scholarly journals Thermionic transport across gold-graphene-WSe2 van der Waals heterostructures

2019 ◽  
Vol 5 (11) ◽  
pp. eaax7827 ◽  
Author(s):  
Md Golam Rosul ◽  
Doeon Lee ◽  
David H. Olson ◽  
Naiming Liu ◽  
Xiaoming Wang ◽  
...  
Keyword(s):  
First Principles ◽  
Van Der Waals ◽  
Electrical Conductance ◽  
Electrical Energy ◽  
Real Space ◽  
Electronic Cooling ◽  
Cooling Curve ◽  
Hybrid Technique ◽  
First Principles Calculations ◽  
Theoretical Predictions

Solid-state thermionic devices based on van der Waals structures were proposed for nanoscale thermal to electrical energy conversion and integrated electronic cooling applications. We study thermionic cooling across gold-graphene-WSe2-graphene-gold structures computationally and experimentally. Graphene and WSe2 layers were stacked, followed by deposition of gold contacts. The I-V curve of the structure suggests near-ohmic contact. A hybrid technique that combines thermoreflectance and cooling curve measurements is used to extract the device ZT. The measured Seebeck coefficient, thermal and electrical conductance, and ZT values at room temperatures are in agreement with the theoretical predictions using first-principles calculations combined with real-space Green’s function formalism. This work lays the foundation for development of efficient thermionic devices.

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

Intriguing electronic structures and optical properties of two-dimensional van der Waals heterostructures of Zr2CT2 (T = O, F) with MoSe2 and WSe2

2018 ◽  
Vol 6 (11) ◽  
pp. 2830-2839 ◽  
Author(s):  
Gul Rehman ◽  
S. A. Khan ◽  
B. Amin ◽  
Iftikhar Ahmad ◽  
Li-Yong Gan ◽  
...  
Keyword(s):  
Optical Properties ◽  
Material Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Van Der Waals ◽  
Transition Metal Dichalcogenides ◽  
Two Dimensional ◽  
First Principles Calculations ◽  
Van Der Waals Heterostructures ◽  
Metal Dichalcogenides

Based on (hybrid) first-principles calculations, material properties (structural, electronic, vibrational, optical, and photocatalytic) of van der Waals heterostructures and their corresponding monolayers (transition metal dichalcogenides and MXenes) are investigated.

scholarly journals First-principles calculations and experimental studies of XYZ2 thermoelectric compounds: detailed analysis of van der Waals interactions

2018 ◽  
Vol 6 (40) ◽  
pp. 19502-19519 ◽  
Author(s):  
Jan-Hendrik Pöhls ◽  
Zhe Luo ◽  
Umut Aydemir ◽  
Jon-Paul Sun ◽  
Shiqiang Hao ◽  
...  
Keyword(s):  
Detailed Analysis ◽  
First Principles ◽  
Van Der Waals ◽  
Experimental Studies ◽  
Van Der Waals Interactions ◽  
First Principles Calculations ◽  
Prediction Of Properties

van der Waals interactions enhanced the prediction of properties in layered thermoelectrics.

Two-dimensional layered Janus-In2SeTe/C2N van der Waals heterostructures for photocatalysis and photovoltaics: first-principles calculations

2020 ◽  
Vol 44 (37) ◽  
pp. 16092-16100
Author(s):  
Xiao-Hua Li ◽  
Bao-Ji Wang ◽  
Hui Li ◽  
Xue-Feng Yang ◽  
Rui-Qi Zhao ◽  
...  
Keyword(s):  
Dft Calculations ◽  
First Principles ◽  
Sustainable Energy ◽  
Van Der Waals ◽  
Two Dimensional ◽  
First Principles Calculations ◽  
Van Der Waals Heterostructures ◽  
Potential Applications

Through DFT calculations, Janus-In2SeTe/C2N heterostructures are found to have great potential applications in the fields of clean and sustainable energy.

First-Principles Calculations in Real-Space Formalism

10.1142/p370 ◽  
2005 ◽  
Author(s):  
Kikuji Hirose ◽  
Tomoya Ono ◽  
Yoshitaka Fujimoto ◽  
Shigeru Tsukamoto
Keyword(s):  
First Principles ◽  
Real Space ◽  
First Principles Calculations ◽  
Space Formalism

Infrared Spectroscopy of Hydrogen in ZnO

2004 ◽  
Vol 813 ◽  
Author(s):  
M.D. Mccluskey ◽  
S.J. Jokela
Keyword(s):  
First Principles ◽  
Experimental Studies ◽  
Wide Band ◽  
Shallow Donor ◽  
Great Promise ◽  
Bulk Single Crystal ◽  
First Principles Calculations ◽  
Wide Band Gap ◽  
Theoretical Predictions ◽  
Good Agreement

ABSTRACTZinc oxide (ZnO) has shown great promise as a wide band gap semiconductor with optical, electronic, and mechanical applications. Recent first-principles calculations and experimental studies have shown that hydrogen acts as a shallow donor in ZnO, in contrast to hydrogen's usual role as a passivating impurity. The structures of such hydrogen complexes, however, have not been determined. To address this question, we performed vibrational spectroscopy on bulk, single-crystal ZnO samples annealed in hydrogen (H2) or deuterium (D2) gas. Using infrared (IR) spectroscopy, we have observed O-H and O-D stretch modes at 3326.3 cm−1 and 2470.3 cm−1 respectively, at a sample temperature of 14 K. These frequencies are in good agreement with the theoretical predictions for hydrogen and deuterium in an antibonding configuration, although the bond-centered configuration cannot be ruled out. The IR-active hydrogen complexes are unstable, however, with a dissocation barrier on the order of 1 eV.

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