Physico-Chemical nanomaterials science

Grain-boundary energy in silicon films
Nakhodkin N.G., Rodionova T.V.
Faculty of Radio Physics, Electronics and Computer Systems, Kiev National Taras Shevchenko University, Vladimirskaya Street 64, 01033, Kiev 33, Ukraine
E-mail: rodtv@univ.kiev.ua

The stability and reliability of solar cells and other devices containing silicon films are determined by the stability of grain boundary in these films [1]. The grain-boundary stability depends on the degree of non-equilibrium of grain boundaries. The most direct indicator of the degree of non-equilibrium is grain-boundary energy [2].
In this work the relative grain-boundary energy in silicon films depending on the deposition conditions and subsequent heat treatment was determined by the method of grain boundary grooves with the use of atomic force microscopy.
Silicon films were prepared by low-pressure chemical vapor deposition on thermally oxidized (100) Si wafers. The films thicknesses were 100-500 nm. Some films were doped with P. Depending on formation conditions, the films had different structures [3]: equiaxial, dendritic or fibrous.
It was shown that the largest dihedral angle and the lowest relative grain-boundary energy are observed in undoped silicon films with a dendritic structure. The next with increasing relative grain-boundary energy are P-doped dendritic and equiaxed films. The smallest values of dihedral angles and the largest values of the relative grain boundary energy characterize the fibrous films.
The mechanism of the phosphorus influence on relative grain-boundary energy has been analyzed. It was shown that annealing of P-doped dendritic silicon films leads to a decrease in the relative grain-boundary energy and to the relaxation of the non-equilibrium structure. Such films are preferred for practical use.

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