Pub Date : 2018-07-25DOI: 10.5772/INTECHOPEN.76900
S. Pradhan, R. Barik
In this research work, without using any resist and lithography techniques, we report clean, surface protected and high quality Topological Insulator (TI) thin film Hall Bar device of millimeter size long. In the magnetotransport measurements, the pronounced effect of weak antilocalization (WAL) behavior has been observed at low temperatures over the range T = 4–10 K and in the low field regions and the WAL cusp disappears as we go from 10 K onwards to higher temperatures, also we find that the high-field mage-netoresistance (MR) is linear in field. With respect to magnetic field (B), the MR behavior seems to be symmetric. We also analyze the thickness dependent weak antilocalization (WAL) behavior, which has been observed in Topological Insulator Bi 2 Te 3 thin film Hall Bar device. For varying thickness, our systematic magnetotransport measurements reveal WAL signals obtain in thicker films whereas below the critical thickness of ~4 nm, a sudden diminishment of the surface transport has been observed by suppression of WAL behavior. The analyzed and pronounced behavior of this effect is also greatly dependent on the temperatures, where the WAL cusps are observed in the low-field regions and at low temperatures.
{"title":"Observation of the Weak Antilocalization and Linear Magnetoresistance in Topological Insulator Thin Film Hall Bar Device","authors":"S. Pradhan, R. Barik","doi":"10.5772/INTECHOPEN.76900","DOIUrl":"https://doi.org/10.5772/INTECHOPEN.76900","url":null,"abstract":"In this research work, without using any resist and lithography techniques, we report clean, surface protected and high quality Topological Insulator (TI) thin film Hall Bar device of millimeter size long. In the magnetotransport measurements, the pronounced effect of weak antilocalization (WAL) behavior has been observed at low temperatures over the range T = 4–10 K and in the low field regions and the WAL cusp disappears as we go from 10 K onwards to higher temperatures, also we find that the high-field mage-netoresistance (MR) is linear in field. With respect to magnetic field (B), the MR behavior seems to be symmetric. We also analyze the thickness dependent weak antilocalization (WAL) behavior, which has been observed in Topological Insulator Bi 2 Te 3 thin film Hall Bar device. For varying thickness, our systematic magnetotransport measurements reveal WAL signals obtain in thicker films whereas below the critical thickness of ~4 nm, a sudden diminishment of the surface transport has been observed by suppression of WAL behavior. The analyzed and pronounced behavior of this effect is also greatly dependent on the temperatures, where the WAL cusps are observed in the low-field regions and at low temperatures.","PeriodicalId":224264,"journal":{"name":"Heterojunctions and Nanostructures","volume":"330 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125585382","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 : 2018-07-25DOI: 10.5772/INTECHOPEN.75736
M. Tshipa, M. Masale
A theoretical investigation of the effects of the parabolic, shifted parabolic, hill-like, and cup-like parabolic confining electric potentials on photoionization cross section (PCS) in a spherical quantum dot is presented. Each of the parabolic potentials is superimposed on an infinite spherical square quantum well (ISSQW) potential. The parabolic potential blueshifts the peaks of the PCS, while the shifted parabolic potential causes a redshift. As the so-called strength of cup-like parabolic potential is increased, the peak of the PCS becomes redshifted for the s ! p transition, but blueshifted for the p ! d , d ! f (and so forth) transitions. On the contrary, an increase in the strength of the hill-like parabolic potential blueshifts peaks of the PCS for s ! p transitions, while it redshifts those of transitions between higher states.
本文从理论上研究了抛物型、移位抛物型、丘型和杯型抛物型约束电位对球形量子点光离截面(PCS)的影响。每个抛物势叠加在一个无限球面平方量子阱(ISSQW)势上。抛物势使PCS峰发生蓝移，而抛物势的位移引起红移。随着所谓的杯状抛物势强度的增加，PCS的峰值在s !P跃迁，但是P的蓝移!D, D !F(等等)转换。相反，山状抛物势蓝移强度的增加使PCS峰的蓝移值增加了5倍。P跃迁，而高态之间的跃迁红移。
{"title":"Photoionization Cross Section in Low-Dimensional Systems","authors":"M. Tshipa, M. Masale","doi":"10.5772/INTECHOPEN.75736","DOIUrl":"https://doi.org/10.5772/INTECHOPEN.75736","url":null,"abstract":"A theoretical investigation of the effects of the parabolic, shifted parabolic, hill-like, and cup-like parabolic confining electric potentials on photoionization cross section (PCS) in a spherical quantum dot is presented. Each of the parabolic potentials is superimposed on an infinite spherical square quantum well (ISSQW) potential. The parabolic potential blueshifts the peaks of the PCS, while the shifted parabolic potential causes a redshift. As the so-called strength of cup-like parabolic potential is increased, the peak of the PCS becomes redshifted for the s ! p transition, but blueshifted for the p ! d , d ! f (and so forth) transitions. On the contrary, an increase in the strength of the hill-like parabolic potential blueshifts peaks of the PCS for s ! p transitions, while it redshifts those of transitions between higher states.","PeriodicalId":224264,"journal":{"name":"Heterojunctions and Nanostructures","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123985798","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 : 2018-07-25DOI: 10.5772/INTECHOPEN.74150
V. Barsan
The chapter illustrates how simple quantum mechanics can sometimes provide quite precise description of nanophysics phenomena. From this perspective, both exact and approximate solutions for the bound-state energy of an electron in a square well are exposed. These results are used to improve the calculation of quantum size effects (QSEs) in ultrathin metallic films, obtained by several authors with simpler models of quantum wells. We show that, for a small (less than 5) number of monolayers, the differences between the predictions of these simpler models, and our approach, are important. Methods to improve the accuracy in the evaluation of various quantum size effects are shortly discussed. Using quantum mechanical-electromagnetic analogies, our results can be used in the study of light propagation in dielectric wave guides.
{"title":"Quantum Wells and Ultrathin Metallic Films","authors":"V. Barsan","doi":"10.5772/INTECHOPEN.74150","DOIUrl":"https://doi.org/10.5772/INTECHOPEN.74150","url":null,"abstract":"The chapter illustrates how simple quantum mechanics can sometimes provide quite precise description of nanophysics phenomena. From this perspective, both exact and approximate solutions for the bound-state energy of an electron in a square well are exposed. These results are used to improve the calculation of quantum size effects (QSEs) in ultrathin metallic films, obtained by several authors with simpler models of quantum wells. We show that, for a small (less than 5) number of monolayers, the differences between the predictions of these simpler models, and our approach, are important. Methods to improve the accuracy in the evaluation of various quantum size effects are shortly discussed. Using quantum mechanical-electromagnetic analogies, our results can be used in the study of light propagation in dielectric wave guides.","PeriodicalId":224264,"journal":{"name":"Heterojunctions and Nanostructures","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126252059","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 : 2018-03-23DOI: 10.5772/INTECHOPEN.74934
Taro Kimura
We provide a systematic analysis of the boundary condition for the edge state, which is a ubiquitous feature in topological phases of matter. We show how to characterize the boundary condition, and how the edge state spectrum depends on it, with several examples, including 2d topological insulator and 3d Weyl semimetal. We also demonstrate the edge-of-edge state localized at the intersection of boundaries.
{"title":"Analysis of Topological Material Surfaces","authors":"Taro Kimura","doi":"10.5772/INTECHOPEN.74934","DOIUrl":"https://doi.org/10.5772/INTECHOPEN.74934","url":null,"abstract":"We provide a systematic analysis of the boundary condition for the edge state, which is a ubiquitous feature in topological phases of matter. We show how to characterize the boundary condition, and how the edge state spectrum depends on it, with several examples, including 2d topological insulator and 3d Weyl semimetal. We also demonstrate the edge-of-edge state localized at the intersection of boundaries.","PeriodicalId":224264,"journal":{"name":"Heterojunctions and Nanostructures","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116210159","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 : 2018-03-08DOI: 10.5772/INTECHOPEN.76152
R. Giraud, J. Dufouleur, L. Veyrat, E. Xypakis, J. Bardarson, S. Hampel, B. Buechner
The next generation of electronic devices based on 3D topological insulators will be developed from advanced functional nanostructures and heterostructures. Toward this goal, single-crystalline nanowires offer interesting opportunities for new developments due to the strong quantum confinement of spin-helical surface Dirac fermions and to the possibility to realize core-shell lateral nanostructures adapted to the control of the elec- tro-chemical potential at the interface with a topological insulator. Here, we review the specific transport properties of 3D topological insulator quantum wires and the influence of disorder. Having a large energy quantization, weakly-coupled Dirac surface modes are prone to quasi-ballistic transport, with some analogies to carbon nanotubes but with spin-textured quantum states weakly coupled by non-magnetic disorder. Due to a small interaction with their environment, these surface modes are good candidates to realize novel quantum spintronic devices, spanning from ballistic spin conductors to localized spin filters. A specific topological mode also holds promises to control chiral edge states and Majorana bound states in truly 1D quantum wires, being tunable with a magnetic field or an electrical gate. Challenges toward these goals are briefly discussed, as well as the need for novel functional heterostructures.
{"title":"Spin-Helical Dirac Fermions in 3D Topological Insulator Quantum Wires","authors":"R. Giraud, J. Dufouleur, L. Veyrat, E. Xypakis, J. Bardarson, S. Hampel, B. Buechner","doi":"10.5772/INTECHOPEN.76152","DOIUrl":"https://doi.org/10.5772/INTECHOPEN.76152","url":null,"abstract":"The next generation of electronic devices based on 3D topological insulators will be developed from advanced functional nanostructures and heterostructures. Toward this goal, single-crystalline nanowires offer interesting opportunities for new developments due to the strong quantum confinement of spin-helical surface Dirac fermions and to the possibility to realize core-shell lateral nanostructures adapted to the control of the elec- tro-chemical potential at the interface with a topological insulator. Here, we review the specific transport properties of 3D topological insulator quantum wires and the influence of disorder. Having a large energy quantization, weakly-coupled Dirac surface modes are prone to quasi-ballistic transport, with some analogies to carbon nanotubes but with spin-textured quantum states weakly coupled by non-magnetic disorder. Due to a small interaction with their environment, these surface modes are good candidates to realize novel quantum spintronic devices, spanning from ballistic spin conductors to localized spin filters. A specific topological mode also holds promises to control chiral edge states and Majorana bound states in truly 1D quantum wires, being tunable with a magnetic field or an electrical gate. Challenges toward these goals are briefly discussed, as well as the need for novel functional heterostructures.","PeriodicalId":224264,"journal":{"name":"Heterojunctions and Nanostructures","volume":"50 3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126761553","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 : 2018-03-06DOI: 10.5772/INTECHOPEN.74935
Lianbi Li
The Si/6H-SiC heterostructure of large lattice mismatch follows domain epitaxy mode, which release most of the lattice-mismatch strain, and the coherent Si epilayers can be grown on 6H-SiC. An interfacial misfit dislocation array is present at the interface that determines the domain ’ s size. In this chapter, transmission electron microscopy (TEM) and high resolution X-ray diffraction (HRXRD) were employed to reveal in-plane orienta- tion, interface structure and growth mode of the Si/SiC heterostructure. Based on the characterizations, residual lattice mismatch and edge misfit dislocation density at the hetero-interface can be precisely controlled. And these characterization methods are applicable for the heterostructures of large-lattice mismatch, except for the heterostructures with different crystal symmetry on the film and the substrate. which releases most of the lattice-mismatch strain, and the coherent Si epilayers can be grown on 6H-SiC. Si(111)/6H-SiC(0001) heterostructure obtained at 900 (cid:3) C has an in-plane orientation relationship of (111)[1-10] Si //(0001)[1-210] 6H-SiC . The Si(111)/6H-SiC(0001) interface has the 4:5 Si-to-SiC matching mode with a residual lattice-mismatch of 0.26% along both the Si[11-2] and Si[1-10] orientations. As the growth temperature increases to 1050 (cid:3) C, the preferential orientation of the Si film transitions to [110]. SAED patterns show that the in-plane orientation relationship is (110)[001] Si //(0001)[10-10] 6H-SiC . Along Si[-110] orientation, the Si-to-SiC matching is still 4:5; along the vertical orientation Si[001], the matching mode is approximate 1:2 and the residual mismatch is 1.84% correspondingly. The atom quantity in one DM period decreases with increasing residual mismatch and vice versa. The Si film epitaxially grows but with MDs at the Si/6H-SiC interface. The MD density of the Si(111)/6H-SiC(0001) and Si(110)/ 6H-SiC(0001) obtained by experimental observations is as low as 0.487 and 1.217 (cid:4) 10 14 cm (cid:2) 2 , respectively, which is much smaller than the theoretical value.
{"title":"Growth Mode and Characterization of Si/SiC Heterostructure of Large Lattice-Mismatch","authors":"Lianbi Li","doi":"10.5772/INTECHOPEN.74935","DOIUrl":"https://doi.org/10.5772/INTECHOPEN.74935","url":null,"abstract":"The Si/6H-SiC heterostructure of large lattice mismatch follows domain epitaxy mode, which release most of the lattice-mismatch strain, and the coherent Si epilayers can be grown on 6H-SiC. An interfacial misfit dislocation array is present at the interface that determines the domain ’ s size. In this chapter, transmission electron microscopy (TEM) and high resolution X-ray diffraction (HRXRD) were employed to reveal in-plane orienta- tion, interface structure and growth mode of the Si/SiC heterostructure. Based on the characterizations, residual lattice mismatch and edge misfit dislocation density at the hetero-interface can be precisely controlled. And these characterization methods are applicable for the heterostructures of large-lattice mismatch, except for the heterostructures with different crystal symmetry on the film and the substrate. which releases most of the lattice-mismatch strain, and the coherent Si epilayers can be grown on 6H-SiC. Si(111)/6H-SiC(0001) heterostructure obtained at 900 (cid:3) C has an in-plane orientation relationship of (111)[1-10] Si //(0001)[1-210] 6H-SiC . The Si(111)/6H-SiC(0001) interface has the 4:5 Si-to-SiC matching mode with a residual lattice-mismatch of 0.26% along both the Si[11-2] and Si[1-10] orientations. As the growth temperature increases to 1050 (cid:3) C, the preferential orientation of the Si film transitions to [110]. SAED patterns show that the in-plane orientation relationship is (110)[001] Si //(0001)[10-10] 6H-SiC . Along Si[-110] orientation, the Si-to-SiC matching is still 4:5; along the vertical orientation Si[001], the matching mode is approximate 1:2 and the residual mismatch is 1.84% correspondingly. The atom quantity in one DM period decreases with increasing residual mismatch and vice versa. The Si film epitaxially grows but with MDs at the Si/6H-SiC interface. The MD density of the Si(111)/6H-SiC(0001) and Si(110)/ 6H-SiC(0001) obtained by experimental observations is as low as 0.487 and 1.217 (cid:4) 10 14 cm (cid:2) 2 , respectively, which is much smaller than the theoretical value.","PeriodicalId":224264,"journal":{"name":"Heterojunctions and Nanostructures","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131798767","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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