Measurements of potential barrier height of grain boundaries in polycrystalline silicon by Kelvin probe force microscopy

In recent years, the importance of polycrystalline silicon has been recognized in electronic device technology, although grain boundaries present in the material often exert a detrimental influence on the electrical properties because of the potential barriers associated with them. However, it is not true that all grain boundaries have similar properties, since they have their own character depending on the orientation relationship between two adjoining grains. We report here the first determination of the potential barrier height for well-characterized grain boundaries in polycrystalline silicon, using Kelvin probe force microscopy. The observed barrier height of the grain boundaries was found to vary in the range 10 to 100 meV depending on the grain boundary character. The most important finding is that the potential barrier height is approximately twice as high at random boundaries as at low-energy coincidence boundaries.