Atomic Transport in Nano-Сrystalline Thin Films

Abstract

Ge and B diffusion was studied in nanocrystalline Si, and Pd and Si self-diffusion was studied in nanocrystalline Pd2Si during and after Pd/Si reactive diffusion. These experiments showed that grain boundary (GB) diffusion kinetic is the same in micro-and nanoGBs, whereas triple junction (TJ) diffusion is several orders of magnitude faster than GB diffusion. In addition, GB segregation and GB migration can significantly modify atomic diffusion profiles in nanocrystalline materials, and atomic transport kinetics can be largely increased in nanograins compared to micro-grains, as well as during reactive diffusion, probably due to an increase of point defect concentration. These observations show that atomic transport in nanometric layers during reactive diffusion is complex, since GBs and TJs are moving and the proportion of GBs and TJs is changing during the layer growth.

Coupling Secondary Ion Mass Spectrometry and Atom Probe Tomography for Atomic Diffusion and Segregation Measurements

“…Figure 8a presents the comparison between the Ge lattice diffusion coefficients measured in Si single crystal (black solid line) and in 40 nm-wide Si nanocrystals (red solid line) (Portavoce et al, 2008, 2010, 2016). Ge diffusion is found to be faster in Si nanocrystals.…”

“…Ge diffusion is found to be faster in Si nanocrystals. The diffusion coefficient in nanocrystals was measured in nanocrystalline Si layers using 2D and 3D simulations from the SIMS profiles shown in Figure 8b (Portavoce et al, 2008, 2010, 2016). The part of the profile mainly depending on lattice diffusion is the Gaussian part centered at the depth of 150 nm.…”

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Fig. 8.Experimental data concerning Ge diffusion in nano-crystalline Si (Portavoce et al, 2016): ( a ) comparison between Ge lattice diffusion coefficients in Si macroscopic single crystal (black line) and Si nanocrystal (red line) versus the inverse of temperature ( T ) normalized to the Si melting temperature ( T m Si ); ( b ) germanium SIMS profiles measured before (open squares) and after (solid squares) Ge diffusion at 850°C compared with the APT Ge concentration profile measured in the same sample after diffusion (solid line); and ( c ) APT volume corresponding to the Ge concentration profile shown in ( b ), only the Ge atoms are presented (red points). The green points correspond to Ni atoms from the Ni layer deposited at room temperature on the sample surface during FIB sample preparation.

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Entropy Generation Optimization in Squeezing Magnetohydrodynamics Flow of Casson Nanofluid with Viscous Dissipation and Joule Heating Effect

“…Kumam et al [ 37 ] studied the MHD nanofluid flow in rotating channels with entropy generation. Alain Portavoce et al [ 38 ] explored transmission of atom in crystalline thin film. Oudina [ 39 ] explored heat transfer in Titania nanofluids in cylindrical annulus with discontinuous heat source.…”