Nguyen Tuan Hung

We theoretically investigate the interplay between the confinement length L and the thermal de Broglie wavelength Λ to optimize the thermoelectric power factor of semiconducting materials. An analytical formula for the power factor is derived based on the one-band model assuming nondegenerate semiconductors to describe quantum effects on the power factor of the low-dimensional semiconductors. The power factor is enhanced for one- and two-dimensional semiconductors when L is smaller than Λ of the

Thermoelectric properties of monolayer indium selenide (InSe) are investigated by using Boltzmann transport theory and first-principles calculations as a function of Fermi energy and crystal orientation. We find that the maximum power factor of p-type (n-type) monolayer InSe can be as large as 0.049 (0.043) W/K2m at 300 K in the armchair direction. The excellent thermoelectric performance of monolayer InSe is attributed to both its Seebeck coefficient and electrical conductivity. The large Seebe

We calculate the thermoelectric power (or thermopower) of many semiconducting single wall carbon nanotubes (s-SWNTs) within a diameter range $0.5--1.5\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$ by using the Boltzmann transport formalism combined with an extended tight-binding model. We find that the thermopower of s-SWNTs increases as the tube diameter decreases. For some s-SWNTs with diameters less than $0.6\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$, the thermopower can reach a value larger than $20

Thermoelectric (TE) material is a class of materials that can convert heat to electrical energy directly in a solid-state-device without any moving parts and that is environmentally friendly. The study and development of TE materials have grown quickly in the past decade. However, their development goes slowly by the lack of cheap TE materials with high Seebeck coefficient and good electrical conductivity. Carbon nanotubes (CNTs) are particularly attractive as TE materials because of at least th

In this Letter, we formulate a mathematical model for predicting experimental outcomes in quantitative phase imaging (QPI) when the illumination field is partially spatially coherent. We derive formulae that apply to QPI and discuss expected results for two classes of QPI experiments: common path and traditional interferometry, under varying degrees of spatial coherence. In particular, our results describe the physical relationship between the spatial coherence of the illuminating field and the

We theoretically investigate a possibility of improving the thermoelectric performance of monolayer InSe through convergence of multivalley energy bands, in which some distinct valleys become almost degenerate. The convergence of energy bands is achieved by applying mechanical strain. We find that the thermoelectric power factor of monolayer InSe can be significantly enhanced by nearly a factor of 3 through the band convergence in both valence (p-type) and conduction (n-type) bands under a biaxi

Abstract Thermoelectric material, which directly converts waste heat to electricity, provides an ecofriendly power generator to reuse heat energy sources. New attempts have started for thermoelectricity of low‐dimensional materials since 1993 when the theory of confinement effect was presented by Hicks and Dresselhaus. Experimental works have been inspired by the theory of confinement to the use of low‐dimensional materials for improving thermoelectric efficiency for more than two decades. In th

Two-dimensional Janus materials have attracted increasing attention in recent years because of their potential as materials for energy applications, such as photocatalysis and thermoelectricity (TE). Here, for the first time, we propose a monolayer Janus structure with the Mexican-hat band, γ-GeSSe, by replacing the S atoms on one side of the synthesized γ-GeS with Se atoms. Using first-principles calculations based on density functional theory (DFT), we show that γ-GeSSe is mechanically, dynami

Using first-principles calculations, we investigate electromechanical properties of two-dimensional (2D) hexagonal and pentagonal materials as a function of electron and hole dopings, in which 2D materials including graphene, chair-like graphane, table-like graphane, penta-graphene (PG), hydrogenated penta-graphene (HPG), and penta-CN2 are considered. We find that the actuation responses such as actuation strain, stress generated, and work area-density per cycle of the 2D materials in the case o

Nonlinear optical responses in second harmonic generation (SHG) of van der Waals heterobilayers, Janus MoSSe/MoS₂, are theoretically optimized as a function of strain and stacking order by adopting an exchange-correlation hybrid functional and a real-time approach in first-principles calculation. We find that the calculated nonlinear susceptibility, χ⁽²⁾, in AA stacking (550 pm/V) becomes three times as large as AB stacking (170 pm/V) due to the broken inversion symmetry in