Thermal stability and optical properties of Si–Ge nanoparticles

Bonham, B.; Guisbiers, Grégory

doi:10.1088/1361-6528/aa726b

Cited by 20 publications

(16 citation statements)

References 65 publications

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“…At the nanoscale, the energy bandgap varies with the size of the semiconductor and it increases when the size is reduced. From Equation (9), it is known that any fermionic (S = 1/2) property, ξ, scales like Δ= 1 ¼ α shape D. Applying the aforementioned fermionic scaling law, [ [58][59][60][61]. The exact same scaling law was obtained by Li et al [62] when expressing the size and temperature-dependency of the electrical conductivity as an Arrhenius equation:…”

Section: Energy Bandgap Of Npsmentioning

confidence: 73%

Advances in thermodynamic modelling of nanoparticles

Guisbiers

2019

Advances in Physics: X

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Among all the computational techniques (Density Functional Theory, Molecular Dynamics, Monte-Carlo Simulations, Nanothermodynamics) used to investigate the properties of nanoparticles, nanothermodynamics is the most unusual one. Indeed, most people still thing that thermodynamics does not apply at the nanoscale; nonetheless, thermodynamic concepts can still be applied at the nanoscale to predict various properties of nanoparticles like melting temperature, energy bandgap . . . In this review, we first introduce the fundamental concepts and methods of nanothermodynamics starting from Hill's contributions to the most recent developments focusing specifically on the relationship between the material property and the following parameters as quantum statistics (Fermi-Dirac or Bose-Einstein), size and shape of the nanoparticle. ARTICLE HISTORY

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Section: Energy Bandgap Of Npsmentioning

confidence: 73%

Advances in thermodynamic modelling of nanoparticles

Guisbiers

2019

Advances in Physics: X

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“…where and are Ge molar fraction in the solid and liquid solutions of Si1-xGex, respectively. Using equations (2-5), the thermal equilibrium conditions for chemical potentials of Si and Ge in equations (6,7) can be rewritten explicitly in terms of the regular solution parameters, latent heats of melting and melting temperatures of the elements, 2,3 as given below…”

Section: Respectivelymentioning

confidence: 99%

Laser-Driven Phase Segregation and Tailoring of Compositionally Graded Microstructures in Si–Ge Nanoscale Thin Films

Aktaş

MacFarquhar

et al. 2020

ACS Appl. Mater. Interfaces

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The ability to manipulate the composition of semiconductor alloys on demand and at nanometer-scale resolutions is a powerful tool that could be exploited to tune key properties such as the electronic band gap, mobility, and refractive index. However, existing methods to modify the composition involve altering the stoichiometry by temporal or spatial modulation of the process parameters during material growth, limiting the scalability and flexibility for device fabrication. Here, we report a laser processing method for localized tailoring of the composition in amorphous silicon−germanium (a-SiGe) nanoscale thin films on silicon substrates, postdeposition, by controlling phase segregation through the scan speed of the laser-induced molten zone. Laser-driven phase segregation at speeds adjustable from 0.1 to 100 mm s −1 allows access to previously unexplored solidification dynamics. The steady-state spatial distribution of the alloy constituents can be tuned directly by setting the laser scan speed constant to achieve indefinitely long Si 1−x Ge x microstructures, exhibiting the full range of compositions (0 < x < 1). To illustrate the potential, we demonstrate a photodetection application by exploiting the laser-written polycrystalline SiGe microstripes, showing tunability of the optical absorption edge over a wavelength range of 200 nm. Our method can be applied to pseudobinary alloys of ternary semiconductors, metals, ceramics, and organic crystals, which have phase diagrams similar to those of SiGe alloys. This study opens a route for direct laser writing of novel devices made of alloy microstructures with tunable composition profiles, including graded-index waveguides and metasurfaces, multispectral photodetectors, full-spectrum solar cells, and lateral heterostructures.

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“…Quantum confinement effect was evidenced in small Ge and GeSi NCs 16 – 18 , enabling bandgap engineering along with composition 19 , shape 20 and strain 21 , 22 leading to tuning of optical and photoelectrical properties of NCs.…”

Section: Introductionmentioning

confidence: 99%

Bandgap atomistic calculations on hydrogen-passivated GeSi nanocrystals

Cojocaru

Lepadatu

Nemneş

et al. 2021

Sci Rep

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We present a detailed study regarding the bandgap dependence on diameter and composition of spherical Ge-rich GexSi1−x nanocrystals (NCs). For this, we conducted a series of atomistic density functional theory (DFT) calculations on H-passivated NCs of Ge-rich GeSi random alloys, with Ge atomic concentration varied from 50 to 100% and diameters ranging from 1 to 4 nm. As a result of the dominant confinement effect in the DFT computations, a composition invariance of the line shape of the bandgap diameter dependence was found for the entire computation range, the curves being shifted for different Ge concentrations by ΔE(eV) = 0.651(1 − x). The shape of the dependence of NCs bandgap on the diameter is well described by a power function 4.58/d1.25 for 2–4 nm diameter range, while for smaller diameters, there is a tendency to limit the bandgap to a finite value. By H-passivation of the NC surface, the effect of surface states near the band edges is excluded aiming to accurately determine the NC bandgap. The number of H atoms necessary to fully passivate the spherical GexSi1−x NC surface reaches the total number atoms of the Ge + Si core for smallest NCs and still remains about 25% from total number of atoms for bigger NC diameters of 4 nm. The findings are in line with existing theoretical and experimental published data on pure Ge NCs and allow the evaluation of the GeSi NCs behavior required by desired optical sensor applications for which there is a lack of DFT simulation data in literature.

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Thermal stability and optical properties of Si–Ge nanoparticles

Cited by 20 publications

References 65 publications

Advances in thermodynamic modelling of nanoparticles

Advances in thermodynamic modelling of nanoparticles

Laser-Driven Phase Segregation and Tailoring of Compositionally Graded Microstructures in Si–Ge Nanoscale Thin Films

Bandgap atomistic calculations on hydrogen-passivated GeSi nanocrystals

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