MIS-HEMT A fabricated without ex situ Al2O3, signifying the effectiveness of the ALD-Al2O3 layer to passivate severe surface states. Of note, when the temperature rises from 298 to 423 K, the values of Id,max and gm,max decrease noticeably, while SS and gate leakage current increase considerably in both MIS-HEMTs A and B. However, MIS-HEMT B demonstrates a lower degradation rate in various device properties at 423 K compared to MIS-HEMT A, implying that ALD-Al2O3 passivation improves thermal stability. Additionally, ALD-Al2O3 passivation reduces the interface state density from 7.48 × 1012 to 5.3 × 1012 cm−2 eV−1, highlighting its critical role in improving overall device performance.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"6 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Realizing fast electron transfer and rapid mass transport in high current density hydrogen evolution reaction (HER) is pivotal and imperative for water electrolysis. Here, we developed Ni/NiMoN Mott-Schottky heterostructures with unique superwettability that can enhance both electron and mass transfer, greatly reducing the energy demand for water splitting. Experimental and density functional theory demonstrate that in situ grown Ni nanoparticles can optimize the dissociation of water molecules from the surface and the adsorption of H*, facilitating the hydrogen spillover process on Ni/NiMoN. The optimized electrode delivers outstanding HER performance with an ultralow overpotential of −231.3 mV at −1000 mA cm−2 and maintains stable operation for 1000 h in alkaline media. An anion-exchange membrane electrolyzer using Ni/NiMoN as cathode can achieve 1000 mA cm−2 at a low voltage of 1.93 V with superstability. Our work paves an efficient way for constructing active and robust Mott-Schottky catalysts toward industrial-level hydrogen production.
在高电流密度氢进化反应（HER）中实现快速电子传递和快速质量传输对于电解水来说至关重要，势在必行。在这里，我们开发出了具有独特超润湿性的 Ni/NiMoN Mott-Schottky 异质结构，它能同时增强电子和质量传输，大大降低了水分离的能量需求。实验和密度泛函理论证明，原位生长的镍纳米粒子可以优化水分子从表面的解离和 H* 的吸附，从而促进镍/镍钴锰酸锂上的氢溢出过程。优化后的电极在 -1000 mA cm-2 条件下具有 -231.3 mV 的超低过电位，在碱性介质中可稳定运行 1000 小时，从而实现了出色的 HER 性能。使用 Ni/NiMoN 作为阴极的阴离子交换膜电解槽可以在 1.93 V 的低电压下实现 1000 mA cm-2 的超稳定性。我们的工作为构建活性和稳健的莫特-肖特基催化剂铺平了一条通往工业级制氢的有效道路。
{"title":"Hydrogen spillover in superwetting Ni/NiMoN Mott-Schottky heterostructures for boosting ampere-level hydrogen evolution","authors":"Hongru Hao, Yu Zhang, Zhe Wang, Shuo Shen, Lingling Xu, Zhe Lv, Yanqing Shen, Bo Wei","doi":"10.1063/5.0250821","DOIUrl":"https://doi.org/10.1063/5.0250821","url":null,"abstract":"Realizing fast electron transfer and rapid mass transport in high current density hydrogen evolution reaction (HER) is pivotal and imperative for water electrolysis. Here, we developed Ni/NiMoN Mott-Schottky heterostructures with unique superwettability that can enhance both electron and mass transfer, greatly reducing the energy demand for water splitting. Experimental and density functional theory demonstrate that in situ grown Ni nanoparticles can optimize the dissociation of water molecules from the surface and the adsorption of H*, facilitating the hydrogen spillover process on Ni/NiMoN. The optimized electrode delivers outstanding HER performance with an ultralow overpotential of −231.3 mV at −1000 mA cm−2 and maintains stable operation for 1000 h in alkaline media. An anion-exchange membrane electrolyzer using Ni/NiMoN as cathode can achieve 1000 mA cm−2 at a low voltage of 1.93 V with superstability. Our work paves an efficient way for constructing active and robust Mott-Schottky catalysts toward industrial-level hydrogen production.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"21 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
J. Brubach, T.-Y. Huang, T. Borrely, C. Greenhill, J. Walrath, G. Fedele, Y.-C. Yang, A. Zimmerman, R. S. Goldman
Semiconductor quantum dots (QDs) are nanostructures that can enhance the performance of electronic devices due to their 3D quantization. Typically, heterovalent impurities, or dopants, are added to semiconducting QDs to provide extra electrons and improve conductivity. Since each QD is expected to contain a few dopants, the extra electrons and their parent dopants have been difficult to locate. In this work, we investigate the spatial distribution of the extra electrons and their parent donors in epitaxial InAs/GaAs QDs using local-electrode atom-probe tomography and self-consistent Schrödinger–Poisson simulations in the effective mass approximation. Although dopants are provided in both layers, the ionized donors primarily reside outside of the QDs, providing extra electrons that are contained within the QDs. Indeed, due to the quantum confinement-induced enhancement of the donor ionization energy within the QDs, a lower fraction of dopants within the QDs are ionized. These findings suggest a pathway toward the development of 3D modulation-doped nanostructures.
{"title":"Dopant vs free carrier concentrations in InAs/GaAs semiconductor quantum dots","authors":"J. Brubach, T.-Y. Huang, T. Borrely, C. Greenhill, J. Walrath, G. Fedele, Y.-C. Yang, A. Zimmerman, R. S. Goldman","doi":"10.1063/5.0244331","DOIUrl":"https://doi.org/10.1063/5.0244331","url":null,"abstract":"Semiconductor quantum dots (QDs) are nanostructures that can enhance the performance of electronic devices due to their 3D quantization. Typically, heterovalent impurities, or dopants, are added to semiconducting QDs to provide extra electrons and improve conductivity. Since each QD is expected to contain a few dopants, the extra electrons and their parent dopants have been difficult to locate. In this work, we investigate the spatial distribution of the extra electrons and their parent donors in epitaxial InAs/GaAs QDs using local-electrode atom-probe tomography and self-consistent Schrödinger–Poisson simulations in the effective mass approximation. Although dopants are provided in both layers, the ionized donors primarily reside outside of the QDs, providing extra electrons that are contained within the QDs. Indeed, due to the quantum confinement-induced enhancement of the donor ionization energy within the QDs, a lower fraction of dopants within the QDs are ionized. These findings suggest a pathway toward the development of 3D modulation-doped nanostructures.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"25 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Hiroto Oguri, Yan Li, Xufei Fang, Atsutomo Nakamura
Anisotropy plays a crucial role in understanding and optimizing the properties of materials with directional dependencies. The hexagonal wurtzite structure, which is a typical crystal structure in compound semiconductors, demonstrates pronounced anisotropy, especially in its response to external stimuli. Recently, mechanical behavior under light illumination has attracted increasing interest especially in semiconductor compounds. In this study, we investigated the anisotropy of illumination effects on the nanomechanical properties of wurtzite ZnO. Four surface orientations—(0001), (0001) 45° off, (11¯00), and (21¯1¯0)—were subjected to nanoindentation creep and nanoindentation hardness tests under controlled light illumination. The indentation depth during nanoindentation creep under light illumination was consistently smaller than that in darkness for all surface orientations, confirming that light suppresses indentation creep deformation, but to different degrees depending on the surface orientation. This suggests that the activated slip systems and the distribution of dislocations play a crucial role in modulating dislocation behavior under light illumination. The nanoindentation hardness followed the trend on the four surface orientations: (0001) > (0001) 45° off > (11¯00) > (21¯1¯0), reflecting anisotropic behavior in nanomechanical properties. Second and subsequent pop-in events were extracted, exhibiting different behaviors depending on the surface orientations, and may play a key role in determining the anisotropy in nanoindentation hardness. Our findings contribute to a comprehensive understanding of the plastic anisotropy under light control in wurtzite ZnO.
各向异性对于理解和优化具有方向依赖性的材料特性起着至关重要的作用。化合物半导体中的典型晶体结构--六方钨锆石结构表现出明显的各向异性，尤其是在对外部刺激的反应方面。最近，光照下的力学行为引起了越来越多的关注，尤其是在半导体化合物中。在这项研究中，我们研究了光照效应对晶圆氧化锌纳米力学性能的各向异性。在受控光照下，对四种表面取向--(0001)、(0001) 45° off、(11¯00)和(21¯1¯0)--进行了纳米压痕蠕变和纳米压痕硬度测试。在所有表面方向上，光照下纳米压痕蠕变过程中的压痕深度始终小于黑暗条件下的压痕深度，这证实了光抑制压痕蠕变变形，但程度因表面方向不同而不同。这表明在光照下，激活的滑移系统和位错的分布在调节位错行为方面起着至关重要的作用。纳米压痕硬度随四个表面取向的变化趋势而变化：（0001）> (0001) 45° off >（11¯00）> (21¯1¯0)，反映了纳米力学性能的各向异性。我们还提取了第二次和随后的弹入事件，它们因表面取向的不同而表现出不同的行为，可能在决定纳米压痕硬度的各向异性方面起着关键作用。我们的研究结果有助于全面了解晶格氧化锌在光控制下的塑性各向异性。
{"title":"Photoplastic anisotropy in nanoindentation of wurtzite ZnO single crystals","authors":"Hiroto Oguri, Yan Li, Xufei Fang, Atsutomo Nakamura","doi":"10.1063/5.0248543","DOIUrl":"https://doi.org/10.1063/5.0248543","url":null,"abstract":"Anisotropy plays a crucial role in understanding and optimizing the properties of materials with directional dependencies. The hexagonal wurtzite structure, which is a typical crystal structure in compound semiconductors, demonstrates pronounced anisotropy, especially in its response to external stimuli. Recently, mechanical behavior under light illumination has attracted increasing interest especially in semiconductor compounds. In this study, we investigated the anisotropy of illumination effects on the nanomechanical properties of wurtzite ZnO. Four surface orientations—(0001), (0001) 45° off, (11¯00), and (21¯1¯0)—were subjected to nanoindentation creep and nanoindentation hardness tests under controlled light illumination. The indentation depth during nanoindentation creep under light illumination was consistently smaller than that in darkness for all surface orientations, confirming that light suppresses indentation creep deformation, but to different degrees depending on the surface orientation. This suggests that the activated slip systems and the distribution of dislocations play a crucial role in modulating dislocation behavior under light illumination. The nanoindentation hardness followed the trend on the four surface orientations: (0001) > (0001) 45° off > (11¯00) > (21¯1¯0), reflecting anisotropic behavior in nanomechanical properties. Second and subsequent pop-in events were extracted, exhibiting different behaviors depending on the surface orientations, and may play a key role in determining the anisotropy in nanoindentation hardness. Our findings contribute to a comprehensive understanding of the plastic anisotropy under light control in wurtzite ZnO.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"56 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Models to describe electrical conduction in quantum dot (QD) constituted films often overlook the effects of geometric disorder. We address related issues by examining the influence of the QD packing fraction (PF) on the charge transport and transmission in QD arrays. Using transfer matrix based algorithms and Monte Carlo simulations, we quantify the transmission across disordered QD assemblies. Our results indicate a critical packing fraction (PFc) of ∼ 0.64, marking a transition from a non-conducting to a conducting state, aligning well with experimental observations and analytical predictions. This study enhances the understanding of transport in QD arrays, with implications for designing efficient electronic devices based on disordered nanoscale systems.
{"title":"Packing fraction related transport in disordered quantum dot arrays","authors":"K. Eshraghi, S. Natani, P. Bandaru","doi":"10.1063/5.0250705","DOIUrl":"https://doi.org/10.1063/5.0250705","url":null,"abstract":"Models to describe electrical conduction in quantum dot (QD) constituted films often overlook the effects of geometric disorder. We address related issues by examining the influence of the QD packing fraction (PF) on the charge transport and transmission in QD arrays. Using transfer matrix based algorithms and Monte Carlo simulations, we quantify the transmission across disordered QD assemblies. Our results indicate a critical packing fraction (PFc) of ∼ 0.64, marking a transition from a non-conducting to a conducting state, aligning well with experimental observations and analytical predictions. This study enhances the understanding of transport in QD arrays, with implications for designing efficient electronic devices based on disordered nanoscale systems.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"25 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Growing a 3D film on a 2D substrate, a process often referred to as quasi-van der Waals (vdW) epitaxy, is generally believed to involve both chemical and vdW interactions at the interface. To date, the competition between chemical and vdW interactions at the interface has yet to be established. In this work, we demonstrate that the chemical activity of deposited species is crucial for determining the structure of the 3D/2D heterointerface. During pulsed laser deposition, the chemical activity of SrTiO3 (STO) can be adjusted by controlling the oxygen partial pressure. Therefore, the relative contributions of chemical and vdW interactions at the STO/mica interface can be tuned. This finding ultimately explains the coexistence of [111] and [001] orientations in STO epitaxy on mica.
{"title":"The competition between van der Waals and ionic interactions at the SrTiO3/mica heterointerface","authors":"Renhong Liang, Shanming Ke","doi":"10.1063/5.0260844","DOIUrl":"https://doi.org/10.1063/5.0260844","url":null,"abstract":"Growing a 3D film on a 2D substrate, a process often referred to as quasi-van der Waals (vdW) epitaxy, is generally believed to involve both chemical and vdW interactions at the interface. To date, the competition between chemical and vdW interactions at the interface has yet to be established. In this work, we demonstrate that the chemical activity of deposited species is crucial for determining the structure of the 3D/2D heterointerface. During pulsed laser deposition, the chemical activity of SrTiO3 (STO) can be adjusted by controlling the oxygen partial pressure. Therefore, the relative contributions of chemical and vdW interactions at the STO/mica interface can be tuned. This finding ultimately explains the coexistence of [111] and [001] orientations in STO epitaxy on mica.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"29 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143660578","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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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