scholarly journals Defect creation and Diffusion under electric fields from first-principles: the prototypical case of silicon dioxide

2019 ◽  
Author(s):  
N. Salles ◽  
L. Martin-Samos ◽  
S. de Gironcoli ◽  
L. Giacomazzi ◽  
M. Valant ◽  
...  
Keyword(s):  
Silicon Dioxide ◽  
Electric Fields ◽  
First Principles ◽  
Defect Creation ◽  
And Diffusion

Ru Passivated and Ru Doped e-TaN surfaces as Combined Barrier and Liner Material for Copper Interconnects: A First Principles Study

2018 ◽  
Author(s):  
Suresh Natarajan ◽  
Cara-Lena Nies ◽  
Michael Nolan
Keyword(s):  
First Principles ◽  
Film Growth ◽  
Early Stage ◽  
Copper Interconnects ◽  
Liner Material ◽  
Critical Dimensions ◽  
Industry Standard ◽  
Cu Film ◽  
Improved Performance ◽  
And Diffusion

<div>As the critical dimensions of transistors continue to be scaled down to facilitate improved performance and device speeds, new ultrathin materials that combine diffusion barrier and seed/liner properties are needed for copper interconnects at these length scales. Ideally, to facilitate coating of high aspect ratio structures, this alternative barrier+liner material should only consist of one or as few layers as possible. We studied TaN, the current industry standard for Cu diffusion barriers, and Ru, which is a</div><div>suitable liner material for Cu electroplating, to explore how combining these two materials in a barrier+liner material influences the adsorption of Cu atoms in the early stage of Cu film growth. To this end, we carried out first-principles simulations of the adsorption and diffusion of Cu adatoms at Ru-passivated and Ru-doped e-TaN(1 1 0) surfaces. For comparison, we also studied the behaviour of Cu and Ru adatoms at the low index surfaces of e-TaN, as well as the interaction of Cu adatoms with the (0 0 1) surface of hexagonal Ru. Our results confirm the barrier and liner properties of TaN and Ru, respectively while also highlighting the weaknesses of both materials. Ru passivated TaN was found to have improved binding with Cu adatoms as compared to the bare TaN and Ru surfaces.</div><div>On the other hand, the energetic barrier for Cu diffusion at Ru passivated TaN surface was lower than at the bare TaN surface which can promote Cu agglomeration. For Ru-doped TaN however, a decrease in Cu binding energy was found in addition to favourable migration of the Cu adatoms toward the doped Ru atom and unfavourable migration away from it or into the bulk. This suggests that Ru doping sites in the TaN surface can act as nucleation points for Cu growth with high migration barrier preventing agglomeration and allow electroplating of Cu. Therefore Ru-doped TaN is proposed as a candidate for a combined barrier+liner material with reduced thickness.</div>

scholarly journals Interface-induced sign reversal of the anomalous Hall effect in magnetic topological insulator heterostructures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Fei Wang ◽  
Xuepeng Wang ◽  
Yi-Fan Zhao ◽  
Di Xiao ◽  
Ling-Jie Zhou ◽  
...  
Keyword(s):  
Hall Effect ◽  
Electric Fields ◽  
First Principles ◽  
Berry Phase ◽  
Condensed Matter ◽  
Anomalous Hall Effect ◽  
First Principles Calculations ◽  
Sign Reversal ◽  
Berry Curvature ◽  
Topological Materials

AbstractThe Berry phase picture provides important insights into the electronic properties of condensed matter systems. The intrinsic anomalous Hall (AH) effect can be understood as the consequence of non-zero Berry curvature in momentum space. Here, we fabricate TI/magnetic TI heterostructures and find that the sign of the AH effect in the magnetic TI layer can be changed from being positive to negative with increasing the thickness of the top TI layer. Our first-principles calculations show that the built-in electric fields at the TI/magnetic TI interface influence the band structure of the magnetic TI layer, and thus lead to a reconstruction of the Berry curvature in the heterostructure samples. Based on the interface-induced AH effect with a negative sign in TI/V-doped TI bilayer structures, we create an artificial “topological Hall effect”-like feature in the Hall trace of the V-doped TI/TI/Cr-doped TI sandwich heterostructures. Our study provides a new route to create the Berry curvature change in magnetic topological materials that may lead to potential technological applications.

Doped graphenes as anodes with large capacity for lithium-ion batteries

2016 ◽  
Vol 4 (35) ◽  
pp. 13407-13413 ◽  
Author(s):  
Liujiang Zhou ◽  
Z. F. Hou ◽  
Bo Gao ◽  
Thomas Frauenheim
Keyword(s):  
Lithium Ion Batteries ◽  
First Principles ◽  
Lithium Ion ◽  
Doping Effect ◽  
Chemical Doping ◽  
First Principles Calculations ◽  
Large Capacity ◽  
And Diffusion ◽  
Li Storage

To understand the chemical doping effect on the lithium (Li) storage of graphene, we have performed first-principles calculations to study the adsorption and diffusion of Li adatoms on boron (B)- and nitrogen (N)-doped graphenes, which include individual and paired B (and N) dopants in graphene.

Mechanisms of Nitrogen Incorporation at 4H-SiC/SiO2 Interface during Nitric Oxide Passivation – A First Principles Study

2016 ◽  
Vol 858 ◽  
pp. 465-468 ◽  
Author(s):  
D.P. Ettisserry ◽  
Neil Goldsman ◽  
Akin Akturk ◽  
Aivars J. Lelis
Keyword(s):  
Nitric Oxide ◽  
Silicon Dioxide ◽  
First Principles ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Functional Theory ◽  
Power Mosfets ◽  
Voltage Instability ◽  
Nitrogen Incorporation ◽  
Effective Mobility

In this work, we investigate the behavior of Nitrogen atoms at 4H-Silicon Carbide (4H-SiC)/Silicon dioxide (SiO2) interface during nitric oxide passivation using ab-initio Density Functional Theory. Our calculations suggest different possible energetically favorable and competing mechanisms by which nitrogen atoms could a) incorporate themselves into the oxide, just above the 4H-SiC substrate, and b) substitute for carbon atoms at the 4H-SiC surface. We attribute the former process to cause increased threshold voltage instability (hole traps), and the latter to result in improved effective mobility through channel counter-doping, apart from removing interface traps in 4H-SiC power MOSFETs. These results support recent electrical and XPS measurements. Additionally, Nitric Oxide passivation is shown to energetically favor re-oxidation of the 4H-SiC surface accompanied by the generation of oxygen vacancies under the conditions considered in this work.

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