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Doping of SiGe core-shell nanowires
No full textDopant deactivation in pure Si and pure Ge nanowires (NWs) can compromise the efficiency of the doping process at nanoscale. Quantum confinement, surface segregation and dielectric mismatch, in different ways, strongly reduce the carrier generation induced by intentional addition of dopants. This issue seems to be critical for the
fabrication of high-quality electrical devices for various future applications, such as photovoltaics and nanoelectronics. By means of Density Functional Theory simulations, we show how this limit can be rode out in core-shell silicon/germanium NWs (SiGe NWs), playing on the particular energy band alignment that comes out at the Si/Ge interface. We demonstrate how, by choosing the appropriate doping
configurations, it is possible to obtain a 1-D electron or hole gas, which has not to be thermally activated and which can furnish carriers also at very low temperatures. Our findings suggest core-shell NWs as possible building blocks for highspeed electronic device and new generation solar cells
Electron Transport in SiGe Alloy nanowires in the Ballistic Regime from First Principles
No full textSilicon−germanium alloying is emerging as one of the most promising strategies to engineer heat transport at the nanoscale. Here, we perform first-principles electron transport calculations to assess at what extent such approach can be followed without worsening the electrical conduction properties of the system, providing then a path toward high-efficiency thermoelectric materials
Silicon−Germanium Nanowires: Chemistry and Physics in Play, from Basic Principles to Advanced Applications
No full textCONTENTS
1. Introduction 1371
2. Growth Techniques, Morphology, and Structural
Properties 1373
2.1. Alloyed Nanowires 1373
2.2. Axial Heterostructures 1375
2.3. Radial Heterostructures 1377
3. Chemical and Physical Properties 1379
3.1. Electronic Properties 1379
3.1.1. Modulation of the Electronic Properties
by Composition Control 1379
3.1.2. Interfaces at Work: Strain, Band-Offset,
and Carrier Gases 1381
3.1.3. Doped Nanowires 1384
3.2. Thermal and Thermoelectric Properties 1385
4. Theoretical Modeling 1389
4.1. Electronic Structure 1390
4.1.1. Quantum Confinement Effect and Band
Offset 1391
4.1.2. Size Effects 1393
4.1.3. Alloying and Interface Effects 1394
4.1.4. Strain Effects 1395
4.1.5. Addition of Impurities 1395
4.1.6. Electronic Transport 1396
4.1.7. Optical Properties 1397
4.2. Phonons and Thermal Conductivity 1398
4.2.1. Breakdown of Fourier’s Law at Nanoscale 1398
4.2.2. Numerical Simulations of Thermal Properties
1398
5. Devices and Applications 1402
5.1. High-Performance Nanoelectronic Components
1403
5.1.1. Si1−xGex Alloy Nanowire Transistor 1403
5.1.2. Si-Shell Ge-Core Nanowire Transistor 1404
5.2. From Quantum Transport to Superconductivity:
SiGe Nanowires As Platforms for
Fundamental Physics Studies 1405
6. Conclusions and Perspectives 1405
Author Information 1406
Corresponding Authors 1406
Notes 1406
Biographies 1407
Acknowledgments 1408
References 140
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Band-offset driven efficiency of the doping of SiGe core-shell nanowires
No full textImpurity doping of semiconducting nanowireshas been predicted to become increasingly inefficient as thewire diameter is reduced, because impurity states get deeperdue to quantum and dielectric confinement. We show thatefficient n- and p-type doping can be achieved in SiGe coreshellnanowires as thin as 2 nm, taking advantage of the bandoffset at the Si/Ge interface. A one-dimensional electron(hole) gas is created at the band-edge and the carrier densityis uniquely controlled by the impurity concentration with noneed of thermal activation. Additionally, SiGe core-shellnanowires provide naturally the separation between thedifferent types of carriers, electron and holes, and are ideallysuited for photovoltaic applications
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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