Diffusion mechanisms of vacancy and doped Si in Al3Ti from first-principles calculations

AbstractThe basic properties of palladium impurities in silicon carbide, such as solubility or diffusion mechanisms, are far from being well understood. In a recent paper I presented a systematic study of stability and kinetic properties of Pd in cubic silicon carbide using first principles calculations. In this paper I focus on the effect of the presence of palladium in silicon carbide, even in very low concentrations, on the kinetic properties of carbon vacancies. I apply a odel of Pd diffusion through a vacancy mechanism on the carbon sublattice and extract the correlation factors leading to an enhancement of vacancy migration, due to the coupling of iffusion fluxes between vacancies and palladium impurities.

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First principles investigation of the diffusion of interstitial Cu, Ag and Au in ZnTe

International Journal of Modern Physics B ◽

10.1142/s0217979215501301 ◽

2015 ◽

Vol 29 (19) ◽

pp. 1550130

Author(s):

Li An Chen ◽

Xing Feng Zhu ◽

Ling Fu Chen

Keyword(s):

First Principles ◽

Global Minimum ◽

Minimum Energy ◽

Relative Size ◽

High Symmetry ◽

First Principles Calculations ◽

Energy Diffusion ◽

Straight Line ◽

Energy Location ◽

Diffusion Mechanisms

The diffusion is of great significance in many applications when the impurities are employed to tune the semiconductor's electrical or optical properties. It is necessary to understand how dopant defects diffuse in semiconductors. Using first-principles calculations, we consider interstitial diffusion mechanisms and calculate the migration barrier energies of interstitial Cu, Ag and Au atoms in II–VI compounds ZnTe. We find that the relative size of dopant and bulk atoms is an important factor which affects the diffusion behavior. The high symmetry Tc site, which is tetrahedrally coordinated by four cation atoms, is the global minimum energy location for Ag and Au interstitials. The size of Cu adatom is small, so Cu is more stable when it locates at the Ta site which is tetrahedrally coordinated by four anion atoms. But the global minimum energy location for Cu interstitials is M site which is of smaller space than Ta. Cu adatoms show an asymmetric curve of energy diffusion barrier with two energetically distinct extremum in the pathway. Ag diffuses along nearly straight line paths along [111] or equivalent directions. Diffusion for Cu or Au deviates from the straight line paths along 〈111〉 avoiding high symmetric sites.

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CALCULATIONS OF SELF-DIFFUSION PROCESS AND COEFFICIENT IN ORDERED B2 AlCo

Modern Physics Letters B ◽

10.1142/s0217984913410340 ◽

2013 ◽

Vol 27 (19) ◽

pp. 1341034

Author(s):

ZHI-SHENG NONG ◽

JING-CHUAN ZHU ◽

YONG CAO ◽

XIA-WEI YANG ◽

ZHONG-HONG LAI ◽

...

Keyword(s):

Diffusion Process ◽

First Principles ◽

Diffusion Coefficients ◽

Density Functional ◽

Nearest Neighbor ◽

The Self ◽

First Principles Calculations ◽

Self Diffusion ◽

Diffusion Mechanisms ◽

Semi Empirical

The self-diffusion process in B2 type intermetallic compound AlCo has been investigated by the first-principles calculations within the frame work of density functional theory (DFT). The obtained mono-vacancy formation, migration and activation energies for four self-diffusion mechanisms, the next-nearest-neighbor (NNN) jump, [110] six-jump cycle (6JC), straight [100] 6JC and bent [100] 6JC diffusion show that the NNN jump mechanism of Co vacancy requires the lowest activation energy (Q = 6.835 eV ) in these diffusion mechanisms, which indicates that it is the main way of self-diffusion in AlCo . The electronic structure including the electron density difference on (-1 1 0) plane as well as atomic Mulliken populations were calculated, and the change of bonding behavior during the [110] 6JC process was discussed in detail. Finally, the self-diffusion coefficients of NNN jump and 6JC mechanisms for AlCo were also studied via the first-principles calculations and semi-empirical predictions, which indicates that the self-diffusion coefficients for NNN jump of Co vacancy show the highest value than the others.

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Novel diffusions of interstitial atoms in II–VI compounds zinc selenide

Modern Physics Letters B ◽

10.1142/s021798491550044x ◽

2015 ◽

Vol 29 (11) ◽

pp. 1550044

Author(s):

Li An Chen ◽

En Hai Jiang ◽

Xing Feng Zhu ◽

Ling Fu Chen

Keyword(s):

Optical Properties ◽

Zinc Selenide ◽

First Principles ◽

Relative Size ◽

First Principles Calculations ◽

Migration Barriers ◽

Diffusion Mechanisms ◽

Dopant Atoms ◽

And Migration ◽

Diffusion Behaviors

The diffusion plays an important role in many applications when the impurities are employed to tune the semiconductor's electrical or optical properties, which make it essential to understand theoretically the microscopic mechanisms governing how dopant defects diffuse. Using first-principles calculations, we compare the diffusion behaviors and migration barriers of interstitial Cu , Ag , and Au atoms in II–VI compounds ZnSe . We consider interstitial diffusion mechanisms and calculate the corresponding activation energies. For noble atoms, we find that the interstitial mediated mechanism is the dominant one. We also find that the relative size of dopant atoms and constituent atoms of II–VI compounds is an important factor affecting the diffusion behaviors. The coupling in ZnSe between Cu d levels and unoccupied host s levels is not as strong as that in CdTe .

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