Pawan Kumar, Kelotchi S. Figueroa, Alexandre C. Foucher, Kiyoung Jo, Natalia Acero, E. Stach, D. Jariwala
Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are the subject of intense investigation for applications in optics, electronics, catalysis, and energy storage. Their optical and electronic properties can be significantly enhanced when encapsulated in an environment that is free of charge disorder. Because hexagonal boron nitride (h-BN) is atomically thin, highly-crystalline, and is a strong insulator, it is one of the most commonly used 2D materials to encapsulate and passivate TMDCs. In this report, we examine how ultrathin h-BN shields an underlying MoS2 TMDC layer from the energetic argon plasmas that are routinely used during semiconductor device fabrication and post-processing. Aberration-corrected Scanning Transmission Electron Microscopy is used to analyze defect formation in both the h-BN and MoS2 layers, and these observations are correlated with Raman and photoluminescence spectroscopy. Our results highlight that h-BN is an effective barrier for short plasma exposures (< 30 secs) but is ineffective for longer exposures, which result in extensive knock-on damage and amorphization in the underlying MoS2.
{"title":"Efficacy of boron nitride encapsulation against plasma-processing of 2D semiconductor layers","authors":"Pawan Kumar, Kelotchi S. Figueroa, Alexandre C. Foucher, Kiyoung Jo, Natalia Acero, E. Stach, D. Jariwala","doi":"10.1116/6.0000874","DOIUrl":"https://doi.org/10.1116/6.0000874","url":null,"abstract":"Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are the subject of intense investigation for applications in optics, electronics, catalysis, and energy storage. Their optical and electronic properties can be significantly enhanced when encapsulated in an environment that is free of charge disorder. Because hexagonal boron nitride (h-BN) is atomically thin, highly-crystalline, and is a strong insulator, it is one of the most commonly used 2D materials to encapsulate and passivate TMDCs. In this report, we examine how ultrathin h-BN shields an underlying MoS2 TMDC layer from the energetic argon plasmas that are routinely used during semiconductor device fabrication and post-processing. Aberration-corrected Scanning Transmission Electron Microscopy is used to analyze defect formation in both the h-BN and MoS2 layers, and these observations are correlated with Raman and photoluminescence spectroscopy. Our results highlight that h-BN is an effective barrier for short plasma exposures (< 30 secs) but is ineffective for longer exposures, which result in extensive knock-on damage and amorphization in the underlying MoS2.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85776569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aditya Dash, R. Sarkar, Abel Mathew, P. V. S. I. O. Physics, Astronomy, National Institute of Technology Rourkela, Odisha, India
The design and fabrication of a cost-effective vibrating sample magnetometer are explained. Improvement in the detected signal can be obtained using an operational amplifier circuit. The fabricated spiral detection coil design enhances the induced voltage obtained as shielding flux is reduced. A homemade setup is obtained by taking a woofer as an actuator and plexiglass as the vibrating medium. Lock-in amplifier analyzed the booster enhanced induced voltage signal by the principle of phase detection. Study of amplified and non amplified signals from the Nickel (99% purity) sample was done. Conversion of induced voltage to magnetization was done by calibration incorporating the coercivity and retentivity measurement. Magnetic oxide can be analyzed using this cost-effective designed Vibrating sample magnetometer. The data obtained from the VSM can conclude the successful operation of the designed magnetometer.
{"title":"Fabrication of economical signal amplified vibrating sample magnetometer with spiral designed detector","authors":"Aditya Dash, R. Sarkar, Abel Mathew, P. V. S. I. O. Physics, Astronomy, National Institute of Technology Rourkela, Odisha, India","doi":"10.1063/5.0030132","DOIUrl":"https://doi.org/10.1063/5.0030132","url":null,"abstract":"The design and fabrication of a cost-effective vibrating sample magnetometer are explained. Improvement in the detected signal can be obtained using an operational amplifier circuit. The fabricated spiral detection coil design enhances the induced voltage obtained as shielding flux is reduced. A homemade setup is obtained by taking a woofer as an actuator and plexiglass as the vibrating medium. Lock-in amplifier analyzed the booster enhanced induced voltage signal by the principle of phase detection. Study of amplified and non amplified signals from the Nickel (99% purity) sample was done. Conversion of induced voltage to magnetization was done by calibration incorporating the coercivity and retentivity measurement. Magnetic oxide can be analyzed using this cost-effective designed Vibrating sample magnetometer. The data obtained from the VSM can conclude the successful operation of the designed magnetometer.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76842574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-13DOI: 10.1103/PhysRevMaterials.5.056002
K. Sankaran, K. Moors, Z. Tokei, C. Adelmann, G. Pourtois
The potential of a wide range of layered ternary carbide and nitride MAX phases as conductors in interconnect metal lines in advanced CMOS technology nodes has been evaluated using automated first principles simulations based on density functional theory. The resistivity scaling potential of these compounds, i.e. the sensitivity of their resistivity to reduced line dimensions, has been benchmarked against Cu and Ru by evaluating their transport properties within a semiclassical transport formalism. In addition, their cohesive energy has been assessed as a proxy for the resistance against electromigration and the need for diffusion barriers. The results indicate that numerous MAX phases show promise as conductors in interconnects of advanced CMOS technology nodes.
{"title":"Ab initio\u0000 screening of metallic MAX ceramics for advanced interconnect applications","authors":"K. Sankaran, K. Moors, Z. Tokei, C. Adelmann, G. Pourtois","doi":"10.1103/PhysRevMaterials.5.056002","DOIUrl":"https://doi.org/10.1103/PhysRevMaterials.5.056002","url":null,"abstract":"The potential of a wide range of layered ternary carbide and nitride MAX phases as conductors in interconnect metal lines in advanced CMOS technology nodes has been evaluated using automated first principles simulations based on density functional theory. The resistivity scaling potential of these compounds, i.e. the sensitivity of their resistivity to reduced line dimensions, has been benchmarked against Cu and Ru by evaluating their transport properties within a semiclassical transport formalism. In addition, their cohesive energy has been assessed as a proxy for the resistance against electromigration and the need for diffusion barriers. The results indicate that numerous MAX phases show promise as conductors in interconnects of advanced CMOS technology nodes.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73935564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jie Chen, Hang Li, B. Ding, Hong-wei Zhang, Enke Liu, Wenhong Wang
The magnetotransport properties in antiferromagnetic half-Heusler single crystals of TbPtBi, a magnetic-field-induced topological semimetal with simple band structure, are investigated. We found that a nonmonotonic magnetic field dependence of the anomalous Hall resistivity in a high magnetic field (B>7T), which come from the change of band structure induced by the Zeeman-like splitting when applying the external magnetic field. The experiment results show that credible anomalous Hall resistivity and conductivity reach up to 0.6798m{Omega}cm and 125{Omega}-1cm-1, respectively. A large AHA up to 33% is obtained in TbPtBi, which is comparable to typical ferromagnetic Weyl semimetal. The analysis of results show it should be attributed to topological band around EF and low carrier density.
{"title":"Large anomalous Hall angle in a topological semimetal candidate TbPtBi","authors":"Jie Chen, Hang Li, B. Ding, Hong-wei Zhang, Enke Liu, Wenhong Wang","doi":"10.1063/5.0033707","DOIUrl":"https://doi.org/10.1063/5.0033707","url":null,"abstract":"The magnetotransport properties in antiferromagnetic half-Heusler single crystals of TbPtBi, a magnetic-field-induced topological semimetal with simple band structure, are investigated. We found that a nonmonotonic magnetic field dependence of the anomalous Hall resistivity in a high magnetic field (B>7T), which come from the change of band structure induced by the Zeeman-like splitting when applying the external magnetic field. The experiment results show that credible anomalous Hall resistivity and conductivity reach up to 0.6798m{Omega}cm and 125{Omega}-1cm-1, respectively. A large AHA up to 33% is obtained in TbPtBi, which is comparable to typical ferromagnetic Weyl semimetal. The analysis of results show it should be attributed to topological band around EF and low carrier density.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74003706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-11DOI: 10.1103/PHYSREVMATERIALS.5.034008
F. Fabre, A. Finco, A. Purbawati, A. Hadj-Azzem, N. Rougemaille, J. Coraux, I. Philip, V. Jacques
We demonstrate room-temperature ferromagnetism with in-plane magnetic anisotropy in thin flakes of the CrTe$_2$ van der Waals ferromagnet. Using quantitative magnetic imaging with a single spin magnetometer based on a nitrogen-vacancy defect in diamond, we infer a room-temperature in-plane magnetization in the range of $Msim 25$ kA/m for flakes with thicknesses down to $20$ nm. These results make CrTe$_2$ a unique system in the growing family of van der Waals ferromagnets, because it is the only material platform known to date which offers an intrinsic in-plane magnetization and a Curie temperature above $300$ K in thin flakes.
{"title":"Characterization of room-temperature in-plane magnetization in thin flakes of \u0000CrTe2\u0000 with a single-spin magnetometer","authors":"F. Fabre, A. Finco, A. Purbawati, A. Hadj-Azzem, N. Rougemaille, J. Coraux, I. Philip, V. Jacques","doi":"10.1103/PHYSREVMATERIALS.5.034008","DOIUrl":"https://doi.org/10.1103/PHYSREVMATERIALS.5.034008","url":null,"abstract":"We demonstrate room-temperature ferromagnetism with in-plane magnetic anisotropy in thin flakes of the CrTe$_2$ van der Waals ferromagnet. Using quantitative magnetic imaging with a single spin magnetometer based on a nitrogen-vacancy defect in diamond, we infer a room-temperature in-plane magnetization in the range of $Msim 25$ kA/m for flakes with thicknesses down to $20$ nm. These results make CrTe$_2$ a unique system in the growing family of van der Waals ferromagnets, because it is the only material platform known to date which offers an intrinsic in-plane magnetization and a Curie temperature above $300$ K in thin flakes.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79563016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-10DOI: 10.1103/PhysRevB.103.155305
Lina Yang, Xiao Wan, Dengke Ma, Yi Jiang, Nuo Yang
Tuning interfacial thermal conductance has been a key task for the thermal management of nanoelectronic devices. Here, it is studied how the interfacial thermal conductance is great influenced by modulating the mass distribution of the interlayer of one-dimensional atomic chain. By nonequilibrium Green's function and machine learning algorithm, the maximum/minimum value of thermal conductance and its corresponding mass distribution are calculated. Interestingly, the mass distribution corresponding to the maximum thermal conductance is not a simple function, such as linear and exponential distribution predicted in previous works, it is similar to a sinusoidal curve around linear distribution for larger thickness interlayer. Further, the mechanism of the abnormal results is explained by analyzing the phonon transmission spectra and density of states. The work provides deep insight into optimizing and designing interfacial thermal conductance by modulating mass distribution of interlayer atoms.
{"title":"Maximization and minimization of interfacial thermal conductance by modulating the mass distribution of the interlayer","authors":"Lina Yang, Xiao Wan, Dengke Ma, Yi Jiang, Nuo Yang","doi":"10.1103/PhysRevB.103.155305","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.155305","url":null,"abstract":"Tuning interfacial thermal conductance has been a key task for the thermal management of nanoelectronic devices. Here, it is studied how the interfacial thermal conductance is great influenced by modulating the mass distribution of the interlayer of one-dimensional atomic chain. By nonequilibrium Green's function and machine learning algorithm, the maximum/minimum value of thermal conductance and its corresponding mass distribution are calculated. Interestingly, the mass distribution corresponding to the maximum thermal conductance is not a simple function, such as linear and exponential distribution predicted in previous works, it is similar to a sinusoidal curve around linear distribution for larger thickness interlayer. Further, the mechanism of the abnormal results is explained by analyzing the phonon transmission spectra and density of states. The work provides deep insight into optimizing and designing interfacial thermal conductance by modulating mass distribution of interlayer atoms.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74967514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-09DOI: 10.1103/PhysRevMaterials.4.114004
Shixin Song, J. Guan, David Tom'anek
We study the stability and electronic structure of previously unexplored two-dimensional (2D) ternary compounds BNP$_2$ and C$_2$SiS. Using $ab$ $initio$ density functional theory, we have identified four stable allotropes of each ternary compound and confirmed their stability by calculated phonon spectra and molecular dynamics simulations. Whereas all BNP$_2$ allotropes are semiconducting, we find C$_2$SiS, depending on the allotrope, to be semiconducting or semimetallic. The fundamental band gaps of the semiconducting allotropes we study range from $1.4$ eV to $2.2$ eV at the HSE06 level $0.5$ eV to $1.4$ eV at the PBE level and display carrier mobilities as high as $1.5{times}10^5$ cm$^2$V$^{-1}$s$^{-1}$. Such high mobilities are quite uncommon in semiconductors with so wide band gaps. Structural ridges in the geometry of all allotropes cause a high anisotropy in their mechanical and transport properties, promising a wide range of applications in electronics and optoelectronics.
{"title":"Low-symmetry two-dimensional \u0000BNP2\u0000 and \u0000C2SiS\u0000 structures with high and anisotropic carrier mobilities","authors":"Shixin Song, J. Guan, David Tom'anek","doi":"10.1103/PhysRevMaterials.4.114004","DOIUrl":"https://doi.org/10.1103/PhysRevMaterials.4.114004","url":null,"abstract":"We study the stability and electronic structure of previously unexplored two-dimensional (2D) ternary compounds BNP$_2$ and C$_2$SiS. Using $ab$ $initio$ density functional theory, we have identified four stable allotropes of each ternary compound and confirmed their stability by calculated phonon spectra and molecular dynamics simulations. Whereas all BNP$_2$ allotropes are semiconducting, we find C$_2$SiS, depending on the allotrope, to be semiconducting or semimetallic. The fundamental band gaps of the semiconducting allotropes we study range from $1.4$ eV to $2.2$ eV at the HSE06 level $0.5$ eV to $1.4$ eV at the PBE level and display carrier mobilities as high as $1.5{times}10^5$ cm$^2$V$^{-1}$s$^{-1}$. Such high mobilities are quite uncommon in semiconductors with so wide band gaps. Structural ridges in the geometry of all allotropes cause a high anisotropy in their mechanical and transport properties, promising a wide range of applications in electronics and optoelectronics.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77966445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-08DOI: 10.1103/PHYSREVMATERIALS.5.043802
Nataliya Lopanitsyna, Chiheb Ben Mahmoud, M. Ceriotti
Atomistic simulations provide insights into structure-property relations on an atomic size and length scale, that are complementary to the macroscopic observables that can be obtained from experiments. Quantitative predictions, however, are usually hindered by the need to strike a balance between the accuracy of the calculation of the interatomic potential and the modelling of realistic thermodynamic conditions. Machine-learning techniques make it possible to efficiently approximate the outcome of accurate electronic-structure calculations, that can therefore be combined with extensive thermodynamic sampling. We take elemental nickel as a prototypical material, whose alloys have applications from cryogenic temperatures up to close to their melting point, and use it to demonstrate how a combination of machine-learning models of electronic properties and statistical sampling methods makes it possible to compute accurate finite-temperature properties at an affordable cost. We demonstrate the calculation of a broad array of bulk, interfacial and defect properties over a temperature range from 100 to 2500 K, modeling also, when needed, the impact of nuclear quantum fluctuations and electronic entropy. The framework we demonstrate here can be easily generalized to more complex alloys and different classes of materials.
{"title":"Finite-temperature materials modeling from the quantum nuclei to the hot electron regime","authors":"Nataliya Lopanitsyna, Chiheb Ben Mahmoud, M. Ceriotti","doi":"10.1103/PHYSREVMATERIALS.5.043802","DOIUrl":"https://doi.org/10.1103/PHYSREVMATERIALS.5.043802","url":null,"abstract":"Atomistic simulations provide insights into structure-property relations on an atomic size and length scale, that are complementary to the macroscopic observables that can be obtained from experiments. Quantitative predictions, however, are usually hindered by the need to strike a balance between the accuracy of the calculation of the interatomic potential and the modelling of realistic thermodynamic conditions. Machine-learning techniques make it possible to efficiently approximate the outcome of accurate electronic-structure calculations, that can therefore be combined with extensive thermodynamic sampling. We take elemental nickel as a prototypical material, whose alloys have applications from cryogenic temperatures up to close to their melting point, and use it to demonstrate how a combination of machine-learning models of electronic properties and statistical sampling methods makes it possible to compute accurate finite-temperature properties at an affordable cost. We demonstrate the calculation of a broad array of bulk, interfacial and defect properties over a temperature range from 100 to 2500 K, modeling also, when needed, the impact of nuclear quantum fluctuations and electronic entropy. The framework we demonstrate here can be easily generalized to more complex alloys and different classes of materials.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82155854","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rujun Sun, Y. Ooi, A. Bhattacharyya, Muad Saleh, S. Krishnamoorthy, K. Lynn, M. Scarpulla
Performing deep level transient spectroscopy (DLTS) on Schottky diodes, we investigated defect levels below the conduction band minima (Ec) in Czochralski (CZ) grown unintentionally-doped (UID) and vertical gradient freeze (VGF)-grown Zr-doped beta-Ga2O3 crystals. In UID crystals with an electron concentration of 10^17 cm-3, we observe levels at 0.18 eV and 0.46 eV in addition to the previously reported 0.86 (E2) and 1.03 eV (E3) levels. For 10^18 cm-3 Zr-doped Ga2O3, signatures at 0.30 eV (E15) and 0.71 eV (E16) are present. For the highest Zr doping of 5*10^18 cm-3, we observe only one signature at 0.59 eV. Electric field-enhanced emission rates are demonstrated via increasing the reverse bias during measurement. The 0.86 eV signature in the UID sample displays phonon-assisted tunneling enhanced thermal emission and is consistent with the widely reported E2 (FeGa) defect. The 0.71 eV (E16) signature in the lower-Zr-doped crystal also exhibits phonon-assisted tunneling emission enhancement. Taking into account that the high doping in the Zr-doped diodes also increases the electric field, we propose that the 0.59 eV signature in the highest Zr-doped sample likely corresponds to the 0.71 eV signature in lower-doped samples. Our analysis highlights the importance of testing for and reporting on field-enhanced emission especially the electric field present during DLTS and other characterization experiments on beta-Ga2O3 along with the standard emission energy, cross-section, and lambda-corrected trap density. This is important because of the intended use of beta-Ga2O3 in high-field devices and the many orders of magnitude of possible doping.
利用深能级瞬态光谱(DLTS)对肖特基二极管进行了研究，研究了CZ生长的无意掺杂(UID)和VGF生长的掺杂zr - ga2o3晶体中低于导带最小值(Ec)的缺陷水平。在电子浓度为10^17 cm-3的UID晶体中，除了先前报道的0.86 (E2)和1.03 eV (E3)水平外，我们还观察到0.18 eV和0.46 eV的水平。对于10^18 cm-3 zr掺杂的Ga2O3，存在0.30 eV (E15)和0.71 eV (E16)的特征。对于Zr掺杂最高的5*10^18 cm-3，我们只观察到一个0.59 eV的特征。通过在测量过程中增加反向偏置，证明了电场增强的发射率。UID样品的0.86 eV特征显示声子辅助隧穿增强的热发射，与广泛报道的E2 (FeGa)缺陷一致。低zr掺杂晶体的0.71 eV (E16)特征也表现出声子辅助隧穿发射增强。考虑到zr掺杂二极管的高掺杂也增加了电场，我们提出zr掺杂最高的样品中的0.59 eV特征可能对应于低掺杂样品中的0.71 eV特征。我们的分析强调了测试和报告场增强发射的重要性，特别是在DLTS和β - ga2o3的其他表征实验中存在的电场，以及标准发射能量、横截面和lambda校正的陷阱密度。这一点很重要，因为β - ga2o3在高场器件中的预期用途和可能掺杂的许多数量级。
{"title":"Defect states and their electric field-enhanced electron thermal emission in heavily Zr-doped β-Ga2O3 crystals","authors":"Rujun Sun, Y. Ooi, A. Bhattacharyya, Muad Saleh, S. Krishnamoorthy, K. Lynn, M. Scarpulla","doi":"10.1063/5.0029442","DOIUrl":"https://doi.org/10.1063/5.0029442","url":null,"abstract":"Performing deep level transient spectroscopy (DLTS) on Schottky diodes, we investigated defect levels below the conduction band minima (Ec) in Czochralski (CZ) grown unintentionally-doped (UID) and vertical gradient freeze (VGF)-grown Zr-doped beta-Ga2O3 crystals. In UID crystals with an electron concentration of 10^17 cm-3, we observe levels at 0.18 eV and 0.46 eV in addition to the previously reported 0.86 (E2) and 1.03 eV (E3) levels. For 10^18 cm-3 Zr-doped Ga2O3, signatures at 0.30 eV (E15) and 0.71 eV (E16) are present. For the highest Zr doping of 5*10^18 cm-3, we observe only one signature at 0.59 eV. Electric field-enhanced emission rates are demonstrated via increasing the reverse bias during measurement. The 0.86 eV signature in the UID sample displays phonon-assisted tunneling enhanced thermal emission and is consistent with the widely reported E2 (FeGa) defect. The 0.71 eV (E16) signature in the lower-Zr-doped crystal also exhibits phonon-assisted tunneling emission enhancement. Taking into account that the high doping in the Zr-doped diodes also increases the electric field, we propose that the 0.59 eV signature in the highest Zr-doped sample likely corresponds to the 0.71 eV signature in lower-doped samples. Our analysis highlights the importance of testing for and reporting on field-enhanced emission especially the electric field present during DLTS and other characterization experiments on beta-Ga2O3 along with the standard emission energy, cross-section, and lambda-corrected trap density. This is important because of the intended use of beta-Ga2O3 in high-field devices and the many orders of magnitude of possible doping.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76557445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shingo Kaneta-Takada, Y. Wakabayashi, Y. Krockenberger, S. Ohya, Masaaki Tanaka, Y. Taniyasu, Hideki Yamamoto
The recent observation of Weyl fermions in the itinerant 4d ferromagnetic perovskite SrRuO3 points to this material being a good platform for exploring novel physics related to a pair of Weyl nodes in epitaxial heterostructures. In this letter, we report the thickness-dependent magnetotransport properties of ultra-high-quality epitaxial SrRuO3 films grown under optimized conditions on SrTiO3 substrates. Signatures of Weyl fermion transport, i.e., unsaturated linear positive magnetoresistance accompanied by a quantum oscillation having a {pi} Berry phase, were observed in films with thicknesses as small as 10 nm. Residual resistivity increased with decreasing film thickness, indicating disorder near the interface between SrRuO3 and the SrTiO3 substrate. Since this disorder affects the magnetic and electrical properties of the films, the Curie temperature decreases and the coercive field increases with decreasing thickness. Thickness-dependent magnetotransport measurements revealed that the threshold residual resistivity ratio (RRR) to observe Weyl fermion transport is 21. These results provide guidelines for realizing quantum transport of Weyl fermions in SrRuO3 near heterointerfaces.
{"title":"Thickness-dependent quantum transport of Weyl fermions in ultra-high-quality SrRuO3 films","authors":"Shingo Kaneta-Takada, Y. Wakabayashi, Y. Krockenberger, S. Ohya, Masaaki Tanaka, Y. Taniyasu, Hideki Yamamoto","doi":"10.1063/5.0036837","DOIUrl":"https://doi.org/10.1063/5.0036837","url":null,"abstract":"The recent observation of Weyl fermions in the itinerant 4d ferromagnetic perovskite SrRuO3 points to this material being a good platform for exploring novel physics related to a pair of Weyl nodes in epitaxial heterostructures. In this letter, we report the thickness-dependent magnetotransport properties of ultra-high-quality epitaxial SrRuO3 films grown under optimized conditions on SrTiO3 substrates. Signatures of Weyl fermion transport, i.e., unsaturated linear positive magnetoresistance accompanied by a quantum oscillation having a {pi} Berry phase, were observed in films with thicknesses as small as 10 nm. Residual resistivity increased with decreasing film thickness, indicating disorder near the interface between SrRuO3 and the SrTiO3 substrate. Since this disorder affects the magnetic and electrical properties of the films, the Curie temperature decreases and the coercive field increases with decreasing thickness. Thickness-dependent magnetotransport measurements revealed that the threshold residual resistivity ratio (RRR) to observe Weyl fermion transport is 21. These results provide guidelines for realizing quantum transport of Weyl fermions in SrRuO3 near heterointerfaces.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81301234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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