Modelling of nanocrystals atomic configurations at nuclei formation

Aim. Study of the model of nucleus-sized nanocrystal and identification of its properties and patterns.

Methodology. A model was developed and numerical calculations were carried out on the example of the binary semiconductor GaAs, which showed that during the spontaneous formation of a nanocrystal, the crystal lattice with an elementary cell size of 0.4 – 0.5 nm is formed, which is greater than the length of the bond of both gallium and arsenic atoms when they are possible combined in the molecule (the sum of atomic radii is 0.273 nm) and less than the lattice constant of gallium arsenide (0.565 nm). The size of the nanocrystal, calculated as the cubic root of the product of the number of atoms and the volume of the unit cell, is 0.6 – 1.4 nm. These values correspond quite accurately to the estimation of the de Broglie wavelength for the electron of the bulk crystal. The bandgap decreases with the number of atoms, varying from the electron affinity of the material (4.1 eV) to the bandgap of the bulk crystal (1.42 eV).

Results. If the size of the nanocrystal is more than the minimum (unit cell), the physical models and approaches used for the bulk crystal are applicable to the nanocrystal.

Research implications. A model of properties of a nanosized system GaAs doped with Zn has been developed that provides prediction of new functionality of these materials.

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